Lec 04 Slope stability - KOCWcontents.kocw.net/KOCW/document/2014/hanyang/parkduhee1/... ·...
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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
CIE3032 지반공학및실험 lecture 04 slope stability 3
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
CIE3032 지반공학및실험 lecture 04 slope stability 4
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
CIE3032 지반공학및실험 lecture 04 slope stability 5
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
CIE3032 지반공학및실험 lecture 04 slope stability 15
Factor of safety
CIE3032 지반공학및실험 lecture 04 slope stability 16
Factor of safety
Also (potential) failure surface
CIE3032 지반공학및실험 lecture 04 slope stability 17
Infinite slopes - Dry
CIE3032 지반공학및실험 lecture 04 slope stability 18
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
CIE3032 지반공학및실험 lecture 04 slope stability 20
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
CIE3032 지반공학및실험 lecture 04 slope stability 23
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=
CIE3032 지반공학및실험 lecture 04 slope stability 25
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
CIE3032 지반공학및실험 lecture 04 slope stability 28
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