FROM MIXTURE THEORY TO BIOTS APPROACH FOR POROUS-MEDIA

Two apparently different approaches ark used in dealing with the mecha nics of a deformable porous medium: mixture theories on the one hand, and purely macroscale theories, which are mainly associated with the w ork of Blot, on the other hand. In the mixture theories; the porous me dium is represented by spatially superposed interacting media, while m acroscale theories assume that standard concepts of continuum mechanic s are still relevant at the macro-level. The aim of this paper is two- fold. First, it is shown that the macroscale field equations derived f rom mixture theories can be reformulated in terms of the measurable qu antities involved in the macroscale theories: Second, it is demonstrat ed how these field equations, including the fundamental inequality obt ained from the second law, entail the existence of a macroscale Psi-po tential upon which a thermo-dynamically consistent formulation of the constitutive equations can be firmly founded. (C) 1998 Elsevier Scienc e Ltd. All rights reserved.