Experimental study on desorption characteristics of gas-containing coal under the action of overburden pressure and water injection

It is easy to form a coupling effect between ground stress and gas, and cause the accident of coal and gas outburst dominated by ground stress during deep mining. In order to improve the accuracy of mine gas disaster prevention, it is urgent to deeply understand the influence of water intervention on the desorption characteristics of gas-containing coal under ground stress. A simulation test device was set up for the effect of water injection on the gas desorption characteristics of coal under overburden stress and water injection by applying overburden stress and injecting water at the same time to the experimental coal sample. Based on the experimental setup, the gas desorption data of coal samples from Guhanshan Mine (GHS) were tested at overburden stresses of 5 MPa, 10 MPa and 15 MPa, moisture content of 0%, 2%, 4% and 6%, and the same inflation amount. By analyzing the experimental data, the influence of overburden stress and water injection on the cumulative gas desorption amount, gas desorption rate, initial gas desorption rate influence coefficient and residual gas content of GHS coal samples was obtained. The result shown that the overburden stress effect increased the cumulative desorption amount and the initial gas desorption rate of the dried coal samples, which promoted gas desorption. With the intervention of water, the cumulative gas desorption amount and initial gas desorption rate of coal samples with large overburden stress became smaller, indicating that the moisture inhibited gas desorption, and the overburden stress effect transitioned from promoting to inhibiting gas desorption. Theoretical analysis shown that the piston effect of overburden promoted gas desorption of dried coal sample. As moisture intervention, it produced a strong capillary resistance in the pores and cracks of coal. With the increasing overburden stress, the coal sample was crushed and compacted, and the capillary resistance became larger as the pore fissures got smaller, resulting in a stronger inhibition of desorption. The experimental results have certain positive significance for an in-deep understanding of the mechanism of hydrodynamic measures to prevent coal and gas outburst.