Study On The Influence Of Repeated Mining On The Stability Of Bedding Rock High And Steep Slope

Bedding rock high and steep slope is a common landform in southwest mountain area.In this paper,taking an underground coal mine in Sichuan Province as the research object,the deformation and failure characteristics of bedding rock high and steep slope under the influence of repeated mining are studied by using the methods of numerical simulation analysis,similar simulation test and theoretical analysis.The similar simulation test method is used to complete the similar simulation test,revealing the deformation mechanism of the cliff under the condition of repeated mining,the deformation and failure process and mechanism of the dangerous rock mass are obtained.On this basis,the stability calculation method of the fault block is proposed,and the stability of the prototype is calculated.The research results are as follows:(1)Using numerical simulation analysis method and reverse slope mining program,the deformation and failure response of high and steep rock slope was studied:1)The relationship between the deformation and failure of high and steep rock slope and the location of goaf,when mining No.3 coal seam,the subsidence of the block on the slope is close to the mining height.The failure mode of slope is mainly ladder failure along the block joints.2)Plastic deformation occurs in the basement of the cliff,which results in fracture and sliding failure.3)After the reverse slope mining,the subsidence curve of the basement strata presents an "inverse s" shape.(2)In this paper,the similarity simulation test method of mining bedding rock high and steep slope is proposed,and the similarity simulation test device is improved.The test results show that the cracks of high and steep slope extend to the inside of the slope,and the distribution of the weak interlayer is ladder shaped.The fracture failure of the steep slope is closer to the collapse failure of the mountain,and the unstable collapse of the dangerous rock at the shoulder of the slope occurs to the free face under the action of rain.Due to the influence of mining,the compressive stress in the slope body is greater than that outside the slope body,and the unloading phenomenon will appear in the rock mass near the fracture.The subsidence displacement curve of the model approximately presents an inverse "s" shape.(3)In the study of the influence of tensile fracture on block stability,the effects of mining weakening and water softening are considered,the weakening phenomenon is described,the weakening coefficient is defined.Based on Mohr Coulomb criterion,the limit equilibrium method is used,the stability of high and steep slope fault block in natural state and saturated state is studied,the relationship between weakening coefficient and stability is obtained.(4)The stability of prototype and model is analyzed by using limit equilibrium theory.The results show that: 1)When the rainfall and underground mining engineering activities act at the same time,the deeper the water filling depth in the fracture,the lower the stability of the fracture block.2)At the end of repeated mining,the fractured dangerous rock mass is not affected by other factors and will maintain a stable state.When affected by rainfall,the mechanical strength of the weak interlayer is weakened,and the dangerous rock mass reaches a critical sliding state,resulting in sliding.