最新刊期
卷 53 ， 期 4 ， 2021
- 摘要：Earth is the only known planet to support human life, thus revealing the mysteries of the deep earth is of great significance to the survival and development of mankind. With the rapid development of human society, earthquakes and geological disasters occur frequently, and dynamic disasters occurred in deep earth engineering are more prominent, which are of unclear mechanism and difficult to predict or prevent effectively. The ultimate cause is that the humans cannot accurately recognize the basic laws of earth science and the coupling relationship between deep earth processes and shallow surface processes. The existing basic scientific researches on deep earth has lagged behind the human practice of deep underground engineering, and the superficial monitoring of traditional geological disaster information has great limitations. On this basis, conducting researches on joint technology of deep earth scientific exploration and geo-hazard prevention and control is of great significance to solve major scientific issues such as resource protection, life evolution and sustainable development. The core goal of “Deep earth– surface” linkage strategic system is the internal relationship between deep earth science and geological disasters, and advanced strategic planning in the field of deep earth science and geo-hazard. The “deep earth–surface” linkage scientific research platform based on typical deep engineering is fully associated with the widely distributed surface disaster information monitoring group, deep earth laboratories in-depth, mining area and deep engineering demonstration base. With the help of blockchain big data technology, the Deep Earth–Surface Intelligence Center will be built to coordinate research platforms of different types and depths in different regions. Finally, on this basis, with the linkage between deep earth and surface as the core, the large-scale scientific system for the linkage detection of deep earth and surface disaster prevention and control should be built, and the strategic research system of deep earth science law and major geological disaster prevention mechanism is comprehensively constructed, so as to serve the national and even global frontier of deep earth engineering, deep earth engineering safety and long-term stability, early warning, prevention and control of major geological disasters, helping China to lead the world in the related fields of deep earth science and geo-hazard.关键词：deep earth science;geological disaster prevention and control;“deep earth–surface” linkage;strategic research
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发布时间：2024-01-10
SCIENTIFIC FRONTIERS
- 摘要：Southwest China is a vast area with a high proportion of mountains, which is the most concentrated area of ethnic minorities. There are many ethnic villages in this area, which are characterized by complex terrain, frequent disasters, fragile ecology, underdeveloped economy and prominent human settlements. In order to improve the disaster prevention ability and living quality of ethnic villages, it is urgent to carry out comprehensive disaster prevention and control and livable performance improvement researches. The project of “Comprehensive Demonstration of Disaster Prevention Technology of Ethnic Villages in Southwest China” focuses on the safety and livability of ethnic villages in Southwest China, and condenses four key scientific and technological issues: 1) The disaster characteristics and breeding mechanism of village; 2) The characteristics of human settlements and “Environment-Construction” interaction mechanism of village; 3) Ecological disaster prevention and control technology with characteristics of low cost in village; 4) Integrated improvement technology of livable performance with characteristics of localization and adaptability in village. Based on these problems, the project carries out research from the following five aspects: intelligent monitoring and management technology of village geological disasters, village fire warning and fireproof building materials technology of village, disaster prevention structure system and enhancement technology of village, environmental pollution prevention and reuse technology of village, adaptive space optimization and residential performance improvement technology of village. The research goal is to form a low-cost, decentralized, ecological and intelligent comprehensive disaster prevention-control technology and an integrated improvement technology of localization, adaptability and livability. Then build a technology system of comprehensive disaster prevention and human settlements improvement in ethnic villages. The project can not only enhance the disaster prevention ability and improve the quality of living environment of ethnic villages in southwest China, but also protect ethnic characteristics and promote sustainable development.关键词：Southwest China;ethnic village;human settlement;comprehensive disaster prevention;livability
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发布时间：2024-01-10 - 摘要：Urban and rural mixed organic waste, including perishable waste and partial agricultural waste, are high yield, complex composition, high water content and nutrient content. Aerobic fermentation is one of the key technologies for the utilization of this resource, but the application is limited in China due to the low conversion efficiency and unknown risk of by-products. Therefore, in view of the bottleneck problem of aerobic fermentation of organic waste in China, the resource utilization technologies of urban and rural mixed organic waste were compared and analyzed, the advantages of aerobic fermentation in the treatment of organic solid waste was clarified, the transformation mode of organic matter in the process of aerobic fermentation was deeply analyzed, and the main problems faced by aerobic fermentation in the treatment of organic waste was revealed. Accordingly, the main factors affecting the efficient stabilization and resource utilization of aerobic fermentation products was further identified. The concept of rapid stabilization and resource utilization of urban and rural mixed organic waste, named as detecting the regulation principle of microbial metabolic network during organic waste aerobic fermentation, was proposed. Meanwhile, intelligent integrated rapid stabilization technology and equipment (intelligent screen display-online monitoring-feedback control) was also developed overcome the technology of directional humification and pollution enhancement in microbial factory, the technology of deep processing-quality evaluation- attribute complementary of resource products to utilize resource products by their characteristics was constructed. In order to provide technical support for the resource treatment of urban and rural mixed organic waste in China, researches and demonstration projects will be carried out to meet the major needs of national science and technology, such as in-situ reduction of organic waste by aerobic fermentation, pollution control in the process, and resource utilization of the end products.关键词：organic waste;aerobic fermentation;stabilization;by-product control;resource utilization
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发布时间：2024-01-10
FOCUS ON STATE KEY RESEARCH DEVELOPMENT PROGRAM OF CHINA
- 摘要：To study the seismic performance of corrugated steel plate concrete-composite shear wall with replaceable component of wall toe, two shear wall specimens were designed and fabricated. The influences of different arrangement forms of corrugated webs on seismic performance of shear wall specimens were analyzed by quasi-static tests and ABAQUS finite element software. The test result indicated that the wall toes of the specimen were destroyed before the main member, and the damage was mainly concentrated on the replaceable components before the ultimate drift ratio was reached. Compared with the horizontal corrugated steel plate concrete-composite shear wall, the lateral bearing capacity of the vertical corrugated steel plate concrete-composite shear wall had increased by 18.3%, the ductility coefficient increased by 28.69%, and the energy dissipation capacity increased by 3.3 times; The rate of bearing capacity degradation and stiffness degradation, the equivalent viscous damping coefficient and the stiffness degradation ratio were all lower, and the initial stiffness of the latter was slightly improved, which demonstrated that the vertical corrugated steel plate concrete-composite shear wall had better mechanical and seismic performance. By comparing the ABAQUS finite element model analyses with the test processes, the failure mode was basically consistent with the test phenomenon, which indicated that the finite element model established in this article had a certain reliability.关键词：replaceable part;corrugated steel plate-concrete composite shear wall;quasi-static test;earthquake resilient structure;finite element analysis
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发布时间：2024-01-10 - 摘要：The water-retention capacity of unsaturated soils is usually reflected by the variation law of soil-water characteristic curve. The important effects of load and temperature on soil-water characteristic curves have been gradually recognized, but the studies considering the combined action of wetting–loading–heating on soil-water characteristic curves are seldom reported, and the analysis of dominant influencing factors is rarer. In order to investigate the water holding capacity of silty clay under combined actions, the dry-wet cycling experiments of silty clay under different vertical stress and temperature conditions were carried out, and the influencing mechanism, characteristics and importance of each factor were analyzed. A prediction model reflecting the combined action of multiple factors was then established. The results show that: 1) With the increase of vertical stress, the air intake value of unsaturated soil increases, the moisture reduction rate decreases, and the hysteresis effect of the wet-dry cycle becomes stronger, which occurs at different temperatures; 2) Compared with the experimental curves under the same vertical stress and different temperatures, it is found that the air intake value of soil is slightly lower at higher temperatures; 3) Vertical stress has the greatest influence on water-retention capacity of soil, but it is confined to the low suction stage; the function of dry-wet cycle ranks second and decays rapidly with the number of cycles increasing; the influence of temperature is small and negligible when suction or density is high; 4) The improved L model based on Logistic curve is more suitable for fitting the soil-water characteristic curve of Badong silty clay than V–G model. In summary, the change of internal pore structure is the main cause of characteristic value change caused by vertical stress, which leads to the difference of water-retention performance; temperature mainly affects the water-retention capacity of soil mass in low stress and low suction stage; the influence of three storage conditions on soil-water capacity of silty clay is ordered as vertical stress>dry-wet cycle>temperature distribution; the modified L model can effectively reflect the evolution characteristics of water-retention capacity of silty clay under combined action of wetting-loading-heating.关键词：soil-water characteristic curve;vertical stress;drying-wetting cycle;temperature;Logistic curve
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发布时间：2024-01-10 - 摘要：With the development of computer technology, grid division technology is becoming more mature. Considering the frequent occurrence of floods due to climate change, the broad extents of calculation domains, the wide range of actual terrain, and the study area usually has narrow and long gullies and wide flooding areas, this paper proposes a structured non-uniform grid model with hierarchical topological relationships combined with a high-resolution model based on GPU acceleration to simulate the surface water flow process. High-quality grids affect the calculation accuracy and efficiency of the model. The principle of grid division is designed based on the gradient change of terrain elevation, and key terrain features are detected in the computational domain that requires high-resolution grids to reliably solve shallow water equations. Moreover, local area grids can be statically encrypted, so that the sensitive area of the water level calculation can be captured more accurately, while reducing the number of calculation grids and reducing the calculation cost. The numerical model adopts Godunov-type finite volume method for spatial discretization, uses the second-order TVD-MUSCL format to improve the temporal and spatial accuracy of the model, and uses GPU parallel technology to greatly increase the running speed of the model without reducing the calculation accuracy. The performance of high-resolution models on non-uniform grids is demonstrated by the more accurate simulation of flood inundation time and inundation area through ideal and practical cases. The results show that the numerical model based on the non-uniform grid has good stability, compared with the uniform grid, its running speed is about 2-3 times under the premise of ensuring the simulation accuracy and the efficiency is further improved on the basis of GPU acceleration. The new model is suitable for simulating large-scale flood evolution and urban inundation processes in complex areas, which has good potential in actual large-scale flood simulation.关键词：shallow water equations;non-uniform grid;flood simulation;Godunov-type;TVD-MUSCL;GPU parallel technology
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发布时间：2024-01-10 - 摘要：The macro mechanical properties of slope are determined by the meso parameters of soil particles and their motion. Although the stress and deformation characteristics of slope at the macro level can basically be obtained by the finite element method based on continuum model, it is difficult to reveal the deformation and instability mechanism of slope in the micro scale, and there are obvious limitations. The three-dimensional DEM–CFD model of fluid solid interaction of coal measure soil slope was established by coupling DEM and CFD. The meso mechanism of coal measures soil slope failure under rainfall was analyzed. The results show that the failure mode of coal measure soil slope simulated by DEM–CFD is mainly of rain erosion, and the slope sliding surface is predicted to be of approximate straight-line section, which is very close to the range of rain erosion of slope in outdoor model test. This shows that the numerical method is suitable to analyze the stability of coal measure soil slope. Micro parameters such as force chain, coordination number and porosity of soil particles in slope will change during the rainfall. For example, the porosity of particles on the top of slope changed from 0.35 in initial state to 0.8 in unstable state. The change of these micro parameters is directly related to the macro mechanical performance of the slope soil. In this paper, the law of the failure evolution of the coal measure soil slope under the rainfall was explained through the analysis of the micro parameters change of the particles. The research results of this paper not only provides theoretical basis for the protection design and construction of the coal measure soil slope in this area, but also provides a new way of analyzing the macro mechanical laws in geotechnical engineering from the micro perspective.关键词：coal measure soil slope;instability mechanism;DEM–CFD fluid solid coupling method;model test;macro and micro analysis
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发布时间：2024-01-10 - 摘要：33 material specimens were tested to explore the mechanical properties of Q460 high-strength steel plate with holes under monotonic tension and low-cycle fatigue loadings. The stress-strain curve, skeleton curve and energy dissipation capacity comparison of the specimens were analyzed. The influence law of the design size of the specimen, the number of openings and the loading mode on the strength, stiffness, ductility and energy dissipation capacity of the specimens with holes were discussed. On this basis, a finite element model of specimen under fatigue loading was established by the ANSYS software to verify the correctness and reliability of the model. The test results showed that round holes have an adverse effect on the mechanical properties of specimens. The holes lead to stress concentration of specimens. Under the fatigue loads, increasing the number of axial holes of the specimens is beneficial to improve the ductility of specimen, but has an adverse effect on the energy dissipation capacity of the steel. Under low-cycle repeated loadings, the specimens usually cracked and destroyed near holes, and the failure shapes are saddle-shaped. The thickness of the specimens has a significant impact on the failure mode and mechanical properties of the high-strength steel. Under the fatigue loads, the damage forms of the opening specimens and the non-open tester are different, and two different fracture forms are exhibited as thickness. With the increase of the design thickness of the specimen, the fracture section shows two forms. With the increase of the thickness of the steel, the mechanical properties of the specimens have improved significantly. As the number of load cycles increases, the ductility of Q460 high-strength steel decreases and the energy consumption capacity increases.关键词：Q460 high-strength steel;perforated high-strength steel plate;low-cycle fatigue loading;ductility;energy dissipation
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发布时间：2024-01-10 -
Similar Materials and Mechanical Properties of Coal–Gas Two-phase Media Based on Solid–Gas Coupling AI导读
摘要：Gas-containing coal is a two-phase dielectric composite material with porous characteristics and solid–gas coupling characteristics. In order to accurately simulate the physical and mechanical properties of gas-containing coal, based on similarity criteria and similarity scales of main control parameters, with more than 80 sets of material matching tests and mechanical parameter tests, a similar material for coal–gas two-phase medium was developed. The similarity between similar materials and raw coal was compared, and based on the new material, a three-dimensional simulation test of coal and gas outburst was performed. The main conclusions were as follows. 1) The elastoplastic parameters and adsorption parameters of new material prepared by pulverized coal and sodium humate aqueous solution as aggregate and binder is similar to raw coal. Similar materials with different elastic-plastic parameters can be prepared by adjusting the material ratio. The adsorption of similar materials is consistent with that of raw coal. 2) The expansion energy of the binary mixture of CO2 and N2 is between CO2 and N2. The proportional coefficient of expansion energy and CO2 volume fraction are quadratic functions. The expansion energy of the mixture with 45% CO2 volume fraction is consistent with that of CH4. The binary mixture of CO2 and N2 can be used as similar gas to CH4, and it is safer than CH4. 3) The new material is highly similar to the physical and mechanical parameters of raw coal containing gas, which realizes the simulation of gas–solid coupling characteristics. 4) A three-dimensional physical simulation experiment reproduces the phenomenon of outburst caused by uncovering coal, and the morphology of outburst holes and the quality of outburst pulverized coal that are close to the field are obtained, which verifies the rationality of similar materials, and also provides a scientific means for further study of the law of outburst and monitoring the precursor information of outburst.关键词：coal and gas outburst;similar materials;solid-gas coupling;three-dimensional similar simulation;ratio test- 785
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发布时间：2024-01-10 - 摘要：In order to study the interlaminar mechanical behavior of regenerated composite pipes with thin-walled lining, tangential and normal tensile failure tests are carried out on the composite pipes with corroded defects and thin-walled stainless steel lining. Based on the test results, a finite element analysis model is established for the repaired pipes with corroded defects. The test results of test specimen under the effect of tangential force show that with the increase of pipe steel corrosion extent with corrosion defects, bonding layer and the base pipe steel strip gradually decreases, the ultimate strength of the interface between the layers increase gradually, and with the increase of the corrosion loss rates, the interface cohesive force has a slight increase. But with the increase of proportion of binding material failure, this increased trend gradually flatten out. The tangential failure of interlayer interface is mainly due to the failure of cohesive force of binder. The test results under normal force show that the failure modes of each specimen are basically the same, and the failure is mainly the failure of cohesive force of the bonding layer. A bilinear constitutive model of tangential stress and relative displacement at interlayer interface of composite pipes is established by difference method. The relation between normal stress and relative displacement at interlayer interface can also be simplified to bilinear constitutive relation. The finite element analysis model is used to analyze the specimen, and the analysis results are in good agreement with the test results. The bilinear interfacial cohesive force model can accurately simulate the interlaminar mechanical properties of thin-walled composite pipes in the finite element model analysis. The research content and results can provide a theoretical basis for the trenchless continuous lining repair technology of buried pipeline.关键词：thin-walled lining;recycled composite pipe;interface mechanical properties;constitutive relation
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发布时间：2024-01-10 -
Study on Road Performance of Stabilized Silt with Sintering Red Mud-asphalt Powder Curing Agent AI导读
摘要：In order to solve the engineering application problems such as low cohesion and poor water stability of silt in the alluvial plain of the Yellow River, the sintering red mud and matrix asphalt were utilized as the main materials to prepare red mud-asphalt powder curing agent (RAC) for comprehensively stabilizing the silt. Setting the optimum dosage of cement as 5% and adding 0, 2%, 4%, 6%, 8% RAC to form stable silt specimens, the compressive strength and uniaxial compressive elastic modulus tests were conducted at 3 d, 7 d, 28 d ages after standard curing, immersion softening, cyclic heating, low-temperature freeze-thaw and high-temperature self-healing methods. The change rules of comprehensive road performance of stabilized silt with different dosage of RAC were compared and analyzed. The scanning electron microscope (SEM) was used to observe the microstructure and pore characteristics of silt, cement stabilized silt and RAC stabilized silt, and then the mechanism of solidification and stabilization was discussed. Combined with the practical application of entity engineering, the road performance of RAC stabilized silt was tested and verified. The results showed that RAC stabilized silt had good mechanical properties and water stability compared to cement alone, the strength of 2%, 4%, 6%, and 8% RAC stabilized silt increased by 110%, 146%, 156%, and 161%, respectively after standard curing of 3 d, and the loss rate of immersion strength at 28 d age is reduced from more than 50% to less than 20%. The strength of cement stabilized silt increased slightly after 5 cycles of heating, but the strength of RAC stabilized silt increases by more than 140% when the dosage was higher than 4%. After the low-temperature freeze-thaw tests, the cement stabilized silt specimen cracked and damaged, the RAC stabilized silt specimen was intact, and the loss rate of strength was less than 15%. The specimen was loaded to 90% ultimate load and heated for 5 times, the strength change rates of 2%, 4%, 6%, and 8% RAC stabilized silt were –8.3%, –2.3%, 8.0%, and 12.9%, respectively. The SEM images showed that RAC stabilized silt had dense cemented aggregates and non-connected microporous structure with uniformly distributed pore diameter less than 1 μm, which were beneficial to improve the water stability and frost resistance of stabilized silt. The asphalt components wet-bonded and wrapped with silt particles and hydration products under high temperature conditions, which accelerated the diffusion to fill the internal pores and micro cracks and realized damage repair and structural reinforcement of stabilized soil. In the entity project, the road base was filled with “4% RAC+5% cement” stabilized silt. After opening to traffic, the overall bearing capacity and service condition of the road were in good condition through field coring and FWD deflection tests. There were no cracks, pits, loose and other damages.关键词：road engineering;stabilized silt;contrast test;road performance;microstructure;sintering red mud–asphalt powder- 1110
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发布时间：2024-01-10 -
Field Test and Positioning Analysis of Reinforcement of Deep Water Submerged Dam by Thrown Stones AI导读
摘要：Submerged dam is a commonly used structure to control the reaches of a braided river, and it is generally located at the entrance of the inlet. The flows in these areas are often complex. It may cause downstream scouring after the completion of the submerged dam and the consequent uneven subsidence. Riprap reinforcement is an important measure of maintaining the function of the submerged dam. The conventional riprap reinforcement project is used in the bank protection. The traditional stone-throwing distance formulas are generally applied to shallow water and related to the water surface velocity, water depth, and the weight of the stones. There is not much study on the riprap reinforcement project in deep water area, and the research on the stone scattering is much less. In this paper, the authors make the first attempt to conduct-field tests for investigating the throwing distance and the enlargement coefficient, and for optimizing the comprehensive scattering coefficient. These field tests were performed at the entrance of the left branch of Hechang-bar, which is located at the lower reach of the Yangtze River, China. Based on the vertical distribution of velocity, the formula of the fall velocity of stone in deep water area, the formula of the throwing distance and the formula of the comprehensive discrete coefficient are derived. These formulas are verified by field data. The research extends the traditional throwing distance formula to the deep water area, and discusses the dispersion degree of throwing stones. The results can provide reference for submerged dam reinforcement works or other similar construction projects.关键词：submerged dam;field test;construction orientation;degree of dispersion- 1010
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发布时间：2024-01-10 - 摘要：The stress state of the cable is related to the safety of the cable system bridge, and the cable force value is an important index to measure the mechanical states of the cable. At present, the difficulty of determining the cable boundary conditions is an important factor affecting the accuracy of the cable force identification results. The ANSYS was used to numerically simulate the cable vibration, and the reliability of the modeling method was verified by the existing cable force calculation formula and the simulation data was generated. Then taken cable length, line density, bending stiffness, first-order frequency, second-order frequency, and third-order frequency as the input parameters, and used cable force as output parameter combined with vibration simulation data to establish BP neural network and generalized regression neural network cable force prediction model. Two neural network cable force prediction models and the existing cable force calculation formula were applied to actual projects for comparison and verification. The results showed that the neural network structure of the BP neural network cable force prediction model was 6–13–13–1, the activation functions between the input layer and the hidden layer 1, the hidden layer 1 and the hidden layer 2, the hidden layer 2 and the output layer were tansig, tansig, purelin, the training algorithm was the L–M optimization algorithm trainlm, the learning rate was 0.1, the number of network iterations was 1 000, the display interval was 100, the mean square error was 0.001, the prediction effect of the cable force prediction model was good, but there was room for further optimization. The best spread value of the generalized regression neural network cable force prediction model was 0.002 15, the prediction effect of the cable force prediction model was better than that of the BP neural network and the existing cable force calculation formula, and the forecast error was basically controlled within 5%. Utilizing the generalized regression neural network to predict the cable force of the bridge can avoid the influence of the judgment error of the cable boundary condition on the accuracy of the cable force recognition result, and improve the accuracy of the cable force recognition, which has a good engineering application value.关键词：cable force;vibration method;BP neural network;generalized regression neural network
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发布时间：2024-01-10 - 摘要：As an effective means for the exploitation of Hot Dry Rock (HDR) resources, the Enhanced Geothermal System (EGS) has broad development prospects and a great utilization value. Therefore, it is particularly important to predict its capacity and longevity. In order to realize the productivity and longevity prediction of the double-well EGS, the productivity and longevity prediction methods of the EGS system under different working conditions were analyzed through theoretical derivation and numerical simulation. Firstly, based on the Dupuit formula and the endothermic formula, the EGS productivity and longevity control equation was established to provide theoretical support for EGS longevity prediction. Then, according to the groundwater flow equation and the heat transfer equation, combined with the Newton’s cooling law, five factors affecting the four unknown parameters in the EGS productivity and longevity control equation were analyzed. The four unknown parameters were the reduction of thermal reserves, the amount of geothermal compensation, the average conversion temperature of production wells, and the shape coefficient of thermal reserves. The five factors obtained were the initial temperature of thermal storage, the injection temperature of thermal medium, the volume of thermal storage, the specific surface area of thermal storage, and the EGS running time. Under the condition of considering the geothermal compensation, the three parameters of EGS with double-well were used to analyze, correct and quantify the influence factors of each unknown parameter when the thermal storage breakthrough occurred, and then obtained the prediction formula of the four unknown parameters changing with the five factors. Based on the above results, a method for predicting the productivity and longevity of the double-well EGS was obtained: using the EGS productivity and life control equation, the prediction formula of four unknown parameters, and the thermal reserve permeability to predict the productivity and longevity of the double-well EGS. Finally, the prediction method of production capacity and longevity of the double-well EGS was used to predict the working conditions of the existing literature and compare them. The two results were in good agreement, which proved the applicability of the control equation and the prediction formula and the accuracy of the prediction method.关键词：Enhanced Geothermal System;Hot Dry Rock;flow–heat coupling;EGS capacity forecast;EGS longevity prediction
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发布时间：2024-01-10 - 摘要：Landslides often occur in steep mountain areas during heavy rainstorms. Establishing landslide prediction models is one of the essential strategies for disaster prevention in mountain areas. The kinematic subsurface-flow approximation and the infinite-slope instability analysis were used to develop a rainfall-induced shallow landslide prediction model. Firstly, the runoff hydrograph and the temporal variation of soil water storage were obtained by calculating the runoff yield and concentration of slope according to the theory of the kinematic subsurface-flow approximation. Then the temporal variation characteristics of saturated water level was studied. Finally, based on the theory of the infinite-slope instability analysis, and the analyzed slope stability the temporal variation of factor of safety was calculated. The Namasia District in Kaohsiung of Taiwan was chosen as a studied area to test the applicability of the model. It was found that the predicted location of landslide occurrence during Typhoon Morakot is consistent with those obtained from satellite images, and the values of the calibrated model parameters are consistent with physical meanings, which shows that the physically based model has good reliability. Moreover, the variation of the slope factor of safety was analyzed by applying double-peak design hyetographs with different rainfall peaks. The result showed that when the rainfall increases, the subsurface flow, and the saturated water level raise quickly to result in the decreasing of factor of safety value. On the contrary, while the rainfall decreases, the rate of subsurface outflow is higher than rainfall intensity, the saturated water level would drop slowly. Hence, the slope factor of safety is increasing and gradually returns to its natural state. Moreover, the influence of soil thickness on slope stability was further studied during the rainstorms. The results showed that factor of safety is reduced as the increasing of the soil thickness. It also reveals that if a low-peak rainfall occurs and followed by a high-peak rainfall, it would result in a higher possibility of landslides. It was expected that this study can give a clear physical explanation for the landslide occurrence and provide a useful tool for landslide prediction.关键词：landslide prediction;kinematic subsurface-flow approximation;rainfall-runoff simulation;infinite slope instability analysis;factor of safety
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发布时间：2024-01-10 - 摘要：Water pressure weakening effect of fractured rock in weak interlayer zone is an important direction of long-term stability research of hydraulic engineering. To study the long-term deformation characteristics of fractured rock in weak interlayer zone of Jinping Ⅰ arch dam under real water pressure, creep tests of pre-fractured marble under different water pressures were carried out on a specific rheological test system. According to the typical creep process curve, the influence of water pressure on the creep deformation, creep rate, creep failure load and long-term strength of fractured rock was analyzed, and the creep failure mechanism of rock was analyzed from the micro perspective basing on the creep failure surface scanning results of marble carried out by SEM. The results showed that with the increase of water pressure, the rock failure modes gradually transit from tensile to shear, and the failure surface tends to be smooth from concave convex serrated shape. The “wedging effect” of pressure water along the fracture accelerates the development of original cracks and promotes the creep development of rock. The larger the water pressure is, the more obvious the “wedging effect” is, the higher the accelerated creep rate is, the shorter the duration of acceleration stage is, the smaller the load grade of creep failure is, and the lower the long-term strength is. The effect of water pressure on the accelerated creep stage is greater than that of the stable creep stage. The increase of water pressure will reduce the long-term mechanical properties of rock and accelerate the creep failure of rock, the long-term strength of fractured rock accounts for 50%～70% of the peak strength of intact rock. It was suggested that the maximum first-order strength in stable creep stage should be taken as the long-term strength of fractured rock. The application of the research results can improve the accuracy of long-term stable operation evaluation of Jinping Ⅰ arch dam, and provide important support for the study of creep constitutive model of fractured rock, which has significant engineering application and theoretical research value.关键词：water pressure;marble;fractured rock;scanning electron microscope (SEM);stepped load;creep property;long-term strength
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发布时间：2024-01-10 - 摘要：The structural and morphological characterization of rock mass is of great significance to the excavation and construction of geotechnical and geological engineering. Digital panoramic borehole camera technology is an important means to obtain the structural morphology of rock mass quickly and effectively in the borehole. In view of the highlighted problems of the existing digital panoramic borehole camera system and its analysis software during the complex environment investigation, a method of fast mosaic and fusion of circular image from original borehole panoramic video was proposed. In this method, the borehole video image is transformed into several ordered narrowband images, and the image features are detected, matched, and filtered, so as to realize the rapid mosaic and fusion of panoramic borehole images. Results show that this method can quickly complete the continuous mosaic and fusion of panoramic video images without the help of a compass or electronic compass and depth encoder. The horizontal resolution, vertical resolution, and the image clarity of the mosaic image are raised by one magnitude. The actual working time can be halved. The process of forming the mosaic image can be intelligent processing and automated analysis. It can reduce the burden of researchers and improve work efficiency. This method can quickly and effectively form a high-quality borehole panoramic image without deviation based on the borehole video image’s inherent characteristics, which promotes the development of borehole camera technology and provides a more convenient and effective technical means for high-precision rock mass engineering investigation.关键词：digital borehole camera;image mosaic;feature detection;data fusion;hole-wall imaging
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发布时间：2024-01-10 - 摘要：Surface roughness of structures is a primary factor that affects the mechanical properties of soil-structure interface. To further study the effect of roughness on shear strength of interface, large-scale direct shear tests were performed on clay-concrete interface under different roughness conditions and the influence mechanism of roughness on peak shear strength of interface was revealed. The results showed that the shear stress-displacement curves of clay-concrete interface exhibited strain-softening under different roughness conditions, and the greater roughness, the more obvious peak point of curve. Increasing roughness could obviously increase the peak shear strength of interface and there existed a critical roughness in terms of its influence on peak shear strength of interface. Morphological characteristics of the shear failure plane of different rough interfaces indicated that the smooth interface mainly occurred shear slip failure during the shearing process, and the friction and occlusion between clay particles and concrete were strengthened with increasing roughness, which resulted in the internal shear failure of clay. The shear strength of interface can be approximately divided into two parts: the shear strength of smooth interface and the shear strength of soil in rough parts. A new peak shear strength model of interface considering roughness was established by introducing a roughness-related coefficient into Jewell’s model and proposing a function to describe the relationship between the coefficient and roughness. Finally, comparison results between calculated value and test value showed that maximum relative error was 11.01% and mean relative error was 4.74%, which verified the accuracy and rationality of the proposed model.关键词：interface;large direct shear test;roughness;peak shear strength
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发布时间：2024-01-10 - 摘要：When Levy type rigid bracing dome is impacted by unexpected load, its structure may collapse continuously, resulting in property loss and casualties, therefore, it is necessary to analyze its progressive collapse performance. According to characteristics of rigid bracing dome, the threshold coefficients of members and its calculation formula were given, and the discriminant criteria and types of progressive collapse were proposed. Damage coefficient based on response difference was proposed, and importance coefficient of members was given. Member importance of levy type rigid bracing dome were analyzed and sorted based on importance coefficient of members. Based on the discriminant criteria of progressive collapse and the results of importance analysis of members, the method and process of progressive collapse analysis were proposed. Progressive collapse performance of structure was analyzed. The influence of both rise span ratio and initial prestress on the progressive collapse performance was discussed. The method of progressive collapse resistance against rigid bracing dome was proposed. The research showed that the progressive collapse types of levy type rigid bracing dome could be divided into non collapse, local collapse and overall collapse. The outer ring bar obtains the largest importance coefficient, followed by the inner ring bar. The smaller rise span ratio is or the larger the initial prestress, the smaller importance of the member will be. When the outer ring member, inner ring member or node is damaged, the structure will collapse continuously, while other members will not collapse. Strengthening the joints and ring members can improve resistance of structure against progressive collapse.关键词：rigid bracing dome;collapse analysis;discriminant criterions;measures against continuous collapse
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发布时间：2024-01-10 - 摘要：The key to the evaluation of freeze-thaw performance of lightweight aggregate concrete after disaster lies in the accurate quantitative description and prediction of its freeze-thaw performance under the specific disaster degree. The initial stress damage of lightweight aggregate concrete was applied by repeated loading to simulate the disaster, and the relative dynamic elastic modulus was taken as the evaluation index to study the freezing-thawing performance of lightweight aggregate concrete with the initial damage degree of 0, 0.05, 0.12, 0.19 and 0.27, respectively. The grey system theory was introduced into concrete frost resistance durability study, the relative dynamic elastic modulus measured data was used to build prediction model of freeze-thaw resistance of stress-damaged lightweight aggregate concrete based on GM(1,1), and corresponding comparation with the revised Loland concrete damage model and accuracy analysis was performed; The GM(1,1) prediction model was used to evaluate the effect of initial stress damage on the frost resistance durability of lightweight aggregate concrete and predict its frost resistance life. The results showed that the initial stress damage could accelerate the freeze-thaw performance degradation of lightweight aggregate concrete, and the higher the initial stress damage degree was, the faster the deterioration rate would be. The average relative error of GM(1,1) model was less than 4.5% under each initial damage degree, and the prediction accuracy of GM(1,1) model was generally higher than that of the revised Loland model. Lightweight aggregate concrete had a good freezing-thawing resistance, and its freezing-thawing resistance life could reach 45 years in central and western Inner Mongolia. When the initial damage degree was 0.05, 0.12, 0.19 and 0.27, the freezing-thawing resistance life was shortened to 30 years, 25 years, 17.5 years and 10 years, respectively. The prediction model of freeze-thaw performance of stress-damaged lightweight aggregate concrete based on GM(1,1) could accurately evaluate the whole process of freeze-thaw performance of the damaged lightweight aggregate concrete after disaster, which provided theoretical basis for guiding the engineering practice of lightweight aggregate concrete in cold and dry regions of north China.关键词：stress damage;lightweight aggregate concrete;freeze-thaw resistance;gray system theory;GM(1,1)
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发布时间：2024-01-10 - 摘要：The strength and deformation characteristics of rockfill materials were influenced by particle breakage. However, most of the studies on particle breakage were under static loading conditions. To investigate the effect of particle crushing on the dynamic characteristics of rockfill materials under small strain conditions, the discrete element method was selected to simulate the dynamic response of granite rockfill materials under different confining pressures. The hexagonal closed packing with different random combinations was used to simulate irregular particle shape. The fragment replacement method was selected to simulate particle crushing. The influence of porosity on dynamic elastic modulus was studied, and the particle breakage law and the frequency distribution of coordination number during cyclic loading were analyzed. The simulation results were in good agreement with laboratory test results. This indicated that the numerical model could reproduce the dynamic deformation characteristics of rockfill materials under different confining pressures. Particle breakage increased the dynamic strain and decreased dynamic elastic modulus under the same confining pressure and dynamic stress. During cyclic loading, the effective coordination number decreased slowly. The sample with particle breakage produced more mechanically unstable particles, and the decrease of effective coordination number was more significant when compared with the sample without particle crushing. Particle crushing accelerated the decay rate of the dynamic elastic modulus with the increase of dynamic strain. The sample with lower porosity had higher effective coordination number and better mechanical property. Under the same stress condition, the sample with lower porosity had larger maximum dynamic elastic modulus and went through less particle breakage. The dynamic elastic modulus decayed slowly with the dynamic strain increasing. The maximum dynamic elastic modulus for the sample with lower porosity was about 1.2 times of that for the sample with larger porosity. The maximum dynamic elastic modulus was mainly related to the effective average principal stress and porosity. The empirical formula proposed by Hardin could be used to describe the relationship between the maximum dynamic elastic modulus, void ratio and average effective principal stress. The results were helpful to understand the deformation law of coarse granular materials and provided reference for the simulation of particle crushing behavior under cyclic loading.关键词：discrete element method;dynamic elastic modulus;particle breakage;porosity
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发布时间：2024-01-10
HYDRAULIC & CIVIL ENGINEERING
- 摘要：In order to solve the problem of low computational efficiency of adaptive beamforming algorithms in ultrasonic imaging, an adaptive beamforming algorithm for ultrasonic array with the combination of spatial sampling and coherence factor was proposed. The maximum decimation factor with different numbers of array elements was deduced according to the beam pattern. The sparse echo data was obtained by spatially sampling the whole array element data using the maximum decimation factor. Therefore, the amount of data used for beamforming was greatly reduced. Taking the spatial sampling data as the input of a beamformer and constructing the covariance matrix as Toeplitz matrix, the adaptive weights of the sampling data were obtained according to the principle of minimum variance. Then, the adaptive weights were modified by introducing the coherence factor to highlight the effective information of the sampling data. Under the case of unequal data and spatial sampling data, the proposed algorithm, minimum variance algorithm and minimum variance algorithm combined with coherence factor were used to simulate the imaging of cracks and cross-drilled holes respectively. The results show that: for unequal data, the imaging quality of the proposed algorithm is between the other two algorithms; in terms of imaging time, compared with the other two algorithms, the average imaging time of the proposed algorithm is reduced by more than 85%. For the same spatial sampling data, the imaging quality of the proposed method is better than the other algorithms; in terms of imaging time, compared with the other two algorithms, the average imaging time of the proposed algorithm is reduced by more than 65%.关键词：beamforming algorithm;spatial sampling;coherence factor;computational complexity
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发布时间：2024-01-10
INFORMATION ENGINEERING
- 摘要：Aiming at the problem of uniform magnetization of steel wire rope in service due to vibration, a radial permanent magnetic ring combined excitation structure was proposed. Firstly, according to Biot Savart law, the magnetic field distribution of permanent magnet ring was modeled. Then, the key parameters affecting the magnetic field distribution of the excitation structure and the influence law on the magnetic field distribution were analyzed theoretically, which provided a theoretical foundation for setting the parameters of the excitation structure. Finally, the uniform magnetization effect of the steel wire rope under normal and vibration operation was simulated and analyzed by using the optimized axial permanent magnet ring combination and radial permanent magnet ring combination excitation structures. The results showed that the magnetization effect of the radial permanent magnet ring combination excitation structure proposed is better than that of the axial permanent magnet ring combination excitation structure with the same volume, and it is easier to install and replace the sensor and magnetic concentrator. The magnetizer is simplified, and the influence of vibration disturbance on the uniform magnetization of wire rope is small. This study lays a good foundation for the quantitative evaluation of mine hoisting wire rope damage in service, and it is of great significance to effectively prevent the occurrence of lifting wire rope fracture accidents.关键词：hoisting wire rope;permanent magnetic ring;excitation;uniform magnetization;vibration
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发布时间：2024-01-10 - 摘要：Progressive cavity pumps (PCP), which uses the ordinary nitrile rubber, are widely used in heavy oil production, and it is prone to failure of the core-burning perforation of the stator bushing. The expensive hydrogenated nitrile rubber is resistant to high temperatures but does not have precise use depth and cross-sectional parameters. In order to solve above problems, first of all, the rubber hyperplastic constitutive model of ordinary nitrile rubber and hydrogenated nitrile rubber is fitted based on the thermal aging and tensile tests. And then, a new finite element model is established based on the one-way decoupling method to decompose the delayed heat generation phenomenon. Finally, the influences of working well depth, interference, and wall thickness on the lagging heat generation are studied, and the orthogonal table of the three factors is listed. The research results show that ordinary nitrile rubber is better than hydrogenated nitrile in working temperature below 70 ℃ (corresponding to the working depth of 1 667 m), but it will suffer serious aging in the deep working temperature or the high temperature environment, which is the main reason for core burn and perforation failure in current applications. Hydrogenated nitrile rubber begins to age at a working temperature of 150 ℃ (corresponding to the working depth of 4 333 m), which is more stable than ordinary nitrile in mechanical properties, so it is reliable. Due to liquid column pressure and rubber aging, the maximum stress between the bushing and the rotor is decreases first and then increases with the increase of working depth. With the increase of the interference, the sealing performance of the PCP improves, and the maximum temperature of the sleeve section increases exponentially. For every 2 mm increase in the thickness of the rubber bushing, the true displacement of the inner wall increases by 0.059～0.067 mm on average, corresponding to the growth rate of 19%～28%. It is concluded that the working depth of 1 667 m is the boundary between the two types of rubber PCP. The interference is the minimum value of 0.5 mm, and the maximum wall thickness is 12 mm under the condition of no leakage. The research results provide theoretical support for reasonably matching the parameters of the stator rubber bushing, which optimizing the stator rubber material, and improving the working performance of the PCP throughout the life cycle.关键词：unidirectional decoupling;constant wall thickness progressive cavity pumps;hydrogenated nitrile;oil recovery technology
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发布时间：2024-01-10 - 摘要：The traditional milling stability prediction approaches has mainly focused on the fixed cutting conditions where the radial cutting widths are constant. The derived outputs are then not appropriate for choosing the chatter free milling parameters on varying cutting conditions where the radial cutting widths are changeable versus time. In this paper, according to the mechanisms of regenerative chatter, a two degrees of freedom milling dynamic model is established by considering both process damping and asymmetric dynamic behaviors of tool center point, where the instantaneous engaging and exit angles caused by the time-varying radial cutting width is also introduced. Time-domain full discrete method is adopted to determine the stabilities of the milling dynamic model within the three dimensional space created by taking account of varying cutting conditions including rotary velocities, axial cutting depths, and radial cutting widths. Following the 3D stability lobe surface being plotted, the entire 3D milling stability prediction methodology can be finally organized. A vertical machining center is selected as the experimental platform on which the milling tests are performed on varying cutting conditions. According to the comparisons between calculated and measured results, the proposed methodology is verified to be capable of predicting the limit stable milling parameters accurately on varying cutting conditions, where the maximum relative error is found 5.9%. It is then beneficial to realize the maximum metal removal rate by optimizing the milling parameters subjecting to the predicted stability.关键词：varying cutting conditions;milling chatter;3D stability;prediction methodology
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发布时间：2024-01-10
MECHANICAL ENGINEERING
- 摘要：In order to improve the denitration performance of La–Mn perovskite catalyst, a series of Ce modified perovskite La–Mn composite oxide catalysts were synthesized by citric acid sol-gel method. The structure, morphology, composition and surface physicochemical properties of the catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), N2 adsorption-desorption (BET) and temperature programmed technology (H2–TPR/NH3–TPD).The results of the activity test showed that the denitration performance of Ce modified perovskite type La–Mn composite oxide catalysts are improved. When the Ce/Mn molar ratio is 0.2, the catalyst has the best denitration activity. The NOx conversion rate could reach 90% at 135 ℃, and maintaining more than 90% NOx conversion in the temperature window range of 135～260℃. XRD results showed that the perovskite type La-Mn composite oxide modified by Ce has porous structure and could maintain the perovskite structure of LaMnO3.15. However, Ce ions do not completely enter the perovskite structure, and some of them cover the catalyst surface in the form of oxides. At the same time, part of Mn ions in the lattice overflow from the perovskite structure in the form of Mn3O4, thus maintaining the structural stability and charge balance. SEM and BET results showed that the specific surface area of the catalyst increases and more active sites are provided after the introduction of Ce, which promotes the denitration reaction. XPS results showed that Ce modified catalyst produces more Mn4+ and chemically adsorbed oxygen, which promotes the oxidation of NO. The results of temperature programmed technology showed that the catalyst modified by Ce has better redox performance and more acidic sites, which is conducive to the denitration reaction. Therefore, Ce modified La–Mn composite oxide could improve the denitration performance by promoting NO oxidation and NH3 adsorption.关键词：Ce modification;La–Mn perovskite catalyst;denitration
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发布时间：2024-01-10 - 摘要：Red mud is a solid waste produced in alumina smelting process and was an important secondary mineral resource, which is rich in rare metals such as Y. Selective leaching of Y from red mud by acetic acid was used to solve the problem of collective dissolution of impurity elements in the process of yttrium extraction from red mud. The effects of acetic acid concentration, liquid to solid ratio, leaching temperature and leaching time on the leaching efficiency of Y were investigated. The solvent extraction was applied to separate Y from the acid leaching solution. The effects of P507 concentration, pH value, extraction time and O/A on the extraction efficiency of Y were studied. Furthermore, XRD, SEM–EDS and thermodynamic theory of leaching and extraction were used to analyze the selective process of leaching and solvent extraction. The results showed that the leaching efficiency of Y, Al and Fe was 83%, 54% and 5%, respectively under the conditions of acetic acid solution pH value of 0.1, liquid to solid ratio of 10 mL/g, leaching temperature of 50 ℃ and leaching time of 1 h, while the Na, K and Ca in red mud were almost dissolved into the solution. Acetic acid could selectively destroy the crystal structure of cancrinite containing Na, K, Ca, Al and Si. The Gibbs free energy change of each metal oxide was less than 0, and the dissolution order was Na2O > K 2O > CaO > Y 2O3 > Al 2O3 > Fe 2O3. The extraction efficiency of Y was more than 99%, and the extraction efficiency of Al and Fe was less than 10% under the condition of P507 concentration of 5%, pH value of 0.5, extraction time of 6 min and O/A of 1∶5, while the extraction efficiency of Na, K and Ca was close to 0. According to the analysis of the McCable–Thiele diagram of Y extraction, Y was further separated from impurities such as Al, Fe, Ca, Na and K by three-stage counter current extraction with P507. The stripping efficiency of Y was close to 100% and the stripping efficiency of Fe was only 29% under the conditions of sulfuric acid concentration of 8% and stripping time of 7 min, and the separation of yttrium and iron was achieved.关键词：yttrium;acetic acid;leaching;solvent extraction;red mud
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发布时间：2024-01-10
CHEMICAL ENGINEERING & MATERIAL ENGINEERING
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