Study On Overlying Rock And Surface Subsidence Law Of Strip Coal Pillar Paste Replacement Mining

With the rapid development and continuous expansion of the city,a large number of coal mining area and the total amount of coal mining continue to grow,resulting in a sharp reduction in the total amount of coal mining resources,which greatly restricts the green sustainable development of coal mining enterprises.In order to solve the problems of low recovery rate and high driving rate brought by strip mining,and realize the effective control of the influence of secondary mining on surface subsidence,this paper compares and analyzes the overburden movement and roof subsidence degree between caving method and paste filling mining method by combining the methods of theoretical analysis,similar material simulation,numerical simulation and field detection.The main conclusions are as follows:(1)Based on the study of the mechanism of "activation" of overburden,the overburden structure models of the bearing structure system of "residual strip coal pillar roof" and "strip filling body roof" bearing structure system are established.Combined with the actual geological and mining conditions,the relationship between the width of the strip coal pillar and the compressive strength of the filling body is analyzed,and the "activation" of the overlying rock for filling and recovering the residual strip coal pillar is analyzed mechanism.(2)Based on the similar material simulation test,the influence of strip mining on the overlying rock structure above the goaf is studied.Through the following three simulation states:the state after mining with caving method to manage the roof after mining,the state after recovering the remaining coal pillar by using the filling method and the state after strip mining with paste filling are obtained.The curve produced by the subsidence of overlying strata within the height range is wavy,and the subsidence activity is obvious.However,the bending subsidence of the strata near the ground is obvious,and the basin is formed by the accumulation of subsidence.The maximum surface subsidence value after caving mining is 650mm.It can be seen from the figure that after the left coal pillar is filled,the maximum surface subsidence value becomes 815.0 mm,but when the left coal pillar is only filled,its subsidence value is only 45.0 mm,which is 120 mm less than the actual mining subsidence value.(3)Through FLAC3D numerical simulation,the movement and deformation law of overburden and ground surface under filling conditions were studied.Compared with the distribution map of elastic-plastic zone of coal and rock before and after coal pillar filling mining,the stress concentration coefficient of caving strip mining was concentrated in the overlying rock above the coal pillar,and the stress concentration coefficient of the solid coal side of the mining boundary was less than that of the coal pillar area;after the pillar filling mining,the stress concentration coefficient of the coal pillar was lower than that of the coal pillar area The second mining with filling greatly expands the scope of the roof fracture area of the original strip goaf,and finally the stress concentration coefficient of the roof decreases,and the stress diffuses to the boundary solid coal.After filling body is used,it forms stable bearing structure with roof strata.(4)Compared with the surface subsidence of strip mining,it is concluded that the surface deformation of filling secondary mining has no obvious increase compared with the previous strip mining.The maximum ground settlement value is 171mm,the inclined deformation is-1.3?1.4mm/m,the inclined deformation is-0.9-0.9mm/m,the horizontal strike deformation is-1.2?0.6mm/m,and the horizontal dip deformation is-0.5?0.4mm/m,which meets the requirements of building protection.