Study On The Influence Of Covering Layer On Slope Stability In Mining Process After Open Pit Turned To Underground

With the deepening of open-pit mining depth,the shallow ore reserves are in short supply.In order to meet the market demand for mineral resources,the open-pit mine has turned to underground mining for the development trend.After the open-pit to underground mining,the slope rock mass is disturbed by the stress of secondary mining on the basis of the destruction of the initial open-pit mining activities.With the development of underground mining,the slope rock mass is further deformed and destroyed,which seriously affects the safe production activities of the mine.The rock mass of the northern slope of Yanqianshan Iron Mine is broken and joints and fissures are developed.A certain degree of slope failure has occurred during the transitional mining period.At present,Qianshanshan Iron Mine has been converted to underground mining,and the stability of the northern slope has become a prominent problem in mine safety.Therefore,taking Qianshaniron Mine as the engineering background,this paper analyzes the influence of overburden on slope stability after open pit to underground mining by means of large-scale indoor similar material model experiment,3DEC numerical simulation and set-up control experiment.The main research work of this paper is as follows:1.Summarize the research status of slope rock mass destruction and instability at home and abroad,and combine with the actual engineering background of Qianshanshan Iron Mine,finally select the profile of the north slope of Openpit as a prototype to carry out large-scale indoor similar material model experiments and numerical simulation research.2.Comparative analysis of several similar materials widely used to simulate rock mass.Considering the experimental conditions and operability,similar materials with river sand,barite powder and paraffin wax as raw materials are finally selected.3.Make standard parts of similar materials,and determine their mechanical parameters through indoor rock mechanics experiments.Combined with similarity theory and mechanical parameters of original rock,finally determine the appropriate matching scheme for subsequent indoor large-scale similar material model experiments.4.Contrast experiment of two cases with and without covering layer,pouring similar material experimental model according to the matching scheme,and simulating the actual underground mining process of the mine,and comparing and analyzing the slope rock mass destruction of the two groups of experiments by combining the slope displacement nephogram monitored by the three-dimensional optical measurement system.5.The 3DEC discrete element numerical simulation software is used to simulate the mining process of underground ore body in Qianshaniron Mine.The failure of open-pit slope rock mass with and without overburden is analyzed and compared with the results of indoor large-scale similar material model experiments.The influence of overburden from open-pit to underground mining on slope stability is further summarized.