# Field and Numerical Investigation of Taihu Resort Cut Slope Failure in Suzhou, China
## 6 Discussion  
In the tourist cities located in eastern China with large populations, resorts and hotels are considered fundamental infrastructures that are expected to be built in safe areas. Inappropriately excavated slopes can become one of the causes of landslides, which contradicts the core objective of safety. Therefore, while the excavation of hillslopes for buildings or resorts continues to expand in many countries due to urbanization, there is a need to understand and investigate the main causes of landslides. Previous research on the stability of slopes has often mainly focused on simulation analysis or geotechnical monitoring examination statistics based on a single working condition or a specific parameter, disregarding the possibility of any further invisible factor that may have a detrimental effect that contributes to slope instability without executing an overall verification analysis under different conditions. By considering a case study of a typical landslide induced by excavation, the temporal and spatial Taihu slope failures were analyzed first based on the monitoring data. An investigation was carried out first in this paper, and two-dimensional numerical simulations were conducted under excavation by stages and different rainfall scenarios. The analysis of the investigated Taihu slope failure during the monsoon rainfall in the Suzhou area found that the slope collapse that occurred at the soil layer of weathered argillaceous siltstone was induced by the cut of the slope at an angle that did not fit the design safety requirements, which led to a significant reduction in shear strength. The rainfall infiltration into the slope caused a gradual increase in the volumetric water content, which caused cracks and abrasion at the slope surface due to plugging the drainage out. Therefore, the investigation results indicated that the main reason for the Taihu cut slope failure is related to the heavy rainfall. Through the analysis of the numerical simulation, the FoS of the slope was effectively reduced during the excavation progress. During the excavation process, the stress, strain, and displacement distributions were significantly affected, and the stress was redistributed to every newly formed surface. On the other hand, the maximum shear strain distribution appears at the toe of the new excavation slope. Due to the deformation analysis, the application of a rainfall condition has a huge effect on the shear strain and displacement distributions of the slope. Figures 19 and 20 show the maximum shear strain and displacement distribution after 15 days of rainfall with different precipitations of moderate and heavy rainfall. Overall, the distribution of shear strain occurs above the toe of the slope and gradually shifts the top of the slope in the form of an upward arc under both rainfall intensities. Clearly, the damage began at the junction (layers contact), continued propagating to the middle of the slope, and continued expanding toward the top of the slope. However, the circular slip surface underwent no change under heavy and moderate rainfall. The displacement characteristic of the slope is particularly large compared with moderate rainfall. The failure surface only occurred  
Figure 18: Evolution of safety factor over time. The soil water retention and stability of the slope with continued rainfall infiltration for 15 days were simulated. It was found that the pore-water pressure, degree of saturation, and volumetric water content increased with the increase in rainfall time and intensity. Additionally, the effect of heavy rainfall on the slope stability was higher than under moderate rainfall for identical rainfall duration, and the slope stability under heavy rainfall reached the minimum safety factor. Therefore, the Taihu landslide was caused by the irrational excavation followed by continuous heavy rainfall.