Method of performing combined drilling, flushing, and cutting operations on coal seam having high gas content and prone to bursts to relieve pressure and increase permeability

摘要

A method of performing coupled drilling, flushing, and cutting operations on a coal seam having a high gas content and prone to bursts to relieve pressure and increase permeability, particularly suitable for relieving pressure and increasing permeability when drilling a through-seam borehole to pre-drain gas belts in a coal mine roadway (4) in a coal seam (2) having a high gas content and prone to bursts. On the basis of the means of pre-draining a gas from the coal seam (2) via the through-seam borehole (3), hydraulic flushing and hydraulic cutting are organically combined by employing a specialized drilling, flushing, and cutting apparatus, and combined operations of low-pressure borehole drilling, middle-pressure flushing, and high-pressure cutting are performed within the drilled borehole to create deformation and displacement in a coal body in the pre-drainage region, and in turn form a network of cracks, such that channels for desorption and mobility of the gas are created to facilitate removal of the gas. The method can enlarge an effective pressure-relief range of each single borehole, increase the permeability of the coal seam, improve gas removal efficiency, reduce the number of pre-drainage boreholes, reduce pre-drainage operation time, and has superior adaptability to coal seams having different storage states. The method can decrease the number of through-seam boreholes by 32.5% and the length thereof by 42.9%, and has a prominent effect in preventing bursts in a coal mine roadway region, thereby significantly accelerating an excavation speed.