| Based on the engineering background of mining under the rich aquifer in Gonggeyingzi Coal Mine, the backfill materials’ composition and proportion was determined, the working principle of roadway mining with backfill was introduced, and the overlying strata movement characteristics with influence factors were studied. For the technology of coal mining with roadway backfill, on the basis of comprehensive analysis of coal mining with roadway backfill cycle and overlying strata bearing structure characteristics, the mechanical models of chain filling body pillar’s stability and the roof ‘s movement and deformation after mining with all roadway backfill were established. With the mechanical models, the stability of chain filling body pillar and the movement and deformation extent of roof after all roadway backfill with different filling rate were analysed. At the same time, the overlying strata fracture mechanical model was established to analyse and calculated the height of water flowing fracture zone, the law of overlying strata movement and deformation and water flowing fracture zone development was further studied by FLAC3 D. At last, the engineering application conditions was introduced. The actual thickness of coal-rock pillar was determined, and the ground influence of roadway mining with backfill was predicted and analysed. The technical effect and benefits analysis indicated that roadway mining with backfill under rich aquifer in Gonggeyingzi Coal Mine had more advantages. Therefore, according to a serious problems of mining with roadway backfill under richaquifer needed to be solved, the main contents of this paper were studied as follow.(1) In combination with the practical situation of mining under water body in Gonggeyingzi Coal Mine, the optimization formula of filling materials was determined, the working principle of mining with roadway backfill was introduced, and the overlying strata movement characteristics with influence factors by mining with roadway backfill were analysed.① Based on the mining geological conditions of Gonggeyingzi Coal Mine, mining with roadway backfill was put forward. The slicing method with roadway backfill was determined, the layer thickness was 3m, and 5 layers in total. The filling rate was designed at 90%.② The ratio of the filling materials optimization was confirmed as the following: cement 3%, coal gangue 30%, fly ash 20%, white ash 10%, inferior sand 13%, the paste-like slurry concentration 76%.③ The working principle of roadway mining with backfill was introduced, the size of backfill-roadway was designed, the backfill-roadway section was rectangular with 4m wide and 3m high; The influence factors of roadway drivage and backfill sequence was analysed, the arrangement of mining with roadway backfill working face was carried on, and the roadway filling process of mining with roadway backfill was design.④ The rock strata movement characteristics and influence factors of roadway mining with backfill were analysed, the subsidence factor, filling quality and lithologic factors were put forward to be the three main factors causing overlying strata movement and deformation in mining with roadway backfill.(2) Based on the analysis method of elastic foundation beam, the mechanical model of chain filling body pillar stability in mining with roadway backfill and roof movement and deformation after all roadway backfill was established, the abutment pressure distribution on the pillar was analysed, the stability as well as the width of the pillar was researched. The roof limit span as well as the roof limit deflection was obtained by analysis of roof strata fracture damage may occur. The influence of the roof limit deflection caused by filling rate was discussed when the roof reached to the limit span.① On the basis of pillar stability mechanical model, the theoretical distribution law of mining compressive stress on filling body pillar was analysed, the compressive stress function expression was obtained. According to the roof movement and deformation after all roadway backfill mechanical model, the maximum value of roof subsidence was deduced. The relationship of roof limit deflection and roof maximum allowed subsidence was discussed under different filling rate to judge whether the roof was fractured and the limit span under the fractured roof.② In combination with the practical conditions of Gonggeyingzi Coal Mine, for bottom slicing method with roadway backfill, combined with the mining compressive stress on filling body pillar formula, the maximum stress on pillar under different pillar width was analysed and calculated; for top slicing method with roadway backfill, from a security point of view, in the case of fracture fully developed, the maximum stress on pillar under different pillar width was also analysed and calculated.③ The width of chain filling body pillar not only affected its stability, but also related to mining and backfill cycles.Considering the factor of safety, recovery efficiency and cycle times, ultimately determined the width of the pillar is 8 m.④ In combination with slicing method with roadway backfill in Gonggeyingzi Coal Mine, the analysis conclusion of bottom and top slicing method with roadway backfill was that its roof all would be fractured, and the roof limit span was calculated. For slicing method from bottom to top, in certain case of the same roof, the coal seam was more thick, to make the top slice not be fractured under slicing method with backfill, the filling rate needed to be a higher request.(3) The formation and influence factors of water flowing fracture zone were analysed, based on the theory of mining with roadway backfill equivalent mining height, the mechanical model of overlying strata fracture was set up, combined with the analysis of the roof movement and deformation mechanical model after all roadway backfill, then the possible height of water flowing fracture zone was analysed.① Put forward combined with the equivalent height of mining with roadway backfill to analyse and predict the height of water flowing fracture zone, the influence factors of mining with roadway backfill equivalent height were summarised, including the roof-to-floor convergence, the height of filling body reached to the roof, and the compression height of the filling body. And the related calculation formula of mining with roadway backfill equivalent height was provided.② The related mechanical analysis of overlying strata deformation and broken was carried out to establish the mechanical model of basic roof beam, the basic roof limit span and deflection were deduced under mining with roadway backfill which provided the method of key strata breakage analysis and water flowing fracture zone height judgment. Combined with the stress equilibrium analysis of the basic roof fractured rock, the criterion of overlying strata fracture developed to fracture zone was provided.③ According to mining with roadway backfill in Gonggeyingzi Coal Mine, the overlying strata limit span and deflection with free subsidence space were carried on theoretical analysis and calculation under mining the main coal seam, the height of water flowing fracture zone was got.④ Combined with the experience formula of water flowing fracture zone in Gonggeyingzi Coal Mine being calculated, compared with the theoretical analysis, the height of water flowing fracture zone calculated by the experience formula was conservative.(4) Based on the finite difference method, the law of overlying strata movement and water flowing fracture zone development under caving method and mining with roadway backfill method was simulated and analysed with the numerical analysis software FLAC3 D. The main influence factors of overlying strata movement and water flowing fracture zone development including the mining thickness, the filling rate and the filling body elastic modulus were simulated and analysed, and through regression analysis, the relationship formula of water flowing fracture zone height changed with various influencing factors was obtained.① With the increase of mining thickness, the height of water flowing fracture zone under caving method and mining with roadway backfill method was increasing first, then tended to be stable, showing a nonlinear relationship. But in the same condition of mining thickness, mining with roadway backfill method would make the less water flowing fracture zone height, showing the mining with roadway backfill method made the control effect of the water flowing fracture height more obvious.② For mining with roadway backfill, with the increase of mining thickness, the maximum principle stress value increased gradually as well as the overlying strata water flowing fracture zone height, the overlying strata vertical stress and displacement. With the increase of filling rate, the maximum principle stress value decreased gradually as well as the overlying strata water flowing fracture zone height, the overlying strata vertical stress and displacement. With the increase of filling body elastic modulus, the maximum principle stress value decreased obviously, as well as the overlying strata water flowing fracture zone height, the overlying strata vertical stress and displacement.③ For slicing method with roadway backfill 15 m coal seam in Gonggeyingzi Coal Mine, with the increase of filling layers, the overlying strata maximum principle stress was increasing, the plastic area scope expanded unceasingly, also the overlying strata damage height along with the change of the plastic zone and the principle stress increased, eventually the water flowing fracture zones height is 33 m, far less than the height of the coal roof to the aquifer bottom.(5) The drivage and backfill sequence of mining with roadway backfill in Gonggeyingzi Coal Mine was designed, the detailed layout of the working face was given, and determined the height of safety waterproof pillar in Gonggeyingzi Coal Mine with the analysis of the surface villages influence of roadway mining with backfill. Finally, the technical effect and benefit analysis was carried on, it showed that mining with roadway backfill under rich aquifer body had superiority in Gonggeyingzi Coal Mine.① According to the actual situation of Gonggeyingzi Coal Mine, based on the above analysis and calculation, the working face of roadway mining with backfill was arranged, the width of chain filling body pillar was designed 8m, and there were three cycles of roadway mining with backfill.② For the roadway mining with backfill in no.6 coal seam, the actual thickness of coal-rock pillar was 111 m, it was more than the 39.8m waterproof coal-rock pillar by calculation and analysis. Therefore, roadway mining with backfill under water in Gonggeyingzi Coal Mine is safe and feasible.③ According to the brick-concrete building damage grade standard, the surface movement and deformation with mining with roadway backfill method at 90% filling rate was predicted to show that after 15 m coal seam mined out with backfill, only a small part of the village needed simple maintenance or repairs, then would not affect the village buildings within the scope of the village for normal use.④ Due to the roadway mining with backfill, the underground water was controlled effectively saving the drainage cost more than six million yuan per year, to liberate the coal resources with controlling effectively the surface subsidence. The economic and social benefits were remarkable. |
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