Assessing the Potential Rapid and Long Travelling Landslides in Sri Lanka: A Case Study of Athwelthota Landslide

Landslides are a significant natural hazard in Sri Lanka, causing colossal damage to infrastructure, property, and loss of life. The country is highly susceptible to landslides due to its mountainous terrain, frequent heavy rainfall, and poor land-use practices. This study focuses on the dynamics of the Athwelthota landslide that occurred in 2017 and on the potential instabilities of the surrounding slopes that were evaluated using LS-RAPID numerical simulation software. The physical properties of the soil were examined by testing samples from the study area using an undrained ring-shear apparatus. Firstly, the geomorphological features in the study area and geotechnical parameters of soil were used to calibrate the LS-RAPID model by simulating the past landslide. The calibrated model then simulates two nearby potential failure slopes to assess the hazard. Additionally, the study discusses the triggering mechanism and causes of the past landslide and the two nearby slopes, considering factors such as heavy rainfall and groundwater. In conclusion, the Athwelthota landslide was found to be a complex phenomenon involving multiple factors, such as rainfall and groundwater table fluctuations.