## 3 Analysis of Physical Model Test Results
### The Progressive Failure Process of Freeze-Thaw Slope Rock Mass  
Figure 6 shows the curves of temperature change, frost-heave force, and slope surface displacement of the model slope during the cooling process. The deformation experienced four stages: frost-heave incubation, frost-heave initiation, frost-heave development, and crack propagation. Frost-heave incubation stage: The temperature on the slope surface drops from 25 \({}^{\circ}\)C to \(-7\) \({}^{\circ}\)C. The fissure water is still liquid at this point, and the stored latent heat is continuously released. As a result, the horizontal and vertical displacement of the slope surface remain constant after a period of fluctuation, and the frost-heaving phenomenon is not obvious. Frost-heave initiation stage: The temperature on the slope surface continues to fall, while the displacement of the L2 measuring point on its upper part increases steadily. The water in the upper section of the fracture freezes at this point, forming an ice plug. As the unfrozen water in the lower part is strictly sealed, the excess hydrostatic pressure is gradually generated under the continuous pressure of the ice plug. It reduces immediately when the osmometer value increases to 7.8 kPa. The reason for this is that after the frost-heave initiation, the frost-heave power is released owing to newly formed microscopic cracks in the weak areas of the rock mass, but the material as a whole retains its ability to bear the load. Frost-heave development stage: The slope surface temperature is maintained at \(-13\) \({}^{\circ}\)C, the freezing rate of fissure water increases, and the unfrozen water content falls. Because the frost-heave force develops rapidly after the ice jam effect forms, the osmometer measurement quickly rises to 19.3 kPa. The frost-heave force, temperature field, and slope deformation all maintain a rather balanced state over time, increasing progressively until they reach their peak. Furthermore, the upper part of the slope surface's horizontal displacement continues to rise, and the upper part's frost-heave force compresses the lower masonry, resulting in two stepped increases in the slope bottom's horizontal displacement. Crack propagation stage: The frost-heave force will squeeze the crack tip through the unfrozen water in the lower part. When the driving force of crack propagation is reached, the crack tip expands, and the frost-heave force is released instantly. According to the monitoring results, the maximum frost-heave force is 19.3 kPa. Because the model's stress similarity constant is 164, the prototype slope's frost heave force can be calculated to be 3.17 MPa. The class III rock mass has cohesion of 0.7 to 1.5 MPa, and the frost-heave force generated is sufficient to cause freeze-thaw damage. Figure 7 shows the osmometer values, slope deformation, and temperature change curves during the heating process of the freeze-thaw cycle. As the temperature rises, the value of the osmometer decreases until it eventually fluctuates around the hydrostatic pressure of roughly 2.2 kPa. Meanwhile, the solid ice melts into liquid water, and the L2 and L7 measuring locations experience 0.2 mm and 0.4 mm of shrinkage deformation, respectively. Other measuring points do not seem to be deformed. The deformation form of the model slope after one freeze-thaw cycle is shown in Figure 8. A crack was formed at the bottom of the weak interlayer f3 due to frost-heave force. The crack propagates to the lower right side first, then develops into an arc to the lower left side. The crack turns to the rock mass's sliding direction under the influence of the rock mass's self-weight. The crack propagation depth is approximately 6 cm, and the crack tip is close to the model boundary. The second freeze-thaw cycle has yet to begin, and crack f3 extends and cuts through the entire upper rock mass. The rock mass staggered due to self-weight and pushed the lower rock mass to slide, resulting in a landslide. Figure 9 shows the slope shape after instability.