Research On Application Of Using High Pressure Water Jet Slotting In Exposing Closed Distance Outburst Seams

With the gradual increase of mining strength, the situation of exposing closeddistance outburst seams happens frequently. In coal mines, when exposing outburstseams in a crosscut, the outburst danger of front seams cannot be ignored. To solve theproblem of outburst danger of contiguous seams, a method that a drainage hole willcross all seams is proposed in this paper. Combined with high-pressure water jettechnique, the coal seams are slotted and the stress field and the crack field will change.The research provides theoretical value and industrial significance for exposingcontiguous seams.In this paper, a method that combined of theory and experiment is used to study thegas migration law of coal seams, which is based on water jet cutting seam mechanism.Compared with the real situations in Leigongshan Coal Mine, numerical simulationsoftware Comsol is used to simulate three different slotting methods. The mainachievements are as follows:（1）The mechanism of high-pressure water jet cutting is that coal seams areslotted and damage as well as failure of coal occur. Then, the original fissure expandsand new destructive fissure formats. As a result, the permeability coefficient of coalseam increases. What’s more, the permeability of coal which in distant regions increasesbecause of the stress reduction.（2）Combined with the situations in Leigongshan Coal Mine, the numericalsimulation software is used to simulate three different slotting methods. The resultsshows: For the reason of cost control, time and efficiency, it is best to choose the No.5and No.9seams as the slotting seams. The minimum pressure relief rate of No.5coalseam is98.6%and92.1%in roof and floor. The same situation appearances in No.9coalseam, which minimum pressure relief rate of roof and floor is106.5%and102.6%.Ifthere is only one coal seam could be slotted, the No.5seam which is in the lower layerwould be a better choice.（3）The industrial tests show: Use the method that drilling disposable constructionborehole, average gas drainage flux and average gas drainage concentration increased13.5and7.8times respectively; What’s more, the quantity of boreholes decreases55.9%and the K1max decreases40percent.