Rock mass watering for rock-burst prevention: some thoughts on the mechanisms deduced from laboratory results

Lots of in-situ experience indicate that water spraying or injection to rock mass before excavation is an effective method for rock-burst prevention in deeply buried hard rock engineering projects. To investigate the underlying mechanisms of rock-burst prevention by watering, a series of uniaxial compression laboratory experiments were performed on three types of sandstone samples under oven-dried and water-saturated conditions. A high-speed camera was used to record the fracture processes of the samples during testing. Experimental results show that the presence of water plays a dramatic weakening role on the uniaxial compressive strength, Young’s modulus, and energy storage capacity of the three sandstones. After water saturation, the failure pattern of rock sample becomes much gentler and less dynamic. Moreover, a simple mechanical model of a roadway containing zonal water-weakening rock mass was established to illuminate the local geo-stress regulation by water penetration. The mechanisms for rock-burst prevention by water are mainly due to the declining energy storage capacity and the lowered stress near the working face.