Study on creep properties and a viscoelastic–plastic constitutive model of slate considering freeze–thaw damage and joint effect

The long-term stability of jointed rock slopes subjected to freeze–thaw (F–T) cycling is a key scientific issue in landslide risk assessment in cold regions, yet the influence of F–T cycling on creep behavior and associated damage mechanisms in jointed rock masses remains unclear. To address this, slate specimens with varying joint angles were collected from landslide deposits in Wet-Freeze Zone II of China. A series of creep tests under F–T cycling was performed to investigate the effects of F–T cycles and joint angle on the creep properties of slate. Based on the experimental observations, a novel anisotropic creep model accounting for F–T damage and joint effect was developed. Model validation against creep test data confirms its ability to reproduce the entire creep deformation process and to capture the influence of joint angle and F–T cycling on creep behavior. The proposed model was further integrated with strength reduction method and applied to evaluate the long-term stability of slopes. The results indicate that the potential landslide direction is directly related to the joint angle, and with increasing F–T cycles, the factor of safety decreases while the plastic zone progressively develop upward along the pre-existing joint planes, extending further with creep duration. These findings enhance understanding of the instability mechanisms for geotechnical slope in cold regions.