Numerical simulation study on pressure relief gas extraction area in ultra thick coal seam mining site

Regarding the selection of pressure relief gas extraction areas in thick coal seam mining sites, numerical simulation was used to study the characteristics of overlying rock collapse and the gas migration law in goaf areas. Subsequently, the key gas extraction areas were identified, and the gas concentration was well controlled after on-site extraction. The results show that the numerical simulation calculation shows that the collapse shape of the overlying rock presents a ladder shape, with a collapse zone of 33.7-36.7 m and a fracture zone of 183.7 m-198.7 m; The gas concentration in the working face tends to gradually increase from the intake airway to the return airway, with the gas concentration increasing towards the deeper part of the goaf. The gas concentration is higher in the upper level of the goaf vertically; Under the U-shaped ventilation mode, the area below the crack zone on the side of the return airway and the upper corner are the areas with the highest gas concentration.After on-site extraction, the gas concentration in the upper corner is about 0.4%, and the gas extraction effect is good.