Landslides 3 Flashcards
how can liquefaction landslides develop in sensitive marine clays (quick clay)?
if salt is leeched out
What are internal causes
factors inside the slope that affect stability
What are three internal causes of mass movement?
- water
- inherently weak materials
- bad geological structures
How does water affect stability in all slopes?
- adds weight (overload)
- increase weathering
- acts as a medium for flows
- decreases shear strength (T_f)
(cuz decrease normal force/stress, which decreases friction)
How does water affect stability in sediment?
- can help or hinder cohesion depending on amount
Sand
- no water = low angle of repose
- some water = high angle
- too much water = very low angle
Solid rock
- reduces shear strength along fractures
- frost wedging or freeze thaw
What is sediment
loose rocks, sand, silt, clay
Fractures
planes of weakness
Describe frost wedging / freeze thaw
in cold climates, water get into cracks/fractures
- expands as it freeze, which forces fractures apart
why might there be a spike in rockfalls below 0 degrees?
freeze thaw
Inherently weak materials
- fail at low angles of repose
- volcanic rock, quick clay
- van Der waals force has an effect
Sand vs Silt vs Clay
- can see sand
can feel
- silt (gritty)
- clay (smooth
describe the role of van der waals force and salt in inherently weak materials
van der waal: electrostatic attraction
- in salt water, particles is attracted to other particles
- shaking filters out the salt
- low salt level = liquefies
Quick clay slides
- not common but very scary
- moderate to fast landslides
- cuz salt leeched out
ex/ in farm lands, at low angles
Adverse geological structures
- unlucky bedding or fracture orientation
- structures angled in unstable direction or layered precariously
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Trigger
a force or event that disrupts equilibrium of a slope and INITIATES MOVEMENT
