###### Abstract  
A common problem in cold regions is the influence of freeze-thaw damage on the stability of rock engineering. Therefore, a series of uniaxial compression tests of sandstone after freeze-thaw treatment was carried out in this study. The purpose was to express the initial damage of rock after freezing and thawing treatment more quantitatively and to study the influence of freeze-thaw damage on the rock crack growth process to provide some reference for the stability evaluation of rock engineering in cold regions. The results showed that the number of freeze-thaw cycles and the lowest freeze-thaw temperature had a significant effect on the rock damage and characteristic stress value, and the number of cycles had a more obvious effect: with an increase in the number of freeze-thaw cycles and a decrease in the freeze-thaw temperature, the initial damage \(D_{NT}\) had an increasing trend. In addition, the intrinsic mechanism of the freeze-thaw effect on the rock characteristic stress was explained from the perspective of a meso-mechanical mechanism. From the inversion results of the acoustic emission (AE) moment tensor, it was found that the proportion of tensile cracks gradually increased with the increase in the initial damage of the rock in the stable and unsteady stages of the rock crack propagation. fontsize  
mechanical properties of rocks after freeze-thaw cycles also change significantly, including the dynamic compressive strength, tensile strength, and elastic modulus [20; 21; 22]. The deterioration mechanism of freeze-thaw cycles on rock mechanical properties is as follows. When the rock material in the saturated state is frozen, the volume of water stored in the fracture expands by 9%. This expansion effect causes a large tensile stress and makes the original cracks propagate further. After thawing, the water will flow through the fractured cracks, further promoting the damage of the rock [23; 24; 25]. Therefore, the effect of the freeze-thaw cycles can be understood as the formation of initial damage to the rock. The mechanical response of the rock during the loading process can be regarded as the coupling effect of the initial damage caused by freeze-thaw cycles and the damage caused by the increased stress. The initial damage caused by freeze-thaw cycles can be observed in a variety of ways, including P-wave velocity, X-ray CT, SEM, and NRM [26; 27; 28]. By assuming that the strengths of the micro-elements inside the rock obeys the Weibull distribution, many researchers have established the stress-strain constitutive relationship of rocks after freeze-thaw cycles [9; 26]. Although these studies have considered the \(D_{0}\) caused by the effect of freeze-thaw cycles and can be in good agreement with experimental results, the determination of \(D_{0}\) often relies on empirical formulas and cannot truly reflect the physical process of rock damage that is caused by freeze-thaw cycles. Therefore, it is necessary to select an appropriate physical parameter to quantitatively characterize the initial damage of rocks after freeze-thaw cycles. During the loading process of rocks, the crack propagation stage can be mainly divided into three stages, that is, the microcrack nucleation stage, stable crack propagation stage, and accelerated crack propagation stage [29; 30]. Accurately identifying the initial crack stress (\(\sigma_{\rm{ci}}\)), crack damage stress (\(\sigma_{\rm{cd}}\)), and peak stress (\(\sigma_{\rm{p}}\)) is of great engineering significance for judging the stability of rocks and predicting the failure of rocks. However, studies on the crack propagation stage of rocks are mainly focused on the conventional loading conditions, and there are relatively few studies on the rock crack propagation stage and the characteristic stress under the conditions of freeze-thaw cycles [31; 32]. Microseismic monitoring technology has been widely used in actual rock engineering to ensure that engineering activities are carried out safely and effectively.