Porotis Medk Under Initz’ab Stress

Fundamental equations are derived for the mechanics of a fluidfilled porous medium under initial stress. The theory takes into account elastic and viscoelastic properties, including the most general case of anisotropy. It includes the theory of stability, and of acoustic propagation under initial stress, and by thermodynamic analogy the dynamics of a thermoelastic continuum under initial stress. Equations are also developed for a medium which is isotropic in finite strain. General variational principles are derived by which problems are easily formulated in curvilinear coordinates or in Lagrangian form by using generalized coordinates. It is shown that the variational principles are a direct consequence of the general equations of the thermodynamics of irreversible processes, and lead to real characteristic roots for instability.