Mechanism of surrounding rock failure and strata movement in complex goaf of metal mines
Taking the east area of Jinshandian iron mine of Wuhan Iron and Steel(Group)Company as a relying project,the engineering geological condition of the mine area and the mining process of the ore body were clarified.The spatial characteristics of surrounding rock failure in complex goaf were analyzed by ground pressure behavior investigation and microseismic fracture monitoring.Combining with the results of three-dimensional numerical simulation,surrounding rock fracture monitoring and roadway failure survey,the failure mechanisms of surrounding rocks in hanging wall and footwall of the mining area were elucidated,and the analysis index of discontinuous deformation of surrounding rock failure(i.e.,failure angle)was proposed based on the plastic failure of rock mass,which was verified by comparing it with the collapse angle index.Furthermore,the strata movement laws in both the plane and profile directions caused by the complex goaf in metal mine were revealed.The results show that the failure of surrounding rock and the ground pressure behavior of roadway are distributed around the goaf.On the plane,the convex shape of the half-moon goaf has a magnifying effect on the failure of the surrounding rocks of its two wings.On the profile,the failure of the haulage roadways in the sublevels has the characteristics of elevation lag.Initially,the failure of the surrounding rock in the goaf is mainly caused by the collapse and caving of the rock mass at its top position.As mining progressed,it develops into the fault-slip-controlled chimney caving failure,and finally expands into the through-slip failure controlled by the rock mass structure.The surrounding rock failure of hanging wall presents the characteristics of toppling-slip failure,while that failure of footwall presents the characteristics of the shear-slip failure tracking the faults and structural surfaces.Moreover,the values and variations of the failure and collapse angles of the surrounding rocks of the hanging wall and the footwall are relatively consistent for various exploration line profiles,and these two angles are approximate to show the first decrease after the tendency to stabilize with the mining process.In addition,the hanging wall goaf(FeⅠ)spreads like a strip,and the failure angles that tends to be stable are approximately the same at different exploration lines,and the larger the inclination angle of the main dominant structural surface,the smaller the stable failure angle.Whereas,the footwall goaf(FeⅡ)is distributed in a half-moon plane shape.The stable failure angle in the middle position of the half-moon is larger compared to its two wings,and this angle decreases with increasing the distance between its location and the middle position.The research results are of great significance for guiding the safety production of the mine and ensuring the normal life of the neighboring residents.
mining engineeringmetal mineunderground miningcomplex goafsurrounding rock failurestrata movement
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