Modeling of rainfall-induced landslides using a full-scale flume test
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Kwangwoo Lee I Jaewook Suk I Hyunki Kim I Sangseom Jeong
Modeling of rainfall-induced landslides using a full-scale flume test
Abstract A flume test was conducted to evaluate the failure mechanism of a rainfall-induced landslide and to develop a physically based warning system. The test was performed at full scale to prevent scale effects, and the flume was a rectangular channel that was 20 m long, 4 m wide, and 2.5 m deep. The volumetric water content and the matric suction were measured at various depths to determine the rainfall infiltration into partially saturated soil. The displacement and tilt were measured at the slope surface, and a video camera was installed to record the slope failure. The results showed that the rainfall infiltration caused the volumetric water content to gradually increase and the matric suction to decrease. The resulting decrease in the soil strength caused soil deformation. Thus, the rainfall induced a landslide. The matric suction and the degree of saturation were used to calculate the generalized effective stress of the solid skeleton to develop a warning system. The stress paths were calculated using the effective mean stress and the deviatoric shear stress. The inflection point of the stress paths can be used to define a threshold for a rainfall-induced landslide warning system. Keywords Rainfall-induced landslide . Full-scale flume test . Warning systems . Partially saturated soil . Effective stress . Stress paths Introduction Landslides are common mass movement processes in mountainous areas, particularly those covered by residual soils overlying extensively weathered granite. Global climate change has affected rainfall patterns and intensity, which can trigger catastrophic landslides (Jeong et al. 2008; Borga et al. 2002). Over 70% of the Republic of Korea is mountainous, and heavier rainfall during the summer season has increased the occurrence of landslides throughout the country (Jeong et al. 2008). Many studies have been conducted on the failure mechanisms of rainfall-induced landslides (e.g., Skempton 1985; Rahardjo et al. 2005; Miao et al. 2014). Rainfall-induced landslides are produced by complex hydrological and geotechnical processes that depend on the slope geometry, the initial state of the slope, and the hydromechanical properties of the soil (Sorbino and Nicotera 2013). These landslides occur as a result of a reduction in the mean effective stresses because of an increase in the pore water pressure or a reduction in the matric suction because of the direct infiltration of rainfall along a sloped surface, which then propagates into the soil through groundwater flow (Alonso et al. 1996; Iverson et al. 1997; Nuth and Laloui 2007). Many laboratory experiments have been performed to elucidate the mechanism of rainfall-induced landslides. Iverson et al. (2000) investigated the contraction of loosely packed soils during rainfall infiltration. Huang et al. (2009) performed a flume test to show that the collapse and washout of the slope toe initiated retrogressive shallow
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