二维饱和沉积盆地地震动响应非线性分析

Nonlinear Seismic Response Analysis of Two-dimensional Depositional Basins

沉积盆地对地震动具有明显的放大效应。利用ABAQUS软件及二次开发平台,编写了基于Davidenkov骨架曲线的VUMAT子程序,对饱和沉积盆地进行了非线性反应模拟。建立不同基岩面坡度的二维T型沉积盆地,输入4条不同频谱特性及幅值的近断层地震波,研究不同盆地基岩面坡度、饱和介质特性、地震波强度等因素对沉积盆地非线性反应规律的影响。研究结果表明,地震波作用可造成饱和沉积盆地发生局部液化,地震波强度越大,液化区分布范围越广,地表处出现了永久塑性变形;地震波强度的增大导致地表土层发生液化的时间提前,且下层土的液化会减弱地震波的传播速度,导致上层地表土发生液化的时间延后;盆地内地表最不利位置随着基岩面坡度的增大逐渐向中心处移动,不同工况下速度峰值放大系数为1.18~3.33。

Near fault seismic motion can lead to significant seismic disasters in the near field area,particularly in regions with sedimentary terrain,exacerbating the potential disaster.In this paper,ABAQUS software and secondary development platform are employed to compile VUMAT subroutine based on Davidenkov skeleton curve,to conduct nonlinear simulation of saturated sedimentary basin,and to establish two-dimensional T-shaped Sedimentary basin with different bedrock surface slopes.Four near fault Seismic wave with different spectral characteristics are selected to input the site with different amplitudes,and the nonlinear response of the site under the action of different basin slopes and seismic wave intensities is studied.It is found that seismic wave can cause liquefaction in saturated sedimentary basin.The greater the strength of seismic wave is,the wider the distribution range of liquefaction area is,and permanent plastic deformation occurs on the surface;The increase of seismic wave strength can lead to the advance of liquefaction time of surface soil layer,and the liquefaction of subsoil will weaken the propagation strength of Seismic wave,resulting in the delay of liquefaction time of upper surface soil layer.As the bedrock surface slope increases,the most vulnerable location on the basin's surface shifts toward the center.Furthermore,the amplification coefficient of peak velocity ranges from 1.18 to 3.33 under various working conditions.