On the effects of inertial coupling on the wave-speeds of elastic-plastic fluid-saturated porous media

The mixture theory of fluid-saturated porous media involves three types of couplings: mechanical, through stress/strain laws, viscous, through Darcy's law, and inertial. Viscous coupling is not involved in the analysis of acceleration waves: for elastic-plastic fluid-saturated porous media it has been shown that complex wave speeds ("flutter instability") or stationary discontinuities ("strain localization") may occur. On the other hand, we show here that the effect of inertial coupling on the elastic-plastic wave-speeds is mainly quantitative and not qualitative: the basic structure of the eigenvalue problem leading to the elastic-plastic wave-speeds remains unchanged.