Effect of bedding structural diversity of coal on permeability evolution and gas disasters control with coal mining

Bedding structure has affected gas flow in coal seam greatly, which also controls gas permeation direction and gas extraction results, and finally it has tremendous influence on prevention and control of gas disaster accidents. Combined with engineering practice of gas disaster prevention and control in China, in this paper, permeability evolution of nature coal in different bedding directions in the condition of loading is studied, and the results showed that in three directions of bedding fractures, permeability of coal which is parallel to bedding planes is the highest; it would be much easier for gas percolation along the bedding planes than other directions. In the unloading process, tension–shear destruction appears in coal sample which is oblique to bedding along the bedding planes, with a sudden increase in permeability. It is difficult for the crack damage from loading process to recover in unloading process, that is, permeability of unloading isn’t just a simple reverse process of loading. Combined with the permeability evolution of the three coal samples in the whole process, three permeability evolution models which include elasticity, plasticity and fracture are proposed. Based on the experimental results, gas extraction using boreholes along coal seam and through coal seam is compared during depressurized mining. Due to the bedding structure of coal seam, a large area of fracture network of “boreholes–bedding fractures” is formed among boreholes through coal seam and bedding structure, which makes the good effect of gas extraction using boreholes through coal seam. Research results will be of important guiding significance for choosing the best gas extraction scheme, layout of setting parameters of drilling boreholes and gas disaster prevention in the underground coal mine. Copyright Springer Science+Business Media Dordrecht 2014