Brittle mechanical characteristics of hard rock exposed to moisture

Rich groundwater content can produce a complex geological environment for underground tunnels. Therefore, the brittle mechanical characteristics of hard rock exposed by tunnelling in a moist environment are of great significance. Uniaxial tests and acoustic emission (AE) analysis of sandstone with respect to different moisture conditions are described in this paper. Moisture-controlled trends of the stress–strain relationship, mechanical parameter variation, maximum instantaneous AE energy, cumulative AE energy and macro crack behaviour were analysed in detail. In addition, X-ray diffraction and scanning electron microscopy were performed to analyse the fracture surfaces of rock at the microscale. Sandstone particles were found to be more likely to slip past each other at high moisture contents, resulting in increased plastic deformation and dissipation of internal energy. Increasing moisture reduces the brittleness of hard rock and the probability of rock burst. The results reveal the mechanical mechanisms cause moisture to affect brittle hard rock and can contribute to the improvement of the design and construction of deep tunnels.