soil mechanics in pavement engineering sf brown

7/24/2019 Soil Mechanics in Pavement Engineering SF BROWN

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Granular Granular

Granular

Granular

Granular

Soil

Soil

Soil

Soil

(a) Gravel road

(c) Asphalt pavement

(e) Composite pavement

(g) Block pavement

Asphaltic

Asphaltic

Cement treated or concrete

Concrete or brickblocks on sand

Asphaltic or cement treated

Granular

Granular

Bitumen seal

Soil

Soil

Soil

Soil

Concrete

Concrete

Cement treated

Rail on sleepers

Ballast (granular)

Sub-Ballast (granular)

(b) Sealed gravel road

(d) Concrete pavement

(f) Heavy duty concrete

(h) Railway

Moving wheelLoad Load

Surfacing

Base

Sub-base

Subgrade

Rails on sleepers

Ballast

Sub-ballast

Subgrade

(a) (b)

Foundation


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1.00.80.60.40.20

120

100

80

60

40

20

0

Time: s

(b)

Verticalstress:kPa

0.80.60.40.2

20

15

10

5

0

Time: s

(a)

Verticalstress:kPa


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E1 1 h1

E2 2 h2

E3 3 h3

E4 4

(x, z)

(x, z)

(x, z)

z

p

contact pressureE, , hYoung's Modulus, Poison's ratio and

thickness for each layer

p

x

x

a

500040003000200010000

5.0

4.0

3.0

2.0

1.0

0

Octahedral shear strain (microstrain)

(a)

Octahedralshearstres

s:psi

504030201051

30000

20000

10000

5000

1000

1st stress invariant: psi

(b)

Resilientmodulus:psi


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8765432100.10

0.05

0.00

0.05

0.10

0.150.20

0.25

0.30

0.35

0.40

0.45

0.50

Time: s

Voltage:V

8 7 6 5 4 3 2 1 0Time: s

Deviatorstress

Axialdeformation Elastic

deformation

Delayed elastic deformation


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Half-space with E200 MPa and 0.45

Pressure600kPa

23 kN/m3E 2000 MPa 0.35

AsphaltLinear elastic

Sub-base 21kN/m3

s 3 kPaKo 1

.0K-model, equation (22)K1 8000K2 0

.70(in kPa) 0.30

Subgrade 20 kN/m3

Brown's model, equation (6)K 50 MPan 0.40 0.45

2.00

1.60

1.30

1.00

0.70

0.50

0.30

0.20

0.10

0.05

0

1.000.800.600.400.300.200.100.050 r: m

z: m


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Resilient

Strain

Chord Modulus

Secant moduli

Strain

Stress

Wheel

lo

ad

Overburden

Original stresses (*, *)

Corrected stresses (, )

*1 =1

(z, )

(*r *) (r )

*3

(z*, *)

Wheel load

Rail

Sleeper

Ballast

Subballast

Subgrade layer 1

Subgrade layer 2

Bedrock


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Number of load applications

Permanentdeformation:mm

20

10

0

Waterremoved

Ingressof water

Material type

Ingressof water

G4G3

G2

G1


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1.0

0.5

0

3.02.52.01.51.00.50

Time: s

(a)

Strain

:%

2.01.61.20.80.40

60

50

40

30

20

10

0

Time: s

(b)

Verticalstress:kPa

Moving wheel load

Pavement structureVerticalstress

Shearstress

Horizontalstress

Typical pavement element

(a)

Vertical stress

Horizontal stress

Shear stress whenwheel moves inopposite direction

Time

Stress

(b)

Shear stress


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(a)

(b)

W

MT

PiPO

z

r

z

z

r

Tocomputer

Strain gaugeddiaphragm

LVDTs

(a)

Loadcell

Testspecimen

Piston

Servohydraulicsupply

LVDT

Actuator

Transducer

To

computer

Cylinder

LVDT

Actuator

Servohydraulicsupply

Proximitytransducers

(b)

Testspecimen


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Hand jack

Pressuresensor

Triaxialcell

Load cell onloading rod

Hydraulic supply

Actuator withservo-value

Pressurecylinder

Hydraulicsupply

Actuator withservo-value

Electroniccontrolsystem

Computer

(a)

(b)

150 mm

180 mmdrainage

membrane

'o' rings toseal membrane

Strain ringshown insection only

LVDT

Rod attachedto location stud

300mm

75mm


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Aluminiumblock withcup fitting

Straingauges

Phospherbronze strip0.56 mm thick

Hollow brasstube 5 mm dia.

'O' ring

Specimen

82mm

CruciformvaneAdjustable

fixing

40 mm


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Geophone

Drop weight

(a)

Drop weight

Loading plate/buffer

Rubber Geophone

Deflection

300mm 200mm 500mm 500mm 500mm

(Typical dimensions)

(b)


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Resistance in theseupper regions dependsupon flexural strength(tensile, cohesion)

Resistance inthis lower region isprimarily dependentupon interparticlefriction (R-value)

Probable pathsof particle flow

Weight of materialoutside of loadalso providesrestraint

Load

Surface

Base

Depth: mm Temp.: C

0

30

22

23

Wheel position

20 cm right-hand side

80 20

140 19

Wheel load

Vehicle speed

16.5 kN

30 km/h

1 s


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Test Series

Temp. C

Symbol

F G

+10 0 +10 +20 +30

Test Series

Frequency

Symbol

varies

P

Cycles to failure

2 x 103 104 105 106 107Tensile

strain:microstrain700

500

100

50

Heavy clay

Sub-base

Base +surfacing

Subgrade

TotalRolled asphaltRolled asphaltBallast

(100 mm)(150 mm)(150 mm)

Deformation:mm

10

8

6

4

2

01968 1969 1970 1971

Year

Rut depth

Load

Bituminous

Granular

Subgrade


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Cumulative Traffic

Tamping

Subgrade

Sub-ballastBallast

Settlement

Traffic: MGT

Sub-ballast

Subgrade

Ballast

Total

Traffic: GN

0 25 50 75 100 125 150 175 200 225

Settlement:in

0.8

0.6

0.4

0.2

0.05 10 15 20 25

0

5

10

15

20

Settlement:mm


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Pavement surface

Formation levelPore pressure

Water table

?

ve +ve

Hydrostaticline

Formation level

Sandyclay

Siltyclay

Sandy clay

SandyGravel

Area E

Sandyclay

Siltyclay

Sandy clay

SandyGravel

Area G

Formation level

Hydrostaticline

Heightabovewatertab

le:m

Heightabovewatertable:m

Pore pressure: kPa

25 20 15 10 5 0

1

2

0

1

2

3


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Compression

Swelling

Mean normal effective stress, p

Effects of construction

C

O P A

P

Deviatorstres

s,q

Compression

Swelling

A

C

P

P

pA pc

Specificvolume,v


Pavementconstruction

Loweringwatertable

F P

D

E

G B

Removal of overburden

P

A

Swelling line


Deviatorstress,q


22/44

Mean normal effective stress p

O A

B XC

Q

Q

CSL (failure)

Deviatorstress,q

Compression

Swelling

CSL (failure)

C

XQBQ

A

Mean normal effective stress p

Specificvolume,v

Notional yield surfaces

Deviatorstress,q

C

XF

Q (Fill)

TSPESP

EWheel loading

Time

q

qr

u

Wheel loading

Time

q

qr

P (Cut)Mean normal effective stress, p

T


23/44

Locus ofvalues forqr= 30 to75 kPa

qr= 125 kPa

Number of load cycles

(a)

Permanentshe

arstrain:%

1 101 102 103 104 105 106 107

2.5

2.0

1.5

1.0

0.5

0

Locus ofvalues forq= 40 to130 kPa

qr= 175 kPa


(b)

Permanentshearstrain:

%

1 101 102 103 104 105 106 107

2.0

1.0

0

3.0

4.0

5.0

6.0

Suction: kPa20 30 40 50 60 70 80 90 1000 10

50

40

30

20

10

0Deviatorstresspulseatonsetof

permanentstrain:kPa

Soil type

Keuper Marl

London Clay

Gault Clay

Confining stress: kPa

0 15 30


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Repeated deviator stress: kPa

0 10 20 30 40 50

Permanentaxialstrain:%

1.0

0.8

0.6

0.4

0.2

0

Deviator stress: psi

Resilientmodulus:psi

0 5 10 15 20 25 30 35 40

16000

14000

12000

10000

8000

6000

4000

2000

0


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Symbol OCR 3

kPa

24102041020

3801907638

40)

))

qr/3

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Resilientmodulus:MPa

300

250

200

150

100

50

0

Elastic stiffness: MPa

Depth:m

Asphalt (Stiffness 7000 MPa)

Granular

Subgrade

6004002000

1

2

3

4

Case B: Water table 1 mCase B: below formation

Case A: Water tableCase B: at formation

Case B

Case A

Repeated deviator stress: kPa

504030201000

10

20

30

40

50

60

70

80

19

32.5

43

76

76

Key

Loach (1987) data

New model fitted

Soil suction: kPa

Resilientmodulu

s:MPa


26/44

Line of equality

Measured resilient modulus: MPa

0 20 40 60 80 100

100

80

60

40

20

0Computedresilientmodulus:MPa

Cyclic shear strain: %310.10.010.0010.0001

Normalizedmodulus:G/Gmax

1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

Vucetic & Dobry 1991(solid lines)

PI=0PI=15

PI=30PI=50

PI=100PI=200

Mexico CityPI>80

PI=4080PI=2040

PI=1020PI=510

Sun et al. 1988(dashed lines)

Resilientshearstrain:

qr/pe

po/pe0 0.1 0.2 0.3

500

400

300

200

100

0.2

0.1

0


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Resilient shear strain: %

Gr/

Go

1.2

1

0.8

0.6

0.4

0.2

00.001 0.01 0.1 1

Predictionpo= 33 kPa, Ro= 18

po= 100 kPa, Ro= 6


28/44

Normal stress p: kPa

Deviatorstressq:kPa

Shear strain(microstrain)

200

160

130

100

70

40

FAILURE

300200100

(a)

100

200

300

400

(15,6)

Normal stress p: kPa

Volumetric strain(microstrain)

Dev

iatorstressq:kPa

100 200

300

400

100

200

400

0

500

200

400

600

800 1

000 1

200

1400

FAILURE

(b)

300

Peak mean normal effective stress: kPa


Pessimumline of fit

Increasing deviator stress1000

800

600

400

200

0

0 50 100 150


29/44

Limit ofresilientstraintests

Normal stress, p: kPa

Deviatorstress,q:kPa

500

400

300

200

100

0 100 200 300

C

A

B

Failure

(a)

Number of cycles

Permanentshearstrain:%

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

1 10 102 103 104 105 106

(b)

C

A

B


30/44

Mean normal effective stress: kPa

Deviatorstress:kPa

Stress paths for resilient strain testing

Stress paths for plastic strain testing

200

100

0

0 100 200


Axialstrain:%

With shearreversal

Triaxial

Recoverablestrain

Permanentstrain

5 10 25 50

0.8

0.7

0.6

0.5

0

.

4

0.3

0.2

0.1

0


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Testing machine

Taperedlugs

3 in2area

Penetrationpiston

6 Cylindricalmould

5

010

20

30

4060

70

80

90

Head


32/44

Deviatorsterss:kPa

20

40

60

80100

CBR: %

(a)

0 2 4 6 8 10


300

200

100

0

CBR: %

(b)

0 2 4 6 8 10

120

80

40

0

Keuper

Marl

M=10

CBR

Mr=17

.6CBR0.64

LondonClay

GaultClay

Resilientmodulus:atdeviator

stressof40kPA:MPa


33/44

Penetration: mm

Plungerload:kN

0 1 2 3 4 5 6 7 8

1.0

0.75

0.5

0.25

0


34/44

Pressuregauge

Adjustablestage

Displacementpump

Dialgauge

Piston forapplyingload to specimen

Liquid

Flexiblediagram

Platen oftesting machine

Load

Head of testing machine

Testspecimen


35/44

Asphaltlayer

Granularlayer

Subgrade

Vertical strain: microstrain

10005000

0.5

1.0

1.5

2.0

Depth:m

Surface deflectionunder centre of load = shaded area


36/44

Measure subgrade characteristics in laboratory

Select aggregate(s)

Measure aggregate characteristics in laboratory

Design foundation

Prepare subgrade

Check in situ performance

Performance satisfactory?

Place aggregate?

Check in situ performance

Performance satisfactory?

Foundation Complete

YES

YES

NO

NO

if aggregate

is unsatisfactory


37/44

C

Fcb

Rcbc

B

Fb Ra

Rb

Rba

Fba

a A

P

2r

h

Limestone

Number of passes1 10 100 1000

predicted

measuredRutdepth

:mm

0

10

20

30

40

50

60

70

80

Granodiorite

Ash

Sand &Gravel

(a)

10 100 1000 10000

predicted

measuredRutd

epth:mm

0

10

20

30

40

5060

70

80

(b)

Granite(550 mm)

Gravel(400 mm)


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soil mechanics in pavement engineering sf brown

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