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以滁州市地震小区划场地为原型,针对由河漫滩、阶地、波状起伏的低丘等组成的典型复合场地,基于ABAQUS软件显式有限元并行计算平台,建立了大尺度场地二维模型,考虑土体的非线性特征,以SH波作为输入地震动,分析了河漫滩-阶地复合场地地震动力响应特征.结果表明,(1)与基岩地震动峰值加速度相比,土层近地表范围内(15m以浅)峰值加速度均表现出明显的放大现象,15m以深土层地震动放大效应随深度增加而逐渐减弱,且随深度增大,PGA放大系数值逐渐小于1.0;(2)土层峰值加速度随着深度增加非单一递减,局部土层深度地震动出现聚集效应,这一现象在河漫滩区表现比较明显;(3)场地不同区域地震动放大效应差异较大,河漫滩区地震动放大效应要明显比阶地低丘区更大;且输入地震动峰值相同时,河漫滩区反应谱特征周期要大于阶地区域,两者差距达0.05—0.15s;(4)随着输入地震动增加,反应谱谱峰向长周期方向移动明显.
Taking the plot of Chuzhou earthquake area as a prototype, a two-dimensional model of large-scale site was established based on the ABAQUS explicit finite element parallel computing platform for typical composite sites composed of river floodplains, terraces and undulating hills. The results show that: (1) Compared with the peak acceleration of bedrock ground motion, the surface dynamic characteristics of the ground surface near the surface (15m With the increase of depth, the amplifying coefficient of PGA is gradually less than 1.0. (2) The peak acceleration of soil layer increases with the increase of depth (3) The amplifying effect of earthquakes in different areas of the site is quite different, and the amplifying effect of earthquakes in the river floodplain area should be obviously larger than that of the terraces The hilly area is larger; and when the input peak value is the same, the characteristic period of the response spectrum of river floodplain area is greater than the terrace area, the difference between the two reaches 0.05-0.15s; (4) Increased earthquake response spectrum peaks shifted to the long period apparent direction.