Numerical Analysis Of Seismic Response Of High Earth-rockfill Dam On The Deep Overburden

In recent years, with the booming development of water conservancy in various aspects, and taking account of the exploitation of water resources, many high earth-rock dam projects are put on the schedule, the high earth-rock dams have become the main developing trend in such field as dam construction. Because of the dam site selections are often limited by the geological conditions, for instance, there are many deep overburdens in the Southwest and Northwest where the water resources are quite abundant, and the Southwest and Northwes of our country belongs to the regions where the earthquakes occur frequently, we must make allowance for the safety of the dams built on the deep overburden foundation when the earthquake happens, and analyze the overburden’s influence on dams.In this paper, the largest section of high earth-rock dam with core wall on deep overburden is taken as research object, seismic problems of high earth-rock dams are studied by means of numerical simulation (2D FEM) from three aspects:the dynamic acceleration response, seismic stability of dam slope, liquefaction. The paper makes the corresponding analysis and prospects in the end of each part by using the equivalent viscoelastic constitutive model and the equivalent linear method in this study. The specific contents of paper are organized as follows:(1)In order to study the impacts on seismic acceleration response of high earth-rock dam during the change of the overburden’s thickness, seismic acceleration peak value and acceleration amplification on the top of the dam are analyzed considering the different height of the dam, the different thickness of overburden layer and the different seismic intensity. The results show that seismic acceleration peak value and acceleration amplification on the top of the dam have decreased trend as the increasing of the overburden’s thickness for the same dam’s height and earthquake intensity. The greater earthquake intensity and the lower the dam, the decreased trend of seismic acceleration peak value shows more obvious.And the greater earthquake intensity, the higher the dam, the decreased trend of acceleration amplification shows less obvious.(2)The specified dam slope’s safety factors are analyzed considering the different height of the dam, the different thickness of overburden layer and the different seismic intensity to study the impacts on seismic stability of dam slope of high earth-rock dam during the change of the overburden’s thickness. The results which are recalculated show that safety factor vary regularly with the increase of the overburden’s thickness, when the earthquake intensity is weak, the safety increases gradually first and tends to unchanged, when the earthquake intensity is strong, it ascended first and then descended.(3) Liquefaction of the dam foundation is computed on the basis of total stress method with liquefied area as a standard. Contrasting the impoundment around the changes of the liquefied area in order to study the impacts on the liquefaction of high earth-rock dam during the change of the overburden’ thickness. Then the effective stress method is performed to check the calculation. The results show that the liquefied area descends gradually first and tends to unchanged when the earthquake intensity is weak, it descends first and then ascends, and changes to upward trend finally when the earthquake intensity is strong. Liquefied area of the dam foundation will appear suddenly reduced under severe earthquake when the thickness of the overburden surpasses the height of the dam. The results of impoundment and effective stress method are largely consistent with the total stress method’s.(4) The dynamic acceleration response, the seismic stability of dam slope, the liquefaction of Shuangjiangkou-high rockfill dam with core wall are calculated. And the results provide some reference data for the project.