Modelling and measuring of cohesion in wet granular materials

Using a Cohesive Discrete Element Method (CDEM), three-dimensional simulations have been performed to investigate the internal tensile stress and the tensile strength and shear strength of fine, cohesive granular materials. Interparticle cohesion is taken into account by modelling liquid bridges in pendular state. The influence of surface roughness is considered by a minimum separation distance of the particles with respect to liquid bridges. Agglomerates of mono-sized spheres have been formed to measure the stress caused by liquid bridges. A good general agreement with Rumpf's equation is demonstrable, and divergences may be explained by the existence of stretched bridges. Spheres and more complex particle shapes have been used for shear and tensile test simulations. Applying negative loads, the yield loci in the tensile range could be measured successfully. A comparison with experimental ring shear tests on glass beads demonstrates a good agreement. (C) 2003 Elsevier Science B.V. All rights reserved.