10 Slope Stability Classification-new

8/3/2019 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.

ES3B6 Geotechnical Engineering


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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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o5cxdQDmCE

be.c

om/watch?v=8

http://www.youtu



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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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/Landslides_e

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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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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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StAMia0Q

/watch?v=

mk

.youtube.com

http://ww



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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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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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slope system


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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slope system


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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6Ma0SVjMHA

be.com/watch?v=H

http://www.youtu



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slope system


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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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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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.


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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10 Slope Stability Classification-new