Static And Dynamic Analysis And Seismic Vulnerability Of Cemented Sand And Gravel Dam

As a water retaining structure,the seismic safety performance of cemented sand and gravel dam not only affects the safety of dam operation,but also poses a major threat to the safety of life and property of downstream people.Therefore,the seismic research of cemented sand and gravel dam has important value.The seismic damage evolution characteristics and vulnerability of cemented sand and gravel dam are studied.The failure probability of the dam under different seismic intensities can be obtained,which provides a scientific basis for the seismic safety evaluation and decision-making of the dam.In this paper,the distribution law of dynamic strength index of cemented sand gravel material is studied on the basis of experiments.The nonlinear time history method is used to analyze the dynamic response,damage evolution process and failure mode of cemented sand and gravel dam under different seismic peak intensity.A comprehensive evaluation method of seismic vulnerability of cemented sand and gravel dam is proposed.The main research contents and conclusions are as follows :(1)In this paper,the stress-strain relationship of cemented sand and gravel materials is obtained by dynamic triaxial test.Based on the Mohr-Coulomb strength criterion,the evolution law of dynamic strength parameters of cemented sand and gravel materials during plastic deformation is obtained.The strain softening model is calibrated to verify the rationality of the strain softening model for cemented sand and gravel dam,which lays a foundation for the numerical analysis of cemented sand and gravel dam.(2)The distribution law of stress and displacement of dam body during dam construction and impoundment is analyzed.Taking Shanxi Shoukoubao cemented sand gravel dam as an example.A three-dimensional construction rolling simulation model is established to simulate the layered rolling construction process of the dam body,and the distribution law of displacement and stress of the dam body during the completion period is studied.Considering the operating conditions of the dam after normal impoundment,the displacement and stress variation of the dam before and after impoundment are compared and analyzed.(3)The variation of acceleration,dynamic stress and dynamic displacement of dam structure under different peak strength is revealed.Based on the strain softening model,reasonable damping form,damping parameters and dynamic load are selected.By setting effective boundary conditions,the dynamic analysis of cemented sand and gravel dam under different seismic intensities(0.1g,0.2g,0.4g,0.6g)is carried out by dynamic time history method.The distribution law of acceleration,dynamic stress and dynamic displacement of dam body is obtained.(4)Comprehensive evaluation method of seismic vulnerability of cemented sand and gravel dam based on efficacy coefficient.Based on the dynamic response data of cemented sand gravel dam under different seismic intensity grades,the limit value of seismic damage grade division of single seismic performance is determined by using the tensile stress of dam body,the displacement of dam top along river and the volume of plastic zone as single seismic index.The comprehensive damage index of the dam body is calculated by using the efficiency coefficient method,combined with the entropy weight method and the scatter degree method,and the seismic vulnerability curve of the cemented sand and gravel dam based on the comprehensive damage index is obtained.The failure probability of cemented sand gravel dam under different earthquake intensities is clarified,which provides a theoretical basis for earthquake disaster prediction and risk assessment of cemented sand gravel dam.