Numerical Simulation And Analysis Of Coal And Gas Outburst By Drilling Of High Pressure Water Jetting

Coal and gas outburst, which threatens the safe production of coal mine, is a kind ofcomplicated dynamical phenomena in mines and one of the most serious natural disasters.Gas outburst can destroy ventilation system, cause gas explosion and heavy loss of life.With mining depth increasing continuously in our country, in condition of mining in thedeep-lying, there are many problems in terms of coal and gas outburst, such as high gaspressure and dense content of coal seam methane.By analyzing the influencing factors of the outburst of coal and gas, based on thephysical and mechanical properties of coal, this dissertation studies the features of high-pressure water under the condition of punching break coal, the mechanics in response ofcoal and rock under the influence of the function of water jets impact dynamic load aswell as the dynamic course and mechanism of breaking coal by using high-pressure water.The boundary conditions are set and mathematic model of high-pressure water isestablished according to the interaction of the basic equations in solid deformation fieldand fluid pressure fields, solid and fluid. The effect of preventing the outburst of coal andgas by using high-pressure water is simulated with the help of the softwares of LS-DYNA and RFPA. The result shows that the drilling of high-pressure water jetting oncoal can form a punching and the punching can cause plasticity and creep deformationunder the function of rock pressure and thus the stress state of coal is changed, the gas isreleased, the original gas pressure is reduced and the risk of the outburst of coal and gasdecreases. By simulating the effect of high pressure water jet’s impact on coal underdifferent conditions, this research finds that the crush area is continuously deepening andextending with the increasing of water jet velocity and the enlarging of water jettingaperture. However, due to the control of the interaction between elements in surroundingrocks, the change of crush area is within certain limitation. Single jetting aperture canseverely affect the coal within limited area. The method of porous impingement can beused when the content of occurrence gas is comparatively large or the coal seam iscomparatively thick. In this way, the break of coal can reach a greater extent and a bettereffect of preventing the outburst of coal and gas can also be achieved.This research can provide technical support for anti-outburst mechanism of high- pressure jet.