A micro finite-element model for soil behaviour: experimental evaluation for sand under triaxial compression

This note evaluates the ability of a combined discrete–finite-element approach to replicate the experimental response of a dry sand under triaxial compression. The numerical sample was created by virtualising the fabric of a Martian regolith-like sand sample obtained from an in situ test using X-ray micro computed tomography; physical properties of the grains obtained from laboratory data were used as input. The boundary and contact conditions were defined according to the experimental test. A key feature of the model is the use of deformable thin-shell elements to represent the numerical membrane, which allows for a realistic failure mode and volumetric deformation. The macroscopic response of the numerical simulation is shown to compare well with the experiment. The contact regions are identified based on their ability to transmit stress and the evolution of the contact normals is shown to correlate well with the macro stress evolution. The computed stress fields within each grain are used to identify the load-bearing grains in the assembly, contributing new insights beyond the commonly reported force chains.