Pressure alternate gas exhausting method by slotting and fracturing coal seams

A pressure alternate gas exhausting method by slotting and fracturing coal seams is applicable to the gas control of complex coal seams in a high-gas-content high-ground-stress area, aims to improve the air permeability of coal bodies and the capacity of drilling gas exhausting, and realizes continuous and efficient drilling gas exhausting of the complex coal seams. According to the pressure alternate gas exhausting method, drill holes to-be-slotted and drill holes to-be-fractured are formed by drilling coal seams to a coal floor; pressure-relief annular slots are formed in the bottom area of a coal seam section by virtue of the rotation of high pressure water jets in the drill holes; ground stress around the drill holes is manually discharged, and internal energy of coal seam gas is released; drilling pressure alternate gas exhausting is performed through designed drilling gas exhausting pipes which can shift the functions of gas exhausting and water injection fracturing; the water injection fracturing of the slotted drill holes and the gas exhausting of the fractured drill holes are performed simultaneously (or the water injection fracturing of the fractured drill holes and the gas exhausting of the slotted drill holes are performed simultaneously). Through alternate and repeated operations, the capacity of continuous and efficient drilling gas exhausting is increased; the effective influence range of drilling gas exhausting is increased by 2-4 times; the air permeability coefficient of coal bodies around the drill holes is increased by 200-500 times; the quantity of exhausted gas of drill holes with lengths of 100 m is increased by 2-5 times, so that the pressure alternate gas exhausting method has higher field application value and social benefits.