Macro-micro responses of crushable granular materials in simulated true triaxial tests

This paper presents simulations of true triaxial tests on crushable granular materials. Considering both the shear and tensile fracture modes of the particle, the Mohr-Coulomb model with tension cut-off is employed as the fracture criterion of single particle. When the particle stresses satisfy the fracture criterion, three new balls are generated to replace the broken particle. The new balls overlap enough within the bounding parent sphere to obey the mass conservation law. A polydisperse assembly consisting of 7935 spheres was isotropically compressed until the desired confining pressure was reached. Then the sample with no bias in initial fabric was subjected to axial compression at a constant minor principal stress under different intermediate principal stress ratios, b. The simulated stress-strain-dilation responses were in agreement with the experimental observations. The macro-micro responses including stress-strain characteristics, fabric tensors, anisotropies, the orientation tensor and force chain characteristics were discussed in details. It is shown that volumetric responses is affected by b. The anisotropies vary with b, but a unique macro-micro linkage exists between the anisotropies and stress ratio, q / p, irrespective of the value of b. A linear relationship is found between the obliquity of and the strength indicator ( using the orientation tensor method.