Slope stability I

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Slope stability I

• EOSC316 Engineering Geoscience

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Landslip trigger processes

• Water
• Toe removal
• Natural
• Artificial
• Head loading
• Vibration

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Folkestone Warren, Kent

• Toe erosion due to extension of harbour wall,
  1905
• Since 1915 slide
• mass concrete toe weights
• drainage adits

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Mt. Huascaran, Peru, 1970

• earthquake triggered
• hit towns of Yungay and Ranrahirca, 18 km away,
  at around 150 km/hr
• Yungay completely buried, 66,000 dead

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Types of landslide

• Rock failure
• failure plane pre-determined

• Soil failure
• failure plane along line of max stress

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Rock failure
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Planar translational slip in rock

• f angle of repose ( angle of friction)
• Factor of safety shear force at failure /
  shear force

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Wedge failure in rock
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Toppling failure, Masada, Israel
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Effect of cohesive strength on bench height in
rock

• Shear stress on sliding plane
• Failure occurs when
• Thus

Area of wedge
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Half dome, Yosemite
Carrara marble quarries, Italy
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Rock failure remedial measures
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Slope failure in unconsolidated material
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Planar versus rotational slip in unconsolidated
material

• Planar slip
• frictional
• cohesionless
• C 0

• Rotational slip
• frictional
• cohesional
• C ? 0

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La Conchita, Santa Barbara, California, Spring
1995
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Planar translational slip

• f angle of repose ( angle of friction)
• Factor of safety shear force at failure /
  shear force

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Planar slip - analysis
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Planar slip in soils

• Cohesionless soils (f0)
• Soils with cohesion (f?0)