Experiment research on gas seepage anisotropy in low-permeability coal

To study the anisotropy of gas seepage in coal seams with low permeability,coal samples were prepared respectively in the parallel bedding direction and the vertical stratification direction of the same coal rock. Tri-axial servo seepage tests on gascontained coal were detected by using a self-developed apparatus. It is found that the permeability of coal samples in the parallel is far greater than that of coal samples in the vertical. With the increase of axial pressure,the permeability of coal samples in the parallel reaches its minimum at the yield point before the peak failure,while the permeability of coal samples in the vertical gets its minimum at the initial period of the elastic stage. The permeability of both the parallel and the vertical nonlinearly increases after the peak failure.