Research and application of technological parameters of ultra-high pressure water jet slotting in deep outburst coal seam

The technology of ultra-high pressure water jet slotting can significantly improve the stress state of deep coal seam and reduce the amount of drilling work. In view of the problem that due to the lack of evidence for the selection of slotting process parameters, it is easy to cause the slotting to penetrate the adjacent borehole by mistake and the effect of pressure relived and permeability enhanced is poor. In this paper, the technological parameters of ultra-high pressure water jet slotting in outburst coal seam under the condition of large buried depth were studied. Firstly, the influence of technological parameters including water jet pressure, slotting time and rotation speed of water jet on the effect of ultra-high pressure water jet slotting was theoretically analyzed; secondly, by field investigation of pressure relived and permeability enhanced effect of water jet slotting under different parameters, the optimum parameters combination of water jet slotting were obtained; finally, the field process verification was carried out in the western belt roadway of Zhaogu No. 2 Coal Mine. The test results show that the gas drainage purity of the optimized coal seam slotting borehole is 3.8 times that of the contrasted borehole, the effective gas drainage radius of the slotting borehole is 2 times that of the contrasted borehole.After slotting, the design parameters of perforating borehole were optimized from 4 m×5 m to 8 m×5 m, and on the basis of the 50% reduction of the drilling work, the time to reach the drainage standard has been shortened from over 12 months to 7 months, and the drainage time to reach the standard has been reduced by about 40%.