Effects Of Inclusion And Topography On Ground Motion

Earthquake is a natural disaster that human beings often suffer,and strong earthquakes always create huge losses to people's life and property.Local irregular geological structure and topography as the hot issue in earthquake engineering research have important influence on ground motion.However,there are few studies on the complex site about the three-dimensional inclusions and canyons.In this paper,based on the three-dimensional finite element numerical simulation,the influence of three-dimensional single inclusion and canyon on the ground motion is studied by using the combination of artificial transmission boundary and finite element method under incident SH waves.The amplification of ground motion and the effects on the PGA and acceleration response spectrum of inclusion and canyon are analyzed by spectral ratio method,and the results are compared with the two-dimensional element numerical simulation results.The horizontal distance from any point to the center of the inclusion or canyon is R,the characteristic length is l,the ratio of the depth of the inclusion or the canyon to the characteristic length is recorded as the aspect ratio N.The main results are as follows:1.The results show that the ground motion amplified with soft inclusion is very significant in the area of R<0.85 l and the maximum amplification is at the center projection of inclusion on the surface;Significant amplification of soft inclusion acts on ground motion only when the aspect ratio is small(N?1?2),and there is no significant amplification when N?1,such as the maximum magnification of the ground motion is 4.2 times that of free field when the aspect ratio N=1/16.2.The frequency range of the ground motion amplified by soft inclusion of 2D numerical simulation is wider than the result of 3D numerical simulation whereas the magnification is smaller than that of 3D numerical simulation.The shallow buried three-dimensional cavity has the greatest influence on the ground motion and its characteristics,the three-dimensional soft inclusions followed,and the three-dimensional hard inclusions mainly show a strong barrier to the seismic waves.3.The influence of 3D canyon on ground motion is less than that of inclusion;The ground motion and the ground motion characteristics in the direction of vertical wave vibration influenced by 3D canyon is more obvious than that in the parallel wave vibration,and the ground motion and the ground motion characteristics of the points on the boundary of the 3D canyon in the direction of vertical wave vibration are the most affected by the canyon;The ground motion and the ground motion characteristics of the internal points of the 3D canyon are most affected at N=2,and the influences decrease as the distance to the projection center R becomes larger;The canyon has little influence on the ground motion and ground motion characteristics when the Aspect ratio N<1/4.