为了改善通风条件,圈定采区的采准巷道往往用通风联络巷道连通(例如,准备沿煤层走向用长壁工作面回采采区时)。在开采采区的过程中,回采工作面常常有必要在这些巷道下面通过。在这些地方常常发生顶 In order to improve the ventilation conditions, the quarried roadway delineating the mining area is often connected by ventilation and contact roadway (for example, when preparing to adopt the longwall face along the coal seam to recover the mining area). In the process of mining the mining area, it is often necessary for the mining face to pass below these tunnels. Tops occur frequently in these places