Effects of gas pressure on bursting liability of coal under uniaxial conditions

Abstract

When exploiting deep high-gas coal seams with a bursting liability, complicated rockburst disaster conditions exist because of the combined influence of stress and gas pressure. An understanding of the influence of gas on the bursting liability of coal can enable an analysis of the mechanism of the rockburst induced by gas pressure and the bursting liability of coal. Using a custom sealed pressure system, experimental studies of coal samples with a bursting liability were carried out under different gas pressure conditions. The experimental results are explained based on the coal structure, the structural effective stress, and the corrosion-damage effect of the gas on the coal. Research results show that: (1) an inverse relationship exists between gas pressure and coal bursting liability; that the duration of dynamic fracture (DT) increases exponentially; and that the elastic strain energy index (WET), bursting energy index (KE), and uniaxial compressive strength (RC) decrease linearly with increase in gas pressure. The coal dissipation energy increases with an increase in pore gas pressure, the elastic strain energy stored before the stress peak reduces, and the elastic energy release rate decreases rapidly. (2) The existence of gas pressure decreases the structural effective stress of the coal body and prolongs the DT; and the destruction mode of coal changes from brittle to ductile failure. Mechanical and corrosion damage caused by the gas decreases the coal strength, the accumulated elastic strain energy, and the coal bursting liability indices, including RC, WET and KE. Rockburst disasters in gas-containing coal seams result from the large-scale fracture of the surrounding coal and rock during mining. Gas reduces the degree of rockburst damage but increases the rockburst frequency in high-gas coal seams with a bursting liability.