10 Slope Stability Classification-new
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Transcript of 10 Slope Stability Classification-new
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Lecture 10
S ope Sta ty ass cat on
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The stren th o rock ma be determined
through several standard laboratory and
in-situ tests. Do not confuse data presentation from
shear tests with Mohrs circles.
From an engineering description of therock mass we can use the Rock Mass Rating(RMR) to estimate its performance.
RMR is a qualitative rather thanquantitative system and must be used withsome caution.
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instability? How can we represent a s ope an t ean le of friction on a stereonet?
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Hill sides - for roads, houses, etc. Cuttings - road and rail
Quarries
Spoil tips, and
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'I Falls
II Topples
es
A. Rotational B. Translational
IV Lateral Spreads A & B
A In Bedrock B. In SoilsVI Complex
(After D.J. Varnes, 'Slope Movements and Types and Processes', in 'Landslides: Analysis and Control', Transportation Res. Board Nat. Ac. Sci., Washington Spec. Rep. 178, pp 11-33, 1978)
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required to
mechanisms and to
analysis detailed
your 6 CATS field.
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Mass in motion travels most of the distance throu h theair. Includes free fall, movement by leaps and bounds,
and rolling of fragments of bedrock or soil.
version/Geologic
ples.htm
dslide%20web
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Movement due to forces that cause an over-turningmoment about a pivot point below the centre of gravity of
the unit. If unchecked will result in a fall or slide.
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Movement involves shear displacement along one or more, ,
visible or may reasonably be inferred.
o a ona : ovemen ue o orces a cause a urn ngmoment about a point above the centre of gravity of the
. .
Translational: Movement predominantly along more or less.
frequently, structurally controlled by discontinuities and
variations in shear stren th between la ers of beddeddeposits, or by the contact between firm bedrock andoverlying detritus.
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rotation
toe heave
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0.
hnique,20
253
-2
An excellent example of translational movementis provided by the slab slide in the Lias clay at
,Rutland.GeoteUppingham, Rutland. At this location, the
landslide resulted from movement on an existing
shear surface ascribed to solifluction under
laynearUppinghaper g ac a con t ons. e s e occurre on a o
Lias clay slope and the sliding surface waslocated at a depth of 1.2 - 1.8m. The length of
bslideintheLiasce s ng mass was a ou m.
70.Ashallowsla
Chandler,R.J.,1
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Disturbed lateralextension movements in a
fractured mass.A: Without a well-definedcontrolling basal shear
sur ace or zone o p asticflow.
B: In which extension of
rock or soil results fromflow of subjacent
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.
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Includes spatially continuous deformation andsuperficial as well as deep creep. Involves extremely
slow deep creep. Involves extremely slow and generallynon-acce era ng eren a movemen amongrelatively intact units. Movements may:
. e a ong s ear sur aces t at are apparent y notconnected,
2. result in folding, bending or bulging, or
3. rou hl simulate those of viscous fluids indistribution of velocities.
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.Movement within displaced mass such that the formtaken by moving material or the apparent
distribution of velocities and displacements resembleo e o v cou u .
Slip surfaces within moving material are usually not
visi e or are s ort- ive .Boundary between moving mass and material in placesmay be sharp surface or differential movement or a
zone of distributed shear.Movement ranges from extremely rapid to extremelyslow.
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ge,2
004
eet:ClimateChan
Severn Va;;ey Railway July 2007
NationBriefin
gSh
s,TheStateofth
ICEWeatMidlan
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Movement is by a combination of one or more of thefive principal types of movement described above.
Many landslides are complex, although one type ofmovemen genera y om na e over e o er acertain areas within a slide or at a particular time.
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.Lagonegroo
rotationuplift
toniciNellAppenni
,pp2
51-294
Black shales (lower Cretaceous)
Alluvial deposits- M
assaPseudo-Tet
rogeologia,Vol.1
(Upper Triassic)
detritus of siliceous schists
981,Movimentidi
logiaApplicat
aeI
andMelidoro,G.,
iaM
eridionale,Ge
Guerricchio,A.
DellItal
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'of the Processes that "Cause" Landslides.
2. Erosion3. Ground subsidence
.
5. Shocks and vibrations
6. Air fall
7 ater re i e chan e8. Compound
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.External process Causal processes Specific effect ongroup stability state of the
slope system (examples
only) Changes in:Weathering:
physical, chemical,
Physical properties - changes inparticle size, etc.
-
Density, unit weight, etc.
Strength
exchange, cements; clayminerals, etc.
-
Vertical and spatialstrength and water
and basal surface, matureregolith, ripening
Total stress, critical
depth, friction, cleftdetermined by slope shape
Weaker discontinuities
wa er pressure
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.External process Causal processes Specific effect ongroup stability state of the
slope system
(examples only)anges n:
Erosion
Geometrical change -
Total stresses
uv a , g ac a , coas a ,
etc.material removal from
, , ,
angle, aspectUnloading - removal of
reng
Permeability
ace or ase o s ope ,expansion, swelling,fissuring, strain
,concentration
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.External process Causal processes Specific effect ongroup stability state of
the slope systemexa les onlChanges in:
Ground subsidence Undermining -mechanical StrengthPhysical support,
solution, leaching,removal of cement,
onso a on
Water concentration
,backsapping, piping
change
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.External process Causal processes Specific effect ongroup stability state of
the slope systemexa les onlChanges in:
Deposition Loading - Water content
fluvial, glacial, massmovement, etc.
solifluction,mudsliding, rockfall, deltaic
Weight, strengthStress
to face or top of
slope
addition, talusaccumulation
Undrained loading Underconsolidation
Pore pressure
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.External process Causal processes Specific effect ongroup stability state of the
slope system
(examples only)anges n:
Shocks and vibrations
Vertical andhorizontal movements
Horizontal stress
- varying frequency,magnitude, intensity,duration
Disturbance tointergranular bonds
and cements
Strength
Water table change Excess pressures
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.External processrou
Causal processes Specific effect onstabilit state of theslope system(examples only)
Changes in:
Air fall
loess, tephra
Mantling with fineregolith (producing a
New materialproperties
surface as possibleshear zone)
Addition of finecomponents to soil
Strength
Perched water tables,piping
Water content
Water pressures
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.External process Causal processes Specific effect ongroup stability state of the
slope system
(examples only)anges n:
Water regime change
eomor holo ical
Surface saturation -flooding, lake bursts,
Water content
and meteorologicaletc.
pressure change -"wet" rainfall years,
intense reci itation
,water table, porepressure, weight
snow and ice melt,drawdown
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be.com/watch?v=H
http://www.youtu
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.External process Causal processes Specific effect ongroup stability state of the
slope system
(examples only)anges n:
Compound
" - "
Liquefaction Strength
run outprocesses after initial
FluidisationAir layer lubrication
ConsolidationFriction
, . .
after bank collapse,seismic slope
Cohesionless grainflow
Heat generationa ure, roc a , etc Rate effects
Chemical effects
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2D Gra hical Re resentation
of 3D Discontinuities
Consider a plane z
discontinuity in 3D.N
The plane is defined t
in y its true ip,
t, and the direction
, ,orientation).
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2D Gra hical Re resentation
of 3D Discontinuities
Imagine passing the
centre of a sphere.
e p anorientation of the
unique great circle on
the circumference ofthe sphere, and
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2D Gra hical Re resentation
of 3D Discontinuities
the normalNormal to plane atcentre of sphere
plane exits thes here at a
unique point the pole of the Point of exit ofnormal on surface ofp ane.
Plane cuttingthrough centre of
sphere is the planespole.
sp ere
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orientation
o e ereone are ymme r ca
dip
Equatorial Polar
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1. Using tracing paper placed over the stereonet, pin ormark the centre point and mark the "Northern" point
of the stereonet as a datum for future reference.2. Place a mark at the point on the outer circle,
corresponding to the direction of true dip , .
3. Rotate the tracing paper until this mark lies on the"E-W "axis", then counting from the outer circle, findthe great circle which corresponds to the true dip,
t ,
and trace it.
4. Rotate back to the original position.
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. .
2. From the point where the great circle crosses the- ax s, coun a ong e - ax s , rougthe centre point. The pole is at this position.
3. Rotate back to the original position.
Poles can also be plotted directly using the.
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plane dip 10o direction 270o
answer: a loci of vectors
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dip
the line of intersection lies along one such vector
direction
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.lie on a common great circle.
. oun e v s ons e weenthese poles along this great
.
represented by these poles.
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95o
145o
(=95+50)
35o
o
50o
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,
be, planar it can be represented by agrea c rc e a o e u e ameway as any discontinuity.
Consider the measurements for four
Face A Di 89 220 Face B Di 75 310Face C Dip 80 020 Face D Dip 70 120
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face Aface B
face Cface D
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90
limiting equilibrium will slip at this angle in
a rec ons.
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categorised by geometry (e.g. Varnes)or cau e e.g. ra e .
An vector or an le can be lotted on
the stereonet or extracted from it.
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Read
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ReadBarnes, G.E., 2010. Soil Mechanics: Principles and Practice. 3rd ed.London: Palgrave Macmillan, pp.417-421.
Waltham, A.C., 2009. Foundations of Engineering Geology. 3rd ed.Abingdon: Taylor & Francis, pp.70-77.
, . .http://pubs.usgs.gov/fs/2004/3072/pdf/fs2004-3072.pdf
Leyshon, P.R. & Lisle, R.J., 1996. Stereographic Projection Techniques:in Structural Geology. Oxford: Butterworth-Heinemann, pp.26-35. QE
601.2.L3 Oversize
W llie D.C. & Mah C.W. 2004 Rock Slo e En ineerin . S on Presspp.34-35, 39-40. TN 291.W9
Goodman, R.E., 1989. Introduction to Rock Mechanics. 2nd ed. New
, . . . .
Goodman, R.E., 1980. Introduction to Rock Mechanics. New York: JohnWiley & Sons, pp.425. QC 137.8.G6
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Barnes, G.E., 2010. Soil Mechanics: Principles and Practice. 3rd ed.on on: a grave acmi an.
Craig, R.F., 2004. Craigs Soil Mechanics. 7th ed. London: E & FN
S on.Goodman, R.E., 1980. Introduction to Rock Mechanics. New York:John Wiley & Sons.
Hudson, J.A., 1989. Rock Mechanics Principles in EngineeringPractice. London: Butterworths.
, . . , . ., .Techniques: in Structural Geology. Oxford: Butterworth-Heinemann.
Priest, S.D., 1985. Hemispherical Projection Methods in Rock. .
Waltham, A.C., 2009. Foundations of Engineering Geology. 3rd ed.Abingdon: Taylor & Francis.
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