Abstract: A series of one dimensional simulation experiments (coal shock tube) showed that two kinds of damage, fracturing or outburst, could take place, when a porous medium containing pressurized gas and bearing compressive stress was suddenly unloaded. The critical condition of outburst is stronger than that of damage. In other words, outburst is a strong kind of damage. Therefore, there exists the case in which the damage condition is met while the outburst condition has not yet been met. Experiments showed a ...