Case study: Oso, Washington, landslide of march 22, 2014-material properties and failure mechanism

Timothy D. Stark, Ahmed K. Baghdady, Oldrich Hungr, Jordan Aaron

Research output: Contribution to journalArticlepeer-review


This paper describes investigation, testing, analysis, and slope history used to determine the two-phase failure mechanism involved in the 2014 landslide near Oso, Washington. The first phase involves a slide mass located above the frequent landslides in the lower portion of the slope and extends to near the slope crest. This slide mass had a large potential energy, which moved downslope, and pushed the water-filled colluvium that had accumulated along the slope toe across the valley, resulting in it flowing almost 1.5 km. Evacuation of the Phase I slide mass left the upper portion of the slope unbuttressed and oversteepened, causing a second landslide (Phase II) but it primarily remained on the source slope because the back edge of the Phase I slide mass prevented further movement and the dense and unsaturated upper soils did not undergo a significant strength loss like the water-filled colluvium.

Original languageEnglish (US)
Article number05017001
JournalJournal of Geotechnical and Geoenvironmental Engineering
Issue number5
StatePublished - May 1 2017


  • Failure mechanism
  • Flow slide
  • Kinematics
  • Landslide
  • Light detection and ranging (LiDAR)
  • Liquefaction
  • Shear strength
  • Slope stability analysis

ASJC Scopus subject areas

  • General Environmental Science
  • Geotechnical Engineering and Engineering Geology


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