Dynamic characteristics and damage mechanism of freeze-thaw treated red sandstone under cyclic impact

To study the strength, deformation characteristic and damage mechanism of freeze-thaw treated rock mass under the action of cyclic dynamic disturbance, the cyclic impact tests of freeze-thaw treated red sandstone under two kinds of impact pressure were carried out to investigate the effects of cyclic impact number and freeze-thaw number on stress wave propagation, dynamic stress-strain curve, peak stress, and peak strain. In addition, the calculation method of cumulative damage factor, which can comprehensive consider the effects of cyclic impact and freeze-thaw, is proposed based on the Lemaitre strain equivalence principle. Finally, the microstructure characteristics of red sandstone after freeze-thaw and cyclic impact are analyzed in detail. Results show that red sandstone specimens treated with different freeze-thaw number show tensile failure mode under cyclic impact load. The cyclic impact number that red sandstone specimen can withstand is negatively correlated with freeze-thaw cycle number, and red sandstone specimen after 75 freeze-thaw cycles treatments reaches the failure state after the first impact loading. Moreover, the cyclic impact number mainly affects the jump point, abscissa corresponding to peak point and amplitude of transmitted waves, and the amplitude of reflected waves. While the freeze-thaw number shows a great effect on the jump point, abscissa corresponding to peak point, and amplitude of transmitted waves during the first impact process. The cumulative damage factor of red sandstone specimen exhibits a good negative correlation with the dynamic peak stress. After the combination effects of freeze-thaw and cyclic impact, the cracks inside red sandstone spread along the grain boundary and connect with the pores to form a complex network. © 2024 Explosion and Shock Waves. All rights reserved.