landslides & related phenomena
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Landslides & Related Phenomena
http://www.youtube.com/watch?v=mknStAMia0Q
Landslides & Related Phenomena
http://www.youtube.com/watch?v=mknStAMia0Q
http://www.youtube.com/watch?v=F31ywRvtNkY
Introduction to Landslides
• Landslide – rapid downslope movement of “coherent” mass
• Slope failure/mass wasting- general term (e.g. mudflows, rockfalls, snow/debris avalanches)
• Subsidence (downward movement)
Introduction to Landslides
Slope Processes and Slope Stability
• “If it’s not a river or a beach, it’s a hillslope, of one ilk or another”– Most common landforms– Appear static; actually are
dynamic • Valley
– Moving downhill• Creep • Avalanche/rock fall
– Moderate events are the most important
• Magnitude• Frequency
Slope Processes and Slope Stability
• Processes
– Slope elements
• Convex slope/crest
• Free-face
– Angle of repose
• Debris slope
• Convex slope/wash slope
Angle of repose:particle sizeparticle shapemoisture content
Angle of Repose
Slope Processes and Slope Stability
• Processes – Slope movements or deformation
• Flowage/flow• Sliding• Falling• Subsidence• Classification
– Type of movement– Slope material– Amount of water present– Rate of movement
Classification of Mass Movement
Creep
Types of Movement
Slope Movements
Slope Stability
• When does a slope fail? • What is the critical threshold that’s exceeded?
Variables:– Material type– Slope– Topography– Climate– Vegetation– Water**– Time.
Landslides & Related Phenomena
http://www.impactlab.com/2008/10/12/the-heyelan-land-slide/
Slope Stability
• Forces on Slopes– Driving forces--tend
to move material down slope
• Weight of material (includes water)*
• Vegetation• Fill material• Building loads
CD
WN
Potential slip plane(clay).
ROCK
A
D = W sin A = driving forcethe downslope component of gravity.
Slope Stability
• Forces on Slopes– Resisting forces--forces that
tend to resist movement• Shear strength
CD
WN
Potential slip plane(clay).
ROCK
A
N = W cos A = the normal component of W contributes to the shear strength along the slip plane contributes to the resisting force.
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