The Mobility of Landslides in Pumice: Insights from a Flume Experiment

• Published in: Water (Basel) Vol. 14; no. 19; p. 3083
• Main Authors: Noviandi, Rozaqqa, Gomi, Takashi, Kharismalatri, Hefryan S., Sidle, Roy C., Ritonga, Rasis P., Shiraki, Katsushige
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.10.2022
• Subjects: Coarse-grained soils; Compressive strength; earthquake-induced landslides; Earthquakes; Environmental risk; Experiments; Fatalities; Fault lines; Fluidizing; flume experiment; Flumes; Geology; Hydrology; Laboratories; Laboratory tests; landslide mobility; Landslides; Landslides & mudslides; Mechanical properties; Mobility; Moisture content; Precipitation; Pumice; Rainfall; Seismic activity; Seismic response; Soil strength; Specific gravity; Topography; Voids; Water absorption; Water content; Japan
• ISSN: 2073-4441; 2073-4441
• DOI: 10.3390/w14193083

Risk of landslide hazards strongly depends on how far landslide sediment travels, known as landslide mobility. Previous studies mentioned enhanced mobility of earthquake-induced landslides in volcanic deposits compared to those from other geologic/soil settings. A flume apparatus constructed at a 1:300 scale was used to examine the mobility of landslides with pumice. Four pumice samples were collected from landslides induced by the 2018 Eastern Iburi earthquake, Hokkaido, Japan. Laboratory tests confirmed the unique low specific gravity of the pumice (1.29–1.33), indicating numerous voids within pumice particles. These voids allowed pumice to absorb a substantial amount of water (95–143%), about 9–15 times higher than other coarse-grained soils. Our flume experiments using various saturation levels (0–1) confirmed the influence of this inner-particle water absorption on pumice mobility. Because a low value of specific gravity indicates a low strength of soil, grain crushing may occur on the pumice layer, causing water from the internal voids to discharge and fluidize the transported landslide mass. Our findings indicate that such earthquake-induced landslides can be as mobile as those induced by rainfall, depending on the initial water content of the pumice layers. These conditions might be associated with water accumulation from previous rainfall events and the water-holding capability on pumice layers.