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6-1
WEDGE FAILURE
Lesson 6
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6-2
LESSON 6 - WEDGE FAILURE
Learning Outcomes -
Identify Geometric Conditions for Wedge
Failure;
Analyze for Wedge Failure using Design Chart;
Apply Wedge Stability Conditions to Rock
Slope Design for Highways.
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6-3
Wedge failure in very
strong granite with
widely spaced joints
(Upstate New York)
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6-4
Wedge formed by
bedding and
orthogonal joints
in sandstone
(US60, Globe, AZ)
Joints
Bedding
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6-5
Conditions for Wedge Failure
Two Intersecting Planes Behind Face
Line of Intersection “Daylights” on Face
Line of Intersection Dips >
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6-6
Wedge Failure Geometry
Flatter of the two
sliding planes is
Plane A
Plane A Plane B
Line of intersection
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6-7
Stereoplot of Wedge Failure Geometry
Direction of sliding
Plane A Plane B
Friction cone Slope face
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6-8
Analysis of Wedge Failure
Factor of Safety F, for Friction only
ForcesDisplacing
ForcesistingReF
i
BA
sinW
tan)RR(F
(6-1)
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6-9
Wedge Stability Charts for Friction Only
Factor of Safety
Plane A is Flatter of Two Sliding Planes
BA tanBtanAF
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6-10
Wedge Stability Chart A
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6-11
Wedge Stability Chart B
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6-12
Student Exercise – Wedge Stability Analysis
Student Exercises No. 1B and No. 5
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6-13
Wedge failure in
sandstone with
orthogonal jointing
(Ankara, Turkey)
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6-14
Wedge failure in shale with orthogonal
jointing; tension on right side (Helena, MT)
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6-15
Potential wedges formed by
discontinuous joints (US23, Flag Pond, TN)
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6-16
Analysis of Wedge Failure
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6-17
Stability Analysis of Wedge using SWEDGE
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6-18
SWEDGE analysis showing wedge geometry (red),
water forces (blue) and external force (purple).
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6-19
Wedge formed by
five planes (I-5, Grants Pass, OR)
LOI
1: Plane A
2: Plane B
3: Upper slope
4: Face
5: Tension crack
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6-20
Wedges
Planar
slides
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6-21
Plane failure on bedding
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6-22
Wedges formed
by bedding and
joints
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6-23
LESSON 6 - WEDGE FAILURE
Learning Outcomes -
Identify Geometric Conditions for Wedge
Failure;
Analyze for Wedge Failure using Design Chart;
Apply Wedge Stability Conditions to Rock
Slope Design for Highways.