Study on pore structure and pressure-sensitive effect of tectonic coal in Huaibei Xutuan mine

In order to discuss pore structure and pressure-sensitive effect of tectonic coal, coal samples of Huaibei Xutuan mine were measured by optical microscope, scanning electron microscope, mercury injection, and triaxial servo-controlled seepage equipment for thermo-fluid-solid coupling to reveal the pore structure and the influence of effective stress on permeability or permeability coefficient of structural coal. The results show that cataclastic structure of tectonic coal is regular, flat and has good connectivity; the pores of primary coal are mainly composed of micropores, micropores and transitional pores are dominant in tectonic coal has. The effective stress of ductile deformed coal has a parabolic relationship with permeability, when the effective stress is lower than 4 MPa, the coal shows obvious permeability sensitivity; when the effective stress is larger than 4 MPa, the coal shows weak permeability sensitivity. This trend is the result of the effective stress and desorption effect. The minimum permeability is caused by adsorption/desorption and effective confining pressure. Compared with the coal in Qinshui basin, coal samples of Xutuan mine have higher permeability damage coefficient.