The Mechanism and Numerical Experiment of Spalling Phenomena in One-dimensional Coal and Gas Outburst

Based on simulation of one-dimensional coal and gas outburst and energy conservation principle, a mechanism on spalling lamination and a formula of the lamination characteristic length were promoted. The performance of simulations in different gas pressure conditions showed that the formula was appropriate to the test results. Before the appearance of spalling lamination, a sudden strain change occurred in failure point which may fail later. During the unloading stress wave's propagation in the coal-gas medium, coal would fail as maximum tensile stress beyond the criterion, and then spalling or crush happened. The spalling lamination was disc-shaped without friction, and cone-shaped with friction. Only when gas pressure was bigger than 10 atmospheric pressures, coal crushed out. But there was no coal-gas outburst under 7 atmospheric pressures.