lec 04 slope stability -...
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CIE3032 지반공학및실험 lecture 04 slope stability 1
LECTURE 04
Slope stability
CIE3032 지반공학및실험 lecture 04 slope stability 2
Slopes
Types of slopes: natural vs. man-madeMan-made slopes: Cut / Engineered slopes
Types of slopes failureFallToppleSlideSpreadFlow
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Slopes
Fall: Sudden detachment of soil and/or rock fragments that fall down a slope / typically occurs in rock slopes
Topple: Forward rotation of soil and/or rock mass / also common in rock slopes
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Slopes
Slide: Downward movement of a soil mass occurring on a surface of rupture (often denoted as a failure surface) representative case of slope failure will be covered in the lecture
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Slopes
Spread: A form of slide by translation. Sudden movement of water bearing seams of sands or silts. Often occurs during earthquakes for shallow slopes (under liquefaction)
Flow: Downward movement of soil mass similar to a viscous fluid. Occurs under heavy rain or earthquakes (under liquefaction)
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A special interest: Debris flow 토석류
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A special interest: Debris flow 토석류
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A special interest: Debris flow 토석류 (우면산)
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A special interest: Debris flow 토석류 (우면산)
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Swedish circle
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Lecture outline
Definition of factor of safety – Limit equilibriumInfinite slopesPlanar failure surface – Culmann’s methodAnalysis of slopes with Circular failure surface
Slopes in homogeneous clay (Swedish circle method)Ordinary method of slicesModified Bishop method
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Factor of safety
The goal of analyzing a slope is to ensure that the slope is going to be safe enough given a certain configuration (soil properties, geometry, externally applied load, pore water pressure regime)
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Factor of safety
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Factor of safety
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Factor of safety
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Factor of safety
Also (potential) failure surface
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Infinite slopes - Dry
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Infinite slopes - Dry
If c’=0, sand will stand at an angle of repose equal to its friction angle sand will stand at an angle of repose equal to its friction angleIf > ϕ, will result in sliding until = ϕ
′ ′ ′
/
′ ′
H
’v=zcosNormal and tangential components of ’v(’v)n=zcos2(’v)t=zcos2
’v
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Infinite slopes - Submerged
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Infinite slopes – Seepage parallel to slope surface, with phreatic line at slope surface
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Infinite slopes – Seepage parallel to slope surface, with phreatic line at slope surface
Equipotential line
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Infinite slopes – Seepage parallel to slope surface, with phreatic line at slope surface
Uside = Uleft – Uright = 0Ubase = wHcos2(L/cos )
= wHLcos
Hcos
Hcos2
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Infinite slopes – Seepage parallel to slope surface, with phreatic line at slope surface
Teq
Ubase
N’
N
W
FS = N’tan/Teq
Teq = Wsin = HLsatsin N = Wcos = HLsatcos N’ = Wcos - Ubase
=HLsatcos - HL wcos =HL ’cos
′
′
FS = ’tan/
= Wsin /(L/cos )= satHsin cos ’ = (-pore pressure)
=(satHcos2 - H wcos2)=(’Hcos2)
′
′
′
′
′
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Finite slope with Plane failure surfaces– Culmann’s method
W=
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Finite slope with Plane failure surfaces– Culmann’s method
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Finite slope with Plane failure surfaces– Culmann’s method
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Finite slope with Plane failure surfaces– Culmann’s method
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Finite slope with Plane failure surfaces– Culmann’s method
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Finite slope with Plane failure surfaces– Culmann’s method
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Finite slope with circular failure surface