Abstract: The fracture and deformation mechanism of sandstone under water-rock interaction was investigated via uniaxial compression acoustic emission (AE) experiment and infrared radiation (IR) observation experiment on both natural and saturated sandstone specimens. The influence of water on the mechanical properties as well as AE and IR changes of sandstone were examined through analyzing the axial stress, AE energy rate, fractal dimension, IR frequency histogram and partial degree of each transformation stage. Results demonstrated that the mechanical properties of sandstone such as compressive strength and bearing capacity were evidently weakened by water. Water inhibited the AE activity and crack development scale of sandstone as reflected by larger average peak energy rate, larger amplitude and longer duration of active energy release phase, as well as better synchronicity of energy rate and stress of natural samples than those of water-saturated samples. The correlation dimensions of AE energy rates of both natural and water-saturated sandstone specimens changed in a cyclic upward-downward trend. The AE of water-saturated samples responded to the discrete disordered development and aggregation ordered development of cracks later than that of natural samples, and the release of energy rate was more disordered than that of natural samples. In the meantime, water enhanced the sensitivity of IR, as reflected by the gradual increase in heating area of water-saturated samples during loading and the large heating area of rock surface during failure. On the contrary, natural samples saw slight and unstable temperature changes during loading, and only some high-temperature points during failure. However, both natural and water-saturated specimens experienced a calm period of temperature change before the peak stress.

Key words: sandstone, acoustic emission, fractal feature, infrared radiation, frequency histogram