最新刊期
卷 58 ， 期 3 ， 2026
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- 摘要：ObjectiveCarbon fiber reinforced polymer (CFRP) lenticular tube wrap-rib reflectors are lightweight, simple in structure, have a high stowage ratio, high deployment reliability, and offer promising application prospects for both small-aperture and several-meter large-aperture deployable antennas. Currently, the application of such deployable reflectors mainly faces two challenges: ensuring the reliability of stowage and deployment strategies under large-deformation wrapping, and achieving and maintaining the surface accuracy of flexible wrap-rib reflectors. This paper proposes a CFRP lenticular tube wrap-rib reflector scheme and investigates its stowage and deployment performance, as well as surface accuracy.MethodsFirst, a 3 m aperture wrap-rib reflector scheme for the X-band was proposed, which includes a central hub, wrap-ribs, metal mesh, side cables, and a locking and unlocking device. The wrap-ribs were made of lightweight, high-strength, and high-stiffness CFRP lenticular tubes, and the [45°/-45°/-45°/45°] lay-up and section design were achieved using prepregs with a single-layer thickness of 0.05 mm. To ensure installation accuracy and deployment rigidity of the wrap-ribs, they were rigidly connected to the central hub. To solve the problem of high stress in the root area of the wrapped wrap-ribs, a method involving the installation of a wrapping guide at the root area of the wrap-ribs was proposed. A finite element model was established based on material parameters obtained from tensile tests, and the stress during the wrapping process of a single CFRP lenticular tube with a wrapping guide was analyzed using an explicit dynamic method. Second, according to the requirements of the X-band, the surface accuracy of the 3 m aperture reflector was estimated using an approximate theoretical formula. The focal length-to-aperture ratio of the reflector and the number of wrap-ribs were determined. Due to the low stiffness of the wrap-rib reflector, the wrap-ribs deform to a certain degree during the reflector forming process, and a back-pillow effect is observed in each sector mesh. Both these factors affect the surface accuracy of the reflector. To address this issue, the shape of the flexible wrap-rib reflector was determined through form-finding analysis. The shape of the lenticular tube wrap-ribs was optimized by combining the form-finding analysis results of the flexible reflector with a genetic algorithm. Finally, a reflector prototype was designed and assembled, and deployment tests, fundamental frequency tests, and surface accuracy measurements were carried out.Results and DiscussionAdding a wrapping guide to the root area of the CFRP lenticular tube wrap-rib can prevent excessive wrapping stress in this area and improve the wrapping performance of the wrap-rib reflector. The focal length-to-aperture ratio of the reflector is 0.55, the number of wrap-ribs is 36, and the root mean square error (RMSE) of the estimated surface accuracy calculated using the theoretical formula is 0.89 mm, which meets the application requirements for the X-band. When the upper edge curve of the reflector wrap-rib lies on the design paraboloid, the surface accuracy of the reflector after form-finding analysis is 1.51 mm, which is significantly higher than the 0.89 mm calculated using the theoretical formula. This discrepancy arises because the elastic deformation of the wrap-ribs and the back-pillow effect of the metal mesh cause the mesh to deviate from its initial position after form-finding analysis of the flexible wrap-rib reflector. Taking the root of the wrap-rib as the origin, the curve equation of the wrap-rib after optimization is
- 摘要：ObjectiveOn-orbit deformation monitoring of large-scale space truss structures is crucial for ensuring the stable operation of space science payloads and enabling the on-orbit assembly and expansion of space structures. Currently, deformation monitoring of these structures faces two challenges: deformation reconstruction of complex assembled structures under thermo-mechanical loads and discontinuous deflection curves caused by hinges. A method integrating Ko displacement theory with least-squares optimization is proposed to address the difficulty in solving deflection curves caused by special assemblies, thereby expanding the application scope of Ko displacement theory. By introducing combined measurement methods, a thermal deformation reconstruction strategy for space truss systems that considers hinge effects is developed.MethodsFirst, the deformation reconstruction of the space truss system was decomposed into two parts: the main truss structure and the solar panel. For the main truss structure, functions for the deformation deflection curves of each main beam were established using Ko displacement theory. Integral functions were solved using deformation strain data and boundary conditions to achieve deformation reconstruction of the main truss structure. Then, displacements,
- 摘要：ObjectiveOn-orbit assembly represents a promising approach for constructing large-aperture space antennas, which are essential for advanced communication, Earth observation, and deep space exploration. However, the modular assembly process inherently introduces cumulative errors, such as surface deviations and potential module interference, due to assembly gaps and alignment inaccuracies. These errors can compromise overall surface accuracy and assembly feasibility. This study aims to develop a deformation adjustment strategy for module units to suppress error propagation, mitigate interference risks, and ensure high assembly precision and system performance.MethodsA comprehensive modeling and analysis framework was established. First, a parabolic antenna model incorporating assembly gaps was developed. Using a planar projection method, nodal coordinates of the module units were generated. A gap conversion model was iteratively applied to determine the spatial positions of modules in each concentric ring. A three-point circumferential docking mechanism and a unidirectional assembly sequence (from the center outward) were designed, resulting in six distinct error propagation chains. Second, an assembly error analysis was conducted based on the concepts of error chains and error balls. A six-degree-of-freedom error model was constructed using the product-of-exponential (POE) method. Random displacement and rotational errors were generated at virtual assembly centers, simulating error propagation along the chains. A 61-module antenna was analyzed to quantify the effects of assembly gap size (100～300 mm) and maximum allowable displacement error (10～40 mm) on cumulative error. Finally, a deformable module configuration was proposed to counteract error accumulation. By releasing nodal degrees of freedom and integrating actuators on the reflective surface, the module could achieve graded adjustment capabilities, from single-face to six-face deformation. A scenario-based adjustment scheme was formulated, dynamically modifying module edge lengths and angles according to the number of contact faces and interference conditions. The feasibility of the design and adjustment strategy was validated through simulations using simplified planar models of the deformable modules.Results and DiscussionsThe error analysis revealed that assembly errors accumulate progressively along the error chains, with a positive correlation with both assembly gap size and maximum allowable displacement error. For instance, with a 200 mm assembly gap and a 10% maximum displacement error allowance, the maximum displacement error at the assembly center reached 16.99 mm. Error accumulation accelerated with increasing module ring numbers, highlighting the risk of exceeding docking mechanism tolerances and causing module interference. Simulation results for deformable modules under various adjustment scenarios (two-, three-, four-, and six-sided adjustments) demonstrated effective shape adaptation to target configurations. Actuator stroke distances and directions were successfully determined for each case. For example, in the two-sided adjustment scenario, one face extended by 50 mm while the other contracted by 24.93 mm, achieving the desired interface matching. The simulations confirmed that the proposed module design and adjustment logic can effectively compensate for misalignments and prevent interference.ConclusionsThis study presents a systematic approach to modeling, analyzing, and mitigating assembly errors in modular on-orbit assembled antennas. The key conclusions are: 1) Assembly errors accumulate along error chains and are proportional to assembly gap size and maximum allowable displacement error. 2) A deformable module unit configuration capable of one- to six-sided adjustments effectively counteracts error-induced misalignments and interference. 3) A scenario-based adjustment scheme enables dynamic module reshaping according to contact and interference conditions. 4) Simplified model simulations verify the feasibility of both the deformable module design and the adjustment strategy. The proposed strategy offers a viable solution for managing error accumulation in large-scale in-space antenna assembly, enhancing both assembly feasibility and operational performance. Future work will focus on detailed freedom analysis and mechanical redesign of deployable hexagonal modules to realize the proposed deformation capabilities in engineering practice.关键词：on-orbit assembled antenna;module deformation adjustment strategy;assembly error analysis;deformable module;module deformation adjustment scheme54|84|0更新时间：2026-05-19
- 摘要：ObjectiveSpace deployable antennas are a new type of space structure developed with the rapid advancement of aerospace technology. In recent years, with China's increasing frequency of space exploration activities, ranging from the Earth‒Moon system to interplanetary space, subsequent aerospace engineering projects have raised urgent demands for deployable antennas that must balance comprehensive performance indicators, including large aperture, lightweight design, and high precision. Meanwhile, kinematic characteristic analysis serves as a crucial approach to validate the feasibility of innovative mechanism designs. Nevertheless, there are relatively few studies on the kinematic modeling of complex space deployable antennas that can be transformed into planar mechanisms. Accordingly, this paper proposes a new configuration of a bionic tree-like deployable antenna mechanism and investigates its kinematic characteristics as a multi-stage, multi-closed-loop mechanism.MethodsFirst, by analyzing the bionic mechanisms of tree branching structures and large-span tree-like support structures and considering the practical design requirements of deployable antennas, design principles for bionic tree-like deployable antenna mechanisms are proposed. Based on the proposed antenna configuration, the overall design and deployment principle are introduced. Second, based on the closed-loop vector method and coordinate transformation method, the rib units are divided into sub-units, and the internal closed-loop circuits within these sub-units are decomposed. Accordingly, the kinematic models of the rib unit and the entire antenna structure are established, which consist of multi-level deployable units connected in series and nested closed-loop circuits. By analyzing the motion characteristics of the outer branching beam and its spatial geometric relationships, spatial coordinate models of key nodes are established. In addition, a driving strategy of "outer rotation parallel, inner rotation zeroing" is formulated, and a corresponding driving strategy model is established for the branching outer beam to avoid interference during the deployment process. Finally, the antenna kinematic model and the branching outer beam driving strategy model are simulated and analyzed using numerical software such as MATLAB, while the branch slider displacements and the key angular displacements during the deployment process are selected for validation. The 30 m-class antenna scaled model is imported into ADAMS for further comparative validation and analysis.Results and DiscussionsThe simulation results indicate that, for the driven branching outer beam, there are displacement deviations between the two simulation results obtained using ADAMS and MATLAB. However, the motion trends are consistent, thereby verifying the correctness of the modeling. The primary cause of the error appears to be inaccuracies in the calculation of the spatial coordinate transformation angles. Additionally, the larger size of the antenna appears to amplify the error. At time t = 0 s, the antenna mechanisms are in a fully retracted state, and there is no interference between the rib units. In the initial phase (t = 1～6 s), the antenna mechanism undergoes a gradual deployment process. The key point J3 of the fixed branching outer beam enters the danger zone after t = 2 s, thereby causing interference. Concurrently, the driven branching outer beam maintains parallel alignment with the plane of the trunk deployable unit through continuous external rotation. Notably, the key point does not enter the danger zone during this period. At t = 50 s, the driven branching outer beam has moved away from the danger zone and is in a state of internal rotation. At this time, the antenna has nearly completed deployment, with most of the displacement achieved. This indicates that, although the trunk slider moves at a uniform speed, the synchronized deployment of the branching deployable unit is mainly concentrated within the first 50 s and is therefore not a uniform-speed motion. At t = 100 s, the antenna is fully deployed. The fixed branching outer beam does not reach its preset position due to the absence of internal rotation to offset both the initial angular displacement and that generated by external rotation. In contrast, the driven branching outer beam reaches the preset position through internal rotation. At this stage, the branching outer beam is coplanar with the branching deployable unit, ensuring that the outer layer of the rope is smoothly tensioned. The branching slider displacement and angular displacement first gradually increase and then gradually decrease during t = 1～6 s, and the trend of the curves is consistent with the motion trajectory of the key point.ConclusionsIn this paper, to address the urgent requirements of future large-scale development, a novel configuration of a large-aperture bionic tree-like deployable antenna mechanism is proposed. The antenna mechanism takes the tree branching structure as the bionic prototype, and kinematic modeling, motion characteristic analysis, and numerical simulation are conducted to investigate its performance. By analyzing the bionic mechanism of tree branching geometry, design criteria applicable to deployable antennas are extracted, thereby providing a theoretical reference for the systematic design of antenna configurations. On this basis, a kinematic parametric model of a deployable antenna with multilevel deployable units connected in series and multiple nested closed-loop mechanisms is established, and the mutual coupling relationships between the antenna structural parameters are clarified, which provides a basis for subsequent optimization of antenna structural design. Furthermore, by analyzing the kinematic characteristics of the antenna branching outer beam during the deployment process, a driving strategy of "parallel external rotation and zero internal rotation" is proposed. This strategy has been shown to be effective in avoiding interference during the deployment process of the branching outer beam. The validity and correctness of this strategy are verified through numerical simulation analysis.关键词：space deployable antenna;structural design;kinematic analysis;spatial geometry modeling;numerical simulation analysis167|373|0更新时间：2026-05-19
- 摘要：ObjectiveWith increasingly stringent requirements for satellite precision in fields such as deep space exploration, remote sensing and navigation, and military reconnaissance, large-aperture modular deployable antennas are becoming a key development trend in astronautical deployable antenna systems. However, due to factors such as the disintegration or explosion of defunct spacecraft, the number of small space debris objects continues to increase year by year, posing a significant threat to their on-orbit service. There is currently limited research on damage identification for large and complex structures, such as deployable antennas. In such cases, accurately identifying damage presents significant challenges, often leading to the misclassification of undamaged components and resulting in reduced identification accuracy. In this paper, an improved two-stage structural damage identification method is proposed by combining Bayesian data fusion and an improved whale optimization algorithm. Numerical simulations of damage identification are carried out on a large-aperture space deployable antenna support structure with 415 rods to verify the identification accuracy of the two-stage method under a certain level of noise interference.MethodsFirst, six damage conditions are designed based on three types of damage: single damage, double damage, and multiple damage. The Bayesian data fusion method is adopted to integrate the cross-model modal strain energy index (CMSEI) and the cross-model modal strain energy change rate index (CMSECR). A damage threshold is defined, and rods with values exceeding this threshold are identified as suspected damaged rods, thereby enabling localization of structural damage. The localization accuracy of Bayesian data fusion is then compared with that of using only CMSEI under noise levels of 0, 0.1%, and 0.2%. Second, to overcome the limitations of the whale optimization algorithm (WOA), such as its tendency to fall into local optima and its insufficient global search capability, a hybrid multi-strategy whale optimization algorithm (HMWOA) is proposed. This approach incorporates multiple improvement strategies, including Sobol sequence-based population initialization and parallel search with dual populations and communication mechanisms. The performance of the proposed algorithm is compared with that of WOA and five other optimization algorithms using six benchmark test functions. Finally, after Bayesian data fusion is used to identify the suspected damaged rods of the deployable antenna support structure in the first stage, the HMWOA algorithm is applied in the second stage to quantify the damage. This process further eliminates non-damaged rods and determines the damage severity of the actual damaged rods.Results and DiscussionFrom the damage localization results of single-damage scenario 1, it can be seen that both methods, CMSEI and Bayesian data fusion, can clearly identify the actual damaged rods at noise levels of 0, 0.1%, and 0.2%. However, Bayesian data fusion achieves more accurate damage localization and reduces the possibility of misclassification, especially at a noise level of 0.2%. From the damage localization results of multi-damage scenarios 4 to 6, it can be observed that the sensitivity of different rod types to structural damage varies. The central vertical rods are the least sensitive to damage, followed by the edge vertical rods, while the chord and diagonal web rods are more sensitive. Therefore, it is necessary to define different damage thresholds for different types of rods. Based on the results of the three working conditions, the damage thresholds are set to 0.001 for central vertical rods, 0.03 for edge vertical rods, and 0.2 for chord and diagonal web rods. The effect of noise on multi-damage scenarios is more significant than that on single-damage scenarios, increasing the number of non-damaged rods misclassified by both methods for damage localization. However, the use of Bayesian data fusion effectively reduces the effect of noise. For damage scenario 4, the damage identification results using CMSEI show that, under 0.2% noise, 31 rods are identified as suspected damaged rods, compared to 8 rods under noise-free conditions. In contrast, using Bayesian data fusion under 0.2% noise results in 11 suspected damaged rods, while only 3 rods are identified in the noise-free case. To verify the solution accuracy and convergence speed of HMWOA, we compare the results of WOA, an improved whale optimization algorithm (MSWOA), the sailfish optimization algorithm (SFO), the sparrow search algorithm (SSA), and the zebra optimization algorithm (ZOA). Six benchmark test functions from CEC2005 are selected to evaluate the performance of the different algorithms. To reduce the influence of randomness on the experimental results, we conduct 30 independent runs and calculate the mean and standard deviation of the solutions. The results indicate that the HMWOA algorithm demonstrates superior accuracy and stability in optimizing functions F1 to F6. In particular, for functions F3, F5, and F6, the advantage of the HMWOA algorithm is most pronounced. Compared with other algorithms, HMWOA also maintains the fastest optimization speed across all six benchmark test functions, significantly reducing computation time. In the damage quantification stage, due to the high accuracy of damage localization using Bayesian data fusion at noise levels of 0 and 0.1%, only the case with a noise level of 0.2% is examined. From the three scenarios of single-damage scenario 1, double-damage scenario 3, and multi-damage scenario 4, it can be seen that, after using Bayesian data fusion in the first stage to identify suspected damaged rods, the HMWOA algorithm in the second stage can further identify the actual damaged rods and accurately determine the damage severity. The damage quantification error is kept within 5%, and no non-damaged rods are misclassified.ConclusionThe results show that using Bayesian data fusion to integrate CMSEI and CMSECR for damage localization yields more accurate identification results. The four improvement strategies effectively enhance the optimization accuracy and convergence speed of the WOA. For complex structures with a large number of rods, the two-stage damage identification method based on Bayesian data fusion and the improved WOA proposed in this paper can accurately identify structural damage.关键词：structural damage identification;Bayes data fusion;improved whale optimization algorithm;cross-model modal strain energy;deployable antenna structure123|297|0更新时间：2026-05-19
- 摘要：ObjectiveSpace membrane antennas possess several inherent advantages that make them highly appealing for aerospace applications: Their very low mass reduces spacecraft launch weight and cost; their high packing efficiency allows compact folding and storage, which is critical when launch volume is limited; and their good environmental adaptability enables operation under extreme temperatures, vacuum, and radiation. Motivated by the growing interest in large planar membrane antennas, a dedicated planar membrane model was designed and fabricated, and a dynamic modal test was conducted to evaluate its tension‒formed structural performance.MethodsFirstly, the form-finding process was used to determine the initial equilibrium shape of the membrane structure under a prescribed pre-stress, and the subsequent tension‒forming process was used to tension the membrane to the target stiffness and geometry; both processes were simulated using the nonlinear finite element method (FEM). The tension‒forming analysis explicitly modeled sliding-friction contact between the cables and their sleeves. To compare with the observed wrinkle patterns, an additional finite element analysis incorporating a wrinkling-corrected membrane constitutive model was performed to obtain the directions of the maximum principal stress under self-weight and initial pre-tension loads. A modal analysis of the test specimen was then conducted using FEM considering the added mass of the surrounding air in ground tests. Finally, the planar membrane specimen was tensioned and tested under three loading cases:Initial pre-tension, low tension, and high tension. The measured wrinkle distributions and modal properties were compared with the numerical results.Results and DiscussionsThe form-finding results showed that the short-span non-semicircular membrane had a more uniform stress distribution, whereas the short-span semicircular membrane exhibited relatively nonuniform stress near the corners, and its catenary radii deviated from the theoretical value. Therefore, the short-span non-semicircular configuration was adopted for subsequent finite element analyses and for the test specimen. In the tension‒forming analysis, friction between the cables and sleeves altered both the direction and magnitude of the membrane principal stresses. The first principal stress shifted from the direction normal to the membrane edge toward the tangential direction. Friction also caused the minimum stress to occur at the cable mid-span and the maximum stress at the cable ends, while membrane stresses in the central region exceeded those near the ends. Compared with the friction-free case, the stress at the cable ends remained almost unchanged, whereas the mid-span cable stress decreased. The normal stress in the x-direction of the central membrane element increased substantially, while the normal stress in the y-direction increased slightly relative to the friction-free case, and the von Mises equivalent stress increased with increasing friction coefficient. Modal analysis, which included the model's self-weight and an added air mass of 1.769 kg/m2, yielded the specimen's natural frequencies and mode shapes. Through the tensioning and modal tests, wrinkle distributions and modal frequencies were measured. Under initial pre-tension, numerous relatively large wrinkles formed in the upper central region, with fine, dense wrinkles along the inner side of the sleeves near the lower edge; increasing tension progressively improved membrane flatness. The wrinkle orientations agreed well with the directions of the maximum principal stress predicted by the wrinkling-corrected membrane constitutive model. Due to the geometric symmetry of the specimen and the high modal density resulting from the membrane's low bending stiffness, the first and second natural frequencies were very close, leading to easy mode coupling; apart from these coupled modes, the measured mode shapes and frequencies matched the numerical results closely, with frequency errors within 10%. These outcomes verify the reliability of the numerical methodology.ConclusionsFriction between the cables and sleeves has a decisive influence on the stress distribution in both the membrane and the cables. The dynamic modal tests clearly captured the model's vibration characteristics under different load levels, and the results were compared with those from the finite element analyses. A detailed comparison between tests and simulations confirms that the tensioning system performs as intended and that the numerical model can reliably predict the actual structural response.关键词：planar membrane;tension‒forming analysis;slip-friction contact;fundamental frequency of membrane;membrane wrinkling;modal test174|360|0更新时间：2026-05-19
- 摘要：SignificanceWith the continuous development of communication satellites, antennas are required to achieve higher gain and larger apertures in order to receive weaker transmitted signals. With the improvement of communication quality, the operating frequency band of satellite antennas also needs to be further increased, leading to increasingly stringent requirements for reflector surface accuracy. Mesh antennas are currently the most widely used type of deployable antenna due to their advantages of a high stowage ratio, low area density, and high profile accuracy. Among these, the pillow effect is one of the main sources of design error in mesh antennas. It causes the antenna surface to deviate from the ideal paraboloid, affects the far-field characteristics of the antenna, and consequently degrades the communication performance of the satellite.ProgressThe pillow effect can be described mathematically as a surface with negative Gaussian curvature. The mechanical behavior of the metal mesh can be explained using the moment-free thin-shell theory in elasticity. Applying a uniform load to the metal mesh can make the principal curvatures have the same sign, thereby forming a surface with positive Gaussian curvature. Inflatable antennas and electrostatic forming antennas represent the most ideal uniform loading modes. However, the gas inside inflatable antennas is prone to leakage in space. Supplying an air source is expensive, and self-curing technology is not yet mature, making it difficult to achieve uniform curing in orbit; therefore, such systems have not been widely applied in practice.As achieving an ideal uniform load is challenging, distributed loading can provide a similar effect. Initially, a group of traction cables is added along the rib thickness direction of single-layer mesh antennas to achieve an equivalent distributed load; however, the tension provided by this method is limited. Therefore, based on double-layer mesh structures, circumferential cables are arranged in pairs along the front and back sides of the radial ribs to further increase the applied tension. The tension capacity of the circumferential cables is much higher than that of the metal mesh, allowing fewer traction cables to achieve higher profile accuracy. However, the front cables of circumferential cable umbrella antennas form small quadrilaterals, and the pillow effect cannot be avoided within each quadrilateral. The tension rod antenna connects the diagonals of these quadrilaterals, transforming the structure into a triangular cable network and enabling finer surface segmentation. However, further improvements in profile accuracy require increased cable mesh density, which leads to greater structural complexity and higher weight.Beyond the moment-free thin-shell theory, reducing the bending stiffness of the shell is another approach to mitigating the pillow effect. Self-resilient antennas, achieved by reducing the shell thickness t, and membrane antennas, achieved by reducing the elastic modulus E, can both eliminate the pillow effect. However, the diameter of self-resilient antennas is limited by autoclave manufacturing constraints, and membrane antennas cannot be deployed independently, requiring additional deployment mechanisms; moreover, their surface accuracy is easily affected by these mechanisms. The size of these single-shell structures is also limited by mold constraints and cannot be further increased. Traditional materials subjected to concentrated loads tend to form surfaces with negative Gaussian curvature, whereas materials with a negative Poisson's ratio exhibit the opposite behavior, forming surfaces with positive Gaussian curvature under external loading. This property provides a new approach to mitigating the pillow effect. Two-dimensional in-plane negative Poisson's ratio materials, such as re-entrant honeycomb structures, chiral structures, and rotating rigid body structures, have been investigated. Hexagonal chiral honeycomb materials exhibit in-plane isotropy and are promising candidates for deployable reflector antennas. Through optimization of traditional hexagonal chiral honeycomb structures, it has been demonstrated that negative Poisson's ratio materials can effectively alleviate the pillow effect in mesh antennas and are feasible for use in mitigating this effect in reflector antennas.Conclusions and ProspectsThis paper summarizes previous research approaches for mitigating the pillow effect and, based on recent results from the authors' research group, explores the feasibility of using the curved-surface bending characteristics of negative Poisson's ratio materials to address this issue. This approach is expected to reduce the number of adjustment points in existing mesh antennas, optimize the antenna structure, and reduce overall mass. In the future, the following aspects require further investigation: 1) design and optimization of negative Poisson's ratio materials; 2) macro-scale homogenization analysis; 3) investigation of the out-of-plane stiffness of the materials; and 4) prototype development and experimental validation.关键词：mesh antenna;anti-pillowing effect;negative Poisson's ratio material;out-of-plane stiffness;membrane structure150|497|0更新时间：2026-05-19
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DEPLOYABLE STRUCTURES AND THEIR APPLICATIONS IN AEROSPACE ENGINEERING
- 摘要：ObjectiveThis study addresses the insufficient understanding of the flow characteristics of such channels in existing research and provides theoretical support for channel regulation and ecological restoration engineering practices to clarify the flow movement laws of meandering branching channels under the coupled effects of discharge and vegetation density.MethodsA generalized physical model test was conducted using the Yujiawan reach of the Xulu section of the Yangtze River as the prototype at the State Key Laboratory of Hydraulics and Mountain River Engineering. The flume was composed of inlet and outlet straight sections and a middle arc section, with the left branch, right branch, and central bar each having a width of 1 m and a longitudinal slope of 3‰. The riverbed was paved with natural sand with particle sizes ranging from 0.5 mm to 10.0 mm. Rigid non-submerged vegetation, with a diameter of 0.8 cm and a length of 30 cm, was arranged in the right branch. Nine groups of clear water steady flow tests were designed using three discharge gradients (55, 70, and 90 L/s) and three vegetation density gradients (0, 0.02, and 0.08). Each test was subjected to constant scouring for 8 hours until the riverbed reached a stable state. Ultrasonic distance-measuring sensors were utilized to measure the water surface elevation at seven cross-sections. The AiFlow video current measurement system, based on improved Particle Image Velocimetry (PIV) technology, was adopted to obtain the surface flow velocity. The variation characteristics of water surface elevation, longitudinal and transverse water surface gradients, surface flow velocity distribution, and the hydrodynamic axis of the channel were systematically analyzed.Results and DiscussionsThe water level of the meandering branching channel was influenced more significantly by discharge than by vegetation density. A stepwise increase in water level was observed with increasing discharge, whereas only a slight rise in water level occurred with increasing vegetation density, and the magnitude of increase in the right branch was slightly greater than that in the left branch. The water level in the diversion area increased due to the backwater effect of the central bar, decreased at the branching mouth with the disappearance of the backwater effect, and then increased along the flow direction in the confluence area due to flow impact and backwater effects. Vegetation exerted a minimal influence on the longitudinal gradient of the channel. The longitudinal gradients in both the diversion and confluence areas increased along the flow direction. In the branching section of the left branch, the longitudinal gradient increased gradually from the branching mouth to the bend apex and then decreased progressively from the bend apex to the confluence mouth. In the branching section of the right branch, the longitudinal gradient first decreased and then increased, reaching a minimum at the bend apex. The transverse gradient of each cross-section increased slightly with increasing vegetation density, with a more pronounced increase in the left branch. The transverse gradient was strongly affected by discharge and increased sharply with increasing discharge. The transverse gradient in the left branch remained positive, whereas that in the right branch was negative at the branching and confluence mouths and positive within the branching section. Under the same inflow conditions, vegetation produced significantly different effects on flow velocity across different channel sections. The flow velocity in the diversion and confluence areas was less affected by changes in vegetation density, whereas clear differentiation was observed in the branching section. With increasing vegetation density, the diversion ratio and flow velocity in the left branch increased, whereas the discharge through the right branch decreased and the flow velocity was reduced. In addition, vegetation in the right branch caused the flow velocity at the branching mouth to deflect toward the concave bank, and the deflection angle increased with increasing vegetation density. The flow-blocking effect of vegetation in the right branch was identified as the primary cause of hydrodynamic axis deflection. Under vegetation cover conditions, the hydrodynamic axis of the right branch in the branching section deflected toward the concave bank, and higher vegetation density brought it closer to the concave bank. Simultaneously, the hydrodynamic axis of the left branch also deflected toward the concave bank due to the increased diversion ratio. The influence of vegetation on the hydrodynamic axis depended on discharge, being significant under low discharge conditions and gradually weakening with increasing discharge. Under low discharge, the hydrodynamic axis showed a noticeable deflection when vegetation density increased from 0 to 0.02, but only slight changes were observed when the density increased from 0.02 to 0.08. Under medium and high discharge conditions, the variation trends of the hydrodynamic axis under different vegetation density gradients remained generally consistent.ConclusionsThe study revealed the regulatory mechanisms of discharge and vegetation density on the flow characteristics of meandering branching channels. It clarified the variation patterns of water surface morphology, flow velocity distribution, and the hydrodynamic axis of such channels under the water-blocking effect of vegetation. The research results can provide theoretical references for flood control and regulation, the rational configuration of beach vegetation, and river ecological restoration engineering in meandering branching channels. The findings are only applicable to scenarios involving rigid, non-submerged vegetation, with a flow velocity of 0.15～0.35 m/s and a vegetation density of 0.02～0.08. Further experimental studies are required to investigate the effects of other vegetation types, such as flexible and submerged vegetation, on the flow characteristics of meandering branching channels.关键词：meander branch channel;vegetation;flow characteristics;steady flow188|561|0更新时间：2026-05-19
- 摘要：ObjectiveUnder the influence of earthquakes and rainfall, loose slopes are highly prone to instability and sliding, triggering a series of secondary landslides and forming multiple granular flow disasters. Baffles are installed in the potential impact areas to reduce destructive forces and limit the accumulation range, and the motion characteristics of multiple granular flows blocked by baffles in a gully are analyzed using the discrete element method to reduce or avoid the hazards of multiple granular flows.MethodsThe influence of the baffle structure on the transport process of multiple granular flows was investigated through numerical simulation. Due to the inability of the continuous medium model to capture detailed information such as particle squeezing and collision during multiple granular flows, the discrete element method, which belongs to the discontinuous medium model, was used for the numerical simulation. Firstly, the calculation method was validated. The physical model reported in the literature was established, and numerical simulations were conducted using the experimental conditions described in the same literature. The accuracy and reliability of the calculation method were assessed by comparing the calculation results with the experimental data from the literature. Secondly, due to significant variations in channel gradient at different locations, the physical model used in the calculation adopted a three-stage slope configuration, and the baffle structure was installed at the position of the second slope. The impact of the baffle structure on the blocking effect of multiple granular flows was obtained by modifying the arrangement of the baffles. Finally, the motion and accumulation of multiple granular flows were calculated using the three-dimensional discrete element method. Based on the analysis of the numerical data, the motion characteristics of multiple granular flows blocked by baffles in a gully were examined.Results and DiscussionsDuring the first sediment supply, the particle velocity along the gully increased with wider lateral spacing but decreased as the spacing and the number of rows increased. The vertical particle velocity decreased as the number of rows increased and the lateral spacing decreased, but it remained relatively insensitive to changes in row spacing. The baffles reduced the downstream sediment supply intensity by approximately 47.6%. The downstream sediment supply intensity exhibited a negative correlation with both the spacing and the number of rows, while it showed a positive correlation with the lateral spacing. The downstream sediment supply time was delayed as the number of rows increased and the lateral spacing decreased, whereas the sensitivity to row spacing remained relatively low. In addition, the closer the location was to the downstream, the smaller the peak average force on the rows became. For instance, considering the baffle arrangement with a lateral spacing of 3 m and a row spacing of 4 m, the peak average force on the second and third rows was only 17.2% and 15.8% of that on the first row. However, the effect of variations in spacing and the number of rows on this parameter remained relatively weak. An increase in lateral spacing has a limited impact on the peak average force on the first row, while the peak average force on the other rows rises accordingly. When particles were supplied again, compared to the first sediment supply, an increase in row spacing caused a corresponding decrease in particle vertical velocity, and the downstream sediment supply time was slightly delayed. The initial value of the average force on the rows increased as the spacing and the number of rows increased, but it showed a negative correlation with the lateral spacing. As the sediment supply continued, increases in spacing, the number of rows, and lateral spacing had a relatively minor impact on the peak average force on the first row. In contrast, the peak average force on the other rows increases accordingly. After particle accumulation, the peak average force on the baffles gradually increases as the spacing and the number of rows increase, and as the lateral spacing decreases, and the closer the location is to the downstream, the greater the peak average force becomes. In addition, the distance and depth of the entrainment process decrease with increases in spacing and the number of rows, and with decreases in lateral spacing, and the entrainment mode shifted from impact failure to a combined mode of impact failure and shear failure. The material composition of granular flows is highly complex, ranging from a few millimeters of sand to several meters of boulders, with a wide particle size distribution. However, the computational cost increases significantly as the number of particles increases. Therefore, the study only conducted simulations for particle diameters ranging from 30 to 150 cm. The influence of particle shape, particle size distribution, channel width, and channel slope on the motion characteristics of multiple granular flows blocked by baffles in a gully was not considered in the simulation. The impact force of multiple granular flows on protective structures remained extremely large. In this study, the baffle structure was treated as a rigid body to investigate its protective effect against multiple granular flows. However, in practical situations, the large forces generated by multiple granular flows could cause deformation or damage to the protective structure. Therefore, the design of protective structures that meet practical requirements needs further investigation.ConclusionsThe results demonstrate that the installation of baffles in the potential impact area of multiple granular flows can reduce their destructive force and limit the accumulation range. The effects of baffles on particle motion velocity, downstream sediment supply, impact force, and sediment deposition patterns studied in the study provide a scientific basis for baffle design for the effective prevention and control of multiple granular flow disasters in mountainous areas.关键词：multiple granular flows;baffles;discrete element method;entrainment mechanism;numerical simulation216|487|0更新时间：2026-05-19
- 摘要：ObjectiveWith the construction of the new Three Gorges water transportation channel, the waterway in the Chuanjing section of the Yangtze River becomes a bottleneck between the downstream waterway of the Jinsha River and the Chongqing section of the upper reaches of the Yangtze River, restricting the full utilization of the transportation capacity of the Yangtze River's golden waterway. The upgrading of the waterway in the Chuanjing section of the Yangtze River is urgent, but traditional waterway improvement measures are difficult to implement due to environmental protection constraints. Therefore, this research explores the feasibility of utilizing the regulating and storage effects of cascade reservoirs in the lower reaches of the Jinsha River to increase the flow of the Yangtze River during the dry season and improve the waterway level by conducting a multi-objective collaborative scheduling study on medium-and long-term navigation and hydropower generation in the reservoir group.MethodsFirstly, based on the demand for navigation and water replenishment during the dry season of downstream rivers, this research aimed to improve the minimum discharge flow of Xiangjiaba Hydropower station as the navigation goal and to maximize the total power generation of cascade hydropower stations as the power generation goal. A multi-objective collaborative adjustment model for navigation and power generation of cascade reservoirs in the downstream of the Jinsha River was constructed, considering constraints such as water balance constraints, reservoir water level constraints, reservoir power generation flow constraints, power plant output constraints, cascade power plant water connection constraints, and non-negative condition constraints. Secondly, this research adopted the commonly used progressive optimization algorithm (hereinafter referred to as "POA algorithm") in the optimization scheduling research of cascade reservoir groups to calculate the multi-objective collaborative scheduling model of navigation and power generation of the cascade reservoirs in the lower reaches of the Jinsha River. The POA algorithm decomposed a multi-stage problem into multiple two-stage problems, with different two-stage problems connected by state variables. The two-stage problem was solved by fixing the state variables of other stages and performing optimization calculations on the selected two-stage decision variables. After solving these two-stage problems, the next two-stage problem was considered, and the previous calculation result was used as the initial feasible solution for the next optimization calculation. The process continued to loop until convergence. Finally, this research considered four cascade reservoirs in the lower reaches of the Jinsha River, including Wudongde, Baihetan, Xiluodu, and Xiangjiaba, as research objects and conducted case studies. This research calculated the hydrological frequency of the measured annual runoff series of the designed hydrological station (Huatan Hydrological Station) of the Wudongde Hydropower Station, and selected 1999, 2003, and 1997 as the years representing wet (25%), normal (50%), and dry (75%) conditions, respectively. Using the water conservancy year (from early June to late May of the following year) as the cycle and ten days as the calculation period, the runoff data of the cascade reservoirs in the lower reaches of the Jinsha River in wet years, normal years, and dry years were used for example calculations. At the same time, for the convenience of comparative analysis of calculation results, the optimization scheduling model (hereinafter referred to as "Model 2") with the goal of maximizing the total power generation of the cascade while considering the minimum output during the dry season was calculated and compared to the multi-objective collaborative scheduling model for navigation and power generation established in this study (hereinafter referred to as "Model 1".Results and DiscussionsBy compared to Model 2, Model 1 significantly increased the minimum discharge flow to the Jiaba Reservoir during the dry season from November to April. The minimum ten-day average flow in the wet year, normal year, and dry year increased from 2 893 m3·s-1, 2 745 m3·s-1, and 2 485 m3·s-1 in Model 2 to 4 165 m3·s-1, 3 391 m3·s-1, and 2 969 m3·s-1, respectively, with increases of 43.97%, 23.53%, and 19.48%, respectively. In Model 1, the discharge flow of the cascade reservoir group during the dry season was normalized, and the storage capacity of the reservoir group was relatively evenly utilized to supplement the river flow during the dry season, which increased the navigation depth of the river downstream of the Jiaba Reservoir and was more conducive to ship passage. The total annual cascade power generation of Model 2 was 339.982 billion kW·h, 31.567 billion kW·h, and 26.533 3 billion kW·h in wet years, normal years, and dry years, respectively. The total annual cascade power generation of Model 1 was 337.739 3, 30.817 2, and 26.263 9 billion kW·h, respectively. Compared to Model 2, the total annual cascade power generation of Model 1 decreased by 0.76%, 1.72%, and 1.02%, respectively. Compared to Model 2, the minimum output of the cascades in Model 1 during the dry season significantly decreased, from 31.702, 30.602 1, and 27.604 million kW in the wet year, normal year, and dry year, respectively, to 20.186 8 million kW, 19.377 6 million kW, and 17.105 1 million kW in Model 1, with reductions of 36.32%, 36.68%, and 38.03%, respectively. The impact of Model 1 on the total power generation and minimum output of cascade reservoirs was mainly concentrated in the dry season. Model 1 achieved a significant increase in the navigation flow of downstream channels of cascade reservoirs during the dry season (43.97%, 22.20%, 19.48%) with small power generation losses (0.76%, 1.72%, 1.02%). However, it had a significant impact on the minimum output of the cascade during the dry season, with reductions of 36.32%, 36.68%, and 38.03%, respectively. However, it was considered that within the entire power system, in addition to the cascade hydropower stations downstream of the Jinsha River, there were other hydropower stations and other types of power sources. Therefore, the impact of the total power output reduction during the dry season of the cascade hydropower stations downstream of the Jinsha River on the power grid was relatively limited and could be supplemented by other power sources. Accordingly, the coordinated scheduling of navigation and power generation through Model 1 balanced the power generation and navigation benefits of the cascade reservoir group and better leveraged the comprehensive utilization benefits of the downstream cascade reservoir group of the Jinsha River.ConclusionsThe research results provide technical support and decision-making references for improving the waterway level of the Yangtze River through multi-objective collaborative scheduling of navigation and hydropower generation in the downstream cascade reservoirs of the Jinsha River. This contributes to the construction of the Yangtze River's golden waterway and supports the implementation of the strategy to build a strong transportation system in China.关键词：the reservoirs in the lower reaches of the Jinsha River;minimum discharge flow;medium- and long-term scheduling;multi-objective collaborative scheduling of navigation‒hydropower generation;the total hydropower generation of hydropower stations338|864|0更新时间：2026-05-19
- 摘要：ObjectiveAs basin water resources management systems become increasingly strict and the penetration rate of new energy rapidly increases, the contradictions between water regulation and power generation in the basin become more prominent under the new conditions. This study proposes a cascaded hydro‒photovoltaic (PV) complementary scheduling method that accounts for the needs of both regulation and power generation. It systematically assesses the risks and benefits associated with cascaded hydro‒PV complementary scheduling. This method aims to achieve adaptive scheduling that satisfies the requirements of water regulation and power generation and provides a decision-making basis for power dispatchers.MethodsFirstly, a day-ahead and real-time nested scheduling model for the cascaded hydro‒PV complementary system, which considered both water regulation and generation requirements, was constructed. The accumulated deviation in water consumption was quantified to evaluate the execution of water regulation tasks and was embedded in real-time scheduling to achieve task prioritization and flexible adjustment. Secondly, based on the risk transfer mechanism, a comprehensive risk evaluation index was developed for the dispatch of hybrid generation systems, encompassing cascaded hydropower, photovoltaic, and hydro‒PV complementary systems. In addition, by leveraging the complementary characteristics of these systems, a comprehensive benefit evaluation index was established for complementary dispatch, covering various categories of power generation and efficiency. This framework provided a solid foundation for analyzing the impacts of hybrid generation system dispatch. Finally, the scheduling and impact analysis methods were validated using the Longyangxia‒Laxiwa‒Qialong photovoltaic complementary system in the upper reaches of the Yellow River as a case study.Results and DiscussionsThe operation of the cascaded hydro‒PV system from Cases 1 to 4 was simulated to evaluate the system’s year-round dispatch effectiveness. The results indicated that, compared to pure hydropower dispatch, Case 2 enhanced power generation by 1.350 billion kW·h and increased power generation revenue by 312 million Yuan. This improvement stemmed from the ability of hydropower to better meet load demand and transmission channel constraints by aligning hydropower output with that of photovoltaic energy, optimizing resource utilization. In comparison to Case 3, Cases 4 and 2 achieved increases in power generation of 119 million kW·h and 810 million kW·h, respectively, while power generation revenue rose by 390 million Yuan and 180 million Yuan. This occurs because the actual water consumption of the power stations decreased sequentially across Cases 3, 2, and 4. The water saved through the day-ahead real-time nested scheduling method gradually raised reservoir levels, enhancing system power generation. However, the increase in power generation attributable to reduced water consumption was only 6% of the increase resulting from PV interconnections. Therefore, coordinating the outputs of water and photovoltaic sources to prevent channel competition is critical for enhancing the system’s generation benefits during day-ahead planning. In terms of efficiency benefits, the water consumption rates at the Longyangxia Power Station for Cases 2 and 4 were reduced by 0.04 m3/(kW·h) and 0.07 m3/(kW·h), respectively, compared to Case 3. In addition, the percentage of the efficient operating area increased by 6.50% and 12.15%, respectively. These improvements are attributed to the complementary scheduling between Longyangxia and photovoltaic (PV) sources. In light of the actual discrepancies in PV output, Case 4 maximized economic efficiency, while Case 3 ensured that the water transfer needs were fully met. Case 2 effectively curbed the downward trend of water discharge from Longyangxia. Regarding the risk of comprehensive utilization destruction, the number of instances for Cases 2, 3, and 4 was 2, 0, and 26, respectively, with the maximum destruction rate reaching 4.18%. In addition, the maximum depth of comprehensive utilization destruction for Case 4 could be reduced from 6.63 million m3 to 3.25 million m3 through the implementation of Case 2. In terms of gate operation risk, Case 3 showed that the Longyangxia Power Station enabled the gate to compensate for the significant reduction in actual PV water generation to the downstream. This resulted in up to 34 gate operations and a water discharge of 0.06 billion m3, whereas the other cases reported no water discharge. In addition, the highest water rejection from the Laxiwa power station was 0.17 billion m3. This situation arose because, during high water level operations, the Laxiwa power station experienced water abandonment triggered by the consumption of incremental water due to the actual bias hours of upstream PV generation. Compared to Case 4, the average daily number of unit startups and shutdowns for the system in Cases 1 through 3 was reduced by 0, 3.07, and 0.10, respectively. In addition, the average daily number of unit traversals through the vibration zone decreased to 4.6, 0.5, and 1.0, respectively. The annual abandoned photovoltaic rate for the complementary system from Case 2 to Case 4, excluding April, reached a maximum of only 1.13%, reflecting a strong capacity for new energy consumption on an annual scale. Overall, the complementary system demonstrated good load tracking ability, with no load loss in Longyangxia, effectively complementing photovoltaic (PV) generation. However, the downstream Laxiwa experienced a load loss rate as high as 0.07% in Case 4. This situation arose because Longyangxia was a multi-year regulation reservoir with minimal daily water level variation, which allowed it to effectively respond to deviations in PV output. In contrast, Laxiwa operated as a day-regulated reservoir, which made it challenging to compensate for significant outflow shortfalls from Longyangxia when deviations in PV predictions occurred, particularly at low water levels, which led to insufficient power generation at Laxiwa.ConclusionsThe proposed scheduling method demonstrates strong adaptability to the requirements of water and power regulation, effectively addressing the adjustment needs of both the power side and grid side. It achieves a balance between the operational benefits and risks of the complementary system. However, in real-time scheduling, careful management of water level safety at downstream day-regulated hydroelectric power stations is essential. This is critical to prevent upstream hydropower stations from deviating from photovoltaic power generation when water levels are either too high or too low, as this can lead to water abandonment or load loss at the downstream power station.关键词：hydro‒photovoltaic complementary operation;hydropower operation;balanced water‒power regulation;impact analysis354|720|0更新时间：2026-05-19
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Mechanism and Computational Modelling of the Erosion Process of Zoige Meadow-type Bending Rivers AI导读
摘要：ObjectiveThe Zoige grassland, a vital water conservation area in the upper reaches of the Yellow River, faces increasingly severe problems of riverbank erosion and collapse. This study is conducted to address this urgent issue, as it exerts a profoundly negative influence on the ecological equilibrium and water conservation functions of the grassland. The principal objective is to achieve a comprehensive understanding of the mechanisms and influencing factors of riverbank erosion, with the aim of providing effective solutions for the protection and sustainable management of this significant ecological region.MethodsThe research focused on the Zoige meadow-type curved river. Comprehensive field investigations were diligently conducted to collect data related to the natural environmental characteristics of the Zoige grassland and the prevailing conditions of riverbank erosion and damage. Advanced analytical techniques were systematically employed to examine soil grain structure, soil thickness, water flow depth, curvature, and seepage. A rigorous analysis of these parameters enabled the development of a targeted computational model. Prolonged monitoring and data collection were performed to assess the effects of flood scouring, vegetation root anchorage, freezing and thawing, and seepage-induced submerged erosion on the riverbanks. The BSTEM (Bank Stability and Toe Erosion Model) was utilized to simulate the erosion amount and erosion rate at the riverbank slope foot, and the results were validated through a combination of detailed field measurements and comprehensive model simulations.Results and DiscussionsThe study disclosed that riverbank erosion in the Zoige grassland was a complex process arising from multiple interwoven factors. The scouring of the lower silt layer and gravel sand layer, in conjunction with the collapse of the upper meadow layer, together with the influences of seepage and freezing and thawing processes, collectively contributed to the erosion phenomenon. The relative magnitudes of the water scouring force and the soil resistance to scouring were identified as critical determinants of bank slope stability. The simulation results of the BSTEM exhibited a certain degree of correspondence with the field observations and provided valuable insights into the erosion processes. However, some disparities were also noted, which emphasized the necessity for further refinement and calibration of the model. The calculation results of both models were compared to the actual retreat distance of the riverbank, and it was observed that both the numerical model and the BSTEM displayed relatively consistent trends with the measured data. Specifically, with respect to the lateral erosion distance, the lateral erosion values calculated by the models were not significantly different from the measured values. In addition, as the bank slope morphology and flow conditions changed, the prediction results of the models also showed corresponding variations. The calculation formula of the BSTEM shared similarities with the self-built model but was more complex because it incorporated the influences of vegetation factors and seepage. The results calculated by the numerical calculation model constructed in this study were more consistent with the measured values than those of the BSTEM, possibly due to adjustments and optimizations made during the model construction process based on actual conditions, along with the introduction of new variables and factors. In terms of the safety factor, the values calculated by the models were essentially consistent with the measured values, which were less than 1, indicating that the eroded bank slopes were unstable and further validating the reliability of the models. Given the possibility that parameter optimization can lead to superior results for the self-built model compared to the BSTEM, the same parameter optimization was applied to the BSTEM for comparison. After optimization, the lateral erosion distance predicted by the BSTEM decreased, the deviation from the measured values increased, and the overall trend also changed. The safety factor also decreased, and significant differences emerged. These results indicated that the parameter-optimized BSTEM failed to achieve results comparable to those of the parameter-optimized self-built model, which more effectively demonstrated the advantages and accuracy of the self-built model. In addition, there were specific differences in the lateral erosion distance and safety factor at different bank slope positions. These differences were primarily influenced by factors such as bank slope morphology, flow conditions, and soil layer parameters. For example, at point R3, the significant water depth and slope drop resulted in a considerable lateral erosion distance, whereas at point H2, although the water scouring force was substantial, the large median particle size of the soil resulted in a relatively small scouring distance.ConclusionsThis comprehensive research made substantial progress in understanding riverbank erosion mechanisms in the Zoige grassland. The constructed computational model, validated through a combination of theoretical simulations and field measurements, demonstrated its scientific validity and reliability. The findings not only contributed to theoretical knowledge in geomorphology and hydrology but also held practical implications for developing effective prevention and control strategies for riverbank erosion. The research emphasized the importance of considering multiple factors and their interactions to understand and manage complex ecological processes. It provides a solid foundation for future studies and conservation efforts aimed at maintaining the ecological integrity and functionality of the Zoige grassland and similar ecosystems.关键词：meadow bend rivers;erosion mechanisms;computational modeling;bank stability209|780|0更新时间：2026-05-19
RIVER PROTECTION AND REGULATION
- 摘要：ObjectiveWind erosion of bare soil is a major source of atmospheric particulate matter pollution in arid and semi-arid regions, posing significant threats to environmental quality and human health. Therefore, an environmentally sustainable and efficient soil stabilization approach is developed by combining biopolymers (pectin and sodium alginate) with enzyme-induced calcium carbonate precipitation (EICP) technology. The research aims to examine the synergistic effects of pectin and sodium alginate on the EICP process, clarify their influence on calcium carbonate crystallization and bonding behavior, and identify the mechanisms responsible for enhancing the wind erosion resistance of treated soils. This study provides a scientific basis for the large-scale ecological application of biopolymer-EICP technology in dust suppression and soil stabilization.MethodsThe experimental investigation was performed using natural loess-type bare soil collected from arid regions in Northwest China. The soil samples were air-dried, passed through a 2 mm sieve, and homogenized to ensure uniformity. Cementation solutions containing various calcium lignosulfonate concentrations of 0.25~1.25 mol/L were prepared and mixed with urease solutions to initiate EICP reactions. The acid-washing method was applied to determine the actual calcium carbonate yield, and an optimal cementation concentration of 1.25 mol/L was selected based on reaction efficiency and cost-effectiveness. Mechanical and physicochemical properties, including calcium carbonate content, wind erosion resistance, surface hardness, pH, and soluble salt content, were evaluated after each curing cycle. Wind erosion resistance was determined using a laboratory wind erosion simulation apparatus, and the mass loss rate of each specimen was recorded to quantify erosion resistance. Surface hardness was measured using a digital Shore hardness tester, while pH and soluble salt contents were analyzed to evaluate the environmental compatibility of the treatments. Microstructural and mineralogical characteristics were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR) to characterize morphological features, mineral phases, and functional group interactions. The integration of macro- and micro-scale characterization provided a comprehensive understanding of the influence of biopolymers on the EICP-induced cementation mechanism.Results and DiscussionsWhen the pectin concentration was below 0.5%, and the sodium alginate was below 1.5%, the presence of biopolymers exerted minimal inhibition on the EICP reaction. Beyond these limits, the calcium carbonate yield decreased due to increased solution viscosity, which hindered ion diffusion. The wind erosion resistance of the treated specimens improved significantly with increasing curing cycles. After four cycles, the mass loss rate of the pectin-EICP-treated specimen decreased to 3.64%, and that of the sodium alginate-EICP-treated specimen decreased to 0.37%, compared to over 48% for the water-treated group. The surface hardness values increased by 186.4% and 132.7%, respectively, relative to the water-treated group. These results demonstrated that both biopolymers markedly enhanced the bonding strength among soil particles through the formation of gel-crystal-particle composite structures. The SEM images revealed that in pectin-EICP-treated specimens, hydrogen bonding and van der Waals forces enabled pectin molecules to form a dense gel network that encapsulated soil grains. In sodium alginate-EICP-treated specimens, calcium ions crosslinked alginate chains to form calcium alginate gels with a stable three-dimensional network. These gels not only filled soil pores but also served as nucleation sites for calcium carbonate crystals. The EICP process then deposited calcite crystals preferentially along the gel network, which created a compact and continuous cementation matrix. The resulting composite structure transformed the loose granular arrangement of the original soil into an integrated and cohesive solid matrix with enhanced resistance to wind-induced particle detachment. XRD and FTIR analyses confirmed that calcite was the dominant crystalline phase of calcium carbonate in both treatments, which indicated that biopolymer addition did not alter the mineral composition but promoted the orderly growth of calcite. Mechanistically, the cooperative action between biopolymer gelation and enzymatic mineralization was identified as the key factor that enhanced soil stabilization. Pectin primarily provided physical encapsulation through hydrogen-bonded gels, while sodium alginate contributed ionic crosslinking with calcium ions, which formed calcium alginate complexes that strongly bonded with calcite crystals. This difference explained the superior erosion resistance of the sodium alginate-EICP system. The gel matrix not only strengthened particle bonding but also regulated the spatial distribution of precipitated calcium carbonate, which improved its uniformity and continuity within the soil matrix. Therefore, the treated soil surface developed a hardened crust layer that was capable of resisting wind shear stress, minimizing dust release. The pH values of all treated specimens ranged between 7.5 and 7.8, and soluble salt contents were below 1.6%, which demonstrated the environmental compatibility of both biopolymer-EICP systems. The treatments did not introduce significant alkalinity or salinity, which made them suitable for large-scale ecological restoration and dust mitigation projects in arid environments.ConclusionsThis study establishes an ecological soil stabilization method by coupling biopolymers with enzyme-induced calcium carbonate precipitation. The results reveal that both pectin and sodium alginate effectively enhance the EICP-induced cementation process through synergistic physical filling and chemical bonding effects. The developed gel-crystal-particle composite structure improves soil compactness, increases surface hardness, and significantly reduces mass loss caused by wind erosion. Therefore, the biopolymer-assisted EICP approach combines the advantages of biogenic mineralization and renewable organic polymers, providing an environmentally sustainable solution for bare soil dust control. The findings provide both theoretical and technical support for the large-scale application of EICP-based ecological curing technologies in dust suppression, slope stabilization, and desertification control. In addition, the findings contribute to understanding the organic-inorganic synergistic mechanism in bio-mediated soil stabilization and provide theoretical and practical support for the development of sustainable geotechnical engineering techniques.关键词：urease-induced calcium carbonate precipitation;the dust of bare soil;calcium lignosulfonate;biopolymers;surface curing136|290|0更新时间：2026-05-19
- 摘要：ObjectiveBiomineralization technology using urease-induced calcium carbonate precipitation (EICP) to cement soil into bricks (referred to as “biobricks”) provides advantages in terms of sustainable development. In this study, Yellow River sediment is introduced into the preparation of quartz sand bricks using sodium alginate+EICP to evaluate the feasibility of Yellow River sediment in improving the strength and durability of biobricks prepared through sodium alginate+EICP.MethodsFirst, compressive strength and flexural strength tests were conducted on quartz sand bricks. Fragments were then collected from the middle sections of the sand bricks damaged during the strength tests, and the calcium carbonate content (C) in the sand bricks was determined using EDTA titration. The water absorption capacity of the sand bricks was analyzed using the immersion method. Based on the strength, C, and water absorption results of the specimens, the effect of sodium alginate doping was analyzed, and the optimal sodium alginate dosage was determined. Then, specimens containing Yellow River silt were prepared, and the optimal grain group and doping amount of Yellow River silt were determined by testing the strength and water absorption of the specimens. The durability of the optimal specimens was investigated under dry-wet cycles, freeze-thaw cycles, and acidic environments, respectively. In addition, the curing mechanism was explored by observing the microscopic images of the specimens using a scanning electron microscope (SEM).Results and DiscussionsThe C of the quartz sand bricks reached the maximum value at a sodium alginate dosage of 1.0%, while the compressive and flexural strengths of the sand bricks reached their maximum values at dosages of 1.5% and 2.0%, respectively. After six dry-wet cycles, the surface particles of ES were severely dislodged, with localized depressions observed on the surface. The mass loss rate reached 10.08%, and the compressive strength decreased to only 0.15 MPa, indicating that the load-bearing capacity was nearly lost. In contrast, ES-0.075-20 maintained a compressive strength of 1.11 MPa after 15 dry -wet cycles, with a mass loss of only 1.94% and no obvious damage, maintaining a relatively intact morphology. Under the same number of freeze-thaw cycles, the unconfined compressive strength of ES sand bricks remained less than one-quarter of that of ES-0.075-20. After 15 freeze-thaw cycles, the unconfined compressive strengths of ES and ES‒0.075‒20 decreased by 77.78% and 51.04%, respectively, while the corresponding mass losses were 2.02% and 0.52%, respectively. The incorporation of Yellow River silt produced a denser internal structure in the specimens and improved their resistance to freeze-thaw cycles.ConclusionsThe improvement in the strength of EICP-treated quartz sand bricks by sodium alginate is attributed not only to the increase in calcium carbonate content, but also to the internal structure of the sand bricks and the morphology of the precipitated calcium carbonate crystals. Sodium alginate provides nucleation sites for Ca2+ precipitation, while the Yellow River sand is encapsulated by calcium carbonate crystals and calcium alginate gel, forming a four-phase unit structure of “calcium alginate gel-calcium carbonate-Yellow River sand-quartz sand”. This structure enhances interparticle cohesion and results in a denser internal structure.关键词：bio-brick;enzyme-induced calcium carbonate deposition;Yellow River sediment;sodium alginate;dry-wet cycle;freeze-thaw cycle364|563|0更新时间：2026-05-19
- 摘要：ObjectiveThis study enhances the physical and mechanical properties of coral sand through an innovative reinforcement technology that utilizes xanthan gum in conjunction with microbial induced calcium carbonate precipitation (MICP). It improves the stability and strength of coral sand, which are critical for various engineering applications, particularly in the construction and reinforcement of island and reef foundations. The significance of this research lies in addressing the limitations of traditional reinforcement methods by incorporating a biopolymer (xanthan gum) into the MICP process, proposing a novel solution with potentially enhanced performance and environmental benefits.MethodsCoral sand samples were prepared with varying xanthan gum contents ranging from 0.5% to 2.0% and were subjected to the MICP process. The microbial culture used in the MICP process facilitated the precipitation of calcium carbonate within the sand matrix. The mechanical properties of the treated coral sand were evaluated using unconfined compressive strength (UCS) tests. These tests measured the maximum load that the samples withstood before failure and provided a quantitative assessment of the reinforcement effect. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses were conducted to observe the microstructural changes and mineralogical composition of the treated samples. These techniques helped explain the nucleation and growth of calcium carbonate crystals facilitated by the presence of xanthan gum. Computed tomography (CT) scanning was utilized to evaluate the internal structure of the samples, with particular focus on porosity and equivalent pore size. This nondestructive method provided insights into the overall compactness and integrity of the reinforced coral sand.Results and DiscussionsThe addition of xanthan gum resulted in a substantial increase in the binding material within the coral sand. Specifically, the binding material content increased by 53.57% to 88.43% with the incorporation of 0.5% to 2.0% xanthan gum, respectively. This enhancement indicated that xanthan gum effectively raised the formation of binding agents within the sand matrix. The unconfined compressive strength of the samples showed remarkable improvement following the addition of xanthan gum. At a xanthan gum content of 1.0%, the UCS reached 6.23 MPa, representing an increase of 2.56 times compared to the control samples without xanthan gum. This significant improvement in strength demonstrated the effectiveness of xanthan gum in enhancing the load-bearing capacity of coral sand. SEM and XRD analyses revealed that xanthan gum provided additional nucleation sites for the formation of calcium carbonate crystals. The presence of xanthan gum facilitated the growth of larger hexahedral rhombic calcite crystals, which contributed to the formation of "xanthan gum-calcium carbonate" agglomerates. These agglomerates played a crucial role in enhancing the bonding strength between sand particles, producing a more cohesive and stable structure. CT scanning results indicated that the addition of xanthan gum significantly reduced the porosity and equivalent pore size of the coral sand samples. The improved particle arrangement indicated a denser and more compact structure, which enhanced the overall stability and durability of the reinforced sand.ConclusionsXanthan gum increases the binding material content within the sand matrix, improving cohesion and stability. The unconfined compressive strength of coral sand is significantly enhanced by the addition of xanthan gum, indicating its potential for high-load-bearing applications. Microstructural analysis shows that xanthan gum raises the formation of larger and more stable calcium carbonate crystals, contributing to stronger particle bonding. The reduction in porosity and pore size, as revealed by CT scanning, highlights the improved compactness and integrity of the reinforced sand. The research demonstrates the theoretical and practical significance of using xanthan gum in conjunction with MICP for coral sand reinforcement. The findings provide valuable insights into the design and construction of island and reef foundation reinforcement projects, providing a novel approach that combines biological and chemical methods to achieve superior performance and environmental sustainability.关键词：microbial induced calcium carbonate precipitation (MICP);coral sand;xanthan gum;mechanical properties;microscopic mechanism312|765|0更新时间：2026-05-19
GREEN GEOTECHNICAL ENGINEERING
- 摘要：ObjectiveThe uplift capacity and safety stability of anchor plates are significantly influenced by factors such as terrain relief, installation methods, and seismic loads during the service phase. This study seeks to derive analytical expressions for the uplift capacity of anchor plates under seismic action, along with the corresponding soil failure curve, to address the problem of the uplift capacity of shallow-buried inclined anchor plates in sloping strata located in high-intensity seismic zones. It further aims to clarify the influence patterns of anchor plate design parameters, soil properties, and seismic forces on the uplift capacity and the extent of soil failure. The research provides theoretical references for the design and construction of strip anchor plate foundations in high-intensity seismic regions, helping to optimize anchor plate design and enhance their safety and stability under seismic loading.MethodsThis study constructed a kinematically admissible velocity field that represented the failure mechanism of the soil mass above the anchor plate. Based on the plastic upper-bound theorem and the pseudo-static method, and incorporating the nonlinear Mohr-Coulomb strength criterion, analytical expressions for the seismic uplift capacity of the anchor plate and the geometry of the soil failure curve were theoretically derived. This methodology integrated the effects of seismic forces simulated via the pseudo-static approach and the nonlinear shear strength characteristics of the soil. A two-stage validation process was employed to verify the correctness and reliability of the proposed theoretical method. First, a parameter degradation analysis was conducted. The computational results of this method were compared to the existing theoretical solutions proposed by Murray et al. through simplifying specific parameters in the derived formulas. The results showed a high degree of consistency in both variation trends and numerical magnitude. Second, further validation was performed through numerical modeling. Twelve sets of numerical simulations under three different working conditions were conducted. The results obtained from these simulations demonstrated a high level of agreement with the theoretical analytical solutions derived in this study, fully confirming the correctness and reliability of the proposed theoretical method.ConclusionsBased on the results, the pullout capacity of the anchor plate is directly proportional to the embedment depth-to-width ratio, initial cohesion, soil unit weight, and ground surface load, whereas it is inversely proportional to the inclination of the anchor plate, surface inclination, nonlinear coefficient, and seismic load. The soil failure range is positively correlated with the seismic load and initial cohesion, whereas it is negatively correlated with the nonlinear coefficient, soil unit weight, ground surface load, surface indination, and the inclination of the anchor plate. This study successfully derives theoretical solutions for the seismic uplift capacity and failure mechanism of shallow-buried inclined anchor plates in sloping ground. The validity of these solutions is rigorously confirmed through comparison to existing theories and extensive numerical simulations. The research outcomes provide a valuable theoretical basis for the design and construction of strip anchor plate foundations in high-intensity seismic areas, contributing to the optimization of anchor plate design and the enhancement of seismic safety and stability.关键词：seismic action;inclined strip anchor plate;pullout capacity;pseudo-static method;upper bound theorem;Slope Strata;Shallow Anchor Plate231|317|0更新时间：2026-05-19
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Effect of Stone Content and Particle Sphericity on the Shear Characteristics of Soil‒rock Mixtures AI导读
摘要：ObjectiveThe DW1280 large-scale direct shear test system is utilized to conduct a series of large-scale indoor direct shear tests, including 24 groups of soil-rock mixtures with different stone contents, compactness levels, and particle sphericities to explore the evolution law of the shear mechanical properties of soil-rock mixtures under the influence of multiple factors, such as particle sphericity, stone content, and compactness.MethodsSelf-developed rock particle processing equipment was utilized to produce four types of particles with uniform size but different sphericity values (S) to ensure the rigor of the experimental study and accurately investigate the influence of rock particle shape on the test results. This approach ensured that the effect of particle shape could be analyzed independently during the experiment, overcoming the limitations of previous studies that unified block stone shapes through numerical simulation and enabling experimental research using real rock particles. In addition, the shear characteristics of soil-rock mixtures under multiple influencing factors were investigated. Through comparative analyses from various perspectives, the variation patterns of soil-rock mixtures under the influence of different factors were identified. Finally, 12 groups of test conditions were predicted using the soil-rock mixture damage model, and the prediction results were compared to the experimental data to ensure the reliability of the predictions. This step not only enhanced the scientific rigor of the research but also further verified the validity and accuracy of the soil-rock mixture damage model.Results and DiscussionsAnalysis of the shear stress-shear displacement curves for particle groups with different sphericity values indicated that, under normal stresses of 50, 100, and 150 kPa, the initial slopes of the shear stress curves were 11.05, 13.19, and 12.72, respectively, which were generally consistent. During the shearing process, the shear strength was mainly governed by the interlocking effect between soil and stone particles and by dislocation friction. However, with the gradual increase in particle sphericity S, the primary contribution to shear strength gradually shifted from the interlocking effect to dislocation friction. Therefore, the fluctuation of the test curves was reduced. These results indicate that the more pronounced the particle angularity, the greater the energy fluctuation generated during turning, rotation, and crushing processes. When the sphericity value reached S=0.886, the peak stress was significantly higher than that of the other three sphericity groups. In contrast, with the increase in sphericity S (S=0.953, 0.981, and 1.000), the peak stress decreased by 15.56%, 9.23%, and 5.43%, respectively, as well as by 22.84%, 16.06%, and 11.80%, and 45.09%, 41.50%, and 32.24%, respectively. This trend demonstrates that the reduction in peak stress gradually increased with increasing particle sphericity. In addition, under the same normal stress, the vertical displacement of the particle groups decreased as the sphericity increased. In addition, the internal friction angle initially increased and then decreased with increasing particle sphericity, whereas the cohesion decreased continuously with increasing particle sphericity. The stone content in the soil-rock mixture is one of the key parameters significantly affecting the overall strength of the mixture. Through detailed analysis of the shear stress-shear displacement curves of the hexahedral particle group under different stone contents, it was observed that the shear strength of the soil-rock mixture increased with increasing normal stress when the stone content remained constant. Under the same normal stress, the shear strength of the soil-rock mixture first increased and then decreased as the stone content increased. When the stone content reached 80%, the shear strength of the mixture attained its maximum value. At this stage, the shear strength and internal friction angle first increased and then decreased with increasing stone content. However, when the stone content exceeded 80%, the cohesion remained essentially unchanged. In addition to the above factors, the compaction degree of the soil-rock mixture was also identified as an important parameter affecting its shear strength. The influence of compaction degree on the strength parameters of the soil-rock mixture showed that, under different normal stresses, when the compaction degree increased from 86% to 90% and 94%, the shear strength of the soil-rock mixture samples increased by 8.3%, 9.3%, and 10.9%, respectively, as well as by 6.6%, 7.9%, and 8.9%, respectively. As the compaction degree gradually increased, the shear strength of the samples also increased. However, when the compaction degree was further improved, the rate of increase in shear strength gradually decreased. Accordingly, these findings further confirm that the factors discussed in this study, including stone content and particle shape, have significant effects on the shear strength of soil-rock mixtures.Conclusions1) With the increase in sphericity S, the angularity of the particles gradually decreases. The shear strength of the soil-rock mixtures gradually changes from being provided by a combination of intergranular occlusal embedding and interparticle friction to being dominated by frictional resistance. Therefore, the shear strength, shear dilatancy, and cohesion c of the soil-rock mixtures decrease. The relationship between the angle of internal friction φ and sphericity S can be described by an exponential function. In addition, the angle of internal friction initially increases and then decreases, reaching a maximum value of 55.22° when the sphericity S=0.953. 2) When the particle shape and compaction remain constant, and the stone content increases from 60% to 100%, the internal structure of the soil-rock mixture changes significantly. The shear stress-shear displacement curve transforms from strain softening to strain hardening. In addition, the shear strength and angle of internal friction φ exhibit a trend of initially increasing and then decreasing, whereas the cohesion c remains basically unchanged after the stone content exceeds 80%. During the shearing process, the particles overturn and crush, and the test curves exhibit a “fluctuating and jumping” phenomenon. 3) With increasing compaction, the interlocking and embedded effects between soil particles and stone particles gradually increase; however, the increase in shear strength gradually decreases. The research results are of great significance for selecting appropriate particle shapes for soil and stone mixtures in practical engineering projects, helping to control the mechanical properties of soil and stone mixtures more accurately and ensure the safety and stability of engineering structures.关键词：particle shape;soil-rock mixture (S‒RM);shear strength;stone content;compaction degree324|587|0更新时间：2026-05-19 - 摘要：ObjectiveLocal mesh modification is one of the important approaches for solving the saturated unconfined seepage model when the fixed mesh method is used. When the finite element method is employed as the calculation tool, the complexity of the mesh modification process, resulting from the restricted shapes of the elements, hinders the development of local mesh modification methods. Therefore, the virtual element method, which is adaptable to arbitrarily shaped polygonal elements, is introduced to solve the two-dimensional saturated unconfined seepage model using the local mesh modification method.MethodsFirst, the basic mathematical equation of the saturated unconfined seepage model was described. Then, the change in water head within an arbitrary polygonal element was expressed using the first-order virtual element, leading to the establishment of the first-order virtual element formulation for seepage analysis. The trial function space V1(Ωe) governed the water head in each element, with the water heads at the vertices defined as the degrees of freedom of the element. The element conductivity matrix and flow vector were derived using the Galerkin method, and the procedure for computing the element conductivity matrix was deduced based on the principles of the virtual element method. The mathematical relationship between the first-order virtual element and classical finite element methods was elucidated. Next, the versatility of element shapes within the virtual element method was utilized to redesign the mesh modification rules of the local mesh modification method, developing a comprehensive solution flow for the saturated unconfined seepage model. The mesh was modified by removing elements located above the free surface while retaining those below it. In cases where an element was intersected by the free surface, it was first removed, and the portion below the free surface was treated as a new element. Update algorithms for the global conductivity matrix and the global flow vector were established to reduce computational costs. Finally, three numerical examples, homogeneous rectangular earth dams, homogeneous trapezoidal earth dams, and heterogeneous rectangular earth dams, were employed to evaluate the calculation accuracy and efficiency of the proposed method. The performance of the proposed method was also compared to other methods based on the finite element method and the numerical manifold method.Results and DiscussionsThe numerical accuracy of the proposed method was evaluated using the analytical solution of the rectangular homogeneous earth dam model as a benchmark. The maximum error identified along the free surface, which occurred at the exudation point on the right side of the earth dam, was a relative error of 0.45%. This result indicated that the proposed method exhibited good numerical accuracy. The method was applied to solve the trapezoidal homogeneous earth dam model and the inhomogeneous rectangular earth dam model. Due to the absence of analytical solutions for these two models, the results were compared to those obtained using Seep software, the local mesh modification method based on the finite element method, and the improved numerical manifold method, which is widely recognized for its high computational accuracy. For the trapezoidal homogeneous earth dam model, Seep software produced the lowest free surface position, while the local mesh modification method based on the finite element method produced the highest. The proposed method yielded a free surface position comparable to that obtained using the improved numerical manifold method, although the exudation point on the right side of the dam was slightly higher. For the inhomogeneous rectangular earth dam model, all methods except the local mesh modification method based on the finite element method exhibited a rapid decline in free surface levels as they approached the sudden change line of the permeability coefficient, followed by slight fluctuations after crossing this line. When ranking the free surfaces of the inhomogeneous rectangular earth dam model obtained using the four methods, the results closely matched those of the trapezoidal homogeneous earth dam model. Under conditions of comparable numerical accuracy, the proposed method employed the virtual element method, which is highly compatible with the finite element method, avoiding the introduction of complex mathematical concepts such as numerical manifolds. Under the same computer configuration, the running times of the proposed method for solving the trapezoidal homogeneous earth dam and the inhomogeneous rectangular earth dam were 14.4 and 8.1 seconds, respectively. In comparison, the running times of the local mesh modification method based on the finite element method were 13.6 and 7.2 seconds, respectively. Therefore, the computational efficiency of the proposed method was slightly lower than that of the local mesh modification method based on the finite element approach. This difference was attributed to the mesh modification strategy of the proposed method, which directly cut the fixed mesh using the free surface, reducing computational time. However, the encryption and intervention of free surface nodes during the iterative process were relatively time-consuming. The encryption of free surface nodes improved calculation accuracy and produced a smoother free surface profile. Therefore, the slight reduction in computational efficiency of the proposed method was considered acceptable.ConclusionsThe results demonstrate the validity and accuracy of the proposed method for solving saturated unconfined seepage. The method overcomes the limitations associated with the restricted element shapes in the local mesh modification approach within the finite element method, establishing the local mesh modification method as a reliable tool for analyzing saturated unconfined seepage. In addition, this advancement expands the application domains of the virtual element method.关键词：virtual element method;saturated unconfined seepage;free surface;local mesh modification;computational accuracy228|585|0更新时间：2026-05-19
- 摘要：ObjectiveExisting studies on the damage and response of underground arch structures under explosive loads have produced relatively abundant results. However, these studies mainly focus on the working conditions of internal explosions or external head-on explosions, while research on the dynamic response characteristics and failure modes of arch structures under external lateral explosive loads with a certain offset angle remains relatively limited. Therefore, to investigate the blast resistance of shallow-buried reinforced concrete arched tunnels under lateral blast loads, a fully coupled three-dimensional numerical model of "TNT-sand-tunnel" is established using the Smooth Particle Hydrodynamics and Finite Element Method (SPH-FEM) coupling algorithm. This study examines the effects of different lateral initiation angles and explosive charges on the dynamic response, damage process, failure modes, and damage levels of the tunnel structure. The research results provide a theoretical basis for the blast-resistant design of tunnel structures.MethodA coupled SPH-FEM algorithm was employed to construct a "TNT-sand" coupled numerical model for simulating the propagation process of explosive shock waves in soil media. A comparative analysis of the velocity and pressure time history curves of typical SPH particles and FEM elements verified the effectiveness of the coupling interaction between SPH particles and FEM elements. The peak pressure obtained from the SPH-FEM explosion simulation was compared to the calculation results derived from the empirical formula provided in the TM5-855-1 manual. The two sets of results showed good agreement, indicating that the adopted coupling algorithm and related material models can effectively simulate the explosive process in soil media. Based on this, a multi-medium coupled numerical model was established to reproduce the on-site explosion test process of concrete slabs. This further verified the accuracy and effectiveness of the SPH-FEM method in analyzing the explosion responses of reinforced concrete structures, confirming that the method can reliably predict the damage evolution process and failure modes of concrete structures under explosive loads. In addition, the anti-explosion performance of tunnel structures under different explosion source positions (45°, 60°, 75°, and 90°) was investigated, and the influence of lateral initiation angles on the anti-explosion performance of tunnel structures was systematically evaluated.Results and DiscussionThe propagation process of explosive shock waves inside tunnel structures under different lateral initiation angles was analyzed, clarifying the differences in shock wave propagation characteristics under different initiation conditions. The influence on the peak displacement of the arch surface was mainly reflected in the gradual attenuation of the peak displacement at the measuring points on the arch surface as the lateral initiation angle decreased, accompanied by a shift in the peak position. Significant differences were observed in the pressure distribution of tunnels under different lateral initiation angles. Specifically, under the direct top explosion condition, the pressure distribution on the arch surface was uneven, and the pressure peak exhibited a gradual attenuation trend from the arch crown to the arch springing. Under lateral initiation angles of 60° and 45°, the pressure peak positions shifted noticeably. Under different lateral initiation angles and explosive equivalents, the pressure peak distribution exhibited an approximately triangular characteristic. As the initiation angle decreased, the pressure peak gradually decreased, and the intensity of the distribution characteristic, namely the steepness of the triangular shape, became weaker. Several additional phenomena were observed. The pressure distribution on the arch surface became more uniform, the compression zone and tension zone of the arch wall shifted to the right, the tension zone of the straight wall on the near-explosion side moved downward, and the tension zone on the far-explosion side shifted toward the arch crown. The failure modes and damage mechanisms of tunnel structures under different initiation angles and explosive equivalents were also analyzed, with the failure volume ratio adopted as the evaluation criterion for assessing the degree of tunnel damage under different explosive amounts and initiation angles. Under identical explosion source conditions, the failure volume ratio of the tunnel exhibited a decreasing trend as the lateral initiation angle decreased. Specifically, under the 45° side-top initiation condition, the failure volume ratio corresponding to 3.0 kg of explosive was 4.70%, 4.12%, and 1.92% lower than those under the 90°, 75°, and 60° initiation conditions, respectively. In addition, the single degree of freedom (SDOF) method was utilized to classify the damage levels of tunnel structures subjected to explosive loads, revealing that both the intensity and position of the load are important factors influencing the explosion response of tunnel structures.ConclusionThe study systematically reveals that the lateral initiation angle has a significant influence on the load distribution pattern along the tunnel arch crown. As the initiation angle decreases, the triangular distribution characteristic of the peak pressure at the arch crown weakens, resulting in a more uniform pressure distribution, although the peak pressure gradually decreases. Under different initiation angles and explosive equivalents, the tunnel structure exhibits symmetric distributions of displacement and stress in the case of vertical overhead explosions. In contrast, lateral initiation produces non-uniform and asymmetric characteristics, resulting in varying degrees of damage to the tunnel structure. The results further clarify that the critical failure point of concrete structures mainly occurs in the tensile stress region as the detonation angle decreases, causing the tensile failure region to become much larger than the compressive failure region. Quantitative analysis was conducted to evaluate the influence of explosive equivalent and detonation angle on the structural damage level. Specifically, the damage level of the tunnel under vertical roof detonation decreased from severe damage to mild damage as the explosive charge decreased. In addition, the maximum displacement of the tunnel exhibited a decreasing trend with the reduction in the lateral detonation angle, and the damage level decreased significantly. These research findings can provide an important theoretical basis and design reference for identifying vulnerable parts of tunnel arch structures under different detonation angles.关键词：arched tunnel;lateral explosion of vault;dynamic response;mode of failure;Damage mechanism;performance for antiknocking196|364|0更新时间：2026-05-19
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Axial Compression Performance of Concrete-filled Square Steel Tube Stub Columns Reinforced with CFRP AI导读
摘要：ObjectiveInternal defects in concrete-filled square steel tube (CFSST) columns reduce bearing capacity, ductility, and other properties. Therefore, it is important to address the adverse effects caused by defects in the core concrete. In this study, these effects are analyzed, carbon fiber cloth is used to strengthen defective CFSST columns, and a calculation formula for the axial compressive capacity of concrete-filled square short columns with concentrated holes is proposed.MethodsTwelve short CFSST columns with no defects, discrete defects, concentrated cavity defects, and single-layer CFRP-reinforced defects were designed, considering parameters such as concrete density loss rate, defect type, defect location, and CFRP reinforcement method. Axial compression tests were conducted on columns without defects and without reinforcement, and failure phenomena under different parameters were observed. The effects of these parameters on load‒displacement curves, load‒strain curves, and ductility were analyzed. Further axial compression tests were conducted on columns with near-wall and central concentrated cavity defects using full-wrap and half-wrap reinforcement methods. By introducing bearing capacity and ductility coefficients, the performance of reinforced specimens was analyzed and compared with unreinforced specimens. Based on Chinese national standards, a reduction coefficient was fitted using multiple linear regression with density loss rate, defect location, and thickness-to-width ratio as variables, and a reduction equation was established. The ultimate bearing capacity was calculated using this equation and compared with experimental values.Results and DiscussionsTest results show that the coating on the steel pipe surface of non-defective specimens gradually folds and bulges when the load reaches 85% of the peak load. With increasing density loss rate, bulging in specimens with discrete defects occurs earlier. Failure in near-wall cavity specimens occurs at the defect location, while central cavity specimens fail near the column center. Reinforced specimens show delayed bulging compared to unreinforced specimens, with full-wrap reinforcement performing better than half-wrap reinforcement. When the density loss rate is less than 5%, discrete defects have little effect on compressive performance. As the density loss rate increases, compressive performance decreases significantly. The ultimate bearing capacity and ductility of CFST‒5% and CFST‒10% decrease by 7.0% and 16.0%, respectively, and ductility decreases by 10.3% and 22.3%, respectively. At a 15% loss rate, bearing capacity and ductility decrease by 26.9% and 26.3%, respectively. Under the same density loss rate, concentrated cavity defects have a greater adverse effect than discrete defects. The ultimate bearing capacity of specimens with central and near-wall cavity defects decreases by 19.1% and 29.8%, respectively, compared with specimens with a 10% discrete defect rate. Near-wall defects have a greater effect than central defects, reducing ultimate bearing capacity by 13.2% compared to central defects. After CFRP reinforcement, the ultimate bearing capacity and ductility of specimens with a 15% density loss rate increase by 9.1% and 14.7%, respectively. For central cavity defects, semi-wrap reinforcement increases bearing capacity and ductility coefficients by 11.8% and 19.5%, respectively, while full-wrap reinforcement increases them by 20.6% and 21.1%. For near-wall defects, semi-wrap reinforcement increases these coefficients by 11.9% and 22.1%, and full-wrap reinforcement increases them by 18.6% and 31.4%, respectively. This indicates that full-wrap reinforcement is more effective than semi-wrap reinforcement. A formula for calculating the bearing capacity of short concrete-filled square columns with concentrated cavity defects was developed using multiple linear regression. The average ratio Nu/Nt between calculated and experimental values is 0.968, indicating good agreement.ConclusionsThe results show that defects in the core concrete of CFSST columns adversely affect bearing capacity and ductility, while CFRP reinforcement improves compressive performance. The proposed formula effectively predicts the bearing capacity of specimens with concentrated cavity defects and can serve as a reference for practical engineering evaluation.关键词：concrete-filled square steel tubular column;defect;axial compression test;CFRP reinforcement;bearing capacity formula139|518|0更新时间：2026-05-19 - 摘要：ObjectiveThe destabilization process of high and steep rock slopes and its influence range are crucial for the safe operation of engineering projects. The FEM-DSDEM numerical simulation method is proposed to simulate the landslide motion process by coupling the finite element me-thod (FEM) with the deformable spheropolygon-based discrete element method (DSDEM) to achieve the numerical simulation of the continuou-discontinuous progressive evolution process of landslides under earthquake action.MethodsThe method uses the finite element method to simulate the bedrock and the deformable spheropolygon-based discrete element method to simulate the landslide body. The fictitious crack model (FCM) and the Mohr-Coulomb criterion were introduced to simulate the transformation from continuous to discontinuous states, including the crushing and shear damage of the landslide body. In addition, a viscous-spring boundary was imposed on the truncated boundary to realize the numerical simulation of the continuous-discontinuous gradual evolution process of the landslide body under earthquake effects. First, the feasibility and accuracy of the FEM-DSDEM numerical simulation method for reflecting the continuous-discontinuous evolution process of materials were verified using the Brazilian disc test and the four-point bending beam impact test. Second, the corresponding calculation program was developed to realize the numerical simulation of the continuous-discontinuous progressive damage evolution process of landslides. On this basis, the numerical simulation of the entire progressive failure process of the Dr2 rock slope at Suofengying Hydropower Station was conducted, and the dynamic characteristics of the landslide body and the spatial distribution characteristics of the accumulation body under three different failure modes, namely shear sliding failure, local collapse failure, and slip failure, were investigated.Results and DiscussionsIn the Brazilian disc test, the peak load at the upper plate was 1 870 kN, and the tensile strength value obtained using the formula was 5.90 MPa, which was 5.36% lower than the input value. The result was within the allowable error range, verifying that the method could simulate the fracture process of brittle materials. In the four-point bending beam impact test, the numerical simulation results of the maximum deflection curve of the beam during the fracture process were compared to the experimental results, and the two sets of results were in good agreement. This finding verified that the method could simulate the fracture process of rock subjected to impact loading. The numerical simulation results of the entire progressive failure process of the Dr2 rock slope at Suofengying Hydropower Station showed that when the Dr2 rock slope became unstable, all sliding modes produced sliding failure along the sliding cleavage surface, accompanied by local collapse failure. The destabilizing movement of the landslide was short in duration, rapid in velocity, and generated a strong impact on the mountains located on the opposite bank of the riverbed. In addition, the accumulation of body formed after a destabilizing failure impacted the river channel, causing destruction and sediment blockage at the water intake. Among the three failure modes, the landslide occurring under the shear sliding failure mode blocked the river channel at the fastest rate. Owing to the insufficient strength of the shear surface, the sediments generated from the primary landslide could also induce secondary landslides within the shear surface. The average displacement of each gage point under the local collapse failure mode was the largest, and the peak velocity at each gage point was also the highest. In contrast, the average displacement at each measurement point was the smallest under the slip failure mode.ConclusionsThis study verified the capability of the FEM-DSDEM method to realize the numerical simulation of the continuous-discontinuous progressive evolution process of landslides under seismic action through the Brazilian disc test, four-point bending beam impact test, and numerical simulation of the entire progressive failure process of the Dr2 rock slope at the Suofengying Hydropower Station. In addition, the research results obtained for the Dr2 rock slope at the Suofengying Hydropower Station can provide numerical simulation solutions for investigating the entire progressive damage process of similar rock slopes. This study investigates the motion process and accumulation patterns of hazardous rock bodies after sliding down the slope under different failure modes. However, the interaction between the hazardous rock body and reservoir water after destabilization into the water was not considered. Therefore, the strong coupling effect and energy transfer between the landslide mass and the fluid can serve as important directions for future research. In addition, this study is based on a two-dimensional model, and some discrepancies can exist between the simulation results and actual conditions. Therefore, future studies can further explore the numerical simulation capability of this method under three-dimensional rock slope models.关键词：discrete element method;finite element method;continuous-discontinuous;viscous-spring boundary;rock slope134|470|0更新时间：2026-05-19
- 摘要：ObjectiveCarbonaceous mudstone exhibits low mechanical strength, water-induced disintegration, and reduced structural compactness. It is widely distributed in the mountainous strata of Southwestern China, where tunneling activities frequently traverse formations dominated by carbonaceous mudstone. The surrounding rocks are subjected to prolonged coupled effects of in-situ stress and groundwater seepage pressure, which complicates the creep behavior of carbonaceous mudstone. Constitutive models are essential for characterizing creep-related mechanical properties and deformation mechanisms. However, current models derived from elastoplastic theory inadequately address hydro-mechanical coupling effects during creep. Therefore, establishing a coupled hydro-mechanical creep constitutive model is imperative for accurate deformation prediction in geotechnical engineering.MethodsThis study conducted laboratory creep tests under hydro-mechanical coupling conditions on carbonaceous mudstone samples collected from secondary lining fracture zones in the Yanglin Tunnel. The experiments revealed the evolution of deformation characteristics and macro-micro fracture mechanisms throughout the creep process. A three-stage nonlinear viscoelastic-plastic creep model incorporating hydro-mec-hanical coupling was developed based on rheological and elastoplastic theories, and parameter identification methods were established. The theoretical curves showed strong agreement with the experimental data, accurately captured the complete creep behavior of carbonaceous mudstone, and demonstrated the model's validity for engineering applications.Results and Discussions1) Creep curves exhibited stepwise progression, with deformation increasing significantly under higher osmotic pressures and reduced maximum bearing capacities. Failure deviatoric stress decreased exponentially with rising osmotic pressure. At constant confining pressure, elevated osmotic pressure shortened the total creep duration before failure. 2) Volumetric strain dilation occurred earlier under 23 MPa osmotic pressures compared to 1 MPa, which indicated accelerated crack initiation and unstable creep progression. 3) Accelerated creep rates manifested as nonlinear increases driven by coupled osmotic-deviatoric stress effects on crack damage evolution, which reflected macroscopic fracture propagation. 4) Under 7 MPa confining pressure, osmotic pressure reduced radial crack control and yielded stochastic failure modes such as composite fractures at 3 MPa. At 14 MPa confining pressure, macroscopic failure patterns became homogenized across osmotic pressures due to enhanced crack confinement. 5) SEM analysis revealed that tensile and shear fractures dominated microscale failure. Osmotic pressure raised intergranular reorganization, including fracture, refinement, and sliding, to form stress-adaptive microstructures. 6) Model-experiment consistency validated the applicability of the model across creep stages, including decay/steady-state creep at low stress and acceleration at high stress, which confirmed its capacity to characterize hydro-mechanical coupling effects.Conclusions1) Osmotic pressure intensifies creep deformation and reduces long-term strength in carbonaceous mudstone, inducing failure under lower deviatoric stresses. 2) Under low confining pressures, osmotic pressure reduces radial crack confinement, increasing stochastic failure mo-des characterized by composite fracture patterns. 3) At the microscopic level, osmotic pressure alters fracture morphologies: tensile fractures exhibit scaly brittle surfaces and root-like patterns, whereas shear fractures display dimples and transgranular cracks. The microstructural fracture patterns correlate well with macroscopic failure modes. 4) The proposed nonlinear viscoelastic-plastic creep model effectively characterizes full-stage creep behavior under varying confining/osmotic pressures. The model parameters derived from laboratory tests produce theoretical curves that closely match the experimental data by considering confining pressure and osmotic pressure as variables.关键词：carbonaceous mudstone;hydro-mechanical coupling;creep characteristics;failure characteristics;creep model91|330|0更新时间：2026-05-19
- 摘要：ObjectiveAccurately understanding the permeability characteristics of rock contact fractures is crucial for the safety evaluation of deep underground engineering. A numerical model for simulating the ideal contact fracture seepage process is proposed based on the lattice Boltzmann method to analyze the evolution of permeability in fractures under localized contact areas, considering the coupling effect between the fluid and contact areas.MethodsThis study applied a random parameter method to construct an idealized contact fracture structure, and the contact ratio and lacunarity were selected to characterize the spatial distribution of contact areas. Based on the lattice Boltzmann method, a second-order accurate half-bounce-back scheme was utilized to describe the coupling mechanism between the fluid and localized contact areas, and a numerical model was proposed to simulate the seepage process in ideal contacted rock fractures. The effectiveness and computational accuracy of the model were validated using two classic examples. Streamline tortuosity and permeability were introduced to characterize the flow morphology, and the effects of fracture contact ratio, spatial distribution of contact areas, and contact geometry on fracture permeability were investigated to analyze the impact of contact areas on fluid flow in rock fractures.Results and DiscussionsUnder the same driving pressure, as the contact ratio within the rock fracture increased, the fluid flow space became more compressed, the seepage path became more tortuous, the flow velocity decreased, and the fracture permeability was reduced. When the contact ratios were 3.95%, 8.28%, 11.77%, 15.56%, and 20.37%, the average seepage velocities were 1.82×10-4, 1.54×10-4, 1.43×10-4, 1.38×10-4, and 1.25×10-4 m/s, respectively. As the contact ratio increased from 3.95% to 20.37%, the fracture permeability decreased from 4.54×10-8 m2 to 3.14×10-8 m2. The spatial distribution of contact areas significantly altered the permeability characteristics of the fractures. At the same contact ratio, a more concentrated distribution of contact areas, indicating a higher lacunarity, resulted in shorter average flow paths around obstacles and a more uniform fluid velocity distribution. The average seepage velocity decreased with decreasing lacunarity. When the lacunarity Λ values were 4.76, 3.21, 2.30, 1.70, and 1.42, the corresponding fracture permeabilities were 4.78×10-8, 4.15×10-8, 3.66×10-8, 3.47×10-8, and 3.18×10-8 m2, respectively. As the lacunarity increased from 1.42 to 1.70, 2.30, 3.21, and 4.76, the fracture permeability increased by 9.1%, 15.1%, 30.5%, and 50.3%, respectively. The shape of the contact area was also an important factor affecting the permeability characteristics. At a contact ratio C=11.77%, with the contact center position and the inclination angle of the elliptical major axis unchanged, an increase in the aspect ratio of the contact area resulted in a smoother geometric shape, a smaller blockage area in the flow direction, enhanced flow capacity, and a higher average seepage velocity, which collectively led to increased fracture permeability. When the aspect ratios were 0.2, 0.4, 0.6, 0.8, and 1.0, the corresponding average seepage velocities were 1.08×10-4, 1.38×10-4, 1.46×10-4, 1.48×10-4, and 1.49×10-4 m/s, respectively, and the permeabilities were 2.71×10-8, 3.46×10-8, 3.65×10-8, 3.70×10-8, and 3.71×10-8 m2, respectively.ConclusionsThis study developed a numerical model to simulate seepage evolution in ideally contacted rock fractures, effectively capturing fluid flow patterns within contact fractures and revealing the influence of local contact on fracture permeability. The main conclusions are as follows: as the contact ratio of a rock fracture increases, the available flow space decreases, leading to a longer fluid flow path, which slows the seepage velocity and reduces permeability. In addition, the flow space within the fracture is negatively correlated with both the average flow velocity and the average pressure drop across the cross-section. When the spatial distribution of contact areas is more dispersed, obstruction to fluid flow intensifies, increasing the tortuosity of the seepage path, reducing fluid velocity, and weakening the fracture flow capacity. When the contact ratio is 11.77%, permeability decreases by 50.3% as the missing item increases from 1.42 to 4.76. When the aspect ratio of elliptical contact areas is small, the geometric shape becomes flat and slender, increasing the singularity of the contact areas and significantly obstructing fluid flow. These results provide essential theoretical support for the quantitative evaluation of permeability characteristics in rock contact fractures.关键词：rock fracture;permeability characteristics;contact ratio;lacunarity;Lattice Boltzmann method233|580|0更新时间：2026-05-19
- 摘要：ObjectiveBlock materials are widely used in various fields of civil engineering, and conducting an in-depth study of the mechanical properties of block materials is essential. Traditional physical tests provide only limited macroscopic strength and deformation characteristics, and emerging technology tests are costly and complex; therefore, numerical simulation, as an effective alternative method, compensates for these deficiencies. This study uses the deformable spheropolygon-based polygon discrete element method to simulate the numerical test of block direct shear, and the standard model of Ⅰ/Ⅱ mixed-mode fracture is introduced to establish a method for simulating the fracture of quasi-brittle materials, simulating the block-breaking behavior during the direct shear process.MethodsBlock direct shear numerical tests on rigid blocks, crushable blocks, and deformable blocks were conducted, respectively. First, the numerical model adopted for the direct shear test of the block was presented, along with the calibration of parameters during the simulation. Then, direct shear tests of rigid blocks were simulated using rounded polygons, and the effects of the degree of rounding of rigid blocks on shear stress, shear dilation, and contraction behavior, and the anisotropy coefficient of the normal contact force were analyzed. Then, DSDEM was utilized to simulate the direct shear test of the crushable block, the stress displacement relationship of the crushable block was investigated, and a sensitivity analysis of the tensile strength of the crushable block was conducted to examine the effect of tensile strength on the shear evolution law. Finally, the shear characteristics of rigid blocks, crushable blocks, and deformable blocks were compared.Results and DiscussionsIn the direct shear tests of rigid blocks, under the same vertical load, the shear stress decreased with increasing circularization radius of the block. The smaller the circularization radius was, the more pronounced the block interlocking effect was, and the greater the resulting shear stress was. With increasing vertical load, the difference in shear stress among blocks with different circularization radii increased. Under different vertical loads, when the degree of rounding was small, the vertical displacement of the top plate first decreased and then increased, and this behavior was weakly affected by the vertical load; when the degree of rounding was large, block dilation was suppressed, and only compression occurred. In addition, as the vertical load increased, the vertical displacement of the top plate decreased; as the degree of rounding of the block increased, the block surface became smoother, rotation during the shear process became easier, and overturning of blocks around the contact area occurred. In the direct shear tests of crushable blocks, the crushing rate of nodal units increased sharply at the early stage and showed no significant increase during the middle and later stages. The shear stress of the blocks increased with increasing vertically oriented load, and the stress displacement curves exhibited a softening trend after the shear stress peak under lower vertically oriented loads. During shearing under a vertical load of 0.30 MPa, the number of fractures occurring in the nodal units increased significantly with increasing horizontal displacement and then gradually decreased after the shear stress reached its peak. When examining the shear mechanical properties of blocks with identical shapes but different tensile strengths under the same vertical load of 1.0 MPa, the fracture rate of the nodal units decreased as the tensile strength increased. When comparing the shear characteristics of rigid blocks, crushable blocks, and deformable blocks, the rigid block consistently exhibited the highest shear stress under the same vertical load. The rigid block can not deform under extrusion, resulting in a significant fixture effect between block corners. The crushable block fractured during the shear process, leading to a looser block arrangement and lower shear stress between blocks. The internal deformation of the deformable block reduced the fixture effect between block asperities, and because the Young's modulus of the deformable block was low, the internal jamming effect during direct shear was weak, resulting in low shear stress.ConclusionsIn the rigid block simulation, a smaller degree of block rounding resulted in a stronger block interlocking effect and higher shear stress. Under larger vertical loads, the degree of block rounding had a more pronounced effect on shear stress, while higher vertical loads inhibited the shear expansion of the specimen and reduced the rate of increase of the anisotropy coefficient of the normal contact force. In the simulation of crushable blocks, shear stress increased with increasing vertical load. Under lower vertical loads, the stress-displacement curve exhibited a strain-softening trend after the shear stress reached its peak, whereas under higher vertical loads, the stress-displacement curve transitioned from strain softening to strain hardening, and no distinct peak was observed. When the tensile strength was low, the degree of block crushing had a greater influence on the shear mechanical properties. In addition, block shear stress increased with increasing tensile strength, and the degree of strain hardening also increased. Under the same vertical load, the shear stress of rigid blocks was the highest, while the shear stresses of deformable and crushable blocks were lower. This result confirms that the direct shear test based on the rigid body assumption has limitations when simulating blocks and cannot accurately characterize the mechanical properties of blocks in such tests.关键词：shear tests;breakable blocks;deformable blocks;spheropolygon;discrete element method182|516|0更新时间：2026-05-19
- 摘要：ObjectiveDeeply excavated expansive soil canal slopes frequently exhibit significant deformation and poor stability due to the combined effects of excavation unloading, wet‒dry cycles, and groundwater level fluctuations. Under the influence of multiple environmental factors, the deformation mechanisms of these slopes are complex and demonstrate pronounced spatiotemporal heterogeneity. Deformation serves as a direct indicator of slope stability, making the analysis of deformation patterns and trends essential for stability assessment. In current engineering practice, deformation data are primarily obtained through discrete point-based monitoring, which captures information only at critical cross-sections or localized areas of the slope. This approach leaves large portions of the slope unmonitored, resulting in limited coverage and creating blind spots in deformation assessment. In addition, the dense deployment of monitoring points increases construction complexity and significantly raises project costs. Therefore, a key challenge in long-distance canal slope safety monitoring involves improving deformation monitoring coverage and cost-effectiveness while maintaining sufficient precision. InSAR technology provides high spatiotemporal resolution, broad coverage, non-contact monitoring capability, and strong adaptability to complex terrain, addressing many limitations associated with conventional point-based methods. This study integrates Small Baseline Subset InSAR (SBAS‒InSAR) with traditional deformation monitoring techniques to obtain multi-scale deformation data, enabling deformation analysis from regional scales to localized sections. In addition, the study develops a self-explaining neural network (SENN) model incorporating an attention mechanism to predict canal slope deformation. The model examines the deformation characteristics, dominant controlling factors, and evolutionary mechanisms of deeply excavated expansive soil slopes, facilitating multi-source data-driven analysis of deformation behavior and its influencing factors. This approach provides scientific support for the safety monitoring and stability evaluation of canal slopes.MethodsFirst, SBAS‒InSAR was employed to process Sentinel‒1A satellite imagery to extract time-series deformation data. The derived displacements were projected onto the vertical direction and were cross-validated with ground-based vertical displacement measurements to evaluate the reliability of the SBAS‒InSAR results. Based on this validation, deformation rate thresholds were established to identify high-risk canal segments, which enabled an analysis of the overall slope deformation trends. Then, a SENN model incorporating an attention mechanism was developed to predict slope deformation. Key influencing factors, including groundwater level, canal water level, air temperature, precipitation, and time-dependent effects, were selected as input variables. The SENN model autonomously extracted critical features and dynamically assigned weights to each factor, predicting cumulative displacements along both the satellite Line-of-Sight (LOS) direction and the inclinometer A-direction. This approach enabled a comprehensive analysis of deformation patterns at the slope surface and at various subsurface depths while clarifying the dominant controlling factors governing expansive soil canal slope behavior.Results and DiscussionsThe study focused on a deeply excavated expansive soil canal section (Stake 8+88612+921) of a major water diversion project and produced the following key findings: 1) The analysis of 128 Sentinel‒1A images from March 2017 to December 2021 revealed that the deformation data obtained through the SBAS‒InSAR method showed a discrepancy of less than 3 mm compared to surface vertical displacement measurements at monitoring points (fourth-stage berm at 9+363 and third-stage berm at 11+400), while the deformation trends remained consistent. This result confirmed the reliability of SBAS‒InSAR for monitoring canal slope deformation. 2) The study section exhibited LOS deformation rates ranging from ‒10 to 24 mm/a, which indicated overall uplift characteristics, with positive LOS deformation showing an annual increase. Using a threshold of 10 mm/a, critical deformation zones were identified, particularly within the 11+80612+921 section, where most areas experienced deformations exceeding 40 mm and reached a maximum value of 97 mm. 3) Inclinometer measurements indicated maximum displacements of 49.51 mm at a depth of 4.5 m below the orifice at the second-stage berm (11+715), 63.80 mm at 1 m below the first-stage berm (11+762), and 67.51 mm at a depth of 1.5 m at the third-stage berm (11+762), with deformation extending to 13.5 m below the orifice. 4) LOS direction deformation was primarily influenced by groundwater level, canal water level, and time-dependent effects. Groundwater level exerted a stronger influence on right-bank deformation, whereas the canal water level more significantly affected left-bank deformation. At the third-stage berm (11+762), A-direction deformation was predominantly controlled by time-dependent effects, followed by temperature effects, while canal water level and rainfall exerted minimal influence. Groundwater level significantly affected surface soils but showed a reduced impact on deeper soil layers. Shallow deformations in expansive soil slopes were mainly controlled by groundwater level, temperature, and time-dependent effects, whereas displacements below a depth of 3.5 m showed a stronger correlation with temperature and time-dependent effects. 5) The 11+700 ~ 11+800 section exhibited continuous surface and internal deformation, with right-bank slopes showing significantly greater deformation than left-bank slopes due to higher groundwater levels. Deformation magnitudes were greater in the first to fourth stage slopes than in the fifth and sixth stage slopes. Deformation mechanisms varied with depth. Deeper soils, which were constrained by overburden pressure, were less affected by groundwater fluctuations, whereas shallow soils showed high sensitivity to both groundwater level variations and temperature changes. The study demonstrated that uplift deformation in this canal section resulted from the combined effects of excavation unloading and hydro-mechanical coupling in expansive soils.ConclusionsThe SBAS‒InSAR technique effectively monitors large-scale canal slope deformation trends by overcoming the spatial limitations inherent in conventional point-based monitoring methods, which often suffer from restricted coverage and sparse measurement points. The attention-mechanism-based SENN prediction model demonstrates high accuracy in forecasting slope deformation patterns while quantitatively evaluating the relative contributions of various influencing factors. This multi-source data integration approach provides comprehensive insights into the deformation mechanisms of expansive soil canal slopes and their controlling factors, providing a scientific basis for slope safety monitoring. The research outcomes serve as valuable references for the long-term monitoring and engineering management of expansive soil canal slopes and propose innovative methodologies for the safety monitoring of similar engineering projects. The demonstrated technical framework exhibits significant practical value for engineering applications, particularly in addressing deformation monitoring challenges in large-scale water conveyance infrastructure.关键词：expansive soil;canal slope;InSAR;deformation;self-explaining neural network (SENN);attention mechanism171|635|0更新时间：2026-05-19
- 摘要：ObjectiveThis study addresses the mechanical challenges associated with calcareous sand in reef construction in the South China Sea. Using the discrete element method, the effects of particle shape and intermediate principal stress on the critical state behavior of calcareous sand are systemically investigated. The objective is to elucidate the underlying deformation and failure mechanisms, providing scientific guidance for foundation design and significant engineering value.MethodsThe PFC3D (Particle Flow Code in 3-Dimension) discrete element method was employed to generate crushable particle models with various shapes representative of calcareous sand. Drained true triaxial compression simulations were conducted to evaluate the effects of particle shape and intermediate principal stress on critical state characteristics. Macroscopic properties, such as shear strength, volumetric strain, and critical state line distribution were evaluated. At the microscale, key descriptors such as coordination number, redundancy ratio, and fabric anisotropy were analyzed to characterize the evolving contact network and internal structure. The combined macro-micro analysis elucidates the mechanisms by which particle morphology and intermediate principal stress govern the critical state response of calcareous sand.Results and DiscussionThe effects of particle shape and angularity on granular material properties were investigated, focusing on stress‒strain relationships, volumetric deformation, critical state lines, and micromechanical responses. Four particle types with increasing angularity—particle a(α = 1.192), b(α = 1.255), c(α = 1.319), and d(α = 1.360)—were analyzed under varying confining pressures (100, 200, 300, 400, and 600 kPa) and intermediate principal stress ratios (b-values: 0, 0.2, 0.4, 0.8). Analysis of the peak stress ratio ((q/p)max) revealed a significant dependence on particle angularity. At a confining pressure of 100 kPa, (q/p)max increased from 1.58 for particle a to 1.76 for particle d. Each increment of 0.068 in angularity led to an average increase of 0.18 in (q/p)max. Variations in the relationship between volumetric strain and major principal strain were also observed. Particle a demonstrated a peak dilatancy rate of 0.39 and a maximum volumetric expansion of 5.81%, whereas particle d had a peak dilatancy rate of 0.70 and a volumetric expansion of 12.71%. Each increase of 0.068 in angularity corresponded to an average increase of approximately 6.90% in volumetric expansion. Critical state line parameters, including the slope (Mcs) and intercept (eГ), were also influenced by particle shape and b-value. For b = 0.8, Mcs increased from 0.923 for particle a to 1.069 for particle d, corresponding to an approximate increase of 0.03 for every 0.068 increase in Mcs Similarly, eГ increased from 1.19848 for particle a to 1.374 67 for particle d, with an average increase of 0.02 per 0.068 increase in angularity. Micromechanical responses demonstrated that the average coordination number (Zcs) was notably affected by particle shape at both 100 kPa and 400 kPa confining pressures. At 100 kPa, Zcs decreased from 3.25 for particle a to 2.95 for particle d. At 400 kPa, these values decreased from 4.10 for particle a to 3.75 for particle d. Each increase of 0.068 in angularity led to a decrease of approximately 0.075 in Zcs at 100 kPa and 0.085 at 400 kPa. The redundancy ratio (Rf) was also influenced by particle shape, with particle a exhibiting a higher redundancy ratio than that of particle d. An increase of 0.068 in angularity resulted in an average decrease of approximately 0.02 in Rf. Additionally, as the void ratio decreased from 0.90 at ecs= 0.2 to 0.75 at ecs =0.4, the redundancy ratio decreased. The coefficients of normal contact anisotropy (ac) and normal contact force anisotropy (an) varied with particle shape. For b = 0, particle a had an ac of 0.25 and an an of 0.35, while particle d had an ac of 0.22 and an an of 0.42. Each increase of 0.068 in angularity resulted in a decrease of approximately 0.007 in ac and an increase of about 0.01 in an. These findings underscore the significant impact of particle shape and angularity on both macroscopic and micromechanical responses, providing new insights into granular material behavior.ConclusionsThe results indicate that increasing particle angularity enhances peak shear strength and volumetric expansion, while an increase in the intermediate principal stress coefficient (b-value) reduces these responses. With increasing particle angularity, the slope of the critical state line in q-p space and the intercept in the e-p space both increase, with varying trends depending on the b-value. Micromechanical analysis shows that higher particle angularity leads to increased normal contact force anisotropy and a decrease in the average coordination number. Conversely, increasing the b-value reduces anisotropy and promotes higher coordination numbers. A strong linear relationship exists between void ratio and redundancy ratio, with the slope of this relationship decreasing as particle angularity increases. Furthermore, the correlation among void ratio, mean principal stress, and redundancy ratio strengthens with increasing angularity, as evidenced by upward shift of the fitted relationship surface in three-dimensional space.关键词：particle shape;medium principal stress;particle fragmentation;critical state;DEM analysis228|821|0更新时间：2026-05-19
- 摘要：ObjectiveAlthough grouting reinforcement techniques effectively enhance the bearing capacity of strata in the short term, the grouted bodies are prone to creep deformation under the combined influence of sustained loading and groundwater pressure. This phenomenon can lead to gradual surface settlement and structural instability, compromising the long-term safety and performance of underground infrastructure. This study investigates the creep behavior of grouted bodies formed in highly permeable silt and sand-gravel strata under coupled axial load and hydraulic pressure. The objective is to systematically examine the creep mechanisms and deformation characteristics, providing theoretical support and practical guidance for long-term stability assessment and deformation prediction of grouting-reinforced strata.MethodsFirstly, silt and sand-gravel aggregates were collected from in situ formations and packed into molds. A permeation grouting method was employed to simulate field grouting conditions. Following grout injection and initial setting, specimen surfaces were leveled and sealed, and the specimens were cured for 28 days under controlled temperature and humidity. Uniaxial compressive strength tests were then conducted to determine the peak strength of the grouted bodies, which served as a reference for subsequent creep loading schemes. Secondly, creep tests were performed under long-term stepwise loading conditions using a pressurized chamber filled with water to apply confining pressure. Each load increment was maintained until creep deformation approached stabilization, after which the next load level was applied, and this process continued until specimen failure. Full creep curves were recorded throughout the process. The effects of stress level on deformation magnitude and creep rate were evaluated, and the long-term strength of the grouted bodies under coupled stress-seepage conditions was derived using the isochronous stress method. Finally, experimental data were fitted using the Burgers model and a nonlinear viscoelastic-plastic model, and key creep parameters were extracted accordingly. A representative numerical model of the grouted stratum was developed using actual site parameters and was implemented in COMSOL Multiphysics to simulate long-term settlement behavior under coupled mechanical-hydraulic conditions.Results and DiscussionsThe creep tests revealed that the time-dependent deformation behavior of the grouted bodies was strongly stress-dependent, and evident stress thresholds were identified at 2.3 MPa for silt and 3.4 MPa for sand-gravel. Below these thresholds, the specimens mainly exhibited decelerating and steady-state creep, with a gradually decreasing strain rate. In contrast, when the applied stress exceeded the thresholds, accelerated creep occurred, which was characterized by continuously increasing axial strain and eventual failure. Significant increases in total axial strain were observed once the stress surpassed the threshold, from 0.200% to 0.403% in silt and from 0.091% to 0.458% in sand-gravel. These results indicated a substantial risk of secondary failure in grouted strata under sustained high stress and emphasized the necessity of incorporating creep effects in design and long-term performance evaluations. Increased loading not only delayed the onset of steady-state creep but also amplified the long-term creep rate. At stress levels of 1.5 MPa and 1.8 MPa, steady-state creep rates approached zero. However, at 2.3 and 3.4 MPa, steady-state creep rates increased significantly, reaching approximately 0.2×10‒4/h. This increase in creep rate under high stress conditions exacerbated the risk of long-term instability. The isochronous stress-strain curves displayed a linear trend under low stress conditions and transitioned to nonlinear behavior with distinct inflection points when the stress exceeded the threshold. These inflection points corresponded to the long-term strength limits of the grouted bodies. Comparisons to actual site loading conditions indicated that operational stresses remained below these limits, which indicated that the grouted strata will remain stable over extended service periods. Both the Burgers and nonlinear viscoelastic-plastic models provided accurate fits to the experimental creep data across all stress levels, with coefficients of determination (R2) exceeding 0.95. Post-grouting settlement curves demonstrated the effectiveness of grouting in mitigating short-term deformation. Numerical simulations showed a high initial settlement rate that progressively attenuated over time. After 50 years, settlement magnitudes at monitoring points were 8, 9, 19, and 24 mm, all of which remained below the critical threshold of 25 mm. These findings validated the long-term stability of the grouted strata and confirmed that reactivation of settlement failure was unlikely in treated zones.ConclusionsCreep tests under stepwise loading are conducted on grouted bodies formed in highly permeable silt and sand-gravel strata. The results reveal that high stress levels significantly increase creep deformation and pose potential threats to the stability of grouted formations. Therefore, the creep behavior of grouted strata should be thoroughly considered in engineering design and service-life assessment. Numerical simulations incorporating laboratory-derived creep parameters confirm that the treated strata are expected to maintain long-term stability without recurrence of settlement-induced failure.关键词：grouted consolidation body;creep test;long-term stability;numerical simulation;ground settlement116|319|0更新时间：2026-05-19
CIVIL ENGINEERING
- 摘要：ObjectiveA few studies have shown that several environmental factors at high altitudes affect cavitation. However, a method that can systematically study the factors and mechanisms of cavitation at high altitudes is unavailable. Cavitation can be described as the growth and collapse of cavitation bubbles. Therefore, it is necessary to study the effect of environmental factors on cavitation bubbles at high altitudes.MethodsFirstly, the approximate analytical solution of the modified Rayleigh‒Plesset equation, containing surface tension, non-condensable gas (NCG), and interaction forces of multi-bubbles, was derived by employing the homotopy analysis method (HAM) for the first time. The scope of application of this solution, which ignored fluid viscosity and thermodynamic effects, was also provided. Secondly, by comparing the results of this approximate analytical solution with experimental data and with existing analytical solutions for single bubbles in the literature, and by calculating the maximum absolute error (Emax), mean absolute error (Ema), and Pearson correlation coefficient (PCC), the validity of this solution was verified. Thirdly, the results of the approximate analytical solution for multi-bubbles were also compared with both numerical calculations by CFD and results reported in the literature. Fourthly, based on this approximate analytical solution, the effects of environmental parameters at high altitudes on cavitation bubbles were systematically analyzed. Instead of traditional one-at-a-time sensitivity analysis (OSA), the effect degrees of these parameters were also evaluated using self-defined parametric sensitivity coefficients (PSC), which indicate the effects of high altitude. Finally, based on the results of the parametric sensitivity analysis of environmental parameters at high altitudes, several engineering suggestions were proposed to prevent or reduce cavitation in hydraulic equipment operating at high altitudes.Results and DiscussionsFor a single bubble, when the adiabatic exponent was 4/3, the PCC was 0.98, the Emax was 2.06×10-4 m, and the Ema was 6.64×10-5 m; when the adiabatic exponent was 5/3, the PCC was 0.98, the Emax was 3.27×10-4 m, and the Ema was 9.81×10-5 m. Both comparisons showed that the approximate analytical solution is valid because the P-value is less than 0.001. To avoid accidental and systematic errors, the approximate analytical solution was also normalized, and the results were compared with experimental data from the EPFL laboratory. The PCC was 0.97, the Emax was 0.04, and the Ema was 0.03. For multiple bubbles, the results of the approximate analytical solution and numerical calculations were compared, yielding a PCC of 0.98. Using this approximate analytical solution, a systematic analysis of the trends and degrees of the effects of environmental parameters on bubble cavitation at high altitudes was conducted. Ambient pressure has the greatest effect on the collapse of cavitation bubbles and is negatively correlated with both collapse time and minimum bubble radius, with maximal PSC values of 10.8% for collapse time and 5.7% for minimum radius. The absolute values of PSC, representing the effect degrees of the number of bubbles, distance between bubbles, initial radius of bubble collapse, liquid temperature, saturation vapor pressure, liquid density, and surface tension on collapse time, are -3.70%, -3.10%, 2.90%, 0.82%, -0.60%, 0.067%, and 0.023%, respectively, in descending order. The absolute values of PSC, representing the effect degrees of the initial radius of bubble collapse, liquid temperature, saturation vapor pressure, liquid density, surface tension, number of bubbles, and distance between bubbles on minimum radius, are 2.5%, 0.6%, -0.3%, -2.1×10-5, -6.6×10-7, 0, and 0, respectively, in descending order. When altitude increases from 0 km to 4 km, considering all the above environmental parameters, the collapse time of bubbles increases by 14%, and the minimum radius increases by 53%. This explains a phenomenon previously observed in numerical calculations: as altitude increases, the pressure during bubble collapse decreases, and the influence range on the hydrofoil increases significantly. Based on the approximate analytical solution and the sensitivity analysis of environmental parameters, suggestions for preventing or reducing cavitation erosion include adjusting parameters that affect bubble cavitation, such as reducing gas content in the fluid and correcting existing empirical parameters in hydro-turbine design.ConclusionsBecause the approximate analytical solution derived using HAM is valid for both single and multiple bubbles, further analysis of the mechanisms by which environmental parameters affect cavitation is supported. Using this approximate analytical solution and the self-defined parametric sensitivity coefficients, the effects of these parameters at high altitudes on cavitation bubbles can be systematically analyzed, providing a simple, intuitive, and comprehensive method for the design, operation, and maintenance of hydraulic equipment at high altitudes.关键词：high altitude;cavitation bubbles;approximate analytical solution;parametric sensitivity analysis407|877|0更新时间：2026-05-19
- 摘要：ObjectiveWith the increasing aging population, stroke and its associated hand hemiplegia have become major health concerns among the elderly. Rehabilitation training during stroke recovery is critical; however, traditional physical therapy methods have limitations in effectiveness, efficiency, and patient experience. This study aims to develop a novel flexible rehabilitation glove to provide a more effective and comfortable rehabilitation training solution for patients with post-stroke hemiplegia.MethodsFirst, the driving performance of shape memory alloy (SMA) wires was investigated, and an electrothermal actuation test platform was built. The electrothermal characteristics and actuation behavior of SMA wires under different conditions were analyzed to verify their feasibility as driving elements in flexible rehabilitation gloves. Second, based on hand skeletal kinematics and rehabilitation requirements, a wearable flexible rehabilitation glove conforming to finger motion was designed, and its reliability was evaluated. Using the muscle-like contraction properties of SMA wires, an SMA-based actuator was developed and integrated into the glove. A comprehensive SMA actuation model, including phase change, constitutive behavior, and electrothermal coupling, was established. Leveraging the self-sensing capability of SMA wires, a constitutive feedforward control model and a PID control model based on displacement feedback were developed and analyzed through simulation to evaluate strain tracking under different waveform signals. Finally, a prototype system, including hardware and control software, was developed, and experiments on active/passive rehabilitation training and assisted grasping were carried out.Results and DiscussionsUnder periodic square-wave power input and a given load, the SMA wire achieved a lifting capacity approximately 200 times its own weight. The temperature increased from room temperature to the phase transition temperature (approximately 80 ℃) in approximately 4 s, initiating deformation and stress generation with similar trends. After approximately 4 s, the SMA wire reached a maximum contraction force of approximately 12 N and displacement of approximately 20 mm. On this basis, a lifecycle test was carried out, and different samples were subjected to periodic cycle experiments. After 10 000 cycles, the maximum contraction remained approximately 20 mm, demonstrating good durability. At the same time, the SMA wire was subjected to constant load with varying power and constant power with varying load conditions. Under constant load with increasing power, the maximum displacement of the SMA wire increased from 2 mm to 20 mm, while the maximum contraction force increased from 1 N to 15 N. Beyond a certain deformation, the response tended to stabilize. When the power exceeds a certain threshold, the maximum deformation of the SMA wire also tended to stabilize. Under constant power with varying load, the SMA wire reached its maximum deformation after a period determined by its material properties. Notably, it was found that an appropriate increase in the initial load could improve the response speed of the SMA wire. Based on the constructed control model, response simulations were performed using sinusoidal and square-wave control signals. The tracking error was small overall, with larger deviations only at the initial and signal transition points, after which the system quickly converged to the expected values, demonstrating good control performance. Furthermore, based on temperature-driven actuation, a PID control tracking experiment using displacement (angle) feedback was conducted. Under closed-loop control, the system accurately tracked the target bending angle and stabilized upon reaching the preset value. Stretching and bending experiments were subsequently conducted on both prosthetic hands and patients. Under bending control, the prosthetic hand achieved bending angles of 30° for the thumb, 65° for the index finger, and 75° for the middle finger. Under stretching control, the fingers gradually extended after 4 s and eventually returned to the initial horizontal position. Based on these results, stretching and bending experiments were further conducted on three groups of patients wearing the device. Under bending control, the average bending angles of the thumb, index finger, and middle finger across the three groups of patients reached 45°, 80°, and 85°, respectively. Subsequently, stretching experiments were conducted, in which all three patient groups returned to the initial state after approximately 4 s. Meanwhile, the tension generated by the rehabilitation glove was measured and stabilized within 2 s, reaching a maximum tension of approximately 5 N, which met the requirements for daily rehabilitation exercises. The final angles measured using a mirror-based method were compared with those obtained from the data glove, with a maximum error not exceeding 5°. Finally, grasping experiments were conducted, in which patients were asked to grasp common daily objects while wearing the rehabilitation gloves. The results demonstrated effective grasping performance across different objects. The measured fingertip force during grasping was approximately 5.5 N, while a force of 4.8 N was achieved when grasping a cup. Electromyographic signals of the arm were compared with and without the glove, showing more stable signals when the glove was worn.ConclusionsThe results demonstrate that the proposed flexible rehabilitation gloves provide effective rehabilitation motion and assisted grasping performance. Compared with traditional designs, they offer improved adaptability and reduced weight, meeting the rehabilitation and assistance needs of different patients.关键词：rehabilitation gloves;flexible actuator;shape memory alloy wire;electrothermal drive301|567|0更新时间：2026-05-19
- 摘要：ObjectiveQuadruped robots gain widespread attention in hazardous and complex tasks such as search and rescue, mine clearance, and steep slope climbing due to their superior terrain adaptability compared to wheeled and tracked robots. However, existing trajectory planning algorithms predominantly focus on slip control and kinematic optimization, often neglecting the biological motion characteristics and walking stability observed in natural quadruped mammals. After millions of years of natural selection, quadruped mammals evolve optimal locomotion patterns, such as leg-lifting backswing and leg-lowering retraction, which minimize ground impact and ensure motion continuity. This study aims to develop a zero-impact foot-end trajectory that integrates biological motion mechanisms to address the limitations of traditional trajectories, including insufficient bionic adaptability, abrupt acceleration at leg lifting and lowering instants, and poor stability in complex environments. The goal is to enhance walking stability, reduce ground impact, and improve the bionic performance of quadruped robots, providing a reliable solution for their practical application in complex terrains.MethodsFirstly, a bionic quadruped robot was designed with reference to the physical characteristics of German Shepherds, a breed known for robust muscles, strong bones, and agile movements. Key structural parameters were determined based on standard German Shepherd dimensions, including a body length of 790 mm, a body width of 440 mm, a body height of 418 mm, thigh and calf lengths of 200 mm each, and an overall weight of 37.5 kg. The robot adopted a front-elbow and rear-knee joint configuration, with four legs symmetrically arranged and motion transmitted through linkages. A two-stage leg structure was simplified for kinematic analysis, and a coordinate system was established at the hip joint to derive the inverse kinematic models of the hip and knee joints. Using geometric relationships and the sine theorem, mapping equations between foot-end position coordinates and joint driving angles were deduced, which laid the foundation for trajectory tracking control. Secondly, a quintic polynomial zero-impact foot-end trajectory was proposed by mimicking the biological motion characteristics of quadruped mammals. The trajectory was divided into a swing phase and a support phase, with separate planning for the x (forward) and y (vertical) directions. In the x-direction, the swing phase was divided into three segments: backswing (0 to T/8), forward movement (T/8 to 3T/8), and retraction (3T/8 to T/2), where T represented the gait cycle (1 s). This design replicated natural mammalian locomotion and reduced impact during leg lifting and lowering. In the y-direction, the swing phase included a lifting segment (0 to T/4) and a lowering segment (T/4 to T/2), which ensured smooth vertical motion. Boundary conditions were defined to achieve zero velocity and acceleration at the beginning and end of the swing phase, eliminating impact between the foot-end and the ground. For comparison, traditional cubic polynomial and composite cycloid trajectories were selected as benchmarks, with identical gait parameters, including a step length of 50 mm and a lifting height of 20 mm, applied to all three trajectories. Finally, comprehensive simulations and physical experiments were conducted to validate the proposed trajectory. ADAMS and Simulink were used for co-simulation: the mechanical model of the robot was developed in ADAMS, while the control system, including inverse kinematic solutions and trajectory generation, was constructed in Simulink. The simulations analyzed joint angles, angular velocities, and acceleration curves for the three trajectories. Physical experiments were performed on the prototype robot equipped with a ZMC432 motion controller. A laser tracker (API R-20 Radian) was utilized to capture the actual foot-end trajectory, and trot gait control experiments were conducted to evaluate walking stability, slip resistance, and motion continuity. The performance of the three trajectories was compared in terms of bionic characteristics, impact reduction, and stability.Results and DiscussionsKinematic analysis verified the correctness of the inverse kinematic models, and smooth and continuous joint angle curves were obtained for all three trajectories. Simulation results showed that the quintic polynomial trajectory exhibited distinct bionic characteristics. In the x-direction, the backswing (15 mm) and retraction (15 mm) segments were clearly observed, whereas the cubic polynomial and composite cycloid trajectories lacked these biological features. Velocity and acceleration curves in both x and y directions confirmed that the quintic polynomial trajectory achieved zero impact at the instants of leg lifting and lowering, with no abrupt changes. In contrast, the cubic polynomial trajectory exhibited constant acceleration slopes that led to potential impact. The composite cycloid trajectory also achieved zero velocity and acceleration at key points but failed to reproduce the backswing and retraction behaviors.Physical experiment results demonstrated that the prototype robot stably walked using the proposed quintic polynomial trajectory. The forward displacement over 10 seconds reached approximately 500 mm, which was consistent with the theoretical speed of 50 mm/s. Laser tracking data indicated that the actual foot-end trajectory closely matched the planned trajectory, with a maximum position deviation of less than 5 mm. This deviation was primarily caused by assembly gaps, frictional contact between links, and slight motor torque insufficiency. Compared to the cubic polynomial and composite cycloid trajectories, the quintic polynomial trajectory significantly reduced slip phenomena, with the slip rate reduced by approximately 30% and 15%, respectively. The robot's center of mass remained stable during locomotion, with vertical fluctuations of less than 10 mm, which confirmed improved walking stability. In addition, the bionic backswing and retraction behaviors effectively reduced ground impact, as evidenced by smoother joint torque curves and lower operational noise.ConclusionsThis study successfully integrates biological motion characteristics into quadruped robot trajectory planning, addressing the limitations of traditional trajectories in terms of bionic adaptability and impact control. The proposed quintic polynomial zero-impact foot-end trajectory, which mimics the leg-lifting backswing and leg-lowering retraction of quadruped mammals, achieves smooth motion with zero impact at critical instants. The designed bionic quadruped robot, developed based on German Shepherd parameters, validates the effectiveness of the trajectory through rigorous simulations and physical experiments. The results demonstrate that the proposed trajectory outperforms traditional cubic polynomial and composite cycloid trajectories in terms of stability, slip resistance, and bionic performance. This research provides a solid theoretical and technical foundation for the development of high-performance quadruped robots and raises their practical application in complex terrains, such as mountainous areas, disaster sites, and unstructured environments. Future work will focus on optimizing the trajectory for dynamic locomotion, such as trotting and galloping, and on enhancing adaptability to variable terrains through real-time sensor feedback and adaptive control algorithms.关键词：quadruped robot;trajectory planning;german shepherd dog;quintic polynomial foot trajectory;trot gait538|3533|0更新时间：2026-05-19
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Multi-objective Optimization of a Rail Profile on Curves for A Mixed Passenger and Freight Railway AI导读
摘要：ObjectiveThe mixed passenger and freight railway operates EMUs, locomotives, freight trains, and ordinary passenger trains. Different wheel profiles run on the same line, which results in a complex wheel-rail matching relationship. Rail profile optimization serves as an important approach to improving the wheel-rail matching relationship. Most existing studies on rail profile optimization focus on passenger-dedicated lines, freight-dedicated lines, or metro lines, and they consider only the matching relationship between a single wheel profile and the rail in the optimization design.MethodsFirstly, the vehicle dynamics models of freight cars, locomotives, and bullet trains were established based on the multi-body dynamics simulation software SIMPACK, and the curve operating parameters were selected based on the actual conditions of a domestic passenger-cargo shared railway line with a design speed of 200 km/h and the "TB 10098—2017 Code for Design of Railway Line". The model was used for wheel rail contact geometry analysis and dynamic performance evaluation. Then, based on the tangential relationship between each arc of the rail surface and the tangential relationship between the arc and the straight line, the arc formula of the rail surface was derived, and six arc parameters that fully represented the rail surface were extracted. The arc program was developed using MATLAB, and the arc parameters were utilized as inputs to generate the rail surface composed of discrete points. Using circular arc parameters as design variables, wheel-rail wear number, contact stress, and derailment coefficient as optimization objectives, and axle lateral force and wheel load reduction rate as constraint functions, a mathematical model for rail profile optimization of passenger-cargo railway curve sections was established. The optimal Latin hypercube method was employed to extract uniformly distributed sample points in the sample space to reduce the computational time cost of the optimization model, and the RBF neural network surrogate model was established to predict the mapping relationship between the design variables and the objective functions based on the sample data. The model was solved using the NSGA- Ⅱ optimization algorithm to obtain the optimized rail profile. The rail wear prediction model of the mixed passenger and freight railway was developed to predict the rail wear evolution law, considering the passing frequency of different vehicle types and the passing weight coefficients of different wheel profiles. Finally, the performance indices of the optimized rail profile and the 60N rail profile were compared and analyzed from three aspects to verify the performance of the optimized rail profile: wheel-rail static contact characteristics, vehicle dynamic performance, and rail wear evolution law under 800 000 wheel passes.Results and DiscussionsThe performance indices of the optimized rail and the 60N rail were compared and analyzed from three aspects to verify the performance of the optimized rail: wheel-rail static contact characteristics, vehicle dynamic performance, and rail wear prediction. The following conclusions were obtained: After applying the optimized rail profile, the distribution of wheel-rail contact points became more uniform, the rolling circle radius difference increased under large lateral displacement, and the vehicle curve negotiation performance improved. Under the R800 m radius curve, the derailment coefficient and axle lateral force were significantly reduced when LM, JM3, and LMA wheel profiles were matched with the optimized rail profile. Under different operating conditions, the derailment coefficient and axle lateral force were improved when the JM3 wheel profile was matched with the optimized rail profile. For the 800 m curve radius, the wear number of the LM wheel profile improved and was reduced by 17%, while the wear numbers of the JM3 wheel profile under 800, 2 800, 3 500, and 4 500 m radius curves were reduced by 56%, 58%, 50%, and 42%, respectively. The wear number of the LMA wheel profile under 800 and 2 800 m radius curves improved significantly, with reductions of 80% and 80%, respectively, while the LMB10 wheel profile showed a reduction of 42% under the 800 m radius curve. After applying the optimized rail profile, the wheel-rail contact stress of LMA wheels under 800 m and 2800 m radius curves was significantly reduced by 59% and 59%, respectively. When the JM3 wheel profile was matched with the 60N rail, it exhibited a higher wheel-rail contact stress level under different operating conditions, and the stress level decreased by an average of 60% after applying the optimized rail profile. After applying the optimized rail profile, the wheel-rail contact stress of the LMB10 wheel under the 800 m radius curve was significantly reduced, with a 44% reduction compared to the 60N rail profile and a 17% reduction for the LM wheel. After the optimization of the rail profile, the issue of rail side wear under 800 and 2 800 m radius curve conditions was resolved. Under other curve radius conditions, the rail wear distribution range became wider, and the maximum wear amount was lower than that of the 60N rail.ConclusionsThe results indicate that the method is suitable for the optimal design of rail profiles in the curved sections of mixed passenger and freight railways, and it can ensure the safety of vehicle operation and curve-passing performance while reducing wheel-rail contact stress and wear rate after optimizing the existing rail profile. The research findings provide a valuable reference for rail profile design and rail grinding in passenger-cargo railways.关键词：Mixed passenger and freight railway;Rail profile design;multi-objective optimization;Vehicle dynamics;Wheel-rail matching314|1211|0更新时间：2026-05-19
MECHANICAL ENGINEERING
- 摘要：ObjectiveThis study combines new nanomaterials with aggregate wrapping technology. Nine groups of recycled concrete with different Nano-SiO2 (NS) contents were prepared using both the ordinary mixing process and the NS-reinforced aggregate mixing process. Concrete performance tests under different mixing processes and NS content conditions were systematically carried out to reveal the influence and mechanism of NS content and mixing process on recycled aggregate concrete performance, providing a basis for the safe and efficient application of recycled coarse aggregate in concrete engineering.MethodsFirst, the slump and slump flow of each group of fresh concrete samples were tested during mixing, and their fluidity, cohesion, and water retention were recorded and compared. Second, the compressive strength, electric flux value, and frost resistance of each group were tested and evaluated. Finally, the microscopic mechanisms of NS content and mixing process effects on recycled aggregate concrete were analyzed using scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR).Results and DiscussionsThe performance tests of fresh concrete show that, provided NS is well dispersed in mixing water, it significantly increases slurry viscosity and enhances the ability of recycled coarse aggregate to be coated by slurry. The 28 d compressive strength of PC samples increased by 18.1%, 27.8%, 30.1%, and 28.5% at NS contents of 0.4%, 0.8%, 1.2%, and 1.6%, respectively. The corresponding increases for GC samples were 32.0%, 39.7%, 36.1%, and 45.7%, respectively. At NS contents of 0.4%, 0.8%, 1.2%, and 1.6%, the electric flux value of recycled concrete prepared by ordinary mixing decreased by 10.0%, 37.0%, 41.6%, and 40.6%, respectively. For the aggregate-wrapping mixing process, the reductions were 25.6%, 47.5%, 48.4%, and 45.2%, respectively. After 150 freeze-thaw cycles, the relative dynamic elastic modulus and mass loss of the C0 sample were 60% and 9.9%, respectively. For PC1‒PC4, the relative dynamic elastic modulus values were 64.6%, 77.1%, 81.4%, and 81.1%, and the mass losses were 5.9%, 4.5%, 4.2%, and 4.0%, respectively. For GC1‒GC4, the relative dynamic elastic modulus values were 73.6%, 83.5%, 81.6%, and 84.6%, and the mass losses were 5.2%, 4.0%, 3.9%, and 3.8%, respectively. Overall, compressive strength, impermeability, and frost resistance show similar trends. These properties increase significantly with NS content when it is below 0.8%. However, for both mixing processes, the influence of NS content on the interface and pore structure becomes stable when the NS content exceeds 0.8%, and agglomeration of NS may negatively affect some mechanical or durability properties. Additionally, at the same NS content, recycled concrete prepared by the NS-reinforced aggregate mixing process shows better mechanical properties and durability than that prepared by the ordinary mixing process. Microstructural tests show that the T2 spectral area of recycled concrete decreases significantly, and the peak shifts to the left with increasing NS content. Meanwhile, the formation of C‒S‒H in the interfacial transition zone becomes denser, and the number and size of pores are significantly reduced. This is because NS enhances the interfacial transition zone while also improving the pore structure of the cement matrix and reducing overall porosity. Notably, this optimization effect is more pronounced in concrete prepared by the NS-reinforced aggregate mixing process.ConclusionsThe addition of NS effectively improves the microstructure of the interfacial transition zone and promotes matrix densification and reduced porosity. The wrapped slurry mixing process enables the directional nano-reinforcement effect and overall nano-modification effect of NS to act synergistically, further enhancing mechanical properties and durability. When the NS content is 0.8%, the workability, strength, impermeability, and frost resistance of recycled concrete are optimized simultaneously. However, higher NS content may reduce some properties.关键词：nano enhancement;recycled aggregate wrapped slurry;recycled concrete;mechanical properties;freezing resistance;interface transition zone437|773|0更新时间：2026-05-19
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Numerical Simulation Analysis of Multiple Physical Fields in Three-phase Submerged Arc Furnace 增强出版 AI导读
摘要：ObjectiveAmong numerous smelting processes, the Rotary Kiln-Electric Furnace (RKEF) process is extensively employed in ferronickel smelting due to its advantages of high metal recovery, reduced harmful elements, and mature process technology. However, several challenges remain, such as excessive energy consumption and significant slag discharge. Therefore, it is crucial to rationally design the geometric dimensions of the submerged arc furnace and seek an effective process optimization scheme to enhance smelting efficiency. The quality of ferronickel alloy is significantly influenced by the temperature of the molten pool, which is difficult to monitor and investigate experimentally during the smelting process. Therefore, a numerical simulation method is employed in this paper to explore the interaction mechanism of multiple physical fields within a submerged arc furnace and to study the influence of furnace temperature on the reduction characteristics of metal oxides.MethodTo explore the coupling mechanism of multiple physical fields in a three-phase submerged arc furnace during the smelting process, a transient three-dimensional mathematical model of the submerged arc furnace was established. This model integrates electromagnetic theory, heat and mass transfer, component reactions, and magnetic field perturbation into a unified computational framework, and solves current continuity equations and component transport equations using user-defined functions (UDFs). Meanwhile, source terms for viscous resistance, inertial resistance, electromagnetic force, Joule heat, and reduction reactions were added to the momentum and energy equations using user-defined functions. First, the distribution characteristics of electromagnetic, temperature, and component fields were analyzed. Meanwhile, the processes of heat transfer, material flow, and energy conversion within the furnace were simulated. Second, the variation of multiple physical fields over time was analyzed. Meanwhile, the reaction characteristics of ferronickel oxide in the submerged arc furnace were studied based on the reduction reaction mechanism of laterite nickel ore. Finally, the effects of different electrode insertion depths on temperature distribution and metal oxide conversion rates were studied.Results and DiscussionsThe distribution of potential contour lines near the arc is dense, indicating a relatively large potential gradient. Affected by this distribution, the current density is mainly concentrated in the arc zone. In addition, the current density between the electrode bottom and the molten pool bottom is significantly higher than in other areas of the molten pool. When the smelting time reaches 40 min, the current flows in from one arc and out through the other two arcs via the charge layer, forming four current paths within the molten pool. Due to the effects of the magnetic field and high-frequency current, the current density on the inner side of the arc is higher than on the outer side, showing clear skin and proximity effects. The distributions of Joule heat and temperature depend on the current density, resulting in a concentration of Joule heat primarily beneath the electrode. The inner side of the arc shows higher Joule heat than the outer side. The temperature below the electrode is higher, forming a high-temperature crucible zone. The maximum temperature in the arc zone is 5 641 K, and the temperature along the central axis of the molten pool first increases and then decreases. Due to the low current density above the arc, the heating rate in the upper molten pool is lower, leading to a lower conversion rate of ferronickel oxide in this region. As the smelting time increases from 10 min to 40 min, the average arc voltage drop increases, the maximum magnetic induction intensity rises from 0.008 9 T to 0.012 0 T, and the maximum Joule heat on the inner side of the arc increases from 2.38 MW·m-3 to 10.30 MW·m-3. When the electrode insertion depth increases from 1.9 m to 2.5 m, the average voltage drop of the three arc zones decreases from 20.67 V to 18.39 V. Meanwhile, the current density between the arc and the molten pool bottom increases, and the magnetic induction intensity rises. As a result, the molten pool temperature increases, and the maximum temperature at the bottom of the molten pool rises from 1 555 K to 1 809 K. However, with increasing electrode insertion depth, the high-temperature zone shifts downward, leading to a gradual decrease in temperature above the arc. The maximum temperature at the molten pool surface decreases from 1 460 K to 1 390 K. Because the reduction of ferronickel oxide depends on the temperature field, controlling the furnace temperature is important for improving conversion rates. After 40 min of smelting, nickel oxide is substantially reduced within the crucible zone. Outside this zone, the conversion rate of nickel oxide is about 8% higher at an electrode insertion depth of H = 1.9 m than at H = 2.5 m. Thus, a shallower insertion depth benefits nickel oxide reduction. However, increasing the electrode insertion depth from 1.9 m to 2.5 m increases the maximum conversion rate of iron oxide in the crucible zone from 41.8% to 51.4%. The insertion depth has little effect on iron oxide conversion outside the crucible zone. The downward shift of the high-temperature region reduces the conversion rate of iron oxide above the arc zone and decreases the conversion rate at the molten pool surface center from 33.7% to 25.6%.ConclusionsThis study clarifies the coupled, non-uniform distribution characteristics of electromagnetic, temperature, and component fields in a ferronickel submerged arc furnace. Current density, Joule heat, and high temperature are mainly concentrated in the arc zone and beneath the electrodes, showing clear skin and proximity effects, while the upper molten pool exhibits insufficient heating and lower metal oxide conversion rates. With prolonged smelting time, the arc voltage drop, magnetic induction intensity, and Joule heat gradually increase, further strengthening the temperature field. Increasing the electrode insertion depth shifts the high-temperature zone downward, raising the bottom temperature of the molten pool and promoting iron oxide reduction within the crucible zone. However, it reduces the temperature and nickel oxide conversion rate in the upper region and at the molten pool surface. A shallower insertion depth favors nickel oxide reduction, whereas a deeper insertion depth favors iron oxide reduction within the crucible zone. Considering the overall conversion performance of ferronickel oxides, an optimal electrode insertion depth of 2.1～2.3 m is recommended for practical smelting, as it can effectively balance temperature distribution and improve the reduction rate of metal oxides in the RKEF process.关键词：ferronickel submerged arc furnace;multi physical fields;numerical simulation;component reaction;porous medium362|799|0更新时间：2026-05-19 - 摘要：ObjectiveCurrently available methods for uric acid detection rely on specialized equipment and complex procedures, which are inconvenient for applications such as point-of-care testing. Therefore, a simple and intuitive strategy for visual monitoring of uric acid levels is highly desired. In this paper, redox-responsive photonic crystal gel microspheres (MPNC) exhibiting iridescent color changes are successfully prepared.MethodsThe MPNC were constructed using poly (N-isopropylacrylamide) (PNIPAM) as the gel matrix, with embedded poly(vinylpyrrolidone)-coated magnetite (Fe3O4@PVP) nanoparticles as one-dimensional photonic crystal elements. During UV-initiated polymerization, precursor droplets containing the monomer N-isopropylacrylamide (NIPAM) were cross-linked into microspheres by four-armed poly (ethylene glycol) acrylamide (PEG) and N,N′-bis (acryloyl) cystamine (BAC) as a double cross-linking system. Simultaneously, the Fe3O4@PVP nanoparticles suspended in the droplets formed well-ordered chain-like photonic crystal structures under a magnetic field and were immobilized in the PNIPAM gel matrix, producing structural color. To obtain the precursor solution, monomer NIPAM, co-crosslinkers PEG and BAC, Fe3O4@PVP nanoparticles, surfactant Triton X-100, and photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-acetone (HMPP) were sequentially dissolved in ethylene glycol. During microfluidic emulsification, the precursor solution (internal phase) was dispersed into droplets by soybean oil containing the surfactant polyisobutylene succinimide (T-154) as the external phase. The reversible conversion between sulfhydryl and disulfide bonds in BAC during oxidation-reduction reactions caused swelling and shrinking of the redox-responsive gel, changing the lattice spacing of the photonic crystals and resulting in significant chromatic changes. The four-arm crosslinking of PEG improved the homogeneity of microsphere volume changes and also served as a stable scaffold. By optimizing the size and concentration of Fe3O4@PVP nanoparticles and the applied magnetic field strength, MPNC with iridescent color responses to hydrogen peroxide (H2O2) were obtained. The response properties of optimized MPNC toward uric acid, as well as their cyclic stability and anti-interference performance, were investigated. Before testing, the gel microspheres were placed in an aqueous solution of the reducing agent DL-dithiothreitol (DTT), forming sulfhydryl groups and fully swelling the microspheres. During detection, the microspheres were transferred into phosphate buffer solution containing uric acid. The H2O2 generated from uric acid catalyzed by uricase oxidized sulfhydryl groups into disulfide bonds. At this stage, the cross-linking degree increased, and the lattice spacing between adjacent nanoparticles fixed in the gel matrix decreased.Results and DiscussionsThe redox-responsive photonic crystal gel microspheres were successfully prepared by microfluidic emulsification with an inner-phase flow rate of 400 μL⸱L-1 and an outer-phase flow rate of 1 000 μL⸱L-1, and with a molar ratio of PEG to BAC of 1∶28, showing regular spherical and uniform morphology. Compared with the high deswelling ratio (DSR) of 0.96 for microspheres without BAC (MPN‒0), all microspheres with BAC (MPN‒1, MPNC‒152, MPNC‒182, and MPNC‒209) showed a lower DSR of 0.38, indicating redox responsiveness. The addition of Fe3O4@PVP magnetic particles had no effect on the size or redox-responsive performance of the MPNC. One-dimensional photonic crystal chains formed by self-assembly of Fe3O4@PVP nanoparticles were observed in scanning electron microscope images of microsphere cross sections. By adjusting nanoparticle size and concentration, it was found that size significantly affected the redox-responsive color change of MPNC, while concentration mainly influenced structural color brightness. The color of MPNC gradually blue-shifted as the magnetic field strength increased from 6 to 16 mT during preparation. At 10 mT, MPNC‒182 prepared with Fe3O4@PVP nanoparticles of 182 nm size and 3 g⸱L-1 concentration showed the widest color change from orange-red to blue before and after H2O2 response, with a diffraction wavelength variation of 140 nm. The diffraction wavelengths of the optimized MPNC under reduction by DTT and oxidation by H2O2 fluctuated slightly around their mean values over six consecutive cycles, demonstrating good stability and repeatability. In the presence of uricase, MPNC showed a wide color change from orange-red (616 nm) to blue (496 nm) for detecting uric acid in the range of 0～0.60 mmol⸱L-1 with a solution volume of 100 µL. The linear correlation between uric acid concentration and diffraction wavelength indicates that MPNC‒182 has high accuracy. If the microsphere color is between green and blue, the uric acid level exceeds 0.42 mmol⸱L-1, indicating a risk of hyperuricemia. To further verify practicality, artificial blood and urine environments were simulated to evaluate interference effects. The maximum wavelength deviation was only 10 nm, indicating satisfactory anti-interference performance and potential for use in body fluid detection.ConclusionsThe results show that MPNC can be used as a colorimetric sensor, providing a simple, intuitive, and versatile strategy for visualizing uric acid levels with the naked eye. This provides theoretical guidance and an experimental basis for the design and fabrication of redox-responsive photonic crystal gels.关键词：uric acid;microfluidics;magnetite nanoparticles;photonic crystal gel microspheres;redox;naked-eye detection264|656|0更新时间：2026-05-19
- 摘要：ObjectiveComprehensive tailings of non-ferrous metals were used as raw materials in this study. By exploring the impact of various components of the precursor liquid on product quality, it was proposed to improve product quality by adding a second additive in the mixed-guiding method. This successfully prepared products with high relative crystallinity and hexagonal prism morphology. This provides a valuable method for preparing high-quality ZSM-5 molecular sieves from silica-aluminum source solid waste and offers a feasible solution for the resource utilization of non-ferrous metal tailings.MethodsThe tailings were thoroughly ground to obtain a particle size between 48 μm and 80 μm. Then, the ground tailings were mixed with NaOH, and alkali fusion activation was carried out in an air atmosphere at 800 ℃ for 2 h, resulting in directly activated tailings. Next, 5.0 g of activated tailings were taken, 30 mL of distilled water was added, and hydrolysis was carried out at 45 ℃ in a water bath for 1 h. Then, the hydrolyzed solution was separated at a centrifugal speed of 6 000 rpm for 20 min, obtaining a blue-green supernatant. This supernatant was used as the synthesis mother liquor, and ethanol (EtOH), TPABr, seed, and a second additive (TA) were added. The molar ratio of the synthesis system was n(SiO2):n(EtOH):n(TPABr):n(TA):n(Seed):n(H2O)=1:y:x:z:0.000 19:105. After stirring for 30 minutes, the pH of the synthesis system was adjusted to 10.8 using concentrated HNO3. After continuing to stir for 1 h, the material was transferred to a 100 mL self-pressure reaction kettle lined with polytetrafluoroethylene and aged at 45 ℃ in a water bath for 12 h. After aging was completed, a hydrothermal crystallization reaction was carried out at 170 ℃ for 24 h. After the reaction ended, the kettle was cooled, and the solid product was filtered, washed to neutrality, dried at 120 ℃ for 24 h, and calcined in an air atmosphere at 550 ℃ for 4 h, finally obtaining the Na-ZSM-5 molecular sieve with the template removed.Results and DiscussionsComprehensive tailings of non-ferrous metals were used as raw materials, and ethanol was used as the main crystal growth promoter to synthesize ZSM-5 molecular sieves through the hydrothermal method. In this system, a small amount of TPABr (n(TPABr)/n(SiO2)=0.03) and seed were added, which enabled the synthesis of ZSM-5 products with a relative crystallinity of up to 99.85%. Compared with traditional synthesis methods, this green mixed method can obtain products with high relative crystallinity while reducing the use of organic amine templates. Although the direct high-temperature alkali fusion activation pretreatment method is more consistent with green principles, it does not completely remove Fe and Ca components in the precursor solution, which slows down or hinders the growth of ZSM-5 crystals and makes the product surface morphology more spherical. Therefore, although the process has a high level of environmental friendliness, there are still problems with product morphology. To address this issue, a green mixed system was proposed in which ethanol replaces part of TPABr, and a small amount of a second additive is added to control product morphology. In screening the second additive, it was found that adding CTAB, ethylene glycol, and glycerol had little effect on product crystallinity, while adding urea caused a downward trend in crystallinity. Among these, after adding ethylene glycol and glycerol, the product developed toward a short b-axis hexagonal prism morphology. In particular, with ethylene glycol, the product exhibited a more well-defined short b-axis hexagonal prism morphology and a relative crystallinity of 100.77%, indicating the best product quality. In addition, the ore-alkali mass ratio used in activation also affected product quality. If the ratio was too low, activation of the tailings might be insufficient. Conversely, if the ratio was too high, the precursor solution might contain a large amount of sodium salts, which would intensify the condensation reaction of nutrients and form amorphous products. This intensification may reduce the availability of nutrients for crystal nucleus formation, thereby decreasing the number of nuclei formed and causing secondary growth or twinning, ultimately reducing relative crystallinity. When the ore-alkali mass ratio reached 1.5, most crystals exhibited a smooth and complete morphology under the guidance of ethanol and ethylene glycol, and the product quality was optimal.ConclusionsComprehensive tailings of non-ferrous metals were used as raw materials. A small amount of ethylene glycol, which has a morphology-directing effect, was added in the mixed-guiding method. This not only reduced the use of organic ammonium template agents but also successfully synthesized ZSM-5 molecular sieves with hexagonal prismatic morphology and a relative crystallinity of 100.77%. In this process, the precursor ratio was n(SiO2):n(EtOH):n(TPABr):n(Ethanediol):n(Seed):n(H2O)=1:1:0.03:0.09:0.000 19:105. This method provides a valuable solution for synthesizing high-quality ZSM-5 molecular sieves using silicon-aluminum solid waste as raw materials and for the resource utilization of non-ferrous metal tailings.关键词：non-ferrous metal tailings;ZSM-5 zeolite;ethanol;product morphology;synthesis process316|492|0更新时间：2026-05-19
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