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SUMMARY:Predicting Long Runout Landslides - Professor Paul M. Santi\, Colo
 rado School of Mine
DTSTART:20200306T140000Z
DTEND:20200306T150000Z
UID:TALK138919@talks.cam.ac.uk
CONTACT:Magdalena Charytoniuk
DESCRIPTION:While our technical ability to model short runout landslides i
 s advanced\, we are weak at predicting when a landslide will suddenly liqu
 efy and run out much farther than expected. For example\, the 2014 SR 530 
 (Oso) Landslide in Washington State collapsed and traveled 450m\, engulfin
 g a neighborhood and killing 43 people. That same year\, the West Salt Cre
 ek Landslide in Colorado abruptly liquefied\, traveling almost 5km at spee
 ds exceeding 65 kph and killing three. Although there were mapped\, prehis
 toric events of similar runout length in these areas\, each recent event c
 ame as a surprise to the community. While there is no systematic way to ac
 curately predict landslide runout distance\, there are several factors tha
 t can be used to estimate both the occurrence of long runout landslides an
 d the expected distance traveled. The H/L (vertical drop over distance tra
 veled) ratio has long been used to characterize landslide movement\, but r
 ecent studies have shown the possibility of using H/L ratios measured from
  landslides in similar geologic settings\, coupled with landslide area\, t
 o establish predictive ranges of future movement. We have also shown that 
 contractive soil behavior\, or densification upon movement with a correspo
 nding jump in porewater pressure\, is related to landslide mobility\, and 
 this can be predicted as a function of dry density\, clay content\, and li
 quid limit. Contractive behavior can be induced in soils below critical-st
 ate density\, and tests we developed using a lightweight deflectometer and
  modified slump test both help predict high soil mobility. Density is affe
 cted by field conditions in the vicinity of a potential landslide\, so loo
 se materials\, tension cracks\, and previous landslide movement all contri
 bute to lower density and higher potential for contractive behavior. Final
 ly\, landslide runout can also be shown to relate to upstream drainage bas
 in contributing area and proximity to surface water features.
LOCATION:CivEng Conference Room (2-54) (Civil Engineering Building)
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