Coal And Gas Outburst Control Using High Pressure Waterjet Slotting Technique

For the past few years, with the increase of the depth of seems mined and the further expand of the mining, there is a phenomenon of"three highs and two lows"(high geostress,more gas,high nonuniformity,low permeability and low strength of the coal) which leads to coal and gas outburst, which restricts the coal industry development.The methods for controlling the outburst such as"advanced borehole and emission""hydraulic punching""high pressure water injection"and"standing shot"are widely used. But these techniques contain some kind of limitations, such as high construction repetition and high over-limit ratio of test rating in outburst control. The limitations of these methods becomes even more serious for heading development rate in coal seam with possible outburst, and it results in low excavation rate and imbalance of mining proparation which has a strong impact on the safety and production.Thesis presents the research on technique of high pressure water jet slotting to control coal and gas outburst during heading development. At first, the author describes the features of the geometric structure of water jet, analyzes the theory of rock breaking by water jet and then studies the mechanism of high pressure water jet slitting to control outburst. Then, numerical modeling method (Flac3D) has been used to analysis the effect of waterjet slotting parameters on outbutst control. Besides, using ANSYS the author simulates the inner flow field of the spinning nozzle, determines the optimum parameter of the high pressure moment nozzle by means of orthogonal test. In addition, the influence of moisture content on the head-on coal cohesion and internal frictional angle is studied via indoor shear tests the in wood road 11112 of Jinjiachong colliery. Finally,high-pressure water jet slitting technology was established after determining other parameters of the slotting system through theoretical analysis. What's more, the author made an experiment in Jinjiachong colliery of Guizhou Province inspecting and analyzing aspects such as the slotting affected areas, rate of advance, gas discharge etc. This experiment proves that this measure is effective in outburst elimination with the coal roadway driving speed rising by 1.5 fold reaping significant economic and social benefit.