A special indirect boundary element method for seismic response of a 3D canyon in a saturated layered half-space subjected to obliquely incident plane waves

A special indirect boundary element method (IBEM) is proposed to deal with the wave scattering of plane P1-, SV- and SH-waves by a 3D canyon cut in a saturated layered half-space. First, the dynamic stiffness matrix method is used to determine the free field dynamic responses. Then, based on Biot's theory, the 3D dynamic Green's functions for uniformly distributed loads and pore pressure acting on an inclined plane in a saturated layered half-space are derived, which is subsequently utilized to construct the scattered fields. Finally, the densities of uniformly distributed loads are determined by introducing boundary conditions, and the total dynamic responses are obtained by superimposing the free and scattered fields. The accuracy of the proposed method is verified via the comparison between the calculated results and those of published literature. The influences of boundary drainage conditions, medium porosity, and soil layering on seismic response are investigated in the frequency domain through parametric analysis. The numerical results show that the influences of boundary drained conditions on dynamic response are apparent, especially for high incident frequency. The effect of porosity on dynamic response seems to more sensitive to undrained conditions. Furthermore, the soil layering will bring an impact on the scattering mechanism of the layered system, appearing difference in the displacement amplitude and its distribution.