Effects of water intrusion on fracture characteristics of hard coal

Abstract Aquifer water can cause serious geological hazards by catastrophically rushing into underground space. The water seepage can increase the moisture content and pore pressure of coal/rock, which can change mechanical behaviour of coal/rock subject to tectonic and abutment stress. Understanding the effect of water intrusion on physical and mechanical properties of coal is the critical research question for safe utilization of deep coal seams under the complex geological conditions. In this paper, the effects of water intrusion on fracture characteristics of coal samples taken from a typical deep coal seam are experimentally studied by quasi-static loading tests. Analytical tools such as AE system is used to continuously log acoustic events and associated energy release for the duration of the experiments to reflect the damage evolution and crack propagation. A coupled fluid–solid numerical model, using PFC software, is developed to simulate the water-coal interaction process for reflecting the energy evolution during loading process of coal samples with or without water soaking. It was determined by this research that hard coal will remain its brittle failure mode even after water infusion.