Monitoring and Modelling of Rainfall-Induced Landslide in Volcanic Soil Slope

Reactivated landslides have often posed a significant hazard to human lives and properties in many regions of Indonesia. In order to mitigate the hazard, a better understanding of mechanism leading to the reactivation of landslides is necessary. For this purpose, a long-term monitoring and numerical analysis of an active landslide in a volcanic soil slope in West Java, Indonesia was conducted. Monitoring instruments consisted of jet-fill tensiometers, inclinometers, open stand-pipes, and a tipping-bucket rain-gage. The records of pore-water pressure responses of the soil slope show that a transient perched water table could develop within the shallow soil profile, and the groundwater table could rise significantly in the middle portion of the slope during heavy rainstorms. Meanwhile, the inclinometer records show the existence of a multiple sliding zone at a maximum depth of about 17 m. Based on the monitoring data, a couple analysis of seepage and slope stability was performed to evaluate the effect of rainwater infiltration on long-term stability of the slope. The numerical results indicated that the total rainfall of at least 550 mm, with intensity of more than 80 mm/day was the triggering hydrological condition for reactivation of the landslide.