Abstract: Drainage influence radius is the basic parameter for borehole layout, but the slot form of high pressure water jet slotting and its effect to borehole drainage influence radius have not been studied systematically. In this paper, slot shape was simplified as a disc according to the laboratory experiment results, and the disc size was analyzed based on the theory of submerged jet. Meanwhile, COMSOL software was used to study drainage influence radius of slotted borehole in different coal seam conditions, and filed tests were carried out. The results show that drainage influence radius of slotted borehole has power function relation with the slotted disc, as well as the permeability, time, and gas pressure, while the significant degree of the influence factors is in sequence of permeability, time, gas pressure and slotted disc. The relative difference of slot volume in actual high-pressure water jet slotting and slotted disc volume determined by theoretical analysis is about 8.33%. Meanwhile, when the drainage time is 130d, the relative difference of drainage influence radiuses between the measured and numerical simulation is 6.20%.

Key words: high pressure water jet；slotting, borehole；drainage influence radius；numerical simulation