Analysis Of Discrete Element Method For Deformation And Failure Of Slope Of Yanqianshan Iron Ore Mine Being Changed For Open Pit Mining To Underground Mining

It has been over90years since Yanqianshan iron ore mine was explored in1920.The mine is now on the stage of the transition from open pit to underground mining.Years of mining has caused more than300-meter high andsteepopen pit slope, and thetransition from open pit to underground mining will lead to more severe slopelandslides and damages. The paper is based on Yanqianshan iron ore and discreteelement method is used to establish the two dimensional model for4representativesections of Yanqianshan iron ore’s northern and southern slopes, numericallysimulating the deformation and failure of northern and southern slopes in thetransitionfrom open pit to underground mining:(1) Geological data of Yanqianshan are collected, section statistics are obtainedthrough analyzing the data from selecting four representative sections, and the twodimensional geological model for the four representative sections is developed.(2) Two dimensional DEM for the characteristics of the failure in the transitionfrom open pit to underground mining is preliminarilyexplored, which contains of:construction method for two dimensional DEM model, that is, the geologicalinformation extraction, the modeling range determination, model simplified methodand model boundary condition specification, including the simplified simulation forstructural planes of discontinuities; determination of rock mechanical and jointparameters of the model; and simulation for underground mining process.(3) Discrete element method is used to simulate the transition from open pit tounderground mining process of Yanqianshan iron ore to obtain the displacementdistribution, joint failure, stress distribution, and plastic zone distribution in themining of northern and southern slopes. The characteristics of slope failure of fourrepresentative sections ofnorthern and southern slopes which are mined to-320mand-500m horizontally is also analyzed in details and the slope failure shapes isdisplayed. Positions and shapes of sliding surfaces in different mining levels areobtained, from which it is concluded that the sliding surface is related to the jointsurface.