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针对由河漫滩、阶地、波状起伏的丘陵地带和残丘等组成的典型复合地形场地,基于ABAQUS软件的显式有限元并行计算集群平台,考虑土体的非线性特征,采用黏弹性人工边界模拟切除的无限域对地震波动的影响,建立了大尺度复合地形真实场地的二维有限元模型,并将基岩地震动视为SH波,分析了不同地貌单元复合场地地震效应特征。结果表明:地形差异引起地表各测点峰值加速度(PGA)及峰值位移(PGD)不同;在相同地震波入射下,河漫滩区地表PGA大于Ⅰ级阶地区域,但其PGD明显小于Ⅰ级阶地区域,且河漫滩区的峰值位移差动较小;场地地表水平加速度反应谱呈双峰及多峰现象,加速度在0.4~1.2 Hz频段放大较多,且加速度反应谱特性与输入地震动相关;特定频段(0.5~1.75 Hz)地震动放大效应与聚集效应比较明显,频率小于0.2 Hz及大于2 Hz时,场地地震动放大特征不显著。低丘区的敏感频率段宽于河漫滩区;观测点的位置影响相应的水平加速度持时大小,局部地形变化将引起地震动持时差异,且持时和输入地震动特性相关。
Aiming at the typical complex terrain composed of river floodplains, terraces, wavy hills and residual hills, an explicit finite element parallel computing cluster platform based on ABAQUS software is proposed, and the viscoelastic artificial boundary simulation is adopted to consider the nonlinear characteristics of soil. Dimensional finite element model of the real site of large-scale composite terrain is established and the seismicity of bedrock is regarded as SH wave. The seismic effect characteristics of composite sites with different geomorphic units are analyzed. The results show that the topographic differences (PGA) and peak displacements (PGDs) are different at each measurement point of the surface. The PGA of the floodplain is greater than that of the first terrace under the same seismic wave incident, but the PGD is obviously lower than that of the first terrace The peak displacement of the river floodplain area is small. The response spectrum of ground surface horizontal acceleration shows bimodal and multi-peak phenomena. The acceleration amplifies more in the frequency range of 0.4-1.2 Hz, and the characteristics of the acceleration response spectrum are related to the ground motions. ~ 1.75 Hz). The amplification of ground motions is not obvious when the frequency is less than 0.2 Hz and greater than 2 Hz. The sensitive frequency of the hilly region is wider than that of the river floodplain. The location of the observing point affects the corresponding horizontal acceleration duration, and the local topography changes will cause the time difference of the earthquakes.