【摘要】 沉积风化作用下土体表现出明显的成层特性和横观各向同性(TI)特性。将更为符合实际的TI介质模型引入到局部地形对地震波的散射问题研究有着重要的理论意义和工程实用价值。本文在TI土层平面外动力刚度矩阵的基础上,推导了斜线均布荷载动力格林函数,进而以该格林函数为基本解建立间接边界元方法研究了TI层状半空间中凹陷地形对平面SH波的散射问题。文中验证了方法的正确性,并分别在频域和时域内进行了数值计算分析。研究表明,TI介质中凹陷地形对SH波的散射与各向同性介质情况存在较大差异,凹陷附近地表位移幅值依赖于SH波的入射角度、入射频率和竖向与水平剪切模量比值;另外土体竖向与水平剪切模量比值对基岩上单一土层场地动力特性有着显著影响,进而使得TI层状场地凹陷附近位移幅值与各向同性情况差异变得更为复杂。更多还原

【Abstract】 Soil shows obvious layered characteristics and transverse isotropic characteristics due to the action of deposition and weathering. It has important theoretical significance and practical value in engineering to introduce the more actual transversely isotropic( TI) medium into the study of wave scattering by local topography. The green’s functions for uniform distributed loads acting on an inclined line is deduced on the basis of the exact antiplane dynamic stiffness matrix. Then the indirect boundary element method is proposed by using these green ’s functions as fundamental solutions,and the wave scattering problem of a canyon in a transversely isotropic layered half-space for incident SH wave is studied. The method is verified and the numerical calculations are performed both in the frequency and time domain. Numerical results show that wave scattering for the TI medium can be significantly different from the isotropic case,and the surface displacement amplitudes around the canyon are strongly dependent on the incident angle,incident frequency and shear stiffness ratio between the horizontal and vertical directions. The shear stiffness ratio affects the self-dynamic characteristics greatly,which in turn makes the difference in surface displacement amplitudes more complex.更多还原