The invention discloses a method for extracting gas from a separation layer below an overlying strata, draining water and grouting through a combined
drill hole and belongs to a mine disaster prevention method. The method for extracting gas from the separation layer below the overlying strata, draining water and grouting through the combined
drill hole includes that installing a
drill site at a transportation roadway of a preparatory work face adjacent to a coalface, constructing the combined
drill hole in the part about to generate the separation layer below the overlying strata above the gob of the coalface in a mode of keeping away from a caving zone, wherein the combined
drill hole is composed of an inside gas extraction
pipe and a water draining-grouting
pipe; after the separation layer is generated, preventing the mine disaster according to the stages that firstly, draining water from the separation layer through the combined
drill hole; secondly, after the gas is gathered in the separation layer after the water in the separation layer is emptied, using the primary combined drill hole to extract the gas from the separation layer; finally, after the water and gas are completely drained and extracted from the separation layer, filling
cement paste to the separation layer through the primary combined drill hole. The method for extracting gas from the separation layer below the overlying strata, draining water and grouting through the combined drill hole is capable of solving the mine disasters of water
bursting in mine, gas outburst (gas emission),
rock burst, surface
subsidence and the like through the combined drill hole, the separation layer water and gas extraction rate is high, and the grouting effect is good.