Study On The Slope Stability Of Side Wall In The Open-pit Coal Mine For Paste Cut-and-Backfill Mining

Due to the need of protection for the open-pit slope and mine field border development in the open-pit coal mines,a large number of coal resources under the side wall can not be fully recovered,which will have a great impact on the service life and production economic benefits of the open-pit coal mine.The use of side shearer or continuous miner and the development of paste backfill technology,which provide the technical conditions and the new development opportunities for the safe recovery of the open-pit coal resources under the side wall in the open-pit coal mine.Because the buried depth of the open-pit coal mine is relatively shallow and the comprehensive lithology of the overlying rock layer is relatively soft,therefore some technology problems may be in trouble for the paste replacing cut-and-backfill mining of coal resources under side wall of the open-pit coal mine.Based on the geological and mining conditions of the open-pit coal mining in Shenyi Coal Mine,Inner Mongolia,this paper has carried out the research on the slope stability of side wall coal paste replacing mining in the open-pit coal mine.The long-term stability of side wall coal paste cut-and-backfill mining slope is deeply analyzed by combining field investigation,theoretical analysis,similar material simulation and numerical simulation.The main conclusions are as follows:(1)Based on the geological conditions of open-pit mining in Shenyi Coal Mine of Inner Mongolia,the mechanical model of paste cut-and-backfill mining in the open-pit coal mine is established,and the reasonable scale of paste cut-and-backfill mining are calculated and analyzed.On the basis of exploring the slope stability of paste cut-and-backfill mining,the influence of displacement and stress distribution on the slope stability of the open-pit coal mine is further compared.This paper revealed the movement law of the overlying strata supported by the backfill body and the coal pillar,and predicted the stable state and the trend of catastrophic evolution of the slope in the open-pit coal mine.(2)Based on the simulation experiment of similar materials,the mining and backfill steps of short side coal paste cut-and-backfill mining in open-pit coal mine are divided into two steps:the first step is to divide the coal seam into several narrow strip coal pillars according to a certain width,numbered 1,2,3 and so on.First,the odd coal pillar is excavated,the first coal pillar is filled after excavation and the next coal pillar is excavated at the same time,finally the upper rock stratum is supported by the backfill body and the even narrow coal pillar;The second step is to extract the coal pillars of even number and fill them in time,until all pillars are excavated and fully supported by the backfill body.The simulation results of similar materials show that paste cut-and-backfill mining can effectively control the stability of short side slope in open-pit coal mine,the maximum subsidence of overlying rock layer is 280.0 mm,and the maximum force of backfill body is 9 kPa.(3)The numerical model of end-side coal paste cut-and-backfill mining is established according to the geological conditions of open-pit mining in Shenyi Coal Mine of Inner Mongolia,and the law of deformation of overlying strata during paste cut-and-backfill mining in open-pit coal mine is studied used the program of ABAQUS/CAE.The maximum displacement occurs in the middle area of short-side mining.The influence of different mining methods on surface subsidence is analyzed first.When the mining length is 70m,the maximum surface subsidence of backfill mining method is 189.4 mm,while that of caving mining method is 294.2 mm.Furthermore,the influence of different mining length on open-pit slope is further analyzed.The roof subsidence increases by 6.9%when the excavation is 70 mm,and by 3.3%when the excavation is 80 m.The results show that the slope subsidence of open-pit coal mine increases with the increase of excavation size in a certain mining depth range,and the influence of physical and mechanical properties of backfill materials on the stability of end-side slope is also obvious.(4)The study on slope stability of paste cut-and-backfill mining in open-pit coal mine shows that paste cut-and-backfill mining can improve the recovery rate of short-side coal in open-pit coal mine and ensure the long-term stability of open-pit slope.Paste cut-and backfill mining technology is not only to reduce the settlement and failure of the slope but also maximize the extraction of end-side stagnant coal resources.The research will have been a great significant to the safe recovery of coal resource under the side wall in the open-pit coal mines...