Methane moving law with long gas extraction holes in goaf

In order to grasp the methane moving law in goaf and provide a theoretical data for gas extraction holes, the height of caving and fractured zones in the stope has been calculated according to the experiential formula and gas movement law has been observed by field and laboratory experiment. It also gives gas moving characteristics with different position of extraction holes. And it has the best gas extraction result when the final holes are arranged around 30m above the coal seam and 10-20m away from the tailentry in horizontal direction. Besides, the height of final holes should be adjusted to the overburden strata structure. When final holes are near the tailentry, their height should be controlled in the upper of regular caving zone; when they are close to the center of face, their height should be controlled at the bottom of fracture zones.