by - Foundation PerformanceSwell Limit 8 to 15 % Near 100 % 4 -10 4-10 3 Shrinkage Limit Tension 6 -10 6-10 5 Air Dry Suction NO YES YES NO 0 0 7 -10 7-10 6 Oven Dry Shrink Swell Water

FOUNDATIONS ON SHRINKING AND SWELLING SOILS

(Prediction of Movement, Construction Issues)

Department of Civil Engineering, Texas A&M University, College Station,

Texas 77843-3136, USA

by

Jean-Louis Briaud, Sangho Moon, Xiong Zhang

J.L. Briaud, Texas A&M University

• ENVIRONMENTAL SOIL STABILIZATION LTD.

Russ Scharlin

Johny Sherwood

• SPENCER J. BUCHANAN PROFESSORSHIP

• GILES ENGINEERING ASSOCIATES INC.

Doug Dayton

ACKNOWLEDGEMENTSJ.L. Briaud, Texas A&M University

• FUNDAMENTAL BEHAVIOR

• SHRINK TEST – WATER CONTENT METHOD

• CASE STUDY

• SMART FOUNDATION

OUTLINEJ.L. Briaud, Texas A&M University

Saturated

uw ≠≠≠≠ 0ua = 0

σσσσ’ = σσσσ - uw

Occluded Air

uw = ua

σσσσ’ = σσσσ - uw

Continuous Air

uw ≠≠≠≠ 0ua = 0

σσσσ’ = σσσσ - ααααu

soil grain water

soil grain waterair

soil grainwaterair


u0+-

hc

αααα ααααT T

Glass

ContractileSkin

Water

- 1,000 kPa

d

Water

ãd

á cos T 4 h

wc ====

mN/m 72 T where ====

h

Atmosphericpressure

hγγγγw

hcγγγγw0 kPa


Pure Water Salt Water

initial state Initial stateafter time, t

after time, th = Osmotic Suction


109 108Bottom of DeepestOcean

105 104Deepest OffshorePlatforms

Compression

103 102Large River

100 %0 0 0

25 to 50 %2 -102 -101Field Capacity

Swell Limit

8 to 15 %Near 100 %4 -104 -103Shrinkage LimitTension

6 -106 -105Air DrySuction NO

YES

YES

NO

007 -107 -106Oven Dry

ShrinkSwellWater

ContentDegree ofSaturation

Suction

pF cm kPaExamplesWater State


Soil State Swell Shrink

Unsaturated Yes No

Saturated Yes Yes

Saturated No Yes

GWL

u0 +-


PHASE DIAGRAMSJ.L. Briaud, Texas A&M University

w

wSW

∆∆∆∆V/V

wSH

wi

∆∆∆∆((((∆∆∆∆V/V)max

0

∆∆∆∆wmaxSaturated orOccluded Air


SHRINK TEST PARAMETERS

Do

Ho H

D

WoW

t = 0 t

SHRINK


SHRINK TEST

Shrink Test

25

20

15

10

5

Shrink Test Example (B/RF1/6)

0.3-0.9 m,Ew = 0.86, w = 17.15 %

1.2-1.8 m, Ew = 0.69, w = 21.66 %

2.1-2.7 m, Ew =0.83, w = 16.03 %

data chosen for calculation of Ew

-0.2 -0.15 -0.1 -0.05 0

Wat

er C

onte

nt, %

Volumetric Strain, ∆∆∆∆V/V


SHRINK TEST RESULTS (1)

0 10 20 30 40 50 60 t, hr

0.0

-0.05

-0.10

-0.15

∆∆∆∆ H/H

o

-0.30 -0.25 -0.20 -0.15 -0.10 -0.05 0 ∆∆∆∆V/Vo

∆∆∆∆ H/H

o f1

f1

0.0

-0.05

-0.10

-0.15

0.4

∆∆∆∆V/Vo-0.30 -0.25 -0.20 -0.15 -0.10 -0.05 0

w

Ew1

1 Ew

wo

wsh wsh

0.3

0.2

0.1

0.0

wo

Porcelain Clay Bentonitic Clay



Porecelain Clay and Bentonite Clay


SWELL TEST

Porous stone

Porous stoneSoil sample

Consolidometer

lOAD

L

∆∆∆∆2∆∆∆∆1

-0.015

-0.010

-0.005

0.000

0.005

0.010

0

Time, hrs

∆∆∆∆ H/H

0.00954

0.00458

-0.00996

Swell withno OverburdenPressure

Swell underOverburdenPressure

Recompressionunder Overburden Pressure

Max. SwellUnder Overburden,(∆H/H)PS

MaximumFree % Swell,(∆H/H)FS

% Recovery,(∆H/H)P

0 50 100 150 200 250 300

Swell Test Example (B/RF1/6 0.3–0.9 m)Swell Test


EXAMPLE OF THE PREMISS METHODJ.L. Briaud, Texas A&M University

∆∆∆∆H/Ho-0.08 -0.06 -0.04 -0.02 0 0.02

∆∆∆∆V/Vo-0.2 -0.16 -0.12 -0.08 -0.04 0 0.04

0.25

0.20

0.15

0.10

0.05

0.00

w

∆∆∆∆D/Do-0.08 -0.06 -0.04 -0.02 0 0.02

0.25

0.20

0.15

0.10

0.05

0.00

0.25

0.20

0.15

0.10

0.05

0.00

ww

Sample(S) Overburden(O)

S (S1)S+O (S2)


S (S1)S+O (S2)


S (S1)S+O (S2)

SHRINK TEST RESULTS (3)

Influence of Vertical Pressure


-0.4 -0.2 0.0 0.2 0.4 0.6 ∆∆∆∆V/Vo

∆∆∆∆ w

0.4

0.2

0.0

-0.2

-0.4

-0.6Bentonic Clay

ShrinkSwell

0.2

0.1

0.0

-0.1

-0.2

-0.3

∆∆∆∆ w

-0.20 -0.15 -0.10 -0.05 0.00 0.05 0.10 0.15 0.20 ∆∆∆∆V/Vo

ShrinkSwell

Porcelain Clay

SHRINK AND SWELL TEST RESULTS

Porecelain Clay and Bentonite Clay


SUCTION VARIATION WITH DEPTH

Suction, u

Dep

th, z

ue0

zmaxSu

ctio

n E

nvel

ope

Suct

ion

Env

elop

e

u(z,t)

∆∆∆∆u(zmax) = 0.1×××× 2∆∆∆∆u0

∆∆∆∆u0∆∆∆∆u0

After Mitchell (1979)


After Mitchell (1979)

z) ) á T /(-(∂ exp Äu 2Äu(z) 0.500====

) Äu(Äw f====0.5

0max ) á T (3.1z ====

characteristic curve

∆u = change in suction at depth z∆u0 = change in suction at ground surfaceT0 = period of weather cycleαααα = diffusion coefficientz = depth below ground surface∆w = change in water contentzmax = maximum depth of water content change

where


After Styron et al. (2001)

30 (%) LL LI ±±±±====××××

)(PI/LL0.6Äw ====


WATER CONTENT VARIATION AS A FUNCTION OF TIME

Ave

rage

Wat

er C

onte

nt

0.35

0.30

0.25

0.20

0.15

0.10

0.05

0.00 Fall Winter Spring Summer Fall Winter Spring 1992 1993 1993 1993 1993 1994 1994

CC = Corpus Christi (0-0.5m)SA = San Antonio (0-0.5m)CS = College Station (0-1.5m)OUTSIDE = Outside the Foundation ImprintUNDER = Under the Foundation Imprint

Time for SA and CC

Time for CS Fall Winter Spring Summer Fall Winter Spring 1993 1994 1994 1994 1994 1995 1995

CC OUTSIDESA OUTSIDE

CC UNDER

SA UNDER CS OUTSIDE

From Posey, Briaud, 1995, Woodfin, Briaud, 1997


Hi

w

∆∆∆∆wiwi

z

w

wi+

∆∆∆∆ wi

wi

εεεεi+ ∆∆∆∆εεεεi εεεεi εεεεv

∑∑∑∑ ∑∑∑∑========i w

iiii E

ÄwfHÄåHS

MOISTURE INDUCED MOVEMENTJ.L. Briaud, Texas A&M University

∑∑∑∑∑∑∑∑ ========i

iiii E

ÄHÄåHS

σσσσ

εεεεi+∆∆∆∆εεεεi εεεεi εεεεvσσσσ ’

ov++++ ∆∆∆∆

σσσσ ’i

σσσσ ’ov

σσσσv

WEIGHT INDUCED SETTLEMENT

σσσσv

∆∆∆∆σσσσ’iσσσσ’ovHi

z

P


PLAN VIEW OF THE SITE

Boring date

# 1 : 06/24/99# 2 : 07/13/99# 3 : 10/25/99# 4 : 02/11/00# 5 : 05/11/00# 6 : 08/11/00# 7 : 11/17/00# 8 : 03/13/01# 9 : 07/15/01

BM1

BM2

W2 RF2

W1

RF1

3m

2m 2m

0.6m

Boringlocation

Boringorder

..0.61m

0.67m

1 - deep.

0.67m

B/W1/7 redrill - deep

0.67m

.

...

. ..1

2 34

5 6

7

..

8

9

.

...

. ..1

2 34

5 6

7

..

8

9

.

...

. ..1

2 34

5 6

7

..

8

9

.

...

. ..1

2 34

5 6

7

..

8

9

NorthSite in Arlington,Texas


SOIL STRATIGRAPHY

Dep

th,m

Legend

RF : Reference

W : Water injected

BM : Benchmark

1.5

2

2.5

3

0.5

1

0

Su = 179.8 kPawmean = 19.74 %h = 3.41 pFLL = 40.4, PL = 17.1

2m 2m

0.6m

Brown Silty Clay, trace fine Sand : Calcareous

γt = 20.4 kN/m3

Ew = 0.869, f = 0.39%SW = 4.31%<0.002= 45.5

NorthA’

W1

20m

10m

10m

RF2

W2RF1

A

BM2BM1

Su = 151.5 kPawmean = 20.73 %h = 3.42 pFLL = 51.3, PL = 22.3

Dark Gray Silty Clay : Trace Fine Sand

γt = 20.3 kN/m3

Ew = 0.752, f = 0.39%SW = 5.17%<0.002= 47.7

A A’

GWL : 4.27 m (Jun./25/99) 4.8 m (Feb./1/01) 4 m (Jul./15/01)

Site in Arlington,Texas


WATER CONTENT AND SUCTION vs. DEPTH

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 1 2 3 4 5

B:Boring B1 B2 B3 B4 B5 B6 B7 B8 B9

Dep

th, m

Suction, pF

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0.00 0.05 0.10 0.15 0.20 0.25 0.3

B:Boring B1 B2 B3 B4 B5 B6 B7 B8 B9

Dep

th, m

Water ContentFooting RF1 at a sitein Arlington, Texas


GARNER’S STUDY (1999)

3 samples at 3 water contents sent to 5 laboratory.

Water Content, %

Sample 1

Sample 2

Sample 3

Suction, pF

Sample 1

Sample 2

Sample 3

Suction, kPa

Sample 1

Sample 2

Sample 3

0 5 10 15 20 25 30 %

0 1 2 3 4 5 pF

0 250 500 750 1000 kPa

0 500 1000 1500 2000 kPa


∆∆∆∆V/Vo

0.30

0.25

0.20

0.15

0.10

0.05

0.00

w

-0.30 -0.25 -0.20 -0.15 -0.10 -0.05 0.00

B/RF1/4 0.3 – 0.9 m, Ew = 0.67 1.2 – 1.8 m, Ew = 0.60 2.1 – 2.7 m, Ew = 1.30

-0.30 -0.25 -0.20 -0.15 -0.10 -0.05 0.00 ∆∆∆∆V/Vo

B/RF2/4 0.3 – 0.9 m, Ew = 0.86 1.2 – 1.8 m, Ew = 0.76 2.1 – 2.7 m, Ew = 1.19

0.30

0.25

0.20

0.15

0.10

0.05

0.00

w

Three SamplesFrom Arlington,Texas

SHRINK TEST RESULTS (2)J.L. Briaud, Texas A&M University

SELECTED SOIL TEST RESULT FOR RF1

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Dep

th, m

0 0.5 1 1.5 2

Ew

0.1 0.3 0.5 0.7

f % SW

0 2.5 5 7.5 10

B3 B4 B5 B6 B7


FOOTING MOVEMENT OVER TWO YEARS

08/1

/199

9

09/1

/199

9

10/1

/199

9

11/1

/199

9

12/1

/199

9

01/1

/200

0

02/1

/200

0

03/1

/200

0

04/1

/200

0

05/1

/200

0

06/1

/200

0

07/1

/200

0

08/1

/200

0

09/1

/200

0

10/1

/200

0

11/1

/200

0

12/1

/200

0

01/1

/200

1

02/1

/200

1

03/1

/200

1

04/1

/200

1

05/1

/200

1

06/1

/200

1

07/1

/200

1

08/1

/200

1

09/1

/200

1

40

30

20

10

0

-10

-20

-30

-40

-50

-60

Dis

plac

emen

t, m

m

Date

RF1

RF2

W1

W2

sum

mer

fall

win

ter

spri

ng

sum

mer

fall

win

ter

spri

ng

sum

mer


RAINFALL AND TEMPERATURE

Date

08/1

/199

9

09/1

/199

9

10/1

/199

9

11/1

/199

9

12/1

/199

9

01/1

/200

0

02/1

/200

0

03/1

/200

0

04/1

/200

0

05/1

/200

0

06/1

/200

0

07/1

/200

0

08/1

/200

0

09/1

/200

0

10/1

/200

0

11/1

/200

0

12/1

/200

0

01/1

/200

1

02/1

/200

1

03/1

/200

1

04/1

/200

1

05/1

/200

1

06/1

/200

1

07/1

/200

1

08/1

/200

1

09/1

/200

1

Rai

nfal

l, m

m

7

6

5

4

3

2

1

0

Ave. Monthly TemperatureAve. Monthly Rainfall

Tem

perature, oC

35

30

25

20

15

10

5

0


WATER CONTENT VARIATION AND MOVEMENT

24

22

20

18

16

Wat

er C

onte

nt, %

Date

30

20

10

0

-10

-20

-30

-40

-50

Dis

plac

emen

t, m

m

Average Measured movements

Average Water content

06/1

/199

9

08/1

/199

9

10/1

/199

9

12/1

/199

9

02/1

/200

0

04/1

/200

0

06/1

/200

0

08/1

/200

0

10/1

/200

0

12/1

/200

0

02/1

/200

1

04/1

/200

1

06/1

/200

1

08/1

/200

1

10/1

/200

1

Average of 4 Footings at a sitein Arlington, Texas


60

40

20

0

−20

−40

−60

Dis

plac

emen

t, m

m

−100 0 100 200 300 400 500 600 700 800

Time, days

RF1+ RF2+ W1+ W24

Average Measured movements

Water Content Method

PREDICTED AND MEASURED MOVEMENTS

Average of 4 Footings at a sitein Arlington, Texas


HOUSES ON EXPANSIVECLAYS

MOST EXPENSIVENATURAL HAZARDIN THE COUNTRY


FOUNDATION SOLUTION

air gap

• Stiffened Slab on Grade

• Elevated Structural Slab on Piers

• Stiffened Slab on Grade & on Piers

• Thin Post Tensioned Slab


HOUSES ONEXPANSIVE

CLAYS

VERY DIFFICULT TO PREDICTTHE SOIL MOVEMENT

(WEATHER, VEGETATION, DRAINAGE)

MUCH EASIER TO DESIGNAN ADJUSTABLE FOUNDATION


SMART FOUNDATIONJ.L. Briaud, Texas A&M University

SMART FOUNDATION

52.5 ft(16 m)

13.1ft (4 m)

52.5 ft (16 m)

3.5 ft (1.1 m)

3.5 ft(1.1 m)

1ft(0.3 m)

1ft (0.3 m)

13.1ft (4 m)


SMART FOUNDATION CONSTRUCTION

Make Cavity Cast Footing & Place Spacer

Excavate Trench Cast Beam

Back Fill

Finish

1ft


COST COMPARISON

Conventional Waffle Slab 16 m ×××× 16 m ×××× 0.1 m Slab on Grade with 0.9 m deep ×××× 0.3 m thick Beams every 4 m $24,000

Smart Foundation 16 m ×××× 16 m ×××× 0.1 m Slab on Grade with 0.9 m deep ×××× 0.3 m thick Beams every 4 m and 1 m ××××1 m ××××0.3 m Footings $26,200

~ 10 % Increase in Cost


Shrinking Excavation Jack up

SMART FOUNDATION ADJUSTMENT

Front View of Jack up Replace Spacer Finish

Back Fill

1ft


FOUNDATION ANALYSIS BY SAFE

Edge drop case beam moment distribution


jacking

Edge drop case+ jacking

beam moment distribution

FOUNDATION ANALYSIS BY SAFEJ.L. Briaud, Texas A&M University

• FUNDAMENTAL BEHAVIOR

• SHRINK TEST – WATER CONTENT METHOD PROPOSED

• SHRINK TEST – WATER CONTENT METHOD VERIFIED

• SMART FOUNDATIONS = ADJUSTABLE SOLUTION

CONCLUSIONSJ.L. Briaud, Texas A&M University

Documents

by - Foundation PerformanceSwell Limit 8 to 15 % Near 100 % 4 -10 4-10 3 Shrinkage Limit Tension 6 -10 6-10 5 Air Dry Suction NO YES YES NO 0 0 7 -10 7-10 6 Oven Dry Shrink Swell Water