Strata Movement Law And The Prediction Method Of Surface Subsidence In Backfilling Strip Mining

Backfilling strip mining is an effective way to liberate coal resource under buildings,water bodies and railway.In view of the deficiency of the theoretical research on the strata movement and surface subsidence control in the backfilling strip mining,based on similar material simulation,numerical simulation and theoretical analysis,this paper systematically analysed the mechanism of strata movement control,the law of strata and surface movement deformation,and the prediction method of surface subsidence.The main conclusions are as follows:(1)The dynamic process of strata movement and destroy are studied by the method of similar material simulation.The results show that the subsidence curve of the strata is similar to that of strip mining,and the subsidence is wavy below the height of a certain height,and the waves gradually disappear during the increase of overburden height,and a continuous subsidence basin has been formed.The roof is mainly bent down and keeps good continuity.The backfill material can effectively limit the lateral deformation of the coal pillar,reduce the destruction of the pillar,and play a positive role in the long-term stability of the supporting structure.(2)The deformation behavior of overburden and surface movement for backfilling strip mining has been analyzed,which are affected by mining width,coal pillar width,mining height and filling rate.The results show that: The overburden subsidence above the coal pillar increase,the overburden subsidence on the top of the working face decrease with the increase of overburden height,they tend to consistent at the wave moving zone.The height of wave moving zone increases with the increases of mining width and coal pillar width,but does not change obviously with the change of mining height and filling rate;The subsidence boundary of overburden gradually increases with the increase of overburden height;The subsidence boundary of overburden increases with the increase of mining width and mining height,and decreases with the increase of filling rate,but does not change obviously with the width of coal pillar change.Surface subsidence and horizontal movement increase with the increase of mining height,and it decreased with the increase of the coal pillar width and filling ratio;The horizontal movement coefficient of the surface does not change with the mining width,the coal pillar with,the mining height and the filling rate.(3)The variation law of roof vertical stress with mining width,coal pillar widthand filling rate in backfilling strip mining is studied by numerical simulation.The formula of roof vertical stress calculation is given and verified.The results show that the relative error between the predicted roof vertical stress and the numerical simulation results is generally less than 20 percent.(4)In order to solve the problem of strata movement and ground subsidence prediction in backfilling strip mining,the plane thin plate model is used as the theoretical mechanical model of roof.Taking the filling body and the coal pillar as the elastic foundation under the roof,combined with the calculation formula of roof stress,the calculation method of roof subsidence is established.Combine the probability integral method of the unequal thickness coal seam,a theoretical model for predicting surface subsidence in backfilling strip mining is established,and the prediction of surface movement and deformation at any point been realized.In order to improve the practical engineering application ability of this prediction model,the equivalent calculation method for surface subsidence of backfilling strip mining is put forward by combining the calculation formula of roof subsidence in backfilling goaf with the probability integral prediction method in strip mining.The feasibility of the method is verified.(5)Taking the example of backfilling strip mining under buildings in Nantun mining area,according to the deformation index of ground building and ventilator room.By using the equivalent calculation method of backfilling strip mining,optimized the backfilling strip mining scheme and predicted deformation in surface.