## 6 Discussion and Conclusions  
Previous studies typically performed conventional triaxial creep tests on rock and soil using small specimen sizes (e.g., 5 cm in diameter; 10 cm in height); however, little research has been conducted on creep in sliding zones containing large particle sizes. In this study, natural and saturated triaxial creep tests were performed to investigate the creep behavior of the Huaipa landslide sliding zone, which has a high rock content. A creep study was conducted using a large triaxial creep apparatus with a specimen size of 30 cm in diameter and 60 cm in height, allowing for a maximum particle diameter of 6 cm. This ensured that the specimens were similar to the natural gradation state, thus making the creep deformation test specimens a more realistic representation of those in the natural state. FLAC3D was used to study the disaster evolution mechanism of the Huaipa landslide. The results show that, when considering only the instantaneous strength and deformation, the slope only experiences unloading uplift at its foot and no overall sliding occurs. After considering the time effect, the slope creeps and slides, with tension damage appearing at the trailing edge, which is consistent with the deformation law. Tension fissures formed on the slope surface within one year of excavation and large-scale slides occurred after one  
Figure 17: Displacement monitoring curves at different locations and depths in the slope. (**a**) Rear region of the slope, (**b**) Middle region of the slope, (**c**) Front region of the slope. month of rainfall. A large number of natural slopes are stable in the short term but unstable after long-term creep deformation. Examples include the Jiudianxia reservoir Yanziping landslide [43], the Huangniba landslide [44], and the Santa Trada landslide, Bozzano [45]. Therefore, the creep characteristics of the rock and soil materials should be fully considered to accurately analyze the deformation and failure characteristics of landslides and evaluate slope stability. In nature, the strength parameter of rock mass is expected to gradually decay with time because of its rheological properties [46]. The results presented here, based on particle fragmentation analysis during sliding zone creep processes, show that particle breakage is an important reason for the weakening of the rock and soil strength with time. Further research concerning the correlation between particle fragmentation, creep time, and strength weakening is needed in subsequent studies. The long-term strength and residual strength of rock and soil are important mechanical indicators to assess whether ancient landslides will become reactive. Interestingly, the weakening mechanisms of both of these indicators have similarities. Fine crack damage within rock mass, fragmentation of the grain angles of soil-rock mixtures, and changes in the grain positions are important mechanisms for the weakening of rock and soil strength. The difference is that the residual strength is the result of strength weakening under a high-stress state, while the long-term strength is the result of strength weakening under a low-stress state. The long-term strength is therefore higher than the residual strength. The stress state of the sliding zone must be fully considered in slope stability evaluations and a reasonable strength index must be selected. Research on the strength loss of rock and soil under high- to low-stress states is also key to revealing the mechanism of landslide initiation damage and landslide reactivation. Technological developments have allowed an increasing number of studies to address changes in the particle position and fragmentation process of soil-rock mixtures [47], thereby gradually clarifying their strength weakening mechanisms.