Influence Of Seismic Wave Type And Incident Direction On Dynamic Response Of High Concrete Faced Rockfill Dam

The construction scale of high rockfill dams in China has highest the most in the world,and its seismic safety has attracted great attention.Most of the high rockfill dams in China are constructed in the western region which is located in the Mediterranean-Himalayashan seismic belt with complex geological structure and the frequent medium and strong earthquake.Once the dam breaks due to the earthquake,it will cause serious losses to people ’s lives and property.Therefore,the seismic safety of high rockfill dams is an important part of dam seismic design.In the seismic safety evaluation of high rockfill dams,the seismic input method has great influence on the calculation of dynamic response of high rockfill dams.Vibration analysis method is still widely used to study the dynamic response of high rockfill dams on rock foundation under seismic action.This method fixes the bottom boundary of the dam foundation and directly applies seismic inertia force on the fixed node.The method simplifies the wave problem of the open system to the vibration problem of the closed system,which ignores the difference of the seismic input caused by the traveling wave effect and the valley terrain,and ignores the influence of the radiation damping of the foundation.The dam-foundation dynamic interaction cannot be manifested,which may lead to deviation of dam seismic response.With the substantial increase in the scale of dam construction,the scale,weight and modulus at the bottom of the dam increase significantly.These factors lead to an increase in the transmitted energy at the dam-foundation interface during the seismic,and the effect of traveling wave effect is enhanced.In addition,due to the randomness of the earthquake and the complexity of the crustal structure,the type and angle of the incident wave are uncertain when the seismic wave propagates to the dam structure.Therefore,high rockfill dam-foundation dynamic interaction cannot be ignored,and the wave analysis method should be used to study the dynamic response of dam.In this paper,the wave analysis method combined with viscoelastic artificial boundary and equivalent nodal load can effectively eliminate the outward scattering wave caused by the structure and simulate the infinite domain characteristics of the foundation.At the same time,it can simulate the propagation process of seismic wave and the ground motion characteristics induced by different valley terrains.Then,dam-foundation dynamic interaction and the influence of seismic wave type and incident direction are systematically studied.Mainly includes the following :(1)Referring to the geometric parameters of some existing and under construction high face rockfill dams in China,a three-dimensional finite element model with different valley widths is established for 250 m high face rockfill dams.The seismic response of the dam is calculated by using the energy open wave analysis method and the energy closed vibration analysis method,respectively.The rationality of the wave analysis method is verified.The distribution laws of dam acceleration and panel dynamic stress under the two analysis methods are compared,and the influence of peak ground acceleration and foundation modulus on dam-foundation dynamic interaction is considered.(2)Aiming at 250 m high face rockfill dam,the dynamic displacement,acceleration and dynamic stress extremum and distribution of the dam are discussed when SH wave,SV wave and P wave are incident in different angles and directions.It is found that the incident angle and direction of different seismic wave types have obvious influence on the dynamic response of the dam.Therefore,it is necessary to consider the incident angle and direction of different seismic wave types to comprehensively and accurately evaluate the ultimate seismic capacity of high face rockfill dams.