###### Abstract  
The quality of excavated and unloaded rock masses on steep and high slopes in cold regions is prone to deterioration, which in turn affects the long-term stability and safety of excavated slopes. Based on a triaxial unloading-damage test of sandstone, the unloading quantity was used to analyze the evolution law of unloading damage; a freeze-thaw cycle test of the unloaded-damaged samples was carried out, and it was found that the average change in porosity and the reloading peak strength damage rate after freeze-thaw increased with the increase in the number of freeze-thaw cycles, and the porosity change characteristics were independent of the value of the confining pressure at the time of the unloading damage. An exponential decay model was used, and based on the average change in porosity after freeze-thaw, a freeze-thaw strength decay model that can take into account the effect of confining pressure was established, and its ability to predict the strength decay of unloaded-damaged rock samples after freeze-thaw was verified by experimental data. The research results provide a reference for the evaluation of freeze-thaw degradation of unloaded rock masses during slope excavation in cold regions. XXXX202212205  
fracture, shear slip and parallel secondary fracture. [PERSON] [14] analyzed the energy evolution characteristics of granite during unloading, where the ratio of dissipated strain energy to total strain energy can describe the degree of deformation damage during the unloading of rock samples. The unloading damage leads to an increase in pore fractures inside the rock sample, which provides an intervention channel for permeable water and intensifies the water-rock coupling, inducing a sharp acceleration in the unloading process or an intensification in the unloading damage [15; 16]. The microstructural characteristics of rock samples with different degrees of unloading damage were studied by nuclear magnetic resonance (NMR) [17; 18]. The studies found that the porosity, T2 spectrum distribution, and T2 peak area of the unloading-damaged rock samples increased with the degree of unloading damage, and the unloading damage of the rock samples was mainly triggered by the increase in the number and size of pores. [PERSON] [19] performed a predictive analysis of the time-lag failure of sandstone unloading damage based on reformed group theory and using a logistic model. [PERSON] [20] used the finite element method to simulate the damage of rocks under unloading conditions and found that the degree of damage was related to the height of the rock sample and the magnitude of the surrounding pressure. Some scholars [21; 22; 23] explored the differences between the physical and mechanical properties of rock samples under different unloading damage conditions and intact rock samples from the perspective of energy analysis, taking unloaded-damaged rock samples as the object. The relationship between the cumulative acoustic emission (AE) counts and the quiet period with the unloading point was also investigated by acoustic emission test experiments, and it was found that the uniaxial damage mode of rock samples changed from shear damage to tensile damage with the intensification in unloading damage. Figure 1: Schematic diagram of the successive effects of slope excavation unloading and freeze-thaw deterioration. In addition, the freeze-thaw erosion induced by the changes in temperature in cold environments causes the deterioration of the quality of the engineering rock mass. Many scholars have systematically studied the damage evolution process, dynamic and static mechanical properties of rocks with different lithologies under freeze-thaw environments, and the effect of freeze-thaw conditions [24; 25; 26; 27; 28; 29; 30; 31].