DEM simulation of mechanical behaviour and bond breakage of different cemented sands

A numerical investigation of the macromechanical behavior and bond breakage of different cemented sands using distinct element method (DEM) is presented. These sand specimens are cemented by means of the contact bond model introduced in a DEM commercial software, PFC^2D and the modified bond model without thickness proposed by Jiang et al (modified Jiang model), respectively. First, the modified Jiang model is incorporated into PFC^2D; Then, a series of biaxial compression tests are performed on specimens with different bond strengths under various confining pressures, and the DEM results are compared and analyzed. The results show that the Jiang sample, whose bond behavior is controlled by the modified Jiang model, exhibits pronounced strain-softening, and shear-dilatancy, and its peak frictional angle increases with bond strength; the PFC sample, whose bond behavior is controlled by the contact bond model, demonstrates strain-softening, shear-dilatancy with high bond strength, but strain-hardening, and shear-shrink under with low bond strength, and its peak frictional angle decreases with bond strength. The simulated results are in accordance with the experimental ones to some extent, especially the Jiang sample can well capture the major mechanical behavior of bonded sands. In addition, the number of broken bond due to tension is lager than that due to shear in the Jiang sample, while they are the same in the PFC sample. The studies on microscopic parameter of the modified Jiang model show that under low confining pressures, the macromechanical behavior and bond breakage form are sensitive to the ratio of tangential bond strength to normal bond strength.