斜入射平面SH波在层状半空间中沉积谷地周围的三维散射

Three-dimensional scattering by an alluvial valley in a layered half-space for obliquely incident plane SH waves

采用直接刚度法计算自由场动力响应,以层状半空间中移动斜线均布荷载动力格林函数模拟散射波场,采用间接边界元方法求解了层状半空间中沉积谷地对斜入射平面SH波的三维散射问题。由于文中采用的层状场地三维动力刚度矩阵是精确的,且用于模拟散射波场的均布移动斜线荷载可以直接施加在沉积交界面处而不存在奇异性,所以本文方法具有很高精度。文中以均匀半空间和基岩上单一土层中沉积谷地对入射SH波的散射为例进行了数值计算,研究表明,沉积谷地对地震波的三维散射与二维散射之间存在本质差别;层状半空间中沉积谷地与均匀半空间中沉积谷地附近地表位移存在显著差异。

The indirect boundary element method （IBME） is used to study three-dimensional scattering by an alluvial valley embedded in a layered half-space for obliquely incident plane SH waves; by using the direct stiffness method to calculate the free-field responses and dynamic Green＇s functions of moving distributed loads acting on inclined lines in a layered half-space to simulate the scatter wave filed responses. The presented, method yields very accurate results for the 3D dynamic stiffness matrixes and the fictitious uniform moving loads can be acted directly on the interface between the alluvial valley and the layered half-space without singularity. Numerical results and analyses are performed by taking the amplification of incident plane SH waves by an alluvial in a uniform half space and in one layer over half-space. The results show that the three- dimensional responses are distinctively different from the two-dimensional responses, and the displacement amplitudes around the valley in a uniform half-space are obviously different from those of in a layered half-space.