远场大地震作用下大尺度深软场地的非线性地震效应分析

基于ABAQUS软件自行研制的并行计算显式算法集群平台，针对苏州城区典型地层剖面，建立了大尺度深软场地的二维精细化非线性有限元分析模型，对人工地震波和大地震远场地震动作用下深软场地的非线性地震效应进行了比较研究。研究结果表明：（1）与人工地震波作用时深软场地的地表峰值加速度放大效应相比，大地震远场地震波作用时的放大效应尤为显著，由于土介质的横向不均匀性及其非线性，使不同地表的峰值加速度放大效应存在明显的变异性。（2）深软场地对周期小于0.3 s的高频地震波均具有显著的滤波效应；大地震远场地震波作用时，深软场地对周期0.85～1.65 s的长周期地震波的放大效应非常显著，但对2.5～7.0 s的长周期地震波呈现出明显的滤波效应。（3）地震动峰值加速度PGA值沿土层深度和横向的分布形态呈现出明显的高低起伏现象，在不同成因的土层更迭面附近及土介质横向不均匀性显著的区域，地震波的局部聚焦放大和过滤减小现象尤为明显，且大地震远场地震动作用时，20 m以浅土层的PGA值呈现出非常显著的放大效应。（4）地震波的频谱特性、土层的横向不均匀性对深软场地地表加速度反应谱? 谱的谱形有显著影响；给出了描述加速度反应谱沿土层深度变化特征的三维谱形曲线，可以直观地展示出深软场地中细长地下结构地震反应可能存在类共振现象的土层深度。

Analysis of nonlinear seismic effects of large-scale deep soft site under far-field large earthquake

Based on the parallel computing cluster platform of ABAQUS, according to the typical stratigraphic profile of downtown area in Suzhou city, a two-dimensional nonlinear analytical model of large-scale deep soft site was established. Comparison of nonlinear seismic effects under artificial seismic wave and far-field ground motion of large earthquake were conducted. The results indicate that: (1) The amplification effect of peak ground acceleration (PGA) under far-field ground motion of large earthquake is especially significant compared with that under artificial seismic wave. There is obvious variability among the PGA of ground surface in different locations due to the horizontal heterogeneity and nonlinearity of ground soils. (2) The deep soft site has a significant filtering effect on the high-frequency ground motion wave whose period is less than 0.3 s. When it is under far-field ground motion, there exists an obvious amplification effect on the long-period seismic wave whose period ranging from 0.85 s to 1.65 s. However, there is also apparent filtering effect on the long-period seismic wave whose period ranging from 2.5 s to 7.0 s. (3) It presents fluctuation phenomenon of PGA distribution with depth and along the lateral direction. There are prominent local focusing effects and filtering reduction phenomenon near the contact surface between different soil layers and in the horizontal heterogeneous soil area; and the PGA amplification effect of soils above 20 m depth is relatively larger than that of other soil layers. (4) Both the spectral characteristics of seismic wave and horizontal heterogeneity of ground soils have obvious influence on the shape of ? spectrum. Besides, three-dimensional curves of spectrum shape those describe the acceleration response spectrum changing with depth are given, which can directly show the soil depth in deep soft site where long and thin underground constructions may occur resonance phenomenon.