Failure mechanism of the Yaoba loess landslide on March 5, 2020: the early-spring dry spell in Southwest China

• Published in: Landslides 2021-09, Vol.18 (9), p.3183-3195
• Main Authors: Wu, Kanglin, Chen, Ningsheng, Hu, Guisheng, Han, Zheng, Ni, Huayong, Rahman, Mahfuzur
• Format: Article
• Language: English
• Subjects: Agriculture; Civil Engineering; Confluence; Earth and Environmental Science; Earth Sciences; Failure analysis; Failure mechanisms; Field investigations; Field tests; Geography; Groundwater; High temperature; Hydrodynamics; Laboratory experiments; Landslides; Landslides & mudslides; Loess; Moisture content; Natural Hazards; Numerical simulations; Rain; Rainfall; Recent Landslides; Saturated soils; Saturation; Shear strength; Snowmelt; Soil; Soil strength; Soils; Water content; Water infiltration
• ISSN: 1612-510X; 1612-5118
• DOI: 10.1007/s10346-021-01703-8

On March 5, 2020, a shallow loess landslide occurred in Yaoba Village, Songpan County, Sichuan Province, posing a severe threat to the lives and properties of 130 villagers. In this study, the landslide’s essential characteristics were identified through field investigations, and the failure mechanism of the landslide was analyzed through numerical simulations, laboratory experiments, and strength calculations. A new mechanism of the Yaoba loess landslide was proposed. The results show that (1) the minimum induced rainfall required for the landslide from the natural unsaturated state into the saturated state at the lowest thickness of 1.4 m was 177.2 mm. The limited amount of previous rainfall was not sufficient to make the landslide soil saturated and unstable. (2) Snowmelt water infiltration caused by abnormally high temperatures was the leading cause of the landslide failure. Based on the strong hydrodynamic conditions in the area and the confluence through the hollow region upstream of the landslide, abnormally high temperatures caused an increase in snowmelt values up to 219 mm. Snowmelt infiltrated into the slope and increased the water content up to a saturation state at 26.67%, making the shear strength of the soil reach the limit equilibrium state and be unstable. The analysis of the Yaoba landslide in western Sichuan that occurred during a dry spell will improve the early warning of groundwater- and snowmelt-induced shallow loess landslides.