最新刊期
卷 50 ， 期 3 ， 2018
- 摘要：Big natural disasters worldwide are deeply affecting survival and development of humankind. How to effectively deal with various types of natural disasters is particularly important. After the 2008 Wenchuan earthquake, public awareness about disasters in China has increased considerably and people’s understanding of disasters has been greatly improved. That " People on the Earth must have disaster awareness and disaster education” has already become the common sense. Owing to its particular regional geological structure, topographic conditions, hydro-meteorology and other factors, the Western China is a region with frequent water-related disasters. Prevention of and reduction in water disasters have been important for overall development of the region and the country. As a high-level research national university in West China, building on the wisdom of water management of the historical Dujiangyan project, Sichuan University has made many innovations. Through engineering and research projects, such as flood discharge and flood control of high dams, structural safety of high dam projects, prevention of mountain torrents,sediment disasters,and landslides, and ecological environmental protection in river basins, Sichuan University has made a series of important achievements. They include: 1) development of meso-scale experiments and simulation techniques to reveal the meso-mechanism of complex water flow phenomena of high dam hydraulics, to establish more reliable criteria and calculation methods, to form a systematic meso-mechanical system, and to innovatively propose multi-level flood discharge mechanism and techniques; 2) new technology of geomechanical model destruction simulation and comprehensive test, which can reveal the overall structural safety response mechanism of high dam engineering, and establishment of a high dam-foundation-reservoir safety evaluation system capable of accurately reflecting the influence of complex geological environments and excessive floods; 3) revealing the " little water with big disaster” mechanism under joint action of mountain floods and sedimentation, and development of the " reduction of scale control and prevention” technology for extreme flood and sediment disasters that can make the uncertainty of the disasters caused by floods and sediments to a preventable scale; 4) introduction of new equipment and technologies such as the three-dimensional laser scanners for landslide deformation monitoring and expansion from " points, lines, and surfaces” to three-dimensional space as a whole, which improves the level of disaster monitoring and early warning of water-powered landslides and disaster emergency response capabilities; 5) a categorized emergency and comprehensive treatment technology for landslide-barrier lakes suitable to various material composition and structural characteristics of landslides and dams; 6) a complete set of methods for ecological water requirement allocation and prediction of water temperature for fish and cascade reservoirs, low-temperature water control, and prediction and regulation of over-saturated total dissolved gas of high dams aiming at characteristics of geography, ecology and environment in southwest region, which has expanded research on ecological and environmental protection from the local engineering and single water environment areas to the overall system of mountain river basins and formed an integrated scientific and technological system that intersects multiple disciplines. At last, aiming at characteristics of water disasters in mountainous rivers in Western China and the general needs for national disaster prevention, mitigation and relief, this paper proposes a series of scientific and technological questions for future research, which will facilitate development of research work in related disciplines for disaster prevention and reduction in the future. The issues include impacts of global climate change on water disasters, coupled disaster environments and regional evolution laws, dynamic processes and catastrophes of water disasters, habitat-biological interaction mechanisms of mutant rivers, ecological evolution mechanism of catastrophic rivers, water disaster risk theory, water disaster monitoring and early warning, collaborative management of water and disaster basins, basic large databases and cloud platforms, and others.关键词：mountain rivers;water disasters;ecological environment protection in river basins;flood discharge and control safety;structural safety of high dam projects;mountain floods and sediment disasters;disaster prevention and mitigation
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发布时间：2024-01-10 - 摘要：Disaster reduction and proper pre-disaster preparedness are an important issue in sustainable development and in achieving the sustainable development goals.Despite frequent natural disasters and huge losses in China,few studies are available on the frequency and affected areas of past disasters.Information of dating,magnitude and scope of past landslides,debris/mud flows,rockfalls,rush floods and earthquakes is critical to understand disaster frequency and to predict future risk of disasters,and is essential to make practical planning of pre-disaster preparedness and disaster reduction.But such information is usually not readily available.Dendrochronology has unique advantages in providing needed information.Growth of trees depends on environmental factors of light,temperature,moisture,soil nutrients and other plants.Changes in a factor can affect tree growth that can usually be easily observed in tree rings.Tree rings record changes in both tree growth rate and environmental conditions.There is a high correlation between tree growth rate changes and environmental changes.With increasing climate change impacts and ever intensifying human activities on the nature,there has been an increase trend in frequency,magnitude,severity and losses of natural disasters.Disasters can directly damage,wound or even kill trees.Disasters can also cause trees to tilt and bend,or affect tree growth rate through eliminating trees or damage to trees.Trees respond to these impacts by changes in tree ring width,or formation of reaction wood,as trees use the available resources to maintain its survival and to make new tissues to replace the damaged ones.In the study of response process and mechanism of trees to natural disasters,a series of research methods/methodologies have been developed in dendrochronology.The study of tree rings can reveal the history and characteristics of past natural disasters.It has great advantages in studying the time and influence of such disasters as earthquake,debris flow,landslides,rush floods,rockfalls in mountains.Recent studies of application of dendrochronology in these disasters are reviewed.New areas of future research interests are proposed.关键词：natural hazards;trees;tree rings;disaster history;disaster frequency
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发布时间：2024-01-10 - 摘要：Existing dam risk analysis methods are suitable largely for a single reservoir/dam and the influence of uncertainty on risk assessment result is not taken into consideration.To overcome these limitations,the Bayesian network theory which can effectively deal with the uncertainty problem was adopted to study the risk of dam failure in a cascade reservoir group.In combination of statistics data and experts' experiences,extreme flood,upstream dam-break flood and strong earthquake were identified as the key risk factors of dam overtopping. Bayesian risk analysis network models of dam overtopping for a single reservoir and successive dam breaking for two cascade reservoirs under single or compound effects of extreme flood,earthquake and upstream dam-break flood were established and used to analyze dam overtopping risk of Houziyan and Changheba,two successive cascade reservoirs in the Dadu river basin,southwestern China.Results show that the overtopping risk magnitudes of cascaded reservoirs under single and compound effects of risk sources are relatively low,and the magnitude of overtopping risk caused by upstream dam-break flood of Houziyan is the least,which is correlated with characteristics of the upstream Shuangjiangkou reservoir,a control cascade in the basin. Both Houziyan and Changheba reservoirs are identified as weak cascades,and their main leading risk factors are excessive flood and strong earthquake,which can serve as an important support for formulating systemic risk prevention and control measures. Validity and practicability of the proposed model were verified through the case study.The solving process was fast and effective,and the identification of the risk factors correlation and the weak cascade reservoir was intuitive and clear. Using model analyses,risk change of cascade reservoirs under single and compound effects of risk sources can be obtained in time and corresponding risk decisions can be made,which is beneficial to rapid development of follow-up risk management and provides a new research way for risk analysis research in hydraulic and hydropower engineering.关键词：risk analysis;Bayesian network;cascade reservoirs;dam overtopping;flood;earthquake
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发布时间：2024-01-10 - 摘要：In order to reveal the relationship between failure modes and slope structures, the field investigation aftershock in Wenchuan area was conducted, especially for the dynamic instability of steep slopes. This study takes two typical slope failure sites, namely, Dazhuping landslide at Gaochuan county and Ganmofang landslide at an county in Sichuan province as the example, by considering the landslide related engineering geological condition and dynamic deformation characteristic, a three-dimensional discrete element numerical simulation on instability mechanism of the two slopes was conducted. The results showed that the mode of hard rock steep bedding slope destruction was a slippage type, while the failure of interbedded steep bedding slope was by a sliding bending. Under the same earthquake, PGA amplification coefficient and the slope height was positively correlated, and PGA amplification coefficient turned a first increasing and then decreasing phenomenon with the increase of elevation. The PGA amplification coefficient of steep bedding hard rock slope was smaller than that of steep bedding interbed slopes. While the amplification coefficient in hard rock slope PGA ranges from 2 to 3, the maximum was in 3/4 of slope surface. The PGA amplification coefficient of interbedded slope ranges from 2.5 to 4.0, with the maximum value located at the top of the slope. In addition, the damage mechanism of hard rock bedding slope could be divided into four stages: the first stage was a slip partly through the locking section; the second stage was shock relaxation; the third stage was the ejection phase; and the fourth stage was a overall instability. For the interbed slope, the first stage was a layer dislocation, the second stage was local lower ejection, the third stage was a continuous crack spreading in the high location, and the fourth stage was a bottom bending failure. The research results can provide technical support for the instability evaluation and mechanism analysis of high steep bedding rock slope in Southwest China.关键词：Wenchuan earthquake;high steep bedding hard rock slope;three-dimensional discrete element;dynamic response;instability mechanism
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发布时间：2024-01-10 - 摘要：Shaking table test is a direct and effective means of seismic response simulation and seismic performance observation of engineering structures,but because the electro-hydraulic servo shaking table system is complex nonlinear system,the performance of shaking table system is apparently affected by the servo valve when the 90° phase-shift frequency of the servo valve is near to the oil-column resonance frequency of shaking table system,so that the effective frequency band of shaking table system is severely affected.The effective frequency band of existing electro-hydraulic servo shaking table is generally from 0.4 Hz to 50 Hz,which is not enough to satisfy the demand of the seismic test of large reduced scale structure.In order to decrease the adverse effect of the servo valve of existing electro-hydraulic servo shaking table system on the system performance,and to broaden the effective frequency band of existing shaking table system,a new control algorithm was proposed by introducing the jerk feedback and jerk feed-forward into the controlling unit on the basis of the three-variable control algorithm.The control effect of the proposed control algorithm was deduced theoretically and analyzed by the system simulation.It was revealed that the oil-column resonance frequency was reduced by the jerk feedback so that the influence of servo valve characteristics on the system performance was decreased,and the effective frequency band of shaking table system was widen from 0.35～54 Hz for the three-variable control algorithm to 0.35～64 Hz for the jerk feed-forward control algorithm,and it was proved that the control performance of the shaking table system was obviously improved by the proposed control algorithm.关键词：seismic simulation test;shaking table;three-variable control;jerk;effective frequency band
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发布时间：2024-01-10 - 摘要：Self-centering reinforced concrete frame is a new type of earthquake resilient structure.Comparing to conventional RC structures,self-centering structure is known for its minimal damage under earthquakes and little residual deformation after earthquakes.Considering the fact that there is none or very little repair needed to restore its functionality after rare earthquakes,self-centering RC frame system is a low cost seismic structure that is very suitable for low-rise frame buildings in high seismic zones.In self-centering structure,beams and columns are connected by clamping force provided by unbonded post-tensioning tendon.By this means,when subjected to severe earthquakes,the gaps at self-centering joints are allowed to open and the columns are allowed to uplift at the base.The opening and uplifting behavior significantly mitigates the damage.After unloading all the gaps between components will close under clamping force,and thus the components restore their original position with negligible residual deformation.The existing researches on self-centering joints were summarized,and the key configuration of self-centering joint was illustrated.Based on this research,a tri-axial self-centering RC frame was proposed.In order to investigate the deformation capacity and mechanical characteristics of the tri-axial self-centering RC frame,a 1∶2.5 scaled model frame was designed and tested under quasi-static load.The configuration of the test model and main test results,including deformation pattern,hysteretic curve,skeleton curve,stiffness degradation and residual deformation were otained.The experimental results showed that:the test model has excellent deformation capacity,and no damage is observed expect some minor cracks under 1/38 roof drift ratio.The damage gradually develops in beam end joint area when the structural deformation continues to increase.Until 1/19 roof drift ratio,base shear is still increasing which implies that there is still reserved capacity in the structure.The residual deformation of the model is minimal,and the residual interstory drift ratio is still permissible after the final cycle of the loading process.关键词：self-centering;reinforce concrete frame;quasi-static test;seismic performance
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发布时间：2024-01-10 - 摘要：A reliability-based optimization design framework for mass uncertain nonconventional multiple tuned mass damper (MTMD) systems was proposed. The structure was modelled as a hybrid-model with multiple tuned mass dampers simplified as lumped masses. Seismic excitation was modelled by the Kanai-Tajimi filtered white noise. State-space representation was adopted to enhance the simulation efficiency. Attenuation relationship and truncated Gutenberg-Richter relationship were used for hazard condition definition. Multiple parameters associated with hazards, the main structure, and multiple tuned mass dampers were considered to be random. The objective function was defined following the unconditional failure probability with multiple limit state bounds, incorporating both structural and excitation uncertainties. A case study based on a thermal power plant with multiple scuttles was carried out to illustrate the framework. The Latin Hypercube Sampling (LHS) method was implemented to reduce the sample size. Drifts of corner columns were considered as structural responses and code limits were set to assess structural failures. By using genetic algorithm, an optimum design was obtained. A parametric study was further performed to study the influence of isolation system type and seismic gap, along with which the pendulum system and collision problem were investigated. It is found that scuttle isolation via the pendulum system is not a better design as expected since the failure probability is not sensitive to the variance of pendulum curvature. By considering scuttle collision as additional factor, the failure probability with the inclusion of this constraint was obtained. The proposed design method is based on structural reliability, which is capable of considering multi-dimensional outputs and corresponding response limits and integrating multiple structural responses into one failure probability.关键词：nonconventional tuned mass damper;mass uncertainty;thermal power plant seismic mitigation;reliability;optimization deisgn
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发布时间：2024-01-10 -
Emergency Treatment and Optimization Technology of Discharge Chute Design for Landslide-dammed Lake AI导读
摘要：Emergency treatments for landslide-dammed lake should be treated in accordance with the principle of " scientifically,safety,proactively and rapidly”.Fast and effective measures should discharge dammed water and lower water level and consider the topography and geologic environment of specific landslide dam conditions.Conventional treatment measures include discharge chute excavation,discharge tunnel excavation,blasting demolition,temporary reinforcement and non-engineering emergency measures.Appropriate measures should be selected considering dam height,storage capacity,material composition and hazard grade of landslide dams.Among these measures,the discharge chute excavation measure owns advantages involving strong feasibility,applicability and practicability.Determing the best position of water intake,defining the centerline and the cross section of discharge chute are the three major topics in the field of discharge chute excavation during the emergency treatment.Based on a highly accuracy DEM model of the landslide dam acquired by terrestrial laser scanners,a new optimization technology of discharge chute design method was proposed,which agree well with the general features of water flows among the landslide dam.This technology simulates water flows on landslide DEM model and finds the best discharging path via using D8 algorithm; During the emergency treatment,this method is performed by optimizing the results,defining the centerline and cross section of the discharge chute,and final determining the design scheme as well as rechecking the discharge capacity.Final,an example in the discharge chute design for the Hongshiyan landslide-dammed lake was analyzed and the results demonstrate that the proposed method is reasonable and feasible.关键词：landslide-dammed lake;emergency treatment;terrestrial laser scanners;optimization technology of discharge chute design;D8 algorithm- 3802
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发布时间：2024-01-10 - 摘要：The historical earthquakes in Chuanjiang catchment were one of main dynamic factors which affect the local sediment yield and fluvial processes. The Wenchuan earthquake is the largest earthquake in the recorded history of the Longmenshan fault. Through historical data collection, field study and theoretical analysis, the effects of various natural factors and human activities on the fluvial processes of the piedmont rivers in Longmen Mountains are explored, and the evolution rules of piedmont rivers damaged by strong earthquakes are revealed, and the piedmont river evolution model and its prediction under the changing environment are proposed. The results show that: after the earthquake, different levels of evolutions of piedmont rivers have taken place in the Longmen Mountains, especially in the Shiting River, with the maximum downcutting depth of 27.0 m at the 105 Provincial Highway after the flood season of 2015; there are many factors affecting the dramatic evolution of piedmont rivers in Longmen Mountains after the earthquake and those factors are mixed and interacted with each other. While " water and sediment supply mutation and dissonance slope” are the main internal causes, " engineering barriers and disorder sand mining” are the main external causes. The piedmont river evolution model and its prediction established by the " hydraulic geometry based on the river critical initiation hypothesis” have good applicability and can be used as reference for analyzing the similar strong earthquake-damaged piedmont rivers.关键词：Wenchuan earthquake;piedmont rivers;processes pattern;runoff-sediment condition;dissonance slope
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发布时间：2024-01-10 - 摘要：Recent earthquakes in the Sichuan Province have contributed to significantly expand the existing ground-motion database for China with new, high-quality ground-motion records. This study investigated the compatibility of ground-motion prediction equations (GMPEs) established by the NGA-West2 project in the US and local GMPEs for China, with respect to magnitude scaling, distance scaling, and site scaling implied by recent Chinese strong-motion data. The NGA-West2 GMPEs for shallow crustal earthquakes in tectonically active regions are considerably more sophisticated than widely used previous models, particularly in China. Using a mixed-effects procedure, the study evaluated event terms (inter-event residuals) and intra-event residuals of Chinese data relative to the NGA-West2 GMPEs. Distance scaling was investigated by examining trends of intra-event residuals with source-to-site distance. Scaling with respect to site conditions was investigated by examining trends of intra-event residuals with soil type. The study also investigated other engineering characteristics of Chinese strong ground motions. In particular, the records were analyzed for evidence of pulse-like forward-directivity effects. The elastic median response spectra of the selected stations were compared to code-mandated design spectra for various mean return periods. Results showed that international and local GMPEs can be applied for seismic hazard analysis in Sichuan with minor modification of the regression coefficients related to the source-to-site distance and soil scaling. Specifically, the Chinese data attenuated faster than implied by the considered GMPEs and the differences were statistically significant in some cases. Near-source, pulse-like ground motions were identified at two recording stations for the 2008 Wenchuan earthquake, possibly implying rupture directivity. The median recorded spectra were consistent with the code-based spectra in terms of amplitude and shape. The new ground-motion data can be used to develop advanced ground-motion models for China and worldwide and, ultimately, for advancing probabilistic seismic hazard assessment (PSHA).关键词：ground motion prediction equations;NGA-West2 project;code-based spectrum;pulse-like ground motions
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发布时间：2024-01-10 - 摘要：Shaking table tests of a 1.5 MW wind turbine model were performed to investigate seismic responses of the wind turbine under ground motions with different spectral characteristics.The wind turbine tower model was carefully designed to satisfy the frequency and mode similarity relations.Blades and infinitely variable motor were installed at the top of wind turbine model to simulate the wind turbine operating conditions.Two suites of ground motions,including long period ground motions and general ground motions with different site soil characteristic periods,along with three classical ground motions,were selected to match the design response spectrum in Chinese standard.Besides,two artificial waves were generated using the trigonometric series superposition method.All ground motions were inputted in three different directions.Acceleration and displacement responses both at the tower top and along the tower,and strain responses at the tower bottom were measured and compared.The test results showed that the wind turbine responses of principle direction and secondary direction have distinct coupling effects and high mode effects.Wind turbine seismic behaviors were quite different under ground motions with different frequency contents.Long period ground motions can lead to amplification of wind turbine acceleration and displacement responses.Besides,different directions of ground motion inputs induced different structural responses.The ground motions with the direction perpendicular to the wind turbine blade plane or with an angle of 45° can lead to amplification of wind turbine responses.关键词：wind turbine;earthquake;shaking table test;ground motion characteristics;response characteristics
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发布时间：2024-01-10 - 摘要：An innovative high-performance low-cost isolator was presented for seismic isolation in economic underdeveloped regions. When this proposed isolator is applied to replace steel sheets with engineering plastic plates within a traditional isolator, the methods of flexible-reinforcement isolators must be used to calculate its mechanical properties . The analytical solutions for this type of isolators are complicated and not easy for engineering application, therefore a simplified method was put forward for computing the simplified solutions for analytical strength, stiffness and stress of the isolator under compression and bending, in which the weighted residual method was employed based on optimal selection of trial functions and the undetermined coefficients of the trial functions were determined by accuracy requirement. Therefore, the simplified formulas of stress distribution, compression stiffness, bending stiffness and strength were formulated and obtained herein. And a characteristic parameter was introduced to analyze the variation of these formulas. Parameter analysis showed that the error of the proposed formulas increases with the increase of the aspect ratio and the characteristic parameter. Subsequently, the valid application scope of these simplified formulas is given. Finally, systematic experimental tests of four different groups of the presented isolators were carried out. Test results showed that, for typical high-performance low-cost isolators, the deviation of the proposed formulas is close to that of the analytical formulas, which verifies the effectiveness of the simplified formulas and the rationality of the proposed method. The proposed method can be extended to isolators in any other shape and of different reinforcing materials, which is propitious for the popularization and application of high-performance low-cost isolation technology in less developed areas.关键词：seismic isolation;isolator;mechanical property;simplified method;weighted residual method
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发布时间：2024-01-10 - 摘要：The inadequacies of existing displacement-based design methods for seismic soil-structure interaction (SSI) systems using equivalent linearization were summarized, with emphases on issues concerning provisions-specified equivalent system damping ratio and design procedures proposed in previous research. A new design method for SSI systems based on inelastic displacement was presented. The suggested method utilized an elastic-perfectly plastic single-degree-of-freedom (SDOF) replacement oscillator to represent an actual SSI system, combined with inelastic displacement spectra. The derivations of formulae for the period of vibration, damping ratio and ductility of the replacement oscillator, the method of constructing design inelastic displacement spectra compatible with their elastic counterparts constructed using the code for seismic design of buildings （GB50011—2010）, and detailed design procedures were given. Based on the proposed formulae, the existing procedures of elastic displacement-based design for SSI systems were modified. An example was provided to illustrate the design process of the new and the modified methods, and the solutions were checked using nonlinear response-history analysis. It was showed that design displacements based on the new method are closer to the response-history analysis results than those obtained using the modified method that deals with linear systems.关键词：displacement-based design;soil-structure interaction;ESDOF oscillator;inelastic response spectrum;equivalent linearization;nonlinear response-history analysis
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发布时间：2024-01-10 - 摘要：Choosing the appropriate ground motion as input is the basis of nonlinear dynamic analysis and incremental dynamic analysis of structures.Firstly,20 suites of near-field ground motion records and 20 suites of far-field ground motion records were chosen and modified to match the targeted design spectrum.Then,taking peak ground velocity (PGV) and spectral acceleration corresponding to the fundamental period of the structure Sa(T1) as intensity measures,dynamic analysis with the single ground motion intensity level and incremental dynamic analysis (IDA) with multiple ground motion intensity levels were conducted on a 5-storey reinforced concrete frame under the aforementioned 4 sets of ground motion records.Engineering demand parameters (EDSS) such as maximum inter-story drift ratios (θmax) and maximum residual inter-story drift ratios (RIDRmax) were obtained.The bias indices to represent the spectral matching effect,the variation of EDPS and the correlation between EDPS and intensity measures were further analyzed.Finally,seismic fragility analyses corresponding to different damage states were conducted based on IDA results.The analytical results showed that the correlation of EDPS with PGV is better than with Sa(T1).Under spectrum-matched near- and far-field ground motion records,the dispersion of EDPS decreases obviously and there is no obvious biases in θmax results.If taking PGV as intensity measure,far-field ground motion induces larger θmax than near-field ground motion.On the contrary,if taking Sa(T1) as intensity measure,near-field ground motion induces larger θmax than far-field ground motion.Prior to collapse of the structure,RIDRmax values corresponding to different damage states under near-field ground motion are larger than the values under far-field ground motion.For collapse state,RIDRmax values under near-field ground motion are less than the values under far-field ground motion.关键词：peak ground velocity;near-filed ground motion;bias;dispersion;correlation;fragility
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发布时间：2024-01-10 - 摘要：The hazard assessment on potential post-earthquake debris flows is an important task and technical basis for disaster prediction and prevention,while related research is limited.Wenchuan was taken as a typical study area.Through data collection,field investigation and remote sensing monitoring,the frequency,the flow quantity and the geomorphic information entropy of post-earthquake debris flow were selected as three key indicators for hazard assessment.Correspondingly,the discharge calculation method of post-earthquake debris flow was improved,the DNWT model was established for dynamic monitoring and quick extraction of the sources of post-earthquake debris flow,and the evaluation index systemfor debris flow hazard was set up.By means of the GIS and the grey system method,the model for evaluating the hazard of post-earthquake debris flows was established,sub-catchments were extracted and selected as hazard assessment units,and the hazard assessment on potential post-earthquake debris flows in the investigated area was conducted.The results show that:1) the proposed DNWT model for extracting debris flow sources can realize the remote sensing identification,dynamic monitoring and automatic extraction of post-earthquake debris flow sources including rockfalls,landslides and their loose accumulations;2) by combining the field investigation with debris-flow discharge calculation data,the discharge calculation formula of debris flow is corrected.The blocking factor of post-earthquake debris flow can increase 1.72-3.46 times,compare with the case before the earthquake,and its discharge increases exponentially;3) based on sub-catchments,geomorphic information entropy is introduced,and meanwhile,it simplifies parameters and procedures for hazard assessment on post-earthquake debris flows and can evaluate the development stage of landforms and the hazard degree of each catchment;4) most of the debris flows in the studied area are in the moderate,high and very high hazard zones and have great potential risks.Among them,there are 89 debris flows in high and very high hazard zones,which are distributed along the main stream of Minjiang River and the valley of Yuzi River,and these areas are crucial for debris flow prevention and mitigation.The research results are consistent with the actual situation and can provide a basis and reference for remote sensing dynamic monitoring,quantitative risk assessment and prevention and mitigation of potential post-earthquake debris flows.关键词：post-earthquake debris flow;hazard assessment;source information extraction model;corrected discharge calculation method;Wenchuan county
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发布时间：2024-01-10 - 摘要：The reasons of main beam displacement and girder falling of a simply supported beam bridge are related to bridge structure as well as theeffect and displacement of site.In order to study the influence of effect and displacement of site in girder falling and to find the failure mechanism of Gaoyuan bridge,which was a simply supported beam bridge and had girder falling in " 5•12” Wenchuan earthquake,a finite element model ABAQUS was employed to simulate the process.The results showed that the relative slipping between pier and main beam was greatly influenced by the local site condition and the slipping distance near river bank was larger than that far away;The weak degree of filed had an obvious influence on the seismic response of bridge,and the slipping distance was enhanced while the site became weaker.The span change and slipping distance increased with the increase of site displacement.When the base rock was identical,the span change of bridge and slipping distance was small and the ability of adapting toand the deformation of each pier was better.The span change slowly decreased in direction of site displacement,and increased from first span to fourth span.The main reasons for longitudinal failure mechanism of girder falling of Gaoyuan bridge at second span was that the bridge was close to the epicenter and Longmen mountain central main fracture zone,where there exist the soft shale in the bedrock,the unfavorable local site conditions,the poor stability of laminated rubber bearing,and the use of lateral block in bridge.关键词：Gaoyuan bridge;site effect;site displacement;failure mechanism of girder falling;finite element method
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发布时间：2024-01-10 - 摘要：Reinforcement effect of reinforced concrete (RC) eccentric compressive column strengthened by steel wire mesh reinforced resin concrete (HTRCS) was researched based on a self-developed reusable loading device.The impacts of number of steel wire mesh and position of reinforcement layer on the failure mode and bearing capacity were analyzed through eight specimens with large eccentricity.Behaviors of two non-strengthened specimens loaded through a conditional device and a self-developed device respectively were compared to analyze the impact of the self-developed device on the force condition of eccentric column.Lastly,finite element software was adopted to analyze the impacts of parameters such as the thickness of reinforcement layer and eccentricity of load on the bearing capacity of specimens in order to further understand the reinforcement mechanism.Results showed that the self-developed loading device not only solve the security problem of vertical loading,but also reflect the actual condition of the column.For specimen strengthened at tensile side,the crack distribution at the tensile side is closely related to the number of steel wire mesh.When the number of steel wire mesh is arranged properly,the crack distribution at the tensile side is a type of reticular.For specimen strengthened at compressive side,the spacing of cracks at tensile side is not related to the number of steel wire mesh.However,the width of crack decreases with the increase of number of steel wire mesh.The bearing capacity of specimen can be improved effectively by HTRCS,while the reinforcement mechanisms are different for different reinforcement positions.The bearing capacity of specimen strengthened at tensile side is mainly controlled by the number of steel wire mesh.The increase of bearing capacity is only 8% for specimen strengthened at tensile side by 2 cm HTRCS without steel wire mesh.The bearing capacity of specimen strengthened at compressive side is mainly controlled by the thickness of reinforcement layer.The increase of bearing capacity can reach to 30% for specimen strengthened at compressive side by 2 cm HTRCS without steel wire mesh.The reinforcement effect of specimen strengthened at the tension side is more obvious than that at the compression side when the ratio of eccentricity to the length of column section along the eccentricity direction is more than 0.7.关键词：steel wire mesh reinforced resin concrete(HTRCS);eccentric compressive column;strengthening test;finite element analysis
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发布时间：2024-01-10 - 摘要：Due to the steep slope of mountainous watersheds and large changes in vegetation,flood responses to rainstorms are complicated.At present,the most widely used formula is the constant index of slope length,effective roughness,effective rainfall intensity and slope.However,the effect of vegetation on the confluence time is implicit in the effective roughness,which makes impossible to directly use the high-precision remote sensing data of vegetation in calculation.In this study,a series of heavy rainfall induced confluence tests under different slopes and vegetation coverage were carried out.By introducing the vegetation coverage factor C and employing the statistical analysis method,the relationship between the flow confluence time on a slope and the vegetation coverage is established.The results showed that the influence of vegetation coverage on the flow confluence time was significant.The flow confluence time increased with the increase of vegetation coverage,and decreases with the increase of rainfall intensity and slope.The flow confluence time under turf vegetation was slightly larger than that under shrubs vegetation.In this study,the vegetation factor was separated from the effective roughness to facilitate the more effective use of vegetation remote sensing data.The calculation accuracy of the flow confluence time on the slope is improved.关键词：vegetation type;vegetation coverage index;slope flow concentration time;artificial rainfall
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发布时间：2024-01-10 -
Energy Dissipation Mechanism of Corrugated Cylinder Metal Energy Dissipator in Rock Shed Engineering AI导读
摘要：The energy dissipator between roof and beam of rock sheds is beneficial for significantly improve the impact resistance of rock shed hold engineering.In this study,a new metal energy dissipator with corrugated structure was proposed to reduce the maximum yield load,stabilize the buckling stage and increase the energy consumption,eventually improving the impact resistance ability of shed hold engineering.The compression tests were conducted to analyze the mechanical behavior of the corrugated tubular energy dissipators with different parameters, and the dynamic finite element method was used to simulate the compression process and compared with the physical model test.Next,by performing the impact tests on the shed hole with different energy dissipator the mechanism of energy disspation device was revealed through the comparatively anylsis of roof’s deflection,the pressure to foundation and energy absorption.The results showed that,compared with the cylindrical damper,using corrugated cylinder metal energy dissipator reduces the initial yield load to about 1/3,and it was more easily to achieve the form of stable axisymmetric buckling process.Numerical simulation showed that when the rock shed subjected to impact loading,the maximum deflection of roof could be reduced by about 47%.At the same time,both the pressure of the rock shed to the foundation and the vibration generated between part of rock shed structure could be reduced to some extent with the change of the impact energy.The magnitude of the energy consumption of corrugated cylinder metal energy dissipator was much higher than that of the commonly used cylinder energy dissipator.Therefore,intalling the corrugated cylinder metal energy dissipator is beneficial for improving the anti-impact ability of rock shed hold engineering.关键词：rock-shed engineering;corrugated cylinder metal energy dissipator;energy dissipation and shock absorption;optimized design- 2711
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发布时间：2024-01-10 -
Experimental Study on Eccentric Compression Behavior of Ultra-high Performance Concrete Columns AI导读
摘要：To study the eccentric compression performance of ultra-high performance concrete (UHPC) columns,seven UHPC columns and one high-strength concrete (HSC) column were tested.Variation parameters include:the steel fibers volume of UHPC,load eccentricity and stirrup ratio of columns.The failure mode,bearing capacity and deformation capacity of the specimens with vertical loading were studied,and the following conclusions were drawn.It is demonstrated that the failure mode of UHPC eccentric compression columns includes large eccentric tension failure and small eccentric compression failure.Large eccentric tension failure mainly showed the following three characteristics:the tensile longitudinal reinforcements were yield,fine cracks appeared in tension zone and the UHPC in compression zone was crushed.However,small compression eccentric failure mainly showed the following two characteristics:less and slighter cracks appeared in tension zone and the UHPC in compression zone was crushed,without the yield of tensile longitudinal reinforcements.Due to the " bridging” effect of steel fibers,the development of cracks were delayed,the number of cracks increased significantly,and the width decreased.The load-deflection curves of large eccentric columns shows a gentle descending section,which shows that the specimens have good ductility.Comparing with HSC column,the cracking loads of UHPC columns increased 44.5% and 59%,and the ultimate loads increased 30.2% and 58.9%.With the increase of steel fiber volume,the carrying capacity of UHPC columns increased by 13.3%～58.9%,and the failure deflection increased by 14.3%～146.5%.With the increase of stirrup ratio,the carrying capacity of UHPC columns increased by 6.2%～11.4%,and the failure deflection increased by 14%～14.8%.The increase of steel fiber volume and stirrup ratio has an effective effect on improving bearing capacity and deformation capability of UHPC columns.Due to the high tensile capacity of UHPC,the contribution of UHPC tensile strength to carrying capacity was considered in bearing capacity formula.And an equivalent rectangular stress diagram was used to simplify the calculation.The theoretical calculation results agree well with the test results.It can provide a theoretical basis for engineering application.关键词：ultra-high performance concrete;eccentric compression column;steel fiber volume;ultimate load;failure deflection- 2839
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发布时间：2024-01-10 - 摘要：In order to comprehensively evaluate the seismic performance of a new type strand anchored precast concrete frame connection,low-cycle repeated loading tests were conducted on 4 prefabricated assembly connections and 1 cast-in-situ connection.The destructive processes and destruction patterns of each connection was investigated,the skeleton curves,energy dissipation capacity and stiffness degradation of the connections were analyzed.The experimental results show that the beam bending damage occurs at all connections,and there are only a few tiny cross-cracks in node area.In the pre-loading stage,all the prefabricated connections have less energy-consuming capacity than the XJ nodes,and the prefabricated connections PC1 and PC2 with additional rebar,the post-loading energy dissipation capability is stronger than that of the XJ and prefabricated PC3 and PC4 connections.Due to the prefabricated connections in the keyway there are new and old concrete interface,resulting in that the stiffness of all the prefabricated connections are less than that of XJ connection.After entering the yielding stage,the keyway hoop encryption and additional reinforcement,making PC1 and PC2 connections stiffness greater than XJ node.In general,the additional reinforcement contributes to the carrying capacity and energy dissipation of the connections.Based on the experimental results,the parametric analysis of the connections was carried out by ABQUAS.The influences of different parameters on the mechanical properties of the prefabricated connections were obtained by changing the axial compression ratio,the concrete strength grade and the additional steel bar diameter in the nodal area.关键词：precast style;prestressed;beam-to-column connections;seismic performance;finite element
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- 2457
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发布时间：2024-01-10 - 摘要：High attention had been drawn to the new anchor bolt materials represented by glass fiber reinforced polymer (GFRP) as the traditional steel anchor bolt show certain disadvantages,including low corrosion resistance and poor durability.However,due to the shortcoming of the GFRP anchor bolt,including relatively low shear strength and elastic modulus,the mechanism of the GFRP anchor bolt to strengthen rock bedded slope need to be further studied.The interaction mechanism between rock mass and anchor bolt was analyzed based on the Winkler's assumption and the loading transfer mechanism.Then the mechanical model of anchor bolt under the action of shear displacement was established and verified.On this basis,by considering some influence factors,such as shear displacement,the angle between the anchor bolt and potential sliding surface and unconfined compressive strength of rock mass,the mechanisms of the GFRP anchor bolt for strengthening rock bedded slope were studied.It is concluded that:1) when the angle between the anchor bolt and the sliding surface was 45°,the GFRP anchor bolt generated shear yield because of a small shear displacement in hard rock,and the GFRP anchor bolt presented tensile yield in soft rock.2) when the anchor bolt yielded,the differences between the resistances of the GFRP anchor bolt for reinforcing different rocks are obvious.The greater the unconfined compressive strength of rock mass is,the smaller the resistance of the GFRP anchor bolt is.In contrast,the differences between the resistances of the steel anchor bolt for different rocks are slight.3) In hard rock,the angle between the anchor bolt and the sliding surface had a great impact on the resistance of anchor bolt.The smaller the angle is,the greater the resistance is.In soft rock,the angle between the anchor bolt and the sliding surface had a small impact on the resistance of GFRP anchor bolt.The GFRP bolt can provide greater resistance for the angle from 5° to 60°.These results can provide some references for anchoring of rock slope and related engineering applications.关键词：GFRP anchor bolt;rock bedded slope;bedding-slip failure;mechanical model;mechanisms
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发布时间：2024-01-10 - 摘要：In view of ambiguity and randomness in the risk assessment of urban underground diseases, a risk assessment model of urban underground diseases based on cloud theory and set pair theory was proposed to quantitatively assess the disease risk. First, according to the relevant standards, the 25 assessment indicators of disease risk were selected from both the probability of risk occurrence and the risk consequences; a four-level risk assessment system and an index quantification standard were established. Second, by introducing the cloud theory in the field of uncertainty artificial intelligence studying the relationship between ambiguity and randomness, assessment indicators were transformed into cloud indicator according to the inverse Gauss cloud algorithm involving the second-order and the fourth-order center distance. Third, comprehensively considering the subjective cloud weight and the objective critic weight, a coupling cloud-critic weight optimized by the least squares method was proposed to distribute weights for cloud indicators, andthe least square method is utilized to combine and optimize the two kinds of weights. After a step-by-step calculation, the cloud indicator can be transformed into a comprehensive cloud. Final, a similarity calculation method of cloud model was proposed based on the set pair potential and the " 3En” rule of Gauss cloud model, by introducing the set pair analysis (SPA) theory. The " 3En” rule of Gauss cloud model counting cloud droplets and performing similarities, differences and counter analysis, and the set pair potential calculating membership degree of comprehensive cloud were used to judge the risk level of disease. Quantitative evaluation of Guiyang road detection engineering project has been carried out utilizing the established model. The evaluation results agreed well with the actual conditions of excavation verification and verified the applicability of the model. In addition, the model was compared with the evaluation model constructed by the analytic hierarchy process, fuzzy comprehensive evaluation and fuzzy analytic hierarchy process method; the results showed that the proposed model in this study achieved the higher evaluation accuracy when compared with the other models. It is thus feasible to apply the proposed model to the risk assessment of urban underground diseases.关键词：disease risk assessment;risk assessment model;cloud model;set pair analysis;urban underground diseases
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- 2003
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- 1
发布时间：2024-01-10 - 摘要：The cantilever beam type is a common form of the upside-down dangerous rock-mass,and it is easily to collapse under earthquake action.Thus,the study on the evaluation method of earthquake-induced bending collapse of the upside-down dangerous rock-mass have great significance on evaluating its security degree.On basis of the calculation theory of the cantilever beam,firstly,the calculating formula for the maximum tensile stress of the cantilever beam type dangerous rock-mass with arbitrary shape under the action of seismic loading and its own gravity has been proposed,and the time-history curve of the maximum tensile stress has been established.At the same time,the tensile failure criterion is considered as the criterion of crack propagation,combined with the relationship between the elastic strain energy and fracture propagation energy,and an approach for calculating the depth of crack has been established to study the crack depth along with the earthquake time.Secondly,according to the shapes of dangerous rocks in real engineering,they are simplified into two special forms:rectangular parallelepiped and cylinder,and has proposed a calculation formula for the critical depth of crack to define the safety factor of dangerous rock under the action of earthquake.At last,a dangerous rock-mass located at the entrance of a tunnel is taken as an example to illustrate the application of the proposed method in this paper.The results show that,under the action of 8.0 magnitude earthquake,the total depth of crack induced by earthquake of this dangerous rock-mass at 14 s is 0.1759 m,which is greater than the critical depth of crack (0.167 m),implying that this dangerous rock-mass would collapse at 14 s.关键词：upside-down dangerous rock-mass;earthquake-induced collapse;crack growth;cantilever beam theory;maximum tensile-stress criterion
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- 2016
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- 2
发布时间：2024-01-10 - 摘要：A large amount of loose accumulation materials is deposited on the surface of mountain areas in Southwest China,and the composition is mainly pebble sediment of wide size distributions.Under the action of earthquake,a large number of loose debris can enter the mountainous river in the form of landslide and debris flows,and subsequently change the sediment supply conditions.To study the effect of seismic action on the movement process and deformation characteristics of loose materials,three dimensional particles discrete element method is applied to simulate the movement and deformation of the loose materials on a slope under different seismic loads,and the influence of seismic wave frequency and amplitude on the movement process of loose materials is analyzed and discussed.The simulation results show that the movement of loose materials on a slope can be divided into three stages:starting acceleration,high-speed sliding and decelerating accumulation,and the smaller the particle size is,the slower the particle velocity is.After the particles enter the river,the large particles are accumulated in the front and the surface,and the small particles are found in the middle and low areas.Besides,the effect of the seismic load can greatly reduce the number of contact,resulting in the reduction of collision between particles and the loss of energy of the particles,which leads to a significant increase in the speed and the distance of the loose materials.With the decrease of the frequency of seismic waves and the increase of amplitude,the increase rate of the moving velocity and the moving distance of the particles is enhanced,which will cause the originally stable loose sediment to enter the river,thus increasing the mass of sediment in the mountainous rivers and the damage level of the flash flood disasters.It can be seen that the earthquake has an important influence on the sediment supply conditions of the mountain rivers,which provides a theoretical basis for further research on the disasters after earthquake.关键词：earthquake;loose materials;contact collision;DEM;numerical simulation
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- 2365
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发布时间：2024-01-10 - 摘要：The experimental data of previous researches on the energy evolution during the rock mass element’s deformation and failure process was analyzed,and the conclusion shows that the releasable elastic strain energy limit of the rock mass element is related to the stress state and lithology.Then,the global failure and instability criterion for the rock mass element under different stress states was derived secondly based on the definition of global failure and instability.Moreover,the criterion for assessing dynamic and static instability of the underground cavern was proposed based on the second law of thermodynamics and the principle of minimum energy.Finally,the dynamic and static stability analysis of an underground tunnel with/without support was brought out based on the example of an underground tunnel under the action of earthquake motion in the construction period,by means of FLAC3D.The results show that the stress-type local instability failure occurred in the underground tunnel in all of static conditions and also the third condition with earthquake occurring,and the stress-type global instability failure most probably occurred in the underground tunnel in the first and second earthquake conditions.After the action of an earthquake,the volume of global failure and instability’s rock mass element was increased by 1553.15 m3、1091.79 m3 and 223.07 m3,in the no-support condition,the shotcrete-bolt support condition and the shotcrete-bolt and lining support condition,,respectively,indicating that the earthquake-resistant effect of the lining support is better than that of the shotcrete-bolt support.The discriminant criterion for dynamic and static instability of the underground cavern proposed in this paper is a useful for the numerical simulations of dynamic and static stability of underground caverns,and the calculation results can provide useful references for the design and construction of underground caverns.关键词：energy;rock mass element;global failure;underground tunnel;stability;earthquake
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发布时间：2024-01-10
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Building Resilience Through Disaster Waste Management—UN Environment’s Experiences and Approaches AI导读
摘要：Integrating disaster waste issue is a critical component of making humanitarian action fit for the future, anticipating global risks and challenges such as increased vulnerability due to climate change and environmental degradation. This requires a fundamental shift towards a model that not only strengthens the response to crises but also learns and adapts in order to anticipate and act before such waste garnered. This article conducted analyses on the characteristics of disasters in the past two decades. Uncertainties confound disaster waste management, including the timing and magnitude of each disaster, and the amounts and types of waste that will be generated. For these reasons alone, disaster waste management must be an integral part of development planning and processes. Making 10 years since the 2008 Wenchuan earthquake, this article highlights that disaster waste management is not only debris clearance or waste management following a disaster, but also includes prevention and pre-disaster preparedness aspects in terms of enhancing resilience of local communities. Such " mainstreaming” ensures that disaster waste management (DWM) will be treated as a priority issue, on an ongoing basis. Based on UN Environment’s experiences and approaches, this paper emphasises that preparedness is the key, and that priority should be accorded to integrating disaster contingency planning in national and city level waste management strategies as well as mainstreaming waste management issues within broader disaster preparedness and response plans and actions. It is envisaged that the issues presented and the gaps identified in this paper will provide a basis for future comprehensive and cohesive research on disaster waste management. In turn, this research can lead to better preparedness and response on disaster waste management.关键词：disaster waste;disaster risk reduction;waste management;Sendai Framework- 2870
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发布时间：2024-01-10 - 摘要：A multi-block model and a corresponding computer program have been developed which predict the kinematics of landslides. Furthermore, a unique event for studying different models simulating the triggering and movement of landslides is the 2008 Wenchuan earthquake in the mountainous region in Sichuan Province of China, which caused a large number of rapid landslides. The purpose of the paper is two-fold: (a) to propose and incorporate into the multi-block model constitutive relations predicting soil response along slip surfaces, and (b) to apply the multi-block model with the constitutive relations at landslides triggered by the Wenchuan earthquake. The proposed constitutive equations predict the shape of the shear stress-displacement response measured in ring shear tests. In the application, four landslides caused by the Wenchuan earthquake were considered. Only in one of these landslides the shear resistance-displacement response along the slip surface has been measured in laboratory tests. At this landslide, the triggering and movement of the landslide was predicted. In the other landslides, back analyses were performed and it was observed that the multi-block model predicted reasonably well the final configuration of all slides. In addition, as the measured and back-estimated total friction angle of all landslides was less than 18°, and the materials along the slip surface were sandy, it is inferred that some, or all of the slip surface during these slides was sheared in an undrained manner and excess pore pressures generated during sliding played a key role in the triggering and movement of these landslides. Concluding, the paper (A) proposed and validated a multi-block constitutive model which can be applied to predict the triggering and movement of earthquake-induced slides and (B) by analyzing four landslides of the 2008 Wenchuan earthquake, it concludes that some, or all of the slip surface during these slides, was sheared in an undrained manner and excess pore pressures generated during sliding played a key role in the triggering and movement of these landslides.关键词：Wenchuan earthquake;multi-block model;seismic displacement;landslides;back analysis;strain softening
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- 2070
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发布时间：2024-01-10
特约稿
- 摘要：In May 2012, the Emilia region of the Po Valley was struck by a seismic crisis with two major events of magnitude Mw 6.1 and Mw 5.9. The first event induced widespread sand blows formed along buried channels and old crevasse splay deposits. In the days immediately following the events, the detailed mapping and sampling of the erupted sand was fundamental to record all the seismically-induced phenomena. The study of a trench dug across large fractures at San Carlo (Ferrara) provided also valuable information on the sand blows mechanism and regome. The sedimentological and compositional characteristics of the fracture-filling materials indicate that the sands were erupted from a layer located between 6.8 and 7.5 m depth. Older and deeper Holocene and Pleistocene sand layers were not apparently involved in the liquefaction phenomena.关键词：sand boils;composition;Emilia Romagna;earthquake
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发布时间：2024-01-10
研究论文
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