Research On Mechanism And Risk Evaluation Of Collapse Induced By Goaf In Panzhihua Coal Mine,Guizhou

The goaf-induced collapse is a mountain collapse caused by the formation of a goaf from underground mining that affects the deformation and destruction of the overlying rock.After the inside of the slope is mined out,the coal pillars in the mined-out area cause overburden deformation,which induces a complex collapse and deformation mechanism of the slope,which brings huge challenges to the risk prevention and control of the mined-out slope.Therefore,carrying out the formation mechanism and risk assessment of collapse under this condition has important practical value and great socio-economic significance.Based on this,this paper takes the mining-induced collapse of the Panzhihua Coal Mine in Shuicheng County,Guizhou Province as the research object.Through data collection and field surveys,the geological environment conditions,collapse and deformation characteristics of the study area,the mining time and distribution of the goaf are investigated.The physical simulation test method is used to study the process and formation mechanism of collapse induced by goaf.Based on the formation mechanism,it is integrated from the aspects of determining the danger range,risk assessment,vulnerability assessment and risk assessment of collapse geological disasters.Based on the analysis,a risk assessment model of geological disasters induced by goafs was constructed to provide a scientific basis for its prevention and control.The main research results obtained are as follows:(1)According to field investigations,the slope in the study area is a gently dipping internal slope,the slope is high and steep and close to the sky,and the rock mass is hard on the top and soft and hard on the bottom.There are five mineable coal seams inside the slope,which has a long history of mining and has formed a four-layer goaf with the characteristics of chaotic mining time,uneven distribution,and large area.The slope is affected by the goaf,the slope rock structure is broken,the surface cracks are developed,the collapse is serious,and there are three large collapses.(2)Based on the results of field surveys,a conceptual model of the collapse of Panzhihua Coal Mine was established.Based on the conceptual model,it was appropriately simplified to establish a physical model with a similarity ratio of 1:600.The ratio test of similar materials was used to select the optimal similarity of various lithologies.Than experiment.The test simulates the process of slope failure and collapse under the conditions of multi-layer mined out and coal pillar extraction.(3)Combining the results of physical simulation tests,slope structure,goaf distribution and deformation characteristics analysis,it is concluded that the formation of the collapse has experienced“removal disturbance-overburden deformation-multi-layer stoping-goaf collapse and cracking-increased deformation-slope The process of cracking and collapse”is divided into“disturbance stage of coal seam stop-multi-layer mined coal pillar stoping subsidence intensified stage-leading edge cracking and penetration stage-collapse final formation stage”,and the instability mode is“settlement-tensile cracking-collapse””.(4)Based on the regression equation theory of the arrival angle of the landslide body,an improved(logarithmic regression equation)formula for the maximum movement distance of goaf-induced collapse(L_max=H/10^{-0.109 logV+0.17}(V?10⁵m³),L_max=H/10^{-0.109 logV+0.22}(V<10⁵m³))is established,and the formula for the maximum movement distance and the cover The method for determining the impact range of goaf-induced collapse geological disasters jointly determined by the range of rock movement;using the basic principles and algorithms of the analytic hierarchy process,according to the signs of deformation,deformation rate,stable state,relative elevation,slope,empty surface,structural surface,slope The risk assessment model of geological disasters induced by mined-out collapse has been established with influencing factors such as body structure,underground mining,and surface engineering.Through the evaluation,the risk of mined-out-induced collapse geological hazards is classified as high risk(7.26?10),medium risk(2.47?7.26),low risk(0?2.47);through the weight of evidence method,a vulnerability evaluation model consisting of hazard-bearing body survey,value accounting,and vulnerability calculation is established,and the vulnerability to geological disasters induced by goafs is obtained.The damage classification is:low vulnerability(V<0.20),medium vulnerability(0.20?V<0.45),high vulnerability(0.45?V).(5)Established a risk assessment system for geological disasters induced by goafs,which is composed of determination of impact scope,risk evaluation,vulnerability evaluation,and risk evaluation.The risk of geological disasters induced by goafs in Panzhihua Coal Mine in Guizhou was evaluated.The high-risk areas are mainly in Panzhihua.The industrial plaza of the coal mine and nearby residential areas,medium-risk areas are located on the west and north east sides.