Selected LandslidesDATE LOCATION TYPE DEATHS 1556 China Landslides-earthquake triggered 1,000,000 1806 Switzerland Rock slide 457 1920 China (Kansu) Landslides-earthquake triggered 200,00019631963 Italy (Vaiont Dam) Italy (Vaiont Dam) Landslide-subsequent flood Landslide-subsequent flood 2,000 2,000 1966 U. K. (Wales) Debris flow-collapse of mining-waste 144 1970 Peru (Mt. Huascaran) Rockfall & debris avalanche 25,000
earthquake triggered 1972 USA (WV) Landslide & mudflow-collapse of 400
mining-waste 1979 Indonesia (Sumatra) Landslide 80 1980 USA (Washington) Avalanche and mudflow 63 1989 Tadzhikistan Mudflow-earthquake triggered 274 1996 Brazil (Recife) Mudflow 49 1999 Venezuela Mudflow 10,000
Weathering & Climate
• Weathering decomposes & disintegrates rock, ____________shear strength & ____ mass wasting.
• Mass movement ______________ in deeply weathered material. (prevalent in tropics)
• Deserts Lack of vegetation (_______________) & cloudbursts frequently produce rapid mass wasting (i.e., mudflows).
Overloading…
• Under natural conditions, a slope’s load is supported by friction of grain-to-grain contacts w/in slope material.
• Overloading __________________________________ w/in slope material.
• Dec. shear strength
Types of Mass Movements
FallsRockfalls
SlidesSlumpRockslides
FlowsMudflowDebris flowEarthflowCreep
Complex movements
Rockfalls: (_________________________)
Slopes are sometimes covered w/ wire mesh to reduce the hazard.
Hawaii
Complex movements {combo of several types}
Debris avalanches
1970 killed 25,000 in Yungay & Ranrahirca
Peru, 1970
• Geologic investigation identifies
• Analysis of a material’s properties (composition, susceptibility to weathering, cohesiveness, & ability to transmit fluids)
(Info is used to assess risks before construction begins.)
Recognize & Minimize Effects of Mass Movement
DewateringDewatering
Ways to dewater:
• Perforated drainpipes inserted horizontally into slopes are used to reduce the amt of water w/in slope material.
Pt. Fermin, CA
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