Study on filling mining design and spatial-temporal evolution law of deformation and failure of roof overburden in Yungang Coal Mine

Taking the filling mining in Yungang Coal Mine 8402 working face as the background, firstly, five gangue slurry with different proportions were prepared, and bleeding rate, setting time and uniaxial compressive strength tests were tested. Reasonable gangue slurry ratios were selected according to the requirements of use and cost, and the design of filling hydraulic support and filling mining technology was carried out. Considering the change of rock mass mechanical parameters with mining stress, based on Hoek-Brown model, FLAC^3D software was used to study and analyze the spatial-temporal evolution law of deformation and failure of roof overburden in 8402 working face with or without filling. The results show that: when the dosage of cement and fly ash is 180 kg/m³ and 210 kg/m³ respectively, it can meet the requirements of filling mining and cost of 8402 working face in Yungang Coal Mine at the same time; under the condition of no filling, the 8402 working face has a periodical pressure step of 18-25 m, and the height of fracture zone is 108 m. While under the condition of 85% paste filling, the periodical pressure step of the working face is 36-40 m, and the height of fracture zone is 43 m; after the working face with 85% paste filling advances 120 m, the maximum subsidence and maximum tilt of the surface are basically kept unchanged at 165 mm and 2.62 mm/m, which are less than the requirements of the code and can ensure the safety of the ground building.