Indirect Boundary Element Method For Modelling 2-D Poroelastic Wave Diffraction By Cavities And Cracks In Half Space

An indirect boundary element method (IBEM) is developed to solve two-dimensional (2-D) wave diffraction by cavities and cracks in a fluid-saturated poroelastic half space. The dynamic Green's functions of forces and fluid source in a poroelastic full-space, rather than their half-space counterparts, are utilized, because of their closed-form expressions. The diffracted wave field is constructed by distributing forces and sources in fictitious densities over the boundaries, based on the single-layer potential theory. The densities are determined by matching the approximate solution with the boundary conditions. The nonuniqueness of integral equation caused by the degenerated geometry of a crack is treated by a zoned approach. The numerical accuracy and stability of the IBEM are verified by comparing with available results in the literature. Problems of wave scattering by cavity and flat crack in saturated half plane are solved. The displacement amplification effect on the free surface is investigated. The numerical solutions show that the response is strongly dependent on factors such as wave frequency, incident angle, the length and depth of the crack, and material properties.