Influence Of The Mechanical Properties Of Soil-Rock Mixture Depth Layer On Dump Slope Stability For Open Pit Mine

This thesis investigated the progressive shear behavior of soil-rock mixture fractures using 2D numerical simulations and laboratory experiments.The particles flow code(PFC2D)was chosen for simulation purposes in this work.The fracture and intact samples were modelled as an assembly of rectangular disks in PFC2 D.By performing shear test simulations in PFC2 D,correlations were obtained between micro and macro properties of the intact sample.To define a set of micro properties corresponding to fracture particles and investigate their effects on shear behavior of planar fractures,a sensitivity analysis of fracture model micro properties including,particle friction coefficient,contact stiffness and confined pressure were carried out.The lab shear tests were conducted using a direct shear test.Both lab experiments and simulations were performed on pseudo-real as well as soil-rock mixture fracture specimens.The directionality in shear strength when the sample was sheared in opposite directions along a horizontal plane was also studied.According to the influencing factors of strength consolidation of soil-rock mixture,the corresponding structural system of influencing factors were established.The shear strength expression of soil-rock mixture was established based on MohrCoulomb criterion,and the shear failure model was combined with the shear failure model.The basic failure modes of soil-rock mixture were also described.The relationship between the three key factors,consolidation pressure,consolidation time,and the shear strength parameters of soil-rock mixture was revealed through consolidation experiments.The average cohesion of soil-rock mixture increased with the increase of consolidation pressure as a quadratic function,while the cohesion of soil-rock mixture decreased with the increase of consolidation time as a logarithmic law.Soil-rock mixture is a geological material that has the properties of rock and soil.The open pit mine waste dump is composed of soil-rock mixture.This thesis investigated the progressive shear behavior and degradation of soil-rock mixture using2 D numerical simulations and laboratory experiments.In this study,the Geo5 Finite Element method(FEM)and Particle flow code discrete element method(DEM)were used to analyze the stability of slope composed of soil-rock mixture.The process of dump accumulation was simulated numerically.According to the calculation results of PFC2 D,the distribution of stress,displacement and plastic zone in the dump was obtained.FOS(factor of safety)for each analytical step in this model was then calculated through the strength reduction method.The limit equilibrium method was used for waste dump stability analysis.The results from this analysis showed that,the waste dump was stable.The potential failure modes of waste dump mainly consisted of the “combined sliding mode” which had circular sliding in the upper side and broken line sliding that cut through gravel-soil layer into a heavily weathered layer in the bottom.This paper documents some of the procedures and approaches utilized for waste dump life-of-mine design analysis.It provides reference for further waste dump optimization.This dissertation includes 35 figures,12 tables,and 111 set of reference.