Experimental analysis of the effects of fluid—solid coupling on the velocity of elastic waves in saturated porous media

Abstract

This paper briefly reviews the characteristics of fluid—solid coupling in the dynamic behaviour of saturated porous media and describes the installation and use of piezoceramic transducers for the simultaneous measurement of longitudinal and rotational waves in triaxial samples. The comparison between longitudinal and rotational wave velocities measured in dry and watersaturated samples is described and analysed in detail. Two soils with different permeability features are investigated. The comparison shows that a reliable interpretation of rotational wave velocities of both permeable and impermeable saturated soils can be obtained if the effects of viscous and inertial couplings are taken into account using Biot's theory. The same conclusions apply to the longitudinal wave velocities of impermeable saturated soils. In contrast, the interpretation of longitudinal wave velocities of permeable saturated soils gives an elastic stiffness value which is underestimated with respect to the value obtained from dry soils. Finally, the accuracy with which the small-strain stiffness of saturated soils can be evaluated from dynamic tests is discussed.