Contact characteristics and wall and corner effect of abandoned dreg based on parallel line characteristics of particles

Abstract

Waste dump sites are extensively produced during the process of engineering constructions. The side slopes of these artificial geological bodies possess waste particles with varying shapes, and the deformation and failure mechanisms are often complex, leading to frequently occurred slope instability events. In this study, we simplified waste particles by defining 4 types of particles with different shapes, which are distinguished by the presence of parallel sides. By performing a series of numerical simulations of direct shear tests, we investigated the wall-corner effect and mesoscopic contact characteristics of the interior of particle deposits. The results prove the existence of wall-corner effect in the waste deposits. Loose particle arrangement and penetrating voids extending along the shear force direction can be observed. The uniform distribution of force chain in parallel-sided waste particles is disrupted, while a circular distribution or the disruption of force chain development is seen in non-parallel-sided particles, indicative of the generation of penetrating voids. When the confining pressure is low, the angle of internal void spaces inside the particles deflects when the shear displacement is 3-6mm, and this deflection in parallel-sided particles is not obvious compared with that in non-parallel-sided particles. Specifically for the hexagonal waste particles, the extension angle is positively correlated with the confining pressure in the early and middle shear stage. Under the effect of increasing confining pressure or shear force, the arrangement of particles gradually become ordered, and the void spaces extend toward the central and corner areas of the shear zone. In practical engineering, these void spaces can be filled with heterogeneous wastes, and drainage measures can be set in the corners of the retaining wall, thereby mitigating the influence of penetrating voids on the stability of waste dump slopes.