Propagation characteristic of Rayleigh waves in orthotropic fluid-saturated porous media

In this paper, the influence of anisotropy of the solid skeleton on the propagation characteristic of Rayleigh waves in orthotropic fluid-saturated porous media is studied from a more general sense based on Biotʹs theory. Firstly, the governing equations for orthotropic fluid-saturated porous media are derived. Then the three-dimensional complex characteristic equations for Rayleigh waves are deduced and their existence conditions are given. Based on the characteristic equations, the Rayleigh wave speeds along arbitrary directions and particle traces in arbitrary sagittal planes are numerically calculated. The effects of anisotropy of the solid skeleton on the propagation characteristic of Rayleigh waves are analyzed in detail. The results show that the Rayleigh waves display different characteristic in orthotropic fluid-saturated porous media from that they have exhibited in isotropic or transversely isotropic fluid-saturated porous media.