Using the self-developed triaxial servo-controlled seepage equipment for thermo-fluid-solid coupling of coal containing methane

a series of tests is conducted on coal samples during the process of gas loading-unloading at different temperatures to simulate the seepage characteristis of coal under the condition of temperature increase induced by increasing depth of mining. Meanwhile

parallel experiments on helium are also carried out to investigate the slippage effect of low permeability coal seam. The experimental results are shown as follows: (1) During the loading process

the axial strain increases and radial strain decreases linearly with the increase of gas pressure. During the unloading process

the strain of coal shows the same trend with the loading. The slope of strain varies with increasing gas pressure and temperature. (2) During the loading process

the permeability of coal shows a quadratic parabola trend with the increase of gas pressure

and it reaches the minimum at about 3.0 MPa. At the early unloading stage

the permeability of coal decreases slowly and then increases with the decrease of gas pressure. The permeability of coal during the loading process is lager than that during the unloading process. (3) Variation of permeability caused by slippage effect during loading process is greater than the amount of unloading process. What’s more

variation of permeability caused by slippage effect declines in an exponential function with the increase of gas pressure.