Study on gas permeability of coal by crack network model (1st Report). Effect of Open and Close of Cracks in Coal on Gas Permeability of Coal.

The purpose of the present study is to prove the mechanism of gas permeability of coal by effect of stress. Practically, Crack network model was supposed for the pore structure in coal. Gas permeability of coal was investigated by calculating the flow admittance which was simulated by the crack networks.As the results of these simulations, a linear relationship was found between a number of crack per unit area and a flow admittance in the case of the crack network made by Monte Carlo method. This result correspond to effect of a failure fracture on gas permeability of coal. Moreover, a exponential relationship was found between a number of block crack for a grid network and a flow admittance in the case of the crack network made by percolation process. This result correspond to effect of compression on gas permeability of coal.