Research On Open-pit To Underground Mining Technology In Chang'an Mining Section

With the rapid development of national economy,a large demand for resources and the depletion of shallow mineral resources,many open-pit mines gradually turn to underground mining.When open-pit mining is underground mining,how to recycle the hanging ore on the exposed slope,how to mine the ore resources at the bottom of the pit,and how to ensure the stability of the open-pit slope are important topics for the successful transformation of production mode,safety,management and sustainable development of the open-pit mine.The overall open-pit mining of Chang'an section of Jinping Chang'an Mining Co.,Ltd.was completed in 2017,and the maximum elevation difference of open-pit slope was 412m.Aiming at the technical problems of converting open-pit to underground mining in Chang'an mine section,through the comprehensive analysis of mine engineering geology,resource reserves and mining status,and using the methods of numerical simulation and theoretical analysis,this paper systematically analyzes the key technical problems of safe mining,such as the impact of underground mining on slope stability,the mining technology of hanging wall in open pit and the mining method of underground mine The in-depth study provides a technical guarantee for realizing safe and efficient mining from open-pit to underground.The details are as follows:1.The numerical simulation of Chang'an mine section is carried out by using discrete element software,and the unexcavated model is taken as the initial model.Based on the initial model,the model after open-pit mining is first simulated.Through the analysis of the simulation results,it is concluded that after the open-pit mining reaches 1520m,the slope is in a stable state except for the cracking and sliding of local bench blocks.Finally,the model after underground mining is simulated,and the analysis of the simulation results shows that the underground mining in the lower part of the open pit has no impact on the surrounding regional facilities.2.FLAC^3D software is used to simulate the stope structural parameters of hanging wall mine,the influence of hanging wall mine mining on the stability of open-pit slope,and the overall mining sequence of underground mine.The study shows that when the pillar width is 8m and the stope span is controlled within 8m,the overall stability of the pillar can be ensured;During the mining of hanging wall ore,there will be certain separation or cracking and sliding in the mining area,but the overall slope is relatively stable and there will be no large sliding failure;For the mining sequence of ore bodies below 1520m,it is recommended to mine from both ends to the middle.3.Combined with the actual production of the mine and the occurrence of the ore body,the shallow hole shrinkage method+non pillar caving method and upward drift(or layered)filling method are selected for comparative study of mining methods.Finally,the shallow hole shrinkage method+non pillar caving method is determined as the open-pit to underground mining method.