Mechanical behaviors and instability of rocks subjected to hydraulic progressive wetting: Acoustic emission and uniaxial compression experiments

In the field of rock engineering, the influence of water is a dynamic process that exhibits varying effects over time and across different locations. To further understand how water influences the mechanical properties and acoustic emission (AE) behavior of rocks, this study conducted uniaxial compression experiments on sandstones with varying degrees of wetting under both natural conditions and water-chemical environments. In addition, the study combined AE equipment with digital image correlation (DIC) to monitor the entire failure process. Using the sliding window algorithm, the variation in the variance of AE characteristic parameters during the process of sandstone loading to failure is analyzed from the perspective of critical slowing down. This analysis enables the effective identification of the early warning signal before failure. The experimental findings suggest that an increase in wetting height results in a gradual decrease in peak stress, accompanied by a concomitant increase in the percentage of shear cracks. The characteristic parameters, including energy, amplitude, and ringing count, all exhibit critical slowing phenomena. The waveform of AE characteristic parameters of the same sample is similar, and the mutation time of the precursor signal is roughly the same. All signals appear in the irreversible plastic deformation stage of microcrack initiation. The integration of critical slowing down theory and the b -value early warning method facilitates a more comprehensive evaluation of the stability of rock mass, thereby significantly enhancing the efficiency and safety of disaster prevention measures.