[hal-00622157, v1] Micromechanical analysis of stress in an unsatured granular medium

The paper is concerned with a micromechanical formulation of force transmission within an unsaturated soil as a three-phase system composed of idealized spherical particles connected by a pore water menisci network. It is proposed here a tensorial effective stress equation that can be viewed as a generalized Bishop’s equation in which the elusive effective stress parameter χ is elucidated. The latter can be expressed as an explicit function of the number of water menisci, particle packing and degree of water saturation. Also, interparticle forces are found to be dependent on the distribution of pore fluid pressure and the contractile skin arising from the interaction of interfaces. Two major findings of this work are: (1) the determination of the analytical relationship between χ and degree of saturation, and (2) the identification of a suction based internal shear effect even under isotropic external loading. The understanding of suction stress and its dependency on the degree of saturation is a longstanding problem both theoretically and experimentally. Second International Symposium on Computational Geomechanics (ComGeo II), 27/04/2011, Cavtat-Dubrovnik, HRV ha l-0 06 22 15 7, v er si on 1 12 S ep 2 01 1 Author manuscript, published in "Second International Symposium on Computational Geomechanics (ComGeo II), CavtatDubrovnik : France (2011)"