Experimental study on shear seepage characteristics of true triaxial coal body under the consideration of gas adsorption

In the process of scientific exploitation of coal resources, complex gas migration behavior often occurs in the coal seam which is often in the true triaxial stress state, but the current physical test cannot reflect the dynamic state of the real force of the gas adsorption on saturated coal body. Therefore, the self-developed true triaxial gas-solid coupling coal body seepage test system has been used to carry out the adsorption seepage test of coal, with methane as the adsorption medium and helium as seepage medium. The mechanism of the effects of methane adsorption on the deformation and permeability of coal in the true triaxial stress environment has been compared and analyzed. The results have shown that 1) Quantitative comparison and analysis with helium adsorption tests show that methane adsorption is affected by the properties of confining pressure-expansion deformation is apt to occur on the side of flexible confining pressure, while small deformation only occurs on the side of rigid confining pressure. 2) In different true triaxial shear stress environments, the greater the intermediate principal stress, the greater the strain rate in the direction of the minimum principal stress of the coal body. 3) The intermediate principal stress effect has a dual effect. There is a difference between the intermediate principal stress effect and the confining pressure effect. When the intermediate principal stress exceeds a certain stress range, the peak strength of the coal body will decrease and its permeability will increase. The research results provide a test reference to the control of coal and gas outburst and the improvement of gas drainage rate. © 2019, Editorial Board of Journal of Mining & Safety Engineering. All right reserved.