The Ball-Surface Normal Contact Experiment Research and Numerical Simulation of Coarse Grained Soil

In this study, 40 groups of normal contact tests under the ball-surface contact condition between the marble spherical samples and the marble cuboid samples were carried out by use of the rock rheological testing system, in which marble spherical samples were used to simulate coarse grained soil particles. The compression breakage laws and mechanical mechanism of the single coarse grained soil particle was obtained by researching failure mode, the broken process and mechanical property of the samples by means of statistical methods. Then, in order to observe the development of this process, the particle contact numerical model was established and a numerical simulation was carried out with PFC3D. Based on the experiment results, it was found that, at the beginning of loading, the coarse grained soil particle was partly broken at the contact point due to stress concentration, and an elastic core was developed after that; then, the increasing of normal contact force caused cracks near the elastic core; finally, crack transfixion occurred and the particle was totally broken. Having observed the broken particles, it was found that elastic cores of which the top surface was a sub-circular plane and the lower part was a cone appeared in all particles. Moreover, the diameter to depth ratio of the elastic core was close to 2:1. In this research, we provided a new way of study on particle breakage behavior of coarse-grained soil by researching the mechanical mechanism of particle breakage in the perspective of particle contact of coarse-grained soil.