On the initiation and movement mechanisms of a catastrophic landslide triggered by the 2008 Wenchuan (Ms 8.0) earthquake in the epicenter area

• Published in: Landslides Vol. 14; no. 3; pp. 805 - 819
• Main Authors: Cui, Shenghua, Wang, Gonghui, Pei, Xiangjun, Huang, Runqiu, Kamai, Toshitaka
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.06.2017; Springer Nature B.V
• Subjects: Agriculture; Catastrophic failure analysis; Civil Engineering; Cyclic loads; Displacement; Dissipation; Earth and Environmental Science; Earth Sciences; Earthquakes; Energy; Energy consumption; Fluidizing; Geography; Instability; Laboratory tests; Landslides; Landslides & mudslides; Liquefaction; Mobility; Natural Hazards; Original Paper; Seismic activity; Seismic energy; Seismic engineering; Seismic stability; Sliding; Slope stability; Slopes; Soil layers; Valleys; China, People's Republic; Mobility; Epicenter area; Large landslide; Wenchuan earthquake; Liquefaction
• ISSN: 1612-510X; 1612-5118
• DOI: 10.1007/s10346-016-0754-y

The Niumiangou landslide (~7.5 × 10 6  m 3 ) was the largest that occurred in the town of Yingxiu (the epicentral area) during the 2008 Wenchuan earthquake. This landslide originated on a steep slope (~30°) that was located directly above the rupture surface of the responsible fault and then traveled ~2 km after flowing down the axes of two gently sloping (<12°) valleys. Evidence at the site indicates that the landslide materials were highly fluidized and underwent rapid movement. To examine the initiation and movement mechanisms of this landslide, we performed a detailed field survey, conducted laboratory tests on samples taken from the field, and analyzed the seismic motion. We conclude that the landside materials were displaced due to seismic loading during the earthquake and that liquefaction may have been triggered in saturated layers above the sliding surface with progressive downslope sliding, which resulted in the high mobility of the displaced materials. The liquefaction of colluvial deposits along the travel path due to loading by the sliding mass enhanced the mobility of the displaced mass originating in the source area. Using an energy-based approach, we estimated the dissipated energy in our cyclic loading test and the possible energy dissipated to the soil layer on the slope by the earthquake. We infer that the seismic energy available for the initiation of the slope failure in the source area may have greatly exceeded the amount required for the initiation of the liquefaction failure. The slope instability might have been triggered several seconds after the arrival of seismic motion.