landslides, part 2 beverly hills slide, feb 2005
Post on 21-Dec-2015
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TRANSCRIPT
Fig. 12.17
Vaiont Reservoir SlideVaiont Reservoir Slide
Debris slide caused reservoir wall to collapse, sent water downstream
Flows
• Mass movements behave like fluids
• Materials include boulders, sand, ice, mix
• Speed varies - barely moving to ~200 mph
• Various types of flow, depending on material, slip surface
Loess Flow
• Dry flows of fine silt deposits
• Example: 1920 China– 160 by 275 km hill of loess flowed after
earthquake– Killed ~200,000 people by burying villages
very rapidly
Debris Flow
• A fluid mass movement of rock fragments supported by a muddy matrix. May move a speeds of up to 100 km/hr!
Mudflow• A flowing mass of
material (mostly finer than sand, along with some rock debris) containing a large amount of water.
• May travel large distances and high speeds
• Can carry particles as large as a house!
Debris Avalanche
• Fast (up to 280 km/hr) downhill movements of soil and rock, usually occurring in humid mountainous regions
Mt Huascaran, PeruMt Huascaran, Peru(before 1970)(before 1970)
Mountain region in Peru, before a Mw 7.7 occurred in the subduction zone offshore
Snow Avalanches
• Snow has same pull from gravity– Can fail in creep, fall, slide, flow
• Snowfall, wind-blown snow load slope towards failure– Also skiers
Snow Avalanche
• Large events - slab of snow breaks away
• Occurs because each layer of snow has different properties– Layers deposited at different times, vary in
strength, hardness, density, thickness
Ways to Reduce Losses Due to Landslides Include:
• Avoid construction in areas prone to mass movement
• Build in a way that does not make naturally stable slope unstable
• Engineer water drainage to prevent strata to become water saturated and prone to fail
Box 12.1
Failure occurs when water-saturated strata slide along slippery clay unit, breaching thin retaining wall
Submarine Movements
• Same types of failures occur underwater
• Example: Hawaii has significant slumps, debris avalanches
• Volcanic flank collapse - whole side of volcano falls off – Leads to tsunami