CONSTITUTIVE DESCRIPTIONS OF MULTIPHASE POROUS MEDIA
多相孔隙介质的本构描述

Based on the Theory of Mixtures, a new method for the constitutive modelling ofsaturated and non-saturated porous media (especially the geomaterials) is proposed and developedin this paper. In the new constitutive modelling, realistic porous media is supposed to be composedof three kinds of mixtures within two levels, the Solid Phase (SP, mixture made up of differentsolid materials or same materials with different inelastic deformation history) and the Fluid Phase(FP, mixture of real fluid and real gas within the porous media) in level one, and material (OverallPhase, OP) made up of the Solid Phase and the Fluid Phase in level two. A set of constitutiveequations are proposed for both SP, FP and OP in the frame of Continuum Mechanics. Besides,phase changes within SP, FP and OP are also considered.From the viewpoint of the proposed model, material properties are determined by the properties of their constitutions and the interactions among every constitute. So the constitutive equationsof each constitute of a mixture (SP, FP or OP) should be known a pirori. The modelling of theinteractions among different constitutes ensure the capability of the model to describe the coupling among different phenomena such as solid deformation and fluid compressibility. The changeof material properties are supposed to be the result of phase changes defined as the variations ofmasses among constitutes.All models based on the Theory of Mixtures are "superimposed continuum models" which putmore attention on the overall properties of material as a whole than on the specific mesostructuresof material studied. For example, it is quite easy and convincing for the model to get the effectiveYoung's modulus and relationship between effective stress and strain of a plane stress plate withan array of Model I crack. But the model is hard to simulate the detail crack propaganda of agiven crack. So the proposed model is more applicable to materials with irregular mesostructuressuch as rock, soil and concrete, where representative elements (REs) are not always available, thanthose with regular mesostructures such as laminated composite materials, where REs are alwaysavailable. Besides, the model is more suitable to simulate the overall properties of material as awhole such as progressive failure, solid-fluid coupling and partial saturation than those of a specificmesostructure such as crack tip singularity.