As an important technology of thick coal seam mining, fully mechanized mining with a large mining height has high mining efficiency. In order to study the roof safety control of large mining height working face, the 122106 working face of Caojiatan coal mine is taken as the engineering background. The numerical simulation method is used to analyze the control ability of roof subsidence when the support strength is 1.2 MPa, 1.4 MPa, 1.6 MPa, 1.8 MPa, 2.0 MPa, and 2.2 MPa. The results show that the support strength of hydraulic support is negatively correlated with roof subsidence. Through theoretical analysis of the mechanical model of the support and surrounding rock under the filling condition, it is shown that the height of the gap between the filling body and roof is the main influencing factor of roof subsidence: the smaller the height of the gap between the filling body and roof, the better the control effect on the roof. Through numerical simulation, the roof subsidence and surface subsidence under different filling rates are analyzed. The results show that when the filling rate increases to 80% the control of roof subsidence achieves better results. Taking production safety and economic benefits into consideration, when the reasonable support strength of the working face is determined to be 2.0 MPa and the filling rate is 80%, the safety control of the working face roof can be ensured.
Aiming at the serious deformation and failure of mining roadway under the condition of high secondary stress in Xuchang Coal Mine, Shandong Province, the deformation law of surrounding rock under the influence of high secondary stress in the original support belt transport roadway was analyzed by the method of field measurement and numerical simulation, and the control scheme of surrounding rock was put forward. According to the actual site conditions of 3318 working face belt transport drift in Xuchang Coal Mine, this paper proposed a new bolt-net support technology scheme with high strength, high stiffness, and asymmetric characteristics and obtained through numerical simulation analysis: (1) when the 3318 working face begins to mining, the distribution of the maximum principal stress in the surrounding rock of the roadway changes from weak symmetry to strong asymmetry, especially the maximum principal stress in the surrounding rock of the two sides; (2) the superposition effect of leading abutment pressure, lateral abutment pressure, and fault structure has a strong influence on the distribution of the maximum principal stress of roadway surrounding rock. The field industrial test shows that the deformation of the surrounding rock at different parts of the belt transport roadway is significantly reduced after the implementation of the double-height asymmetric bolting support. Among them, the deformation of the roof decreases from 630 mm to 185 mm, the deformation of the left wall decreases from 550~620 mm to 150~170 mm, and the deformation of the right wall decreases from 600 mm to less than 180 mm. The nonuniform deformation degree of the top side is within 1~1.13, indicating that the anchor mesh composite bearing structure is uniformly deformed as a whole, and the overall bearing capacity of the structure is realized.
Coal mine backfilling mining controls the movement of overlying rock and surface subsidence by backfilling the fractured rock mass into the goaf. The compaction mechanical performance of the fractured rock is the key to the effectiveness of overlying rock control. In order to optimize the control effect of crushed gangue overlying rock, this article focuses on the regulating effect of gangue particle size grading on mechanical properties. Through research on the physical properties of gangue and natural graded gangue compaction experiments, the porosity of gangue crushing and the process of gangue crushing are analyzed. It is shown that the gangue material has good load-bearing performance in terms of physical structure, and the elastic modulus has an absolute effect on the compression characteristics of gangue particles. Through storage analysis of the natural grading experiment phenomenon, it was found that the alarm height for gangue not to be blocked is 20m. Through laboratory experiments, the compression characteristics of group B samples were analyzed, and it was found that the particles showed a trend of first increasing and then decreasing under the coupling effect of particle size and particles of different sizes. Through the analysis of particle strain energy density and breakage energy, it is concluded that the strain energy density of the sample from high to low is B1, B2, B6, A5, B5, B4, and the breakage energy consumed to reach the sample broken state from low to high is A5, B6, B5, B4, B3, B2, B1, so the B6 group samples have the best economic benefits. Through analysis from the perspective of filling rate, it was found that the B6 group of samples has the best control effect on the overlying rock. Thus providing suggestions for optimizing the efficiency and effectiveness of backfill mining.
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