Failure Processes of Rainfall-Induced Flow Slides Using A Large Scale Model Slope

Chaminda Gallage, Tharindu Abeykoon and Taro Uchimura

Flow slides are considered to be universal type landslides as such events are commonly reported in various geological and geotechnical conditions, predominantly attributing mobilised soil flows capable of advancing longer distances at higher speeds. Thus, flow slides are classified as one of the most disastrous landslides. Hence the prior identification of failure mechanism of flow slides is vital in mitigating adverse impacts. A large-scale instrumented model slope was employed to study the failure processes of rainfall-induced flow slides. The model slope was instrumented with pore- water pressure transducers, volumetric water content sensors, digital cameras, and linear variable differential transducers to measure surface displacements. The test was performed on Tsukuba river sand (D50 = 0.55 mm), and the failure behaviour was analysed. The analysis highlighted that the higher moisture contents present in loose soils result in a significant rise in pore-water pressure reducing the shear strength of soil mass. Thus, a sliding surface is generated in the upper slope, and failed slope mass compresses the lower slopes, triggering rapid and catastrophic flow slides. The study concludes that the measurement of pore-water pressure, moisture content, surface displacement, and surface deformation velocities provide notable precursors to rapid flow slides, mitigating adverse impacts of flow slides.