A material point method analysis of failure mechanism and kinematic behavior of rainfall-induced landslide

Rainfall-induced landslides are a frequent and severe natural hazard in the southern regions of Ethiopia. These occurrences substantially threaten the welfare of workers, equipment, and the efficient completion of construction projects. This paper provides an insight into the mechanism and kinematic behavior of rainfall-induced landslides in southern Ethiopia. A comprehensive investigation was carried out on the Jinka landslide, a notable case study in June 2018. The investigation involved Material Point Method numerical simulations, which were informed by extensive geotechnical investigations and laboratory tests. Historical landslide events and rainfall data were also systematically analyzed to establish critical rainfall thresholds for predicting landslide occurrences. It was observed that excess pore water pressure near the sliding surface significantly reduces effective stress, leading to a notable decrease in shear resistance and increased soil mobility. The landslide followed a regressive pattern, initiating from the lower toe, propagating through the middle sections, and ultimately reaching the upper crest. The kinematic parameters of the sliding mass demonstrated varying velocities, with the mass sliding downslope exhibiting a greater velocity than the block positioned above it. The kinematic characteristics indicate that the landslide exhibits distinct movement patterns relative to varying microtopography. Additionally, threshold analysis revealed that the critical rainfall that triggers landslides is the maximum daily rainfall of 44 mm with 30 days antecedent rainfall of 304 mm and the minimum average daily rainfall of 4 mm with 30 days antecedent rainfall of 378 mm. The results indicated that soil saturation from rainfall diminishes strength and increases the acceleration of sliding masses, while antecedent rainfall is pivotal in landslide events. This study can provide a reference for understanding the mechanism of the landslides induced by rainfall and guidelines for future infrastructure planning and early warning systems in the region.