Micro-mechanical failure analysis of wet granular matter

We employ a novel fluid-particle model to study the shearing behavior of granular soils under different saturation levels, ranging from the dry material via the capillary bridge regime to higher saturation levels with percolating clusters. The full complexity of possible liquid morphologies Scheel et al. (Nat Mater 7(3):189-193, 2008. doi:10.1038/nmat2117) is taken into account, implying the formation of isolated arbitrary-sized liquid clusters with individual Laplace pressures that evolve by liquid exchange via films on the grain surface Melnikov et al. (Phys Rev E 92(022):206, 2015. doi:10.1103/PhysRevE.92.022206). Liquid clusters can grow in size, shrink, merge and split, depending on local conditions, changes of accessible liquid and the pore space morphology determined by the granular phase. This phase is represented by a discrete particle model based on contact dynamics Brendel et al. (Contact dynamics for beginners. Wiley-VCH, Weinheim, 2005. doi: 10.1002/352760362X.ch14), where capillary forces exerted from a liquid phase add to the motion of spherical particles. We study the macroscopic response of the system due to an external compression force at various liquid contents with the help of triaxial shear tests. Additionally, the change in liquid cluster distributions during the compression due to the deformation of the pore space is evaluated close to the critical load.