Slope stability I EOSC316 Engineering Geoscience.
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Transcript of Slope stability I EOSC316 Engineering Geoscience.
![Page 1: Slope stability I EOSC316 Engineering Geoscience.](https://reader035.fdocuments.net/reader035/viewer/2022062321/56649f285503460f94c3ffb3/html5/thumbnails/1.jpg)
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
shearfo rce
norm a l fo rce
w e igh t
• = angle of repose (= angle of friction)• Factor of safety = shear force at failure / shear force
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Wedge failure in rock
angle of repose,
intersection of joint set
Factor of safety = tan / tan
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Toppling failure, Masada, Israel
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Effect of cohesive strength on bench height in rock
h
wcos wsin
a
a = h/sin
• Shear stress on sliding plane:
• Failure occurs when:
• Thus
hwC
hw
a
wC
sincos
sinsin
cos
Ch
w cossinsin2
tan2
cossin2
2hw
hh
Area of wedge
cossinsin
tan2
cossinsintan2
2max
22
Ch
or
Ch
h
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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
shearfo rce
norm a l fo rce
w e igh t
• = angle of repose (= angle of friction)• Factor of safety = shear force at failure / shear force
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Planar slip - analysis
angle of repose,
angular range where failure possible
intersection of joint set
Factor of safety = tan / tan
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Planar slip in soils
GW L
Slipsurface
hw
h r
n = h /hw r
• Cohesionless soils (φ=0)
• Soils with cohesion (φ≠0)
tan
tanwnF
tan
tan
cossinw
r
n
h
CF