Mechanical behavior of sandstones under water-rock interactions

Water-rock interactions have a significant influence on the mechanical behavior of rocks. In this study, uniaxial compression and tension tests on different water-treated sandstone samples were conducted. Acoustic emission (AE) monitoring and micro-pore structure detection were carried out. Water-rock interactions and their effects on rock mechanical behavior were discussed. The results indicate that water content significantly weakens rock mechanical strength. The sensitivity of the mechanical parameters to water treatment, from high to low, are Poisson ratio (u), uniaxial tensile strength (UTS), uniaxial compressive strength (UCS), elastic modulus (E), and peak strain (e). After water treatment, AE activities and the shear crack percentage are reduced, the angles between macro fractures and loading direction are minimized, the dynamic phenomenon during loading is weakened, and the failure mode changes from a mixed tensile-shear type to a tensile one. Due to the softening, lubrication, and water wedge effects in water-rock interactions, water content increases pore size, promotes crack development, and weakens micro-pore structures. Further damage of rocks in fractured and caved zones due to the water-rock interactions leads to an extra load on the adjoining coal and rock masses, which will increase the risk of dynamic disasters.