Abstract: In this paper, in order to resolve the problem of gas and coal outburst in the drilling process of coal seam with high concentration of gas and low permeability, the gas-outburst prevention technology of high pressure hydraulic-cutting seam through layer was developed, which is integrated by drilling and seam cutting. Numerical simulation method was used to compare the pressure relief effects of borehole drilling and high pressure hydraulic-cutting seam. The results show that the pressure relief effect of high pressure hydraulic-cutting seam is much better than that of seam drilling. The cutting slit has broken the “bottleneck effect” around the drilling hole, and the extension of fractures and weak planes in coal mass is transformed into interlaced transfixion fracture network, which increases the permeability of coal mass and promotes the gas release. Industrial experiments indicate that compared with general method of coal seam drilling, the high pressure hydraulic-cutting seam through layer produces a better effect of pressure relieving and permeability improving, while the flow of drilling gas extraction and disturbance volume of coal mass have increased substantially, which improves the gas extraction efficiency.

Key words: high-pressure swirling water jet, coal seam cutting, pressure releasing, gas and coal outburst