###### Abstract  
Seasonal freeze-thaw environments are one of the key factors that aggravate the mechanical strength decay of excavated and unloaded rock masses on reservoir banks in cold areas. To study the time-dependent mechanical properties of an excavated and unloaded rock mass on a bank slope under freeze-thaw action, triaxial unloading tests were carried out on sandstone, freeze-thaw tests simulating freezing strength were conducted, and triaxial creep tests were implemented with graded incremental loading on unloaded specimens subjected to freeze-thaw action. The test results showed that the total deformation of the unloaded specimens is significantly increased compared with the conventional specimens, and the lateral direction is more likely to produce creep behaviour than the axial direction. The level of confining pressure determines the level of creep deformation of unloaded specimens and affects the variation law of creep rate. The creep behaviour of the unloaded specimens is aggravated by freeze-thaw action and, the longer the freezing period, the larger the creep strain share, and the creep rate increases significantly. The creep damage pattern of the unloaded specimens subjected to freeze-thaw action is mainly manifested as shear damage, and the creep process intensifies the derivation of tension-type cracks in the specimens. The higher the confining pressure of the unloaded specimen, the more obvious the plastic characteristics and the weaker the brittle characteristics during creep failure. The freeze-thaw action significantly reduces the long-term strength of the unloaded specimen, which is approximately 50-55% of the instantaneous strength. The long-term strength decays significantly with an increasing freezing period, and the research results can provide a theoretical reference for the evaluation of the long-term stability of excavated and unloaded rock masses in cold areas. cold region slopes; unloaded rock mass; unloading test; freeze-thaw action; creep properties +
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triaxial compression. [PERSON] [15] proposed a creep model for the excavation unloading behavior of rock that can describe the deformation of the rock with time after being unloaded. Currently, most of the studies have simulated the excavation unloading process by applying an unloading stress path to the original rock samples, and the damaged rock mass after excavation unloading is rarely considered as the object of study. The differential characteristics of the unloaded damaged rock samples and the original rock samples can be found in [16]. In addition, with the further shift of China's engineering construction to the northwest, the environmental problem of seasonal freezing and thawing in the site area has become more and more prominent, which seriously affects the stability of the excavation slope. Rock material is a three-phase material consisting of solid particles, water, and air. When the temperature is too low, the water stored in the pores of the rock is converted from the liquid phase to the solid phase, and the volume expands by about 9% [17; 18], which exerts a frost swelling force on the surrounding rock, thus accelerating the deterioration of the rock structure and making the excavation slope more dangerous. [PERSON] [19] summarized the main factors affecting freeze-thaw damage in rocks, including the pore structure characteristics, effective water content, cooling rate, freezing period, and minimum temperature of the rock. [PERSON] [20] studied the changes in the internal fine structure of rocks during freezing and thawing using CT scanning and electron microscopy, and found that water in the pores of rocks undergoes a water-ice phase change under low temperature conditions, causing rock particles to fall off, fractures to increase, and porosity to increase, which leads to lower longitudinal wave velocity, lower quality, and lower strength of rocks.