Effective stress principle for partially saturated granular media

Conference · Fri Jan 01 00:00:00 EST 1982

OSTI ID:7059247

McTigue, D F; Wilson, R K; Nunziato, J W

A granular or porous medium with any number of fluid phases in the pores is considered. The motivation stems primarily from concern for the fluid flow and matrix deformation in partially saturated media, a typical example being a soil or rock containing interstitial water and air. The heart of the following developments lies in the choice of constitutive equations for the forces of interaction between the various components of the mixture. Thermodynamic arguments are used to motivate the form of the interaction terms. As a result, a concept of effective stress emerges which agrees with previously proposed models and capillary effects are identified clearly in a thermodynamic context. The resulting theory is illustrated by examining some simple problems in partially saturated media. First, we specialize to the case of a linear elastic matrix, and show how capillary suction reduces the porosity. Second, we consider the problem of one-dimensional consolidation of a partially saturated half-space in which the air is free to escape. The problem for the fluid pressure reduces to a nonlinear diffusion problem, similar to that for horizontal infiltration, with a saturation front propagating downward into the medium. No water drains through the surface. The results for the fluid pressure also indicate that the granular medium undergoes larger elastic deformation than in the saturated case. We also comment briefly on the effects of porosity gradients on consolidation.

• Research Organization: Sandia National Labs., Albuquerque, NM (USA)
• DOE Contract Number: AC04-76DP00789
• OSTI ID: 7059247
• Report Number(s): SAND-82-1977C; CONF-820843-2; ON: DE82020408
• Resource Relation: Conference: US-Japan seminar on new models and constitutive relations in the mechanics of granular materials, Ithaca, NY, USA, 22 Aug 1982
• Country of Publication: United States
• Language: English

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