Permeability characteristics of coal containing gangue under the effect of adsorption

In order to find out the influence of adsorption on gas flow characteristics in coal seam, we analyzed the influence of gangue on permeability characteristics of coal, and then deduced the calculation method of the equivalent permeability of the specimen containing gangue. The gas flow characteristics under different conditions of pulverized coal sample, sand sample and coal containing gangue (simulated coal seam containing gangue) were studied using self-developed device “a test device for cracked coal-rock mass of gas migration characteristics”, and then the experimental results were analyzed. The results show that: the coal seam adsorption causes the swelling deformation of coal matrix, reduces the coal seam porosity and the coal seam permeability, and the swelling deformation of coal matrix and gas pressure conform to the rule of quadratic function. The two gangue layers with different porosity both can promote the equivalent permeability. However, the promotion effect is different with the increase of the thickness of the gangue layer. The existence of the gangue layer does not change the relation between permeability and gas pressure, and the both still conform to the quadratic function. The Klinkenberg effect of the gangue coal is weakened, and the slip factor is linearly negative to the thickness of the gangue. With the increase of the gas pressure, the extrusion coefficient of the two phases of coal and gangue first decreases and then increases.