Abstract:

In the earthquake prone inland environment of China, the evaluation of site stability has drawn more and more attention.For the study of large site dynamic response characteristics of Yanqing new city planning region, this paper firstly found out the Quaternary overburden layer and the spatial distribution of fractures in Yanqing new city planning region; secondly, it established a 3D simulation model for planning region using FLAC3D based on numerical simulation; thirdly, it made a simulation of the site dynamic response in planning region; and lastly, it described the characteristics of site dynamic response by defining the coefficient of site speed response. The results reveal the following aspects: in the typical sites of soil-rock composite,different thicknesses of the Quaternary overburden layer could lead to different levels of site speed response under the low-frequency shear-wave excitation, and while the Quaternary overburden layer gets thicker,the coefficient of site speed response gets greater and the degree of dynamic amplification gets higher; in the complex site of underlying fracture, the shear wave propagation path becomes very complicated,and the fracture has an amplification effect to the coefficient of surface speed response,while the amplification level is related with the distribution form and development scale of fractures.

Key words: Quaternary overburden layer, underlying fracture zone, low shear wave, coefficient of site speed response, numerical simulation