The Characteristics Of Surrounding Rock Mass Plastic Zone To Uncovering Coal In Crosscut And Study On Of Gas Extraction Drilling Parameters

Taking the uncovering coal in crosscut of nan tong No. 6 as the experiment specimen,through laboratory experiments by field sampling, the rules how the effective stress and different gas adsorption influenced the coal permeability were found out. At the same time through the numerical analysis and theoretical analysis,fracture of uncovering coal in crosscut regions were predicted, and established the finite deformation of the coal rock of solid -gas coupling model. Through careful analysis of drilling drainage characteristics and the law of gas flow, and some laboratory experiments ,the change law of the parameters of methane extraction were educed。To sum up, the main research results and conclusions of this paper are as follows:①Through laboratory experiments by field sampling ,the rules how the effective stress and different gas adsorption influenced the coal permeability were found out. The coal permeability and effective stress has a negative correlation. The reason is that the effective stress increasing compresses the coal rock crack so that the seepage channels are reduced. The coal matrix will swell by adsorbing gases so as the openings of fracture become small, and then the coal permeability is lowered.②Giving the rock failure criterion, and applying to the coal rock specimen validation, obtaining the fracture failure criterion of coal. Introducing the rock mass stability coefficient R, when R≥1, rock is not destroyed,through numerical simulation of uncovering coal in crosscut, research results are as follows: the region of fracture of uncovering coal seam in cross-cut on the Formation is a dynamic evolution process,when the distance between working face of rock tunnel and coal seams becomes closer and closer, the fracture area becomes larger and larger. The working face will have the sign of destruction when the distance between the rock tunnel and working face coal seam become very closer.③Established coal in gas-solid coupling model which reflects the change of porosity and permeability, by analyzing the model to educe an effect regularity of gas pressure, porosity and permeability in the gas extraction surroundings, obtained optimal design parameters of gas extraction.