关键词: 复合地形场地, 不同地貌单元, 土体非线性, 地震效应特征

Abstract: Based on the explicit finite element method and 32 CPU parallel computing cluster platform of ABAQUS, considering the heterogeneity of ground soils, a large-scale refined two-dimensional finite element nonlinear analytical model for a multi-geomorphic composite site that consists of alluvial flat，terraces，undulating hilly terrain and monadnock is established in the time domain. The SH wave is taken as the bedrock earthquake motion and nonlinear seismic effect characteristics of the composite site are analyzed. The results show that: (1) the peak ground acceleration(PGA) and peak ground displacement(PGD) of different observation points on the ground surface vary with each other, which is caused by the terrain differences. When it’s under the same input ground motion, the ground surface PGA of alluvial flat area shows obviously larger than that of the first terrace area, however, the PGD of alluvial flat is smaller than that of the first terrace, and the PGD difference is relatively smaller in the alluvial flat area. (2) The horizontal acceleration response spectrum of ground surface appears a double-peak or multi-peak phenomenon, the amplification of ground motion seems outstanding in the frequency band from 0.4 Hz to 1.2 Hz. Moreover, the acceleration response spectrum is related with the input ground motion. (3) The amplification effect and focusing effect of seismic motion are more obvious in specific frequency band(0.5 Hz to 1.75 Hz), when the frequency is lower than 0.2 Hz or higher than 2 Hz, the seismic amplification characteristics are not apparent. (4) The location of observation point has influence on the acceleration duration，the changing terrain may cause difference of seismic motion duration，besides，the motion duration, in some way, is dependent on the input ground motion characteristics.

Key words: composite site, multi-geomorphic unit, nonlinear characteristics of soil, seismic effect characteristics