Propagation of weak perturbations in cracked porous media

A three-velocity, three-pressure mathematical model is proposed which enabl es one to study wave processes in the case of a double porosity, deformable , fluid-saturated medium. This model takes account of the differences in th e velocities and pressures in pore systems of different characteristic scal es of the pores, fluid exchange between these pore systems and the unsteady forces due to interphase interactions. It is established that a single tra nsverse and three longitudinal waves: one deformation wave and two filtrati on waves, propagate in such a medium. The existence of two filtration waves is associated with the two different characteristic scales of the pores an d the difference in the velocities and pressures of the fluid in these pore systems. The filtration waves decay considerably more rapidly than the def ormation and transverse waves. The velocities of the deformation and transv erse waves are mainly determined by the elastic moduli of the skeleton. The velocity and decay of the first filtration wave depend strongly on the int ensity of the interphase interaction force while the velocity of the second filtration wave depends strongly on the rate of mass exchange between the pores and the cracks. The rate of decay of the second filtration wave is si gnificantly higher than that of the first filtration wave. (C) 2000 Elsevie r Science Ltd. All rights reserved.