# Field and Numerical Investigation of Taihu Resort Cut Slope Failure in Suzhou, China
## 7 Conclusions and Recommendations  
The failure mechanism of slopes associated with excavation or rainfall has received much attention from various soil researchers globally in the last two decades. A landslide often results from inadequate geological examination prior to the final design, poor soil structure conditions, or steep slope geometry, which can increase the possibility of failure under external conditions. In this paper, a comprehensive instability investigation of the Taihu slope located in Suzhou was carried out. According to the results of the analyses, the main conclusions are as follows:  
1. According to the collected monitoring data analysis, the investigation results showed that the collapse was related to two factors: the poor soil structure after excavation, which destroyed the balance of the slope, and the continuous rainfall infiltration during the monsoon rainfall that raised the groundwater table, which increased earth pressure and caused a decrease in shear strength. Therefore, an abrasion at the toe slope surface occurred, which triggered a sliding zone that formed in the body of the slope and led to the failure. 2. Numerical simulation results show that during the slope excavation process, the horizontal stress distribution was gradually demolished, which is redistributed after each excavation stage and changes over time as more material is removed. As continuous excavation progresses, horizontal compressive stress increases gradually, and tensile stress appears within the slope body in the weathered argillaceous siltstone strata. Figure 21: Safety factor evolution of slope affected by excavation and different rainfall intensities. This effectively reduces the factor of safety. Thus, the excavation of the slope has an enormous impact on stress distribution and the stability of the slope. 3. On the other hand, after every formed excavation, the shear strain and displacement distributions are redistributed and transferred to the revised toe position of the slope surface. Therefore, at the final excavation stage, the shear strain generated above the toe of the slope precisely at the junction of the soil and rock zone and shifted upward into the middle of the soil layer in the form of an upward arc until the crest of the slope. The displacement distribution mainly exhibited a concentrated pattern at the weathered argillaceous siltstone. Through the analysis, it was found that the inclination of the soil and rock strata on the slope had a considerable influence on the shear strain distribution, including the slope failure path. Additionally, the slope stability factor dropped from 4.103 at the original slope to 1.241 at the fourth excavation stage, which put the whole slope in an unstable state. 4. Under various rainfall scenarios, the continuous rainwater infiltration increases the volumetric water content, thus gradually increasing the pore-water pressure in 15 days of heavy rainfall, moving the pressure head toward the front layer of the weathered argillaceous siltstone layer. Therefore, the rainfall intensity has a great impact on the pressure head, which reduces the slope stability factor dramatically, which obviously causes a weakening in the shear strength, resulting in large displacement. Consequently, the FoS of the slope decreased from 1.241 to 1.02 in 15 days of heavy rainfall, which was the minimum safety factor indicated, and the slope is highly qualified to fail. In this study, the stability assessments indicated that the excavations had an influence on the stability of the slope, which caused a huge reduction in the shear strength. Combining the field monitoring and numerical analysis results, the heavy rainfall after the excavation of the slope affected slope stability, which shows a remarkable reduction in the safety factor. Unfortunately, such poor structure excavation of the Taihu cut slope went against the slope stability. Therefore, it is necessary to conduct reinforcement with an accurate drainage system to protect the slope from the risk of failure and erosion.