A particulate-scale investigation of cemented sand behavior

In this paper, triaxial tests and numerical simulations using the discrete element method (DEM) are combined to explore the underlying mechanisms of the unique behavior of artificially cemented sands. The experimental results show that strength enhancement, volumetric dilation, and the shear banding associated failure mode are observed in Portland cement sand;; these features become more pronounced with increasing cement content. Different responses are found in gypsum-cemented sand even though both types of cemented sand specimens were prepared under very similar void ratios before shearing. The DEM simulations on the Portland cement sand were carried out under two particular arrangements (i.e., the use of small cementing particles and flexible membrane boundaries). The simulation results reveal that particles in the bonding network jointly share the loading and many micro force-chains associated with cementation are created. Compared with uncemented sand, a more stable and stronger force-chain complex subjected to smaller force concentration is formed in cemented sand, which gives rise to higher strength. Intensive bond breakage, concentrated relative particle movement, column-like force chains, great particle rotation, and high local porosity are found inside the shear band. The bonded clusters remain at large strains to help stabilize the particle arch and therefore to maintain the volumetric dilation.