福州盆地地震效应特征的一、二维模型对比研究

基于ABAQUS软件的显式有限元并行计算集群平台,采用大尺度二维精细化有限元非线性分析法,数值模拟福州盆地基岩和地形起伏及土层分布的横向非均匀性对场地地震效应特征的影响,并与一维等效线性波传法的分析结果进行对比。结果表明:二维非线性模型能反映出盆地基岩起伏对地震动的聚焦效应及土层分布的局部横向非均匀性对地震波的聚集效应;一维分析给出的土层PGA放大系数随深度单调递减,二维分析给出的盆地土层峰值加速度呈现出随深度增加而非单调递减的特征;较之一维等效线性波动模型,大尺度二维非线性模型对地震波低频放大特性具有更好的模拟能力;应充分重视盆地微地形和土层结构的横向不均匀性所导致的地震效应特殊现象的存在对工程的不利影响。

Large-scale two-dimensional nonlinear FE analysis vs. one-dimensional quivalent linearization analysis on seismic effect of Fuzhou Basin

Based on the explicit FE method and 32 CPU parallel computing cluster platform of ABAQUS,considering the inhomogeneity of ground soils and concave-convex fluctuation of topography and bedrock surface,large-scale refined two-dimensional(2D) FE nonlinear analytical models for Fuzhou Basin were established in the time domain.Meanwhile,one-dimensional(1D) analysis models by equivalent linearization method were established for the sake of contrast.The results indicate that the 2D nonlinear analytical models show a more obvious seismic amplification effect,also there are focusing effect caused by the fluctuant bedrock surface and topography in the 2D models.the PGA display a non-monotonic decreasing characteristics with depth and a greater focusing effect of some particular soil layers by the 2D model,while the 1D results turn out that the PGA decreases monotonously with depth,In some degree,the large-scale 2D nonlinear analysis could truly reflect the notable PGA amplification effect in particular period;also it has a better simulating ability of low frequency amplification.In general,it will bring obvious errors by the 1D model when the soil layer distribution is inhomogeneous and the terrain or bedrock surface is obviously fluctuant.