Failure prediction and microcracks development based on acoustic emission and energy evolution for different rocks treated with freeze-thaw weathering

Freeze-thaw weathering pointedly deteriorates rocks' strength and plays a significant role in rockmass instability in cold regions. Therefore, acoustic emission (AE) signals and energy evolution during uniaxial compressive loading were used to predict failure and estimate the microcracks evolution of sandstone, marble, and granite under freeze-thaw weathering. Moreover, the AE energy mutation rate (AEEMR) was evaluated from AE signals to identify the pre-failure peaks of rock deformation. The AE signals, i.e., AE energy, have successively traced the distinct stage characteristics during the loading process. The AEEMR curves consecutively enhanced the pre-failure peaks of AE energy curves. Further, the ratios of dissipation to the total energy (R-DT), elastic to dissipation energy (R-ED), and energy dissipation rate (EDR) were adopted to predict the violent failure of different rocks. The results demonstrated that the precursory information of R-DT and R-ED was more manifest than that of EDR curves. The R-DT and R-ED gave precursory points earlier than EDR. It was also observed that the freeze-thaw weathering affected the failure and precursory time of rocks. Furthermore, the microcracks evolution was assessed using the (average frequency) AF and (the gradient of the waveform rise) RA values distribution line and 2D Kernel density estimation (KDE) map. The freeze-thaw weathering barely influenced the cracks' transformation from tensile to shear, but the tensile cracks were further espoused notably. The outcomes of this research work will be beneficial in understanding the failure mechanism and prediction of different rocks under extreme frigid environments.