Wave velocity evolution law and mechanical index attenuation model of limestone under different freeze-thaw cycles

• The mechanical characteristics and crack propagation mechanism of rock specimens under different freeze-thaw cycles were explored. • The changes in physical parameters and mechanical properties of rock specimens under different freeze-thaw cycles were obtained. • The rock mechanics index attenuation model was established based on experimental results. • The main failure mode of rock specimens under different freeze-thaw cycles was obtained. The most important problem in cold regions was the disaster caused by freeze-thaw(F-T) cycles, which was mainly caused by the deterioration of physical and mechanical properties of rock masses in cold regions. The damage, strength degradation, and deformation of rock masses continued to increase under F-T cycles, which would directly affect the safety of rock engineering. To explore the mechanical characteristics of F-T damage and crack propagation mechanism of rock specimens under uniaxial compression conditions, experiments were conducted on limestone from mines in Hejing County, Xinjiang. The changes in physical parameters and mechanical properties of rock specimens under different F-T cycle times were obtained through F-T cycle tests, stress-strain tests, ultrasonic detection tests. The initiation, propagation, and penetration mechanisms of internal cracks in F-T limestone under uniaxial stress were analyzed, and the rock mechanics index attenuation model was established based on experimental results. The rock wave velocity gradually decreased and followed an exponential decay model as the number of F-T cycles increased. The coefficient of rock F-T resistance decreased in a three-stage pattern of the "initial stage - stable stage - accelerated stage" of F-T damage. The main failure mode of rock specimens under F-T cycles was crack mode. With the increase of F-T cycles, surface cracks increased and deepened gradually, mostly distributed longitudinally. The compressive strength, elastic modulus, Poisson's ratio, and dynamic elastic modulus of limestone all decreased with the increase of F-T cycles, and the decreasing trend followed an exponential decay model. The uniaxial compression failure mode of limestone under F-T cycles exhibited splitting or splitting shear characteristics.