  A numerical study of multi-phase granular materials based upon
micro-mechanical modelling is proposed. Discrete element simulations are used
to investigate capillary induced effects on the friction properties of a
granular assembly in the pendular regime. Capillary forces are described at the
local scale through the Young-Laplace equation and are superimposed to the
standard dry particle interaction usually well simulated through an
elastic-plastic relationship. Both effects of the pressure difference between
liquid and gas phases and of the surface tension at the interface are
integrated into the interaction model. Hydraulic hysteresis is accounted for
based on the possible mechanism of formation and breakage of capillary menisci
at contacts. In order to upscale the interparticular model, triaxial loading
paths are simulated on a granular assembly and the results interpreted through
the Mohr-Coulomb criterion. The micro-mechanical approach is validated with a
capillary cohesion induced at the macroscopic scale. It is shown that
interparticular menisci contribute to the soil resistance by increasing normal
forces at contacts. In addition, more than the capillary pressure level or the
degree of saturation, our findings highlight the importance of the density
number of liquid bonds on the overall behaviour of the material.
