Deformation and damage of pressure-relieved gas extraction wells in deep mining under thick surface soil and their prevention: With Guqiao of Huainan mine as an example

Based on the engineering practice of Guqiao coal mine, combining with the physical simulation experiment and field monitoring results, the deformation and damage failure of surface drilling for deep well pressure relief mining and their prevention in thick alluvium were studied. The results show that drilling damage is the key factor for the damage of ground pressure relief gas extraction. Under the influence of mining, the damage of the surface gas extraction well is mainly deformation and fault section, and the damage depth is different, mainly concentrated in the middle and lower part of the loose layer and the middle upper part of the rock. In the condition of well drilling and completion, the end hole position of the drilling well is arranged near the fault and "O"-type ring is more conducive to pressure relief gas drainage. The overlying strata separation, stress concentration, vertical breakage and the "lever effect" caused by the overlying strata caused the destruction of the surface gas extraction well, and this phenomenon occurs from the bottom to the top many times, which is the main cause of the deformation and damage of the surface wells. The influence of coal mining on the stress of roadway and roof in front of the working face can reach 320 meters and 350 meters respectively, the influence of relative displacement on the track can reach 50m in front of the working face and 200m in the rear. The relative displacement in the middle of the stope is much larger than that at the edge of the stope, which is more likely to lead to drilling damage. By optimizing the well structure, improving the cement-completion construction technology and reasonable well location layout, it can effectively prevent the deformation and damage of the surface drilling in pressure relief mining and achieve stable and efficient gas extraction.