Study On The Movement Deformation Law Of The Overlying Strata And Surface In Minging Thick Coal Seam Using Downward Slicing Longwall Paste Backfilling Technology

The contradiction between coal resource mining and subsidence damage has a long history,especially the mining of thick coal seams has a huge impact on the damage of surface and buildings(structures).Although backfill mining is an effective way to replace the "three unders"pressed coal,but due to the large differences in the control mechanism,mining technology and equipment of overburden and surface subsidence between backfill mining and caving mining,the backfill mining of thick coal seams(>4m)under villages still needs to be further studied in the aspects of overburden rock,surface subsidence control mechanism and supporting technology of mining and filling technology.This paper takes the downward slicing longwall paste backfill mining in the thick coal seam under the village of Horsinghe Coal Industry in Shanxi as the engineering background,through similar simulation,theoretical analysis,numerical simulation and probabilistic integral method based on equivalent mining height,surface subsidence prediction comprehensive research methods were used to analyze the overburden rock and the surface movement and deformation law of the downward slicing longwall paste backfill mining in the thick coal seam under the village,the main results are as follows:(1)The research on the evolution law of displacement field,fissure field and stress field of overburden under the condition of 80%and 90%filling rate under thick coal seam downward slicing longwall paste backfill mining,the results show that when the filling rate is>80%,the roof has no fracture and obvious penetrating cracks,the amount of rock subsidence above the basic roof is significantly reduced compared to the direct roof,affected by the repeated mining in the lower slice,after the original stable upper layer is left with new unfilled space,the roof continues to sink,the minnng fracture continues to develop,and the secondary pressure.After the filling rate reaches 90%,only the overall deformation of the overburden rock occurs,and the basic roof structure remains relatively intact,the continuous curved beam formed effectively controls the settlement deformation of the overburden rock.(2)Based on the results of similar simulation tests,a mechanical model of continuous curved basic top elastic foundation beams in thick coal seam with downward slicing longwall paste backfill mining was established,the influence of different factors on the abutment pressure and basic roof flexure deformation of the filling stope has been studied.Through orthogonal test,the primary and secondary relationships of the factors that affect the basic roof subsidence degree under multi-factor coupling are determined:filling rate>elastic modulus of filling body>coal seam depth>basic roof thickness>basic roof elastic modulus>coal body elastic modulus.(3)The FLAC3D numerical simulation software was used to study the stress evolution law of surrounding rock and the characteristics of overburden and surface movement and deformation during downward slicing longwall paste backfill mining in thick coal seam under different filling rates and elastic modulus of different filling bodies,according to the research,the numerical simulation results of the two factors show that the mining pressure of the stope appears to have a similar trend:when the filling rate and elastic modulus of the upper slice mining increase,the stress value of the filling body increases slowly,which controls the roof subsidence.During the lower slice backfill mining,the compaction degree of the upper slice filling body is weakened due to repeated mining,its supporting pressure is reduced and the degree of uneven distribution is increased,the range of the increased stress area in front of the coal wall of the working face is reduced,and the range of the area of reduced stress above the sope is increased.The surface subsidence value and inclination deformation value during downward slicing longwall paste backfill mining decrease with the increase of the filling rate and the elastic modulus of the filling body,when the elastic modulus of the filling body is 0.5GPa,the filling rate is?85%or the filling rate is 90%,and the elastic modulus of the filling body is?0.3GPa,the surface building is in the level I damage level.(4)The prediction theory of ground movement and deformation based on the probabilistic integral method of downward slicing longwall paste backfill mining based on the equivalent height model,and backstepping to know that the design area is inclined to the downward slicing longwall paste backfill mining during full mining the effect of deformation on the damage of surface buildings is greater than that of horizontal and curvature deformation,and the minimum filling rate of the layered layer is 86%when the damage level of the surface building is controlled within the range of class I.At this time,the subsidence coefficients of the upper and lower slice in the design area were 0.092 and 0.101 respectively,which controlled the surface subsidence well.It provides a basis for the filling rate and reasonable filling cost control of the downward slicing longwall paste backfill mining in the thick coal seam of Holsinghe Coal Industry.