Experimental Study on Damage Evolution Characteristics of Granite Under Short-Term Freeze–Thaw Cycles

Rock engineering problems in short-term freeze-thaw zones and short-term freeze-thaw cycles can lead to a reduction in rock strength, thereby inducing engineering disasters. Granite in short-term freeze-thaw zones was selected as the research object. Taking the freezing time (1 h) required for the internal temperature of the rock to reach the target freezing temperature as the reference, freeze-thaw cycle tests with durations of 1 h, 2 h, and 3 h were carried out in sequence. Combined with uniaxial compression acoustic emission (AE) tests, the effects of freeze-thaw duration and freeze-thaw cycle number on the physical and mechanical properties and AE characteristics of the rock were systematically investigated. A multi-index damage characterization system was established. Results show that: (1) Both freeze-thaw duration and cycle number show a positive correlation with the attenuation of peak strength and elastic modulus. (2) With the increase in freeze-thaw duration and cycle number, the AE cumulative ringing count rate and cumulative energy rate show an exponential decay trend. (3) Their proportion shows an increasing trend with the increase in freeze-thaw duration and cycle number. (4) Establishing a multi-index coupled damage variable to replace the traditional single-index characterization can improve the objectivity and reliability of freeze-thaw damage assessment.