11

REVISITATION

OF

EXPANSIVE SOILS

ROBERT L. LYTTON, PhD

Foundation Performance Association

Houston, Texas

December 13, 2006

22

Building Foundations

Pavements

Embankments, Cuts and Slopes

CONSTRUCTED WORKSIMPACTED BY

EXPANSIVE SOILS

33

Site Investigation

Laboratory Characterization

Relating Field-to-Lab Properties

CONSTRUCTED WORKSIMPACTED BY

EXPANSIVE SOILS

44

Slabs

Drilled Shafts

Basements

Retaining Walls

Design Methods

Building Foundations

55

Pavements

New Construction

Airport

Highway

Reliable Design Methods

Sulfate Swell Problem

Remediation

66

Embankments, Cuts, and Slopes

Shallow Slope Failure

Downhill Creep

Dams and Levees

77

Site Investigation

Boring and Sampling

Resistivity

Conductivity for Soluble Sulfates

Ground Penetrating Radar

88

Site Investigation

Depth of the Active Zone

Moisture Active Zone

Movement Active Zone

Vegetation

Crack Fabric in Soil Masses

Field-to-Laboratory Diffusivity Ratios

99

Index Properties

Suction Measurement

Diffusivity Measurements

Constitutive Relationships

Shallow Foundations

Major Earthworks

Laboratory Characterization

1010

1111

1212

1313

1414

1515

1616

1717

1818

1919

2020

2121

2222

2323

2424

2525

2626

2727

2828

2929

3030

3131

3232

3333

3434

3535

3636

3737

Dry Season

(-) Suction Ground Surface

Wet Season

Equilibrium

Dep

th

3838

3939

4040

4141

4242

Equilibrium Soil Suction vs. TMIEquilibrium Soil Suction vs. TMI

Note: Modified curve and equation ofcurve provided in 3rd Edition Manual.

4343

Diffusion Test SetupDiffusion Test Setup

4444

PsychrometerPsychrometer Installation Installation

4545

Diffusion CoefficientDiffusion Coefficient

Diffusion Coefficient for BHC 2

3

3.5

4

4.5

5

5.5

6

100 1000 10000 100000

Drying Time (minutes)

Su

cti

on

, u

(p

F)

L = 15.93 cm

x = 14.23 cm

ua = 5.91 pF

u0 = 3.51 pF

he = 0.54 cm-1

á = 0.001 cm2/min

4646

4747

DEPTHBELOW

SOILSURFACE

CRACKING SPACING

SOURCE : MICHAEL KNIGHT PH. D. DISSERTATATION, GEOLOGY UNIVERSITY OF MELBOURNE (AUSTRALIA) 1972

4848

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

Rel

iabi

lity

Field α/laboratory α0

4949

5050

5151

Design Program - Winpres

5252

Design Program - Winpres

60.0

80.0

100.0

120.0

140.0

160.0

180.0

200.0

0 5 10 15 20 25 30

Time (yrs)

Inte

rna

tio

na

l R

ou

gh

ne

ss

In

de

x (

IRI)

(in

/mil

es

)

SN 5.06 in, ACP 4.0 in, LTS 2.5 ft, Inert 2.5 ft

SN 5.28 in, ACP 4.5 in, LTS 2.5 ft, Inert 1.5 ft

SN 5.50 in, ACP 5.0 in, LTS 2.5 ft, Inert 1.5 ft

SN 5.72 in, ACP 4.0 in, LTS 3.0 ft, Inert 1.5 ft

Flexible Pavement

FWD 10,000 psi

Reliability 90 %

ADT (T= 0) 42,850

ADT (T=30) 67,950

W18 8,415,520

IRI versus Time

5353

5454

ROOT ZONE

Crack Spacing Gets Larger with Depth

5555

RUNOFF WATER

DRY LIMIT

WET LIMIT

4.0

2.0

4.0

2.5

pF

SUCTION RANGE

BETWEEN CRACKS

WATER

SOAKS

INTO

SOIL 2.0

5656

SULFATE SWELLING PROBLEMS

LIME +

SULFATE +

WATER +

CLAY = PAVEMENT BUCKLING

5757

Williamson County Soil MapWilliamson County Soil Map

5858

MagnetometerMagnetometer

5959

Variation of Sulfate along slope of theVariation of Sulfate along slope of thesurfacesurface

12345678B1

C3C5

0

5000

10000

15000

20000

25000

30000

Sulfates

(ppm)

Depth

Locations

6060

Stability Models or Phase DiagramsStability Models or Phase Diagrams290 Soil - Depth of 24-inches290 Soil - Depth of 24-inches

5 6 7 8 9 10 11 12 13 14–5

–4

–3

–2

–1

0

1

2

3

pH

log

a S

O4--

290 Soil B1 2ft @ pH12 Extract

¢

Al(OH)4

-

Al(SO4)

2

-

C4AH

13

Ettringite

Gibbsite

Monoaluminosulfate

25°C

Sac hin Kunagal l i Mon May 10 2004

Dia

gra

m A

l(O

H)

4-,

T

=

25

°C

, P

=

1

.01

3 b

ars

, a

[m

ain]

=

1

0–4.5

53

, a

[H2

O]

=

1

, a

[ SiO

2(a

q)]

=

1

0–7

.46

, a

[C

a++]

=

1

0–2.4

67

; S

up

pre

sse

d:

Gro

ssu

lar

Soluble Sulfates= 18,700 ppm

6161

VOID RATIO CONSTITUTIVE SURFACEVOID RATIO CONSTITUTIVE SURFACEOF A SOIL AT ARLINGTON, TEXASOF A SOIL AT ARLINGTON, TEXAS

0

0.6

1.2

1.8

2.4

3

0

1.2

2.4

3.6

4.8

6

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

Void Ratio

e

Mechanical

Stress

log 10 ( !m-u a )

(kPa)

Matric Suction

log 10 ( u a -u w ) (kPa)

0.60-0.70

0.50-0.60

0.40-0.50

0.30-0.40

0.20-0.30

0.10-0.20

0.00-0.10

6262

6363

6464

6565

Building Foundations

Pavements

Embankments, Cuts and Slopes

CONSTRUCTED WORKSIMPACTED BY

EXPANSIVE SOILS

6666

REVISITATION

OF

EXPANSIVE SOILS

ROBERT L. LYTTON, PhD

Foundation Performance Association

Houston, Texas

December 13, 2006