3D DEM Simulations of Drained Triaxial Compression of Sand Strengthened Using Microbially Induced Carbonate Precipitation

A discrete-element method (DEM)-based numerical model was developed to simulate the triaxial compression response of sand strengthened using microbially induced carbonate precipitation (MICP). A three-dimensional (3D) sphere packing algorithm that uses a particle-growth model was used to generate the initial assemblage of particles. A parameter identification approach was used to evaluate the five microscale parameters of the DEM model (two elastic and three rupture parameters) using experimental results from drained triaxial compression tests on sand. The interparticle friction angle was found to be the most influential of the five parameters with respect to modeling the constitutive response. A particle homogenization approach was used to model the particles when they are strengthened with low amounts of calcium carbonate (<1% by mass). The particle contacts are assigned a cohesive shear strength when higher amounts of calcium carbonate (1% by mass) are present to model the effect of cementation between sand grains. This DEM model was shown to be capable of adequately simulating the drained triaxial compressive response of MICP-strengthened sands. The increase in microstructural heterogeneity as the carbonate content is increased was visualized through normal contact force distributions. The model can be used to estimate the desired level of cementation for the design of MICP treatment strategies with minimal experimentation.