北京延庆新城规划区场地动力响应数值模拟

在地震多发的中国内陆环境下，场地稳定性评价越来越引起重视。为了研究北京延庆新城规划区大型场地动力响应特征，在分析延庆新城规划区第四纪覆盖层和断裂的空间分布规律基础上，基于数值模拟方法，运用有限差分数值模拟软件FLAC3D建立了规划区三维仿真模型，并对新城规划区场地动力响应进行了仿真，最后通过定义场地速度响应系数来刻画场地动力响应特征。结果表明：对于“土岩组合”的典型场地，在低频剪切波的激励下，第四纪覆盖层的厚度将引起不同程度的场地速度响应，第四纪覆盖层越厚，场地速度响应系数越大，动力放大程度越高；对于下伏断裂的复杂场地，剪切波传播路径变得极其复杂，断裂对地表速度响应系数有放大作用，放大程度与断裂分布形式和发展规模有关。

Numerical Simulation Study on the Site Speed Response of Yanqing New City Planning Region in Beijing

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.