Design of Structures to Resist the Pressures and … · Design of Structures to Resist the...

Design of Structures to Resist the Design of Structures to Resist the Pressures and Movements of Pressures and Movements of

Expansive SoilsExpansive Soils

Robert L. Lytton

Texas A&M UniversityFoundation Performance Association

December 12, 2007

http://www.foundationperformance.org/

1

Acknowledgements Acknowledgements

Gyeong-Taek HongRong Luo

Charles P. AubenyRifat Bulut

Jorge A. ProzziXiaoyan Long

Anshuman ThakurEeshani Sood

2

Topics (1/2)Topics (1/2)

• Soil properties• Suction envelopes

ClimatesTrees Drainage

• Pavement designConcrete and asphalt Stabilized layers Vertical and horizontal moisture barrier

3


• Shrinkage cracking design• Shallow slope failure• Slab-on-ground design• Drilled pier design

Lateral pressuresStresses, strains, movementsComparison with field measurement

• Retaining wall designLateral pressuresStresses, strains, movementsComparisons with measurements

4

Volume ChangeVolume Change

(Lytton, 1977)⎛ ⎞ ⎛ ⎞⎜ ⎟ ⎜ ⎟⎝ ⎠ ⎝ ⎠

f fh 10 σ 10

i i

ΔV h σ= - log - logV h σ

γ γ

Volume–Mean Principle Stress-Suction surface

Δ Δ⎛ ⎞= ⎜ ⎟⎝ ⎠

H VfH V

⎡ ⎤Δ = ⎢ ⎥⎣ ⎦∑ i ii=1 i

Δ Δn Vf z

V

0.67 0.33 pFf = 0.5 when drying; f = 0.8 when wetting

f = − Δ

⎛ ⎞⎜ ⎟⎝ ⎠

5


(Covar

and Lytton, 2001)

Partitioning Database on Mineral Classification

6500 Data from SSLOf National Soil Survey Center

6


⎛ ⎞⎜ ⎟⎝ ⎠

σ h1= h1+

hθθ

γ γ

∂∂

⎡ ⎤⎢ ⎥⎣ ⎦

h 0% - 2μm= �

% -No.200 sieveγ γ

Zone III (Covar

and Lytton, 2001)

% 2%% .200c

mfNo sieve

μ−=

−

PI / %fc

LL /

%fc

(Lytton, 1994)

7

Exponential Suction Profile for Extreme Exponential Suction Profile for Extreme Wetting and Drying ConditionWetting and Drying Condition

0

2

4

6

8

10

12

14

2 3 4 5

Suction (pF)

Dept

h (ft

)

Wet

Equil.

Dry

0

2

4

6

8

10

12

14

0 0.2 0.4 0.6

Volumetric Water Content

WetDry

0

2

4

6

8

10

12

14

0 1 2 3

Vertical Movement (in)

WetDry

Fort Worth Interstate 820

⎛ ⎞ ⎛ ⎞⎜ ⎟ ⎜ ⎟⎜ ⎟ ⎜ ⎟⎝ ⎠ ⎝ ⎠

e onπ nπU(Z,t) = U +U exp - Z cos 2πnt - Zα α

⎛ ⎞⎜ ⎟⎜ ⎟⎝ ⎠

e onπU(Z) = U +U exp - Zα

Mitchell (1979)

MoistureActive zone

8


(Lytton, 1977)⎛ ⎞ ⎛ ⎞⎜ ⎟ ⎜ ⎟⎝ ⎠ ⎝ ⎠

f fh 10 σ 10

i i

ΔV h σ= - log - logV h σ

γ γ

Volume–Mean Principle Stress-Suction surface

Δ Δ⎛ ⎞= ⎜ ⎟⎝ ⎠

H VfH V

⎡ ⎤Δ = ⎢ ⎥⎣ ⎦∑ i ii=1 i

Δ Δn Vf z

V

0.67 0.33 pFf = 0.5 when drying; f = 0.8 when wetting

f = − Δ

⎛ ⎞⎜ ⎟⎝ ⎠

9

Lateral Pressure CoefficientsLateral Pressure Coefficients

(Lytton et al., 2006)

01 sin ' 1 sin '1 sin ' 1 sin '

ndK ek

φ φφ φ

⎛ ⎞⎛ ⎞− += ⎜ ⎟⎜ ⎟+ −⎝ ⎠⎝ ⎠

Conditions Ko (after McKeen, 1981) e d k n

Cracked 0 0 0 0 1

Drying (Active) 1/3 1 0 0 1

Equilibrium (at rest) 1/2 1 1 0 1

Wetting (withinmovement active zone) 2/3 1 1 0.5 1

Wetting (belowmovement active zone) 1 1 1 1 1

Swelling near surface(passive earth pressure) 3 1 1 1 2

(after Holtz and Kovacs, 1981)

φ ' = 0.0016PI2 - 0.3021PI + 36.208R2 = 0.9978

0

5

10

15

20

25

30

35

40

0 20 40 60 80 100Plastic index, PI

Inte

rnal

fric

tion

angl

e, φ

'

10

Volumetric Moisture Content and Suction Volumetric Moisture Content and Suction CurvesCurves

(Lytton et al., 2006)

5

4

3

2

6

0

1

Volumetric Water Content θf θsat

Suct

ion

(pF)

D

A

S1

1

κθf

γγ

w

d

S1

pF0

=5.622+0.0041(% clay fines)

S = -20.29+0.1555(LL)-0.117(PI)+0.0684(-#200)

11

Pavement Design on Expansive Pavement Design on Expansive SoilsSoils

13

Pavement TreatmentsPavement TreatmentsPavement

Stabilized Soil

Inert soil

Subgrade

Barrier

Bar

rier

Pavement Section

WIDTH OF PAVEMENT,83 FT

10 FT6 FT 12 FT 12 FT 12 FT12 FT 7 FT

27 FT

14

Transverse Distribution of Vertical Transverse Distribution of Vertical MovementsMovements

d (ft)Swel

ling

Shrin

kage

(in)

-1.5

-0.5

0.5

1.5

2.5

3.5

0 10 20 30 40

Section ASection BSection C

15

Field ConditionsField Conditions

0

2

4

6

8

10

12

14

2.0 3.0 4.0 5.0

pFD

epth

(ft

Root zone

Moisture active zone

Wilting point 4.5 pFField capacity Equilibrium

πα

⎛ ⎞= ± ⎜ ⎟⎜ ⎟

⎝ ⎠0( ) exp -e

nU Z U U Z

= −e 3.5633exp( 0.0051TMI)U

16

Roadside Drainage Conditions

HillSlope

Valley

Cut

Flat

Fill

2.3 pF

Longitudinal Drainage

Lateral Slope

2.0 pF 2.0 pF

2.5 pF 2.2 pF 2.2 pF

2.6 pF 2.3 pF 2.3 pF

Thornthwaite

Moisture Index (TMI, 1948)Climatic Conditions

100 60

p

R DEFTMIE−

= R = runoff moisture depthDEF =deficit moisture depthEp

= evapotranspiration

17

Calculated Vertical MovementCalculated Vertical Movement

18

Comparison of PVR with Case Study Comparison of PVR with Case Study ResultsResults

No Treatments

2.0

0.0

2.0

Swel

l

2.0

0.0

2.0

Swel

l

(IN)

New methodPVR

Fort Worth A

Shrin

kSh

rink

Atlanta Edge

M F

Austin

Outer W

heel P

athEdgeOuter

EdgeOuter

EdgeOuter Edge

Outer

B C

19

Acceptable Predicted PerformanceAcceptable Predicted Performance

2.0

2.5

3.0

3.5

4.0

4.5

0 10 20 30

Fort Worth Interstate 820 A

SI

Time (yrs)

Flexible Pavement

60

100

140

180

0 10 20 30Time (yrs)

IRI

20

Acceptable Predicted PerformanceAcceptable Predicted Performance

60

100

140

180

0 10 20 302.0

2.5

3.0

3.5

4.0

4.5

5.0

0 10 20 30

Austin State Route 1

Rigid Pavement

SI

Time (yrs) Time (yrs)

IRI

21

Loss of Serviceability Increase of Roughness

Predicted Roughness with Time

Time (yrs)

2.5

3.0

3.5

4.0

4.5

0 10 20 30

Time (yrs)

SI IRI

Total

Soil

Traffic

Soil

60

80

100

120

140

0 10 20 30

Soil

Traffic

Total

Fort Worth Interstate 820 B

22

SUBGRADE MOVEMENTS COMPARED WITH PVR FOR A MINIMUM ACCEPTABLE TREATMENT

Flexible Pavement

Case SitesEdge

Fort Worth

A

B

C

Atlanta

Austin Main

Frontage

Outer Edge Outer

Swell

PVR

Shrink Total

New Method

0.78

0.72

0.02

(IN)

0.30

0.37

0.66

0.72

0.73

1.12

1.06

0.43

0.58

1.50

1.45

1.14

1.36

0.80

1.24

0.61

0.57

0.42

1.08

0.49

0.84

2.08

2.08

1.21

1.28

1.45

1.94

1.20

1.20

0.81

0.88

1.13

1.17

Avg. 0.67 in 1.1 in

23

Longitudinal Cracking over Expansive Longitudinal Cracking over Expansive SoilSoil

• Expansive soilExperience volumetric change when subjected to moisture variation

• Longitudinal crackInitiate in shrinking expansive subgradePropagate to pavement surface

24

Practice of Geogrid ReinforcementPractice of Geogrid Reinforcement

FM1915 (Milam County, Texas)

25

Practice of Lime TreatmentPractice of Lime Treatment

26

Stress Analysis on Subgrade SoilStress Analysis on Subgrade Soil

• Stress variable for saturated soil: σ-uw

•

Stress variable for unsaturated soil: σ-ua , ua -uw

•

Soil suctionThe affinity of soil for waterMatric suction: negative water pressureOsmotic suction: soluble salts in the soil water

•

Constitutive equation to estimate the volumetric strain of unsaturated soil:

⎟⎟⎠

⎞⎜⎜⎝

⎛−⎟⎟

⎠

⎞⎜⎜⎝

⎛−⎟⎟

⎠

⎞⎜⎜⎝

⎛−=

Δ

i

f

i

f

i

fh h

hVV

ππ

γσσ

γγ πσ 101010 logloglog

27

⎟⎟⎠

⎞⎜⎜⎝

⎛−⎟⎟

⎠

⎞⎜⎜⎝

⎛−⎟⎟

⎠

⎞⎜⎜⎝

⎛−=

Δ

i

f

i

f

i

fh h

hVV

ππ

γσσ

γγ πσ 101010 logloglog

where

VVΔ = volumetric strain;

ih = initial value of matric suction; fh = final values of matric suction; iσ = initial value of mean principle stress; fσ = finial value of mean principle stress; iπ = initial value of osmotic suction;

fπ = finial value of osmotic suction;

hγ = matric suction compression index;

σγ = mean principal stress compression index; and

πγ = osmotic suction compression index.

28

Without Geogrid ReinforcementWithout Geogrid Reinforcement……

Subgrade (Expansive soil)

Asphalt

CL

BaseCrack

29

With Geogrid ReinforcementWith Geogrid Reinforcement……

Subgrade (Expansive soil)

Asphalt

CL

Base

Geogrid

30

Mechanism of Geogrid ReinforcementMechanism of Geogrid Reinforcement

P P P P

Asphalt

Base

Subgrade

Travel direction Depth

31

0.000

0.020

0.040

0.060

0.080

0.100

0.120

0.140

0.160

0.180

0.200

0 400 800 1600 3200 6400 12800

Geogrid Stiffness (kN/m)

Stre

ss In

tens

ity F

acto

r (M

Pa*m

^.5)

0

10

20

30

40

50

60

70

80

90

Geo

grid

Ten

sile

Str

engt

h (k

N/m

)

Number of Crack=1

Number of Crack=2

Number of Crack=3

Number of Crack=4

Number of Crack=5

Upper Tensile Strength

Lower Tensile Strength

Geogrid Tensile Strength

32

Transverse Stress Distribution in Pavement (Full Restraint)

33

Transverse Stress Distribution in Pavement (Crack at Edge of Shoulder)

34

Transverse Stress Distribution in Pavement with Treated Layer

35

SlabSlab--onon--GroundGround DesignDesign

48

Dry Season

(-) Suction Ground Surface

Wet Season

Equilibrium

Dep

th

53

Equilibrium Soil Suction vs. TMIEquilibrium Soil Suction vs. TMI

55

ROOT ZONE

Crack Spacing Gets Larger with Depth

56

RUNOFF WATER

DRY LIMIT

WET LIMIT4.0

2.0

4.0

2.5

pF

SUCTION RANGEBETWEEN CRACKS

WATERSOAKSINTOSOIL 2.0

58

DEPTHBELOW

SOILSURFACE

CRACKING SPACING

SOURCE : MICHAEL KNIGHTPH. D. DISSERTATATION, GEOLOGYUNIVERSITY OF MELBOURNE (AUSTRALIA) 1972

59

Field to laboratory diffusion coefficient ratio (ContField to laboratory diffusion coefficient ratio (Cont’’d)d)

Rel

iabi

lity

Field α/laboratory α0

60

Drilled Pier Design Drilled Pier Design

Retaining Wall DesignRetaining Wall Design

61

Lateral Earth Pressure Concept (1/5)Lateral Earth Pressure Concept (1/5)Suction Change

62

Lateral Earth Pressure Concept (2/5)Lateral Earth Pressure Concept (2/5)

Suction Change

( ) ⎛ ⎞⎛ ⎞⎜ ⎟⎜ ⎟

⎝ ⎠ ⎝ ⎠

hh

σσ

2ε-1-f ti

h 0 t if

z3 hσ = k z = σ 10 -2 h 2

γγ

γ γγ

Lateral PressureDue to Suction Change

63


Lateral PressureDue to Suction Change

Limited by Soil Strength

64


(Small Suction Change)At Rest Earth Pressure

65

Lateral Earth Pressure Concept (5/5)Lateral Earth Pressure Concept (5/5)Zone

I

II

III

Zmp

66

UPWARDMOVEMENT

ANCHORZONE

REINFORCING

DRILLED PIER

68

Severe damage to a reinforced concrete columns due to differential heave, in Saudi Arabia (Al-Shamrani

and Dhowian, 2003)

69

Retaining WallsRetaining Walls

EXPANSIONPRESSURE

RESISTINGPRESSURE

70

3 –

4 ft

72

Horizontal Earth Pressure in Expansive Horizontal Earth Pressure in Expansive SoilsSoils

73

Zone I

Zone II

Zone III

Mov

emen

tac

tive

zone

Anc

hor z

one

Heave

Zero Swell

Zmp

Richards and Kurzeme

(1973) 4 times the overburdenJoshi and Katti

(1980) 42 psi

@ 3 ft, lab Komornik

(1962)

55 psi

@ 3 ft, labBrackely

and Sanders (1992) 12 psi

@ 3 ft, field

Horizontal Swelling Pressure Model

( )′mpz tan 45 + /2 = 5 - 7 ftφ

( )⎡ ⎤⎛ ⎞⎢ ⎥⎜ ⎟

⎝ ⎠⎢ ⎥⎣ ⎦′i

2

mp= zXZ z tan 45 +φ /2 1-H

Horizontal Active zone

Zmp

= 3 -

5 ftJoshi and Katti

(1980); Komornik

(1962);Brackely

and Sanders (1992); Symons et al. (1989)

( )′h tσ = 1- sin zφ γ

74

Mean angle of the fissure to the horizontal = 43 degree

Silckensides

occurs in soil which has PI >30, -2μm>30

Leeuhof

test site at Vereeniging, South Africa

Fissures caused by a passive failure of the soil resulting from the horizontal pressure during seasonal swelling of the clay

Williams and Jennings (1973)

0

2

4

6

8

10

12

14

16

0 5 10 15 20 25

Horizontal Pressure (psi)

Prediction197919801981Vertical

Zone I(Passive Failure)

Zone II(Passive)

Zone III(at Rest)

Zone II(Passive)

0

2

4

6

8

10

12

14

16

2 3 4 5

Suction (pF)

Dept

h (ft

)

0

2

4

6

8

10

12

14

16

0 1 2 3 4

Swelling Movement (in)

Prediction

Measured

0

2

4

6

8

10

12

14

16

0 10 20

Shear Strength (psi)

Seasonal range of suction(In situ psychrometers)

Maximum pressures measuredat four depths in 1979,1980,1981(In situ pressure cells)

Zmp

= 3.8 ft

Brackely and Sanders (1992)Natural horizontal pressures measured in field

Komornik (1962)Measured horizontal pressures in the large scale pile test

0

1

2

3

4

2 3 4

Suction (pF)

Dept

h (ft

)

0

1

2

3

4

0 2 4 6 8

Swelling (in)

Prediction

Measured

0

1

2

3

4

0 20 40 60


PredictionMeasuredVertical

Soil PropertiesLL

76 %PI

48 %#200

90 %-2μm

62 %

Site Kibbutz Mizra, Israel

Sand seam

Kim and O’Neill (1998)Axial behavior of the pier

Test Site Stratigraphy(NGES-UH)

Schedule of Rebar and Concretein Drilled Shaft


Bar versus Time(1 bar=100 kPa) Uplift Force versus Time

55

34

193.1 pF

3.7 pF

4.1 pF


0

2

4

6

8

10

12

14

0.0 1.0 2.0

Swelling (in)

Prediction

Measured

0

2

4

6

8

10

12

14

0 5 10


Prediction

Vertical

0

2

4

6

8

10

12

14

-0.6 -0.4 -0.2 0.0 0.2

Pile Movement (in)

Prediction

Measured

0

2

4

6

8

10

12

14

0 50 100 150

Axial Stress (psi)

Prediction

Measured

0

2

4

6

8

10

12

14

2.5 3.5 4.5

Suction (pF)

Dept

h (ft

)

Case Study of Bending Behavior of the PierUneven Wetting with Same Initial Condition

0

2

4

6

8

10

12

2.0 2.5 3.0 3.5 4.0

Suction (pF)

Dep

th (f

t)

0 5 10

Active Zone (ft)2.0 2.5 3.0 3.5 4.0

Suction (pF)0 2 4

Swelling (in)0 2 4

Swelling (in)

( )tan 45 / 2mpZ φ′⋅ +

NGES-UH Site (Kim and O’Neill, 1998)

0 10 20

Horizontal (psi)-20 -10 0

Horizontal (psi)-10 0 10

Shear Stress (psi)

-10 0 10

Shear Stress (psi)



-4.0 -2.0 0.0

Deflection (in)-200 -100 0 100

Lateral Load (lb)

Prediction

At Rest

-40000 -20000 0 20000 40000

Bending Moment (lb-in)-2000 -1000 0 1000 2000

Shear Force (lb)



83

Retaining Wall DesignRetaining Wall Design

Katti et al. (1979)Measured horizontal pressures in the large scale retaining wall test

Black cotton soil, IndiaLL

81.5 %

PI

38.3 %#200

96.0 %

-2μm

56.0 %

3 months saturation

0

1

2

3

4

5

6

7

8

2 3 4

Suction (pF)

Dep

th (f

t)

0

1

2

3

4

5

6

7

8

0 2 4 6

Swelling Movement (in)

Prediction

Measured

0

1

2

3

4

5

6

7

8

0 20 40 60


PredictionMeasuredVertical

Air

dry

initi

al c

ondi

tion

100%

Sat

urat

ion

Katti et al. (1979)Measured horizontal pressures in the large scale retaining wall test

Case Study of Bending Behavior of the Retaining Wall

0

2

4

6

8

10

12

2.5 3.0 3.5 4.0

Suction (pF)

Dept

h (ft

)

2.5 3.0 3.5 4.0

Suction (pF)0 1 2

Swell (in)

-10 -5 0

Horizontal (psi)0 5 10

Horizontal (psi)0 1 2

Swell (in)


-150 -50 50

Lateral Load (lb)

0

2

4

6

8

10

12

-10 -5 0

Deflection (in)-50000 0 50000

Bending Moment (lb-in)-2000 0 2000

Shear Force (lb)


Case Study of Bending Behavior of the Retaining Wall

89


• Shrinkage cracking design• Shallow slope failure• Slab-on-ground design• Drilled pier design

Lateral pressuresStresses, strains, movementsComparison with field measurement

• Retaining wall designLateral pressuresStresses, strains, movementsComparisons with measurements

88


• Soil properties• Suction envelopes

ClimatesTrees Drainage

• Pavement designConcrete and asphalt Stabilized layers Vertical and horizontal moisture barrier

Design of Structures to Resist the Design of Structures to Resist the Pressures and Movements of Pressures and Movements of

Expansive SoilsExpansive Soils

Robert L. Lytton

Texas A&M UniversityFoundation Performance Association

December 12, 2007

http://www.foundationperformance.org/

Design of Structures to Resist the Pressures and … · Design of Structures to Resist the...

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