Experimental study on uniaxial compression failure modes and acoustic emission characteristics of fissured sandstone under water saturation

Widely distributed fissures in the open-pit slope (especially those which are in water-rich conditions) determine the slope stability. In order to study the effects of water and fissures on rock's mechanical properties and corresponding acoustic emission characteristics, red sandstones containing dual-fissure with different angle configurations were prepared for uniaxial compression tests along with acoustic emission (AE) monitoring in this study. The impacts of water content and fissure angles on rock strength, failure mode and acoustic emission characteristics were analyzed. Moreover, the kernel density estimation (KDE) was accepted to quantify the AE events spatial distribution, then distinguishing difference between dry and saturated rocks' failure modes. This study reveals that the presence of water in the rock lowers of the rock strength and decreases the amounts of secondary cracks and acoustic emission counts. As the fissure angle increases, both the rock strength and acoustic emission counts increase and the failure mode shifts from the tension failure to the shear failure. The b value was highly sensitive to crack propagation, reaching around 0.5 when the rock was finally destroyed under different water conditions. AE events mainly gathered in the location where the main cracks occurred. The maximum KDE density points of dry sandstone changed from concentrated state to dispersed state before failure, while the maximum density points of saturated sandstone always gathered in the middle of rock. The results of this paper lay theoretical foundations for monitoring and pre-warning of engineering rock failure in water environment.