Hydraulic cutting and gas explosion combined enhancing extraction method for fracturing coal body in drill hole

The invention discloses a hydraulic cutting and gas explosion combined enhancing extraction method for fracturing a coal body in a drill hole. The hydraulic cutting and gas explosion combined enhancing extraction method is suitable for high-efficiency extraction of underground gas of a coal mine. The enhanced extraction method comprises the following steps: firstly, forming a slot by using a hydraulic cutting technology, relieving the pressure and increasing permeability, and desorbing and gushing gas; secondly, pressing air into a sealed drill hole by using an air pump, wherein the air and the gushed gas from the drill hole form gas mixed gas with the concentration of 9-10 percent; detonating the mixed gas by an ignition device to form an explosive shock wave; fracturing the coal body under the guiding action of the slot. The slot provides a greater explosion space, so that the power of explosion is enhanced and a fracture network in the coal body can be fully constructed; besides, the adsorption potential of gas can be remarkably reduced and the desorption and the flowing of the gas are promoted by the heat effect generated by explosion, so that the aim of enhancing the gas extraction of a coal bed with high-concentration gas and low permeability is achieved. The enhanced extraction method has the advantages of safety, reliability, low cost, simplicity, feasibility, time conservation and force conservation; the influence range of effective pressure relief of single holes can be remarkably widened, and the extraction rate of the gas in the coal bed is increased by over 80 percent.