Exact solutions for one-dimensional transient response of fluid-saturated porous media

Based on the Biot theory, the exact solutions for one-dimensional transient response of single layer of fluid-saturated porous media and semi-infinite media are developed, in which the fluid and solid particles are assumed to be compressible and the inertial, viscous and mechanical couplings are taken into account. First, the control equations in terms of the solid displacement u and a relative displacement w are expressed in matrix form. For problems of single layer under homogeneous boundary conditions, the eigen-values and the eigen-functions are obtained by means of the variable separation method, and the displacement vector u is put forward using the searching method. In the case of nonhomogeneous boundary conditions, the boundary conditions are first homogenized, and the displacement field is constructed basing upon the eigen-functions. Making use of the orthogonality of eigen-functions, a series of ordinary differential equations with respect to dimensionless time and their corresponding initial conditions are obtained. Those differential equations are solved by the state-space method, and the series solutions for three typical nonhomogeneous boundary conditions are developed. For semi-infinite media, the exact solutions in integral form for two kinds of nonhomogeneous boundary conditions are presented by applying the cosine and sine transforms to the basic equations. Finally, three examples are studied to illustrate the validity of the solutions, and to assess the influence of the dynamic permeability coefficient and the fluid inertia to the transient response of porous media. Copyright (C) 2010 John Wiley & Sons, Ltd.