DYNAMIC ANALYSIS OF POROUS MEDIA IN TIME DOMAIN USING A FINITE ELEMENT MODEL

Abstract

The mechanical behavior of porous media is governed by the interaction between its solid skeleton and the fluid existing inside its pores. The interaction occurs through the interface of grains and fluid. The traditional analysis methods of porous media, based on the effective stress and Darcy's law, are unable to account for these interactions. For an accurate analysis, the porous media is represented in a fluid-filled porous solid on the basis of Biot's theory of wave propagation in poroelastic media. Because of irregular geometry, the domain is generally treated as an assemblage of finite elements. In this investigation the numerical analysis for the field equations governing the dynamic response of fluid-saturated porous media is formulated and employed for the study of transient wave motion. A finite element model is developed and implemented into a computer code called DYNAPM for dynamic analysis of porous media. The weighted residual standard Galerkin method is used for development of a finite element model, and the analysis is carried out in time domain considering the dynamic excitation. The 8-node plane strain elements are applied for discretization of domains. A Newmark time integration scheme is developed to solve the time-discretized equations. This scheme is an unconditionally stable implicit method. Finally, some numerical examples are presented to verify its accuracy and show the capability of the developed model for a wide variety of porous media dynamic behaviors. Obtained results show good agreement in comparison with the other numerical and analytical data.