ABSTRACT
In unsaturated porous media, it is well known that the degree of saturation affects not only the shear strength of the material, but also its volume and hydraulic properties (Sheng 2011). For dry porous media, the repulsive force between the contacting grains can usually be accurately described by an elasto-plastic contact model (Mitchell & Soga 2005). For water-bonded particles, however, a specific attractive force exists: the meniscus produces a suction, which, in turn, generates inter-particle compressive forces, named capillary forces, whose mechanics depends on the degree of saturation of the medium. At low saturations (the pendular regime; Bear 1972), the capillary force depends on the separation between the two grains, the radius of the liquid bridge, interfacial tension and contact angle (Lian et al. 1993). At high saturations (the funicular regime; Bear 1972), negative water pressure acts all around the particle. Generally, the capillary force depends on the grain sizes and the local geometry of the grains (Scholtès et al. 2009).
