Abstract: In order to explore the seepage laws of gas(methane) from different bedding direction fractured coal samples under the same stress loading and unloading condition, experiments were carried out on the parallel and vertical bedding direction raw coal samples employing a self designed and modified three stress axis gas penetration simulation experiment device. The results showed that in the stress loading process, both the permeability values of the two coal samples decreased with the increase of effective stress, the values decrease by 99.01% and 80.49% respectively when the effective stress was loaded to the maximum value. In the stress unloading process, the values increased with the decrease of effective stress and the change was small at the beginning of unloading, the values recovered to 87.45% and 68.8.5% of the minimum values respectively when the effective stress unloaded from 11.65 to 8.98 MPa, that the increased amplitude of the values are 736.78% and 99.67% when the effective stress unloaded to 4.98 MPa, and that the increase amplitude of the value of parallel bedding direction coal sample was much bigger under the same unloading condition.

Key words: loading and unloading, fracture coal body, seepage characteristics, raw coal samples, borehole layout