An indirect boundary element method to model the 3-D scattering of elastic waves in a fluid-saturated poroelastic half-space

Abstract

The indirect boundary element method (IBEM) is extended to solve the scattering of elastic waves by three-dimensional (3-D) subsurface irregularities in a fluid-saturated poroelastic half-space. The Green׳s functions of inclined circular loads and fluid source in a poroelastic full space are deduced based on Biot’s theory. According to the single-layered potential theory, the scattered waves are constructed by using fictitious uniform loads and fluid source distributed on the boundary elements on the scatterer surface, and their magnitudes are determined by the continuity or traction-free boundary conditions. Accuracy verification illustrates that this proposed method can deal with 3-D wave scattering problems in an infinite poroelastic medium conveniently and accurately. Then, the scattering of plane waves by a 3-D canyon is investigated. Numerical results indicate that: the scattering of waves in a poroelastic half-space strongly depends on the incident frequency and incident angle; the 3-D amplification effects both on the displacement and pore pressure appear to be more significant than the corresponding 2-D case; medium porosity of the half space also plays a key role on the wave scattering, especially for obliquely incident waves at the critical angle, and the influence of drainage condition seems to be more considerable for high porosities.