Particle breakage and micromechanical characteristics of calcareous sand during shearing

Based on the discrete element method, the numerical simulation of the shear test for calcareous sand was carried out to explore the particle breakage and micromechanical mechanism of calcareous sand in the shear process. The results show that the particle breakage can reduce the peak strength of calcareous sand, and make the bulk deformation change from dilatancy to shrinkage. The particle breakage is concentrated in the shear band; with the increase of axial strain, the degree of particle breakage increases, which is also positively correlated with confining pressure and axial strain. The contact forces are redistributed when the particles are broken; the dominant direction of the contact forces in the strong force chain is consistent with σ1, always in the vertical direction, while the dominant direction of the contact forces in the weak force chain is consistent with σ₃, in the horizontal direction, and it gradually deflects to the vertical direction with increasing axial strain; the anisotropy of the contact normal also decreases significantly after particle breakage. The magnitudes of the contact forces in the strong and weak force chains conform to the Weibull distribution. After particle crushing, the magnitudes of the contact forces decrease significantly, and the numbers of the contact forces increase significantly, and the percentage of the weak forces increases significantly, which leads to the decrease of the strength of the sample.