Study On Induced Caving Process Of Cemented Backfill And Stope Stability Of The Second West Mining Area In Longshou Mine

The West Second Mining Area of Longshou Mine is planned to switch to sublevel caving without sill pillar,and the overburden is formed by the upper part cementing backfill and overburden by induced caving.In order to avoid the safety hazards such as mine shocks and impact waves caused by the collapse of large-area cemented filling bodies affecting the normal mining of mines,it is necessary to reduce the impact vibration energy as much as possible.Through the analysis and research on the induced collapse process and the stability of the stope in the upper cemented backfill,it is important for mining to propose a safety measures to promote caving of cemented backfill as soon as possible.This paper collected,sorted out and investigated the mining status and relevant engineering geological conditions of the mining area,used the combined method of "beam" theoretical analysis and FLAC3D numerical model simulation to analyze the cave-in process and collapse rule of cemented backfill.At the same time,according to the principle of similar material experiment,the corresponding physical model experiment of similar material was developed and completed.The attenuation law of vibration wave velocity along with the increase of cushion thickness is analyzed.The reasonable cushion thickness is obtained.The following results are obtained:1)Through theoretical calculation and numerical model simulation analysis,the tensile stress of the cementing backfill is greater than its tensile strength.With the increase of stoping path or row spacing,the maximum principal stress and settlement displacement of cemented backfill increase gradually,and the volume geometry of plastic zone increases.At this point,the bottom of the cemented backfill will be unstable and be damaged from the central position,and the collapse is dominated by tensile failure.2)Geological disaster of underground and ground subsidence occurred of the Second West Mining Area are different failure forms under different stress states.The collapse mode of cemented backfill and overburden conforms to the mode of "local collapse of cemented backfill+collapse of overburden monolithic plunger".And the surface may have stepped settlement.3)With the continuous recovery of ore in the stope,the upper collapse of the whole rock column may occur secondary disintegration and form scattered pieces,which eventually lead to funnel-shaped collapse pits on the surface.The caving process of cemented backfill can be controlled by expanding the effective exposed area of goaf,and the caving process of cemented backfill will go through a cycle of "caving-stabilization-re-caving-re-stabilization".4)It is thought that three mining roadways be taken simultaneously,which the distance between the approaches is 15m,and the rectangular goaf with a span of 45m and an exposure area of 396m2 can be formed,which can fully meet the requirements of caving.5)According to the law of vibration attenuation of physical model impact test of similar materials,combined with the formula of minimum thickness of safety cushion layer,it is suggested that the thickness of safety cushion should be 5m of the Second West Mining Area in Longshou Mine.To sum up,to adopt three adjacent roadways to simultaneously mine and ensure the safety cushion thickness in goaf reaches 5m,which can promote caving of cemented backfill as soon as possible and ensure the safety and stability of the stope.