EOSC 114 Landslides Exam Questions and Correct Answers Already Passed
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Module
EOSC 114 Landslides
Institution
EOSC 114 Landslides
EOSC 114 Landslides Exam Questions and Correct Answers Already Passed
Where and when was the Oso landslide? - Answer- Washington State 2014
What happened during the Oso landslide? - Answer- - March 22, 2014 10:37 AM
- 45 days of heavy rain
- collapse of layers of glacial sediment
- "fast mo...
EOSC 114 Landslides Exam Questions
and Correct Answers Already Passed
Where and when was the Oso landslide? - Answer- Washington State 2014
What happened during the Oso landslide? - Answer- - March 22, 2014 10:37 AM
- 45 days of heavy rain
- collapse of layers of glacial sediment
- "fast moving wall of mud"
- hit river, caused tsunami
- 43 fatalities (original reports of 200 missing)
Seismic trace of the Oso landslide - Answer- - event sent seismic waves detectable
over 200 km away
- the seismic data shows multiple collapses, but 2 major ones approximately 3 minutes
apart
Did the people think the landslide was predictable? - Answer- they did not think that it
could have been predicted
however, when looking at the history of landslides in the area, there were some around
that could have helped to predict that another one would occur
At what rate do soil creeps move? - Answer- soil creeps move at mm/year
Landslide cause and effect - Answer- Cause:
reduces shear strength or increases shear stress
Trigger:
initiates motion (can only have one)
Effect:
fall, slide, flow, or complex movement
once we identify a hazard we move to mitigation (solving the problem)
Mitigation - Answer- - start with investigation and monitoring
- all of this is expensive
- in some cases, especially very slow slides, it is cheaper to repair damage and ignore
the landslide
, Investigation - Geologic Mapping - Answer- map materials and properties on site -->
predict type of failure
- glacial sediment = rotational landslide more likely
- igneous/metamorphic rocks without soil cover = rockfall/slide more likely
Investigation - Hazard Mapping - Answer- landslide hazard maps may be used to plan
the "best" route for a new highway, pipeline or rail line; i.e. one that minimizes the
number of major landslide hazard areas encountered
Investigation - imaging and modelling - Answer- LiDAR imagery is a technique used to
scan the surface topography of the Earth. The technique 'sees through' trees
- technique used to see where previous landslides have occurred
Three types of mitigation - Answer- after investigation, three paths to mitigate landslides
1) avoidance - move to a different area, avoid problem
2) prevention - do something to make sure landslides don't occur or don't occur when
people are there
3) protection - armor or strengthen the area that might be affected if landslides occur
Avoidance - Answer- in almost all cases avoidance is too expensive
scenarios:
- buying all the property in a town
- moving a completed highway
- or convincing someone to leave a family home
before the 2014 Oso landslide a buyout program was considered but not implemented
Prevention - Answer- removal of material
- very simple
- remove the material (somehow)
- too expensive for many situations, but cheaper than avoidance
- pretty good for some rockfalls
Prevention - Stabilizing Slopes - Answer- slopes undercut when building roads?
apply a resisting force at the bottom. Retaining walls, or gabions
sliding rock?
apply rock bolts (rock anchors)
Prevention - Anchors - Answer- cables anchored in stable rocks and tightened by nuts
at surface
Prevention - Drainage - Answer- too much water?
remove with drainage pipes
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