The meso-scale. Fractures as thin layers in Biot media and induced anisotropy

Abstract

A fluid-saturated poroelastic isotropic medium with aligned fractures behaves as a transversely isotropic and viscoelastic (TIV) medium when the predominant wavelength is much larger than the average distance between fractures. Here fractures are modeled as extremely thin and compliant porous layers. P-waves travelling in this type of medium generate fluid flow and slow (diffusion) Biot waves, causing attenuation and dispersion of the fast modes (mesoscopic loss). This chapter presents a set of compressibility and shear time-harmonic experiments on highly heterogeneous fractured poroelastic samples to determine the five complex and frequency dependent stiffnesses characterizing the equivalent TIV medium. These experiments are identified with boundary-value problems which solutions are computed using the finite element procedures.