Cell Structure of 2D Cohesive Granular Solid

This study presents an analysis of granular cell, defined by the smallest loop of grains in contact, observed in 2D cohesive granular materials using Discrete Element simulations. The adopted particle interaction is the combination of non-contact DLVO force and linear contact repulsion. 9000 mono-sized disk particles were randomly generated in a double-periodic space with a very loose unjammed state, and then compressed isotropically to keep its uniformity by equilibrating the external isotropic compressive stress with agglomeration stress. The external stress was increased stepwise to reproduce the oedometer test in soil mechanics. Then we investigated the granular cell statistics for each loading step. What we found is the following: (1) Within the examined pressure range, the e − log p curve can be well approximated by a straight line, and the effect of interparticle friction appears to be negligible. However, the mean coordination number z shows a clear dependence on interparticle friction. (2) The distribution of cell volumes transitions from a power-law to an exponential form as the external load increases. This suggests that the larger cells are mechanically weaker and tend to collapse earlier. (3) The average cell shape becomes more circular with increasing external load, indicating that circular cells are more stable under compressive stress than elongated ones. Those results suggest that the granular cell approach is also applicable and effective for analysing cohesive granular systems.