The Analysis Of The Influence From Seismic Oscillation To Free Field Under Layered Foundation

In recent years, the construction of Nuclear Power Plant spring up like mushrooms. Considering our country is multi-national earthquake and nuclear power structure is particular, that carrying out ground motion study of nuclear site actively is very important. And because natural site is considered multi-layered, studying the seismic wave propagation in layered soil becomes a very important problem. The classical treatment of these problems is given in Refs . This topic is under the background of nuclear power project studied by our teaching and research office in recent years, consider different free site information applications and use a new approach. The specific content reads as follows:(1) According to the natural soil is stratified, that can divide the soil to different layers. Considered the soil located above the base-rock, seismic excitation is given at the base-rock. That can use the precise integration algorithm to obtain the seismic response of ground surface and then establish the relationship between the input seismic excitation at the bottom of the free field and surface seismic response. That can also find out the dynamic stiffness of the field. Compared with the traditional method, this method solves problems in frequency and wave number domain, which is accuracy and effectiveness. Especially in the complex layered soil, the more can show the superiority of the precise integration algorithm.(2) When using the precise integration method to obtain the dynamic stiffness of the field, that can combine with the extended W-W algorithm to undertake the computation of the field's eigenvalues. The combination of the precise integration method and the extended W-W algorithm can find out the number of eigenvalues corresponding to different ground for any given frequency range and the frequency value self. That can also get the mode shape of the ground corresponding to vibration frequency in surface. Using the extended W-W algorithm will not leak any frequency values in the range of the given frequency, which reflects the accuracy of this algorithm.(3) Using the exact method to calculate the response spectrum of the input seismic excitation at the bottom of the filed and the seismic response in the surface corresponding to the input seismic excitation under any condition. That can make compared and analyzed between them.