Numerical Simulation Of The Influence Of Key Layers On Surface Subsidence Movement Range

Underground coal seam mining often causes surface subsidence,causing casualties and property losses,making the study of rock movement and subsidence issues an important issue.When the moving angle of coal mining design is too large,it will lead to the surface buildings or other production facilities located in the surface moving subsidence area,which not only causes economic losses,but also poses a huge hidden danger to the safety of coal mine personnel.Combining the key layer theory to study mining subsidence can effectively reflect the actual situation of surface subsidence in the goaf,and can explain the formation mechanism of surface cracks,thereby improving the prediction accuracy of the surface subsidence range and degree,so as to achieve safe and rational mining of coal mines.purpose.Based on the data collection and on-site investigation,this paper summarizes the influence law of the overlying strata on the surface subsidence in the goaf,and understands the effect of the overlying lithology on the surface subsidence.At the same time,the mechanism of action of the key layer is studied,and the key layer location of the study area is determined according to the actual situation of the study area.Then the midas numerical model is used to simulate the coal mining subsidence in the study area,and combined with the field crack monitoring data,the accuracy of the numerical simulation results is verified.According to the results of three-dimensional numerical simulation of mining subsidence in the study area,the mining subsidence law under key strataconditions is analyzed from the aspects of displacement,stress and strain of overlying strata in the goaf.The results show that there are stress concentration phenomena in the overlying strata of goaf,including the compressive stress concentration area formed by gravity at the key strata and the boundary of goaf.The key strata are articulated rock blocks formed by the breakage of key strata,and the transverse compressive stress is formed under the action of gravity;the shear stress concentration area mainly in horizontal direction is formed due to the stress release to the working face on both sides of the goaf,and the bulging stress concentration area of the floor of the goaf is caused by the folding deformation to the goaf due to the unloading rebound.Finally,based on the mining subsidence in the study area,the displacement and stress changes of the overburden strata under different key types of the structure are simulated,and the control effects of the key layers of different structural types on the movement and deformation of the overburden are discussed.The results show that:(1)the existence of the key layer is effective in slowing down the subsidence of the surface of the goaf;(2)there is little relationship between the downhill boundary angle and the rock formation,and the upper boundary angle is related to the key layer.The existence of the key layer increases the moving angle of the mountain,thus reducing the surface subsidence range;(3)the extrusion stress mainly concentrates on the key stratum and forms articulated rock beam,which makes the key stratum the main load carrier of the overlying stratum and controls the movement of the overlying stratum;(4)in the case of the same depth of mining,the closer the key strata are to the goaf,the thicker the overlying strata of the key strata are,the smaller the deformation and damage that can spread to the surface,and the smaller the degree of surface subsidence.