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.

中文翻译：

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用半空间中的空腔和裂纹模拟二维多孔弹性波衍射的间接边界元方法

开发了一种间接边界元方法 (IBEM) 来解决流体饱和多孔弹性半空间中空腔和裂缝的二维 (2-D) 波衍射。多孔弹性全空间中力和流体源的动态格林函数被利用，而不是它们的半空间对应物，因为它们的封闭形式表达式。基于单层势理论，衍射波场是通过在边界上以虚拟密度分布力和源来构建的。通过将近似解与边界条件相匹配来确定密度。由裂纹退化几何引起的积分方程的非唯一性用分区方法处理。通过与文献中的可用结果进行比较，验证了 IBEM 的数值精度和稳定性。解决了空腔散射波和饱和半平面扁平裂纹问题。研究了自由表面上的位移放大效应。数值解表明响应在很大程度上取决于波频率、入射角、裂纹的长度和深度以及材料特性等因素。