Numerical Simulation Of The Gas-solid Coupling Of Vitical Shaft Cutting Through Coal Seam And Outburst Prevention Technique

Shaft cutting through outburst coal seam is a major security problems in vertical shaft construction today. With the increase of depth of coal mining each year, the risk of cutting through outburst coal seam are also increasing, seriously restricts the safe and efficient production of mine.In this dissertation,it combins theoretical analysis, numerical simulation and field test investigation.Research on the mechanical characteristics of vertical shaft cutting through gassy coal and rock and outburst prevention technique systematically.First of all, based on gassy coal effective stress principle, through reasonable assumptions and simplified, the gas and solid coupling equation of gassy coal is constructed. Then, to embed the gas-solid coupled equations of COMSOL Multiphysics software, analyzes the different diameter of the shaft excavation, different gas pressure and the thickness of security rock pillars shaft uncovering coal working face in the process of the stress distribution of coal and rock mass around. And the the seepage properties of the coal seam.According to the mechanical characteristics of vertical shaft cutting through gassy coal and rock, design the fan intensive extraction from borehole extraction for gas. It has obtained the very good protection effect.Numerical simulation results show that the different diameter of the shaft excavation, under the condition of different gas pressure and the thickness of security rock pillars, the stress distribution are similar. There are high pressure area,relief area and the original rock stress area.The high pressure area is around the vertical shaft. Because of the existence of vertical shaft excavation process, the coal and rock stress balance of the original are redistributed.Before work face (below) is the "funnel" relief form area. The center of the work face is the maximum unloading area.Well with the excavation diameter, reserved safety thickness of rock pillars is smaller, the greater the stress, high range and the peak value, the greater the scope of the pressure relief area. The pore gas pressure of gassy coal is larger, the effective stress of coal is lower, the greater the strength reduction of coal. With the continuous increase of gas pressure, the plastic deformation damage area around working face will increase and the coal.Coal and gas outburst, the easier it is to happen. Applying the fast measuring pressure technology to measure the pressure of11-2coal, the pressure could be reached only in2days and the pressure is1.22MPa.The coal seam has the danger of coal and gas outburst.According to the mechanical characteristics of Pansan coal mine’s deep shaft cutting through11-2coal seam.Through the adoption of sector intensive boreholes extraction gas only28days, extraction gas15951m3, methane drainage rate is as high as57.7%.Residual methane pressure is0.32MPa and residual methane content si2.85m3/t.Effectively reduces the gas pressure and gas content of coal seam.And around the shaft lining constituted a range of preventing coal and gas outburst occurred in safe areas. outburst prevention effect is remarkable.