Research On Limit Depth Of Open-Pit Mining In Bayan Obo East Mine

The Bayan Obo Iron Mine is a large-scale open-pit mine that is associated with various metals such as iron,rare earth and niobium.At present,the open-pit mine of the East Mine of the mine has entered the stage of deep concave mining,and is less than 100 m away from the designed minimum mining elevation.The dilemma of pit stop production.Recovering deep resources and protecting rare earths,a national strategic resource,has become a comprehensive problem that must be solved in mining.Open-pit mining or underground mining,which mining method is conducive to fully recovering mineral resources under the premise of safety,there are still many disputes in mines.Based on this situation,this thesis will combine the actual situation of the mine,comprehensively consider both safety and economic benefits,and use the 3DMine threedimensional visualization mining software to calculate and excavate to determine the limit depth of open-pit mining in the East Mine.Finally,in order to ensure that the obtained limit depth is scientific and reasonable,and to clearly and intuitively understand the relevant mechanical conditions of the most unstable slope at this limit depth,the FLAC 3D numerical simulation software is used to stabilize the most unstable slope.The simulation is carried out to further verify the rationality of this open-pit mining limit depth in actual engineering.The main results of the research are as follows:(1)According to the characteristics of the mine ore body and the current mining conditions,use 3DMine to establish a three-dimensional surface model,ore body model,geological database and block model of the current mining situation,and build a threedimensional analysis platform for the mine;(2)Using the block report function of 3DMine to calculate the ore volume of the ore hanging outside the boundary of the East Mine and the Dongjielegele ore section at the periphery of the boundary,it is calculated that the total ore volume above the 1320 m elevation is 93.6972 million tons,and the total ore volume from 780 m to 1320 m is calculated.The volume was 141.5684 million tons.It is estimated that there are a lot of resources available for exploitation below the 1230 m elevation;(3)The mine mineral product plan is iron concentrate and rare earth concentrate.The economic and reasonable stripping ratio of the mine is 5.84 calculated by the concentrate cost method;with the help of 3Dmine,the final slope angle is preliminarily determined to be 45°.Optimize the open-pit boundary from two aspects,calculate the boundary stripping ratio under different mining depths,and compare the boundary stripping ratio with the economically reasonable stripping ratio according to the principle of determining the limit depth of open-pit mining,and determine that the limit depth of open-pit mining is 1114 m elevation;(4)In this thesis,the FLAC3 D numerical simulation software is used to analyze the stability of the slope at the extreme depth of mining,and the slope models of different slope angles are designed for the most unstable typical slope,respectively,from the displacement,vertical stress,shear strain increment and Safety factor and other aspects were analyzed to understand the final slope stability state,and according to the analysis results,the final slope angle was determined to be 45°,and the rationality of the open-pit mining limit of the East Mine was verified from the perspective of safety.