Slope Stability Analysis and Hazard Potential Assessment in Zhongxing Village, Kaohsiung City: Numerical Simulation under Extreme Rainfall and Earthquake Scenarios Using STEDwin

In recent years, extreme climate events characterized by heavy rainfall and seismic activity have significantly intensified the risks of slope disasters in Taiwan's mountainous regions. This study focuses on Zhongxing Village, Liugui District, Kaohsiung City, Taiwan, an area marked by steep topography and a recurrent history of severe landslides and debris flows. The primary objective is to evaluate slope stability under diverse environmental scenarios using numerical simulation. The methodology utilizes the STEDwin slope stability analysis software, specifically employing the Bishop method, which is based on limit equilibrium theory. A representative geographic profile near Shanping Villa was established, with soil parameters calibrated from 16 localized borehole records obtained from engineering geological databases. The analysis examines three critical conditions: normal, heavy rain, and earthquake. The findings indicate that under normal conditions, the factor of safety (FS) is 1.30, which falls short of the official standard threshold of 1.5 for permanent slope structures. Under the heavy rain scenario (with groundwater at the surface), the FS drops drastically to 0.66, representing a critical 49.23% reduction in stability. In the earthquake scenario, incorporating parameters from the 2016 Meinong earthquake, the FS reached 1.01. These results align closely with historical records from Typhoons Morakot and Kaemi, highlighting significant risks to Shanping Villa, Shanping Forest Road, and Highway 27. In conclusion, the drastic rise in the groundwater level is the primary driver of slope failure in this region. The study recommends the prioritized implementation of deep drainage systems, such as drainage galleries, to enhance soil effective stress. Furthermore, establishing a real-time monitoring and early warning system is essential to facilitate mandatory evacuations during extreme rainfall, thereby ensuring public safety and infrastructure resilience.