Research on gas percolation and catastrophe behaviour of gas-bearing coal under low index

Abnormal gas emission, coal and gas outburst may occur on the coal seam whose gas pressure and content are below catastrophe threshold, when the mine is deeply exploited. In order to study this catastrophe mechanism, solidfluid coupling experimental system with single degree of freedom and bidirectional loading is proposed. Gas percolation and catastrophe behaviour are studied through low pressure loading in this experiment, obtaining the following conclusions: 1) gas flow curve of gas-bearing coal shows asymmetric U shape; 2) coal sample suffers catastrophe gas emission after its rupture and instability under low pressure of 0.4 MPa and 0.15 MPa; 3) stress threshold of catastrophe gas-bearing coal sample is negatively related with coal gas pressure; 4) primary fracture of gas-bearing coal sample is consolidated when elastic deformation reaches 50% similar to 60% of elastic process, blocking gas percolation. However, gas percolation channel will be reopened after one yield or several yields.