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Time Rate ofConsolidation

1D THEORY OF CONSOLIDATION TIME-INDEPENDENT ANALYSIS

LOG EFFECTIVE STRESS

VOID

RATIO

H =H*C

1 + eo

Log (2

1

)

Cr

1

Cc

1

PRECONSOLIDATIONPRESSURE( pc)

Rebound COMPRESSION INDEX

COMPRESSION INDEX

Primary Consolidation

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LOG TOTAL STRESS

VOID

RATIO

1D THEORY OF CONSOLIDATION TIME-DEPENDENTANALYSIS

UNDRAINED LOADING:

PORE PRESSURE GENERATION

NO CHANGE IN EFFECTIVE STRESSES

NO SETTLEMENT

INITIAL STRESS

FINAL STRESS

Primary Consolidation

LOG TOTAL STRESS

VOID

RATIO

1D THEORY OF CONSOLIDATION TIME-DEPENDENT ANALYSIS

DRAINED LOADING:

PORE PRESSURE DISSIPATION

INCREASE IN EFFECTIVE STRESSES

SETTLEMENT

INITIAL STRESS

FINAL STRESS

Primary Consolidation

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Terzaghis 1D Theory

Flow of Water under Stress

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Excess PWP Variation with Depth

clay

open

openz

Hdr

z=0 top open

z=1 middle

z=2 bottom open

Two way drainage

Excess PWP variation with Depth

clay

open

closedz

Hdr

z=0 top open

z=0.5 middle

z=1 bottom closed

One way drainage

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Excess PWP variation with Depth

Time Factors for constant

Excess pwp with depth

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Average Degree of Consolidation

Average Degree of Consolidation

wrt Time

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Excess pwp Distributions

dr

v

v

H

tCT

2=H Hdr=H/2

Hdr=HH

Open drainage

Open drainage

Open drainage

Closed drainage

1D Average Degree of Consolidation across

a layer

Time Factor Tv

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Oedometer Test

=P/A

Record for each stress

increment ():Change in height ofspecimen with time

t=0, ue=0%, t=

hw= /w

t=1, ue=100%

t=2, ue=50%

Determining Cvusing Log Time Method

dr

v

v

H

tCT

2=

50

2

50

2

50 2196.0

t

H

t

HTC

drV

v

==

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Determining Cv

using Root Time Method

dr

v

v

H

tCT

2=

90

2

90

2

90 2848.0

t

H

t

HTC

drV

v

==

Settlement Magnitude wrt Time

( )

c

timec

S

SU=

Sc(time)=U Sc

Where U is degree of consolidation

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How good are predictions

0

0.5

1

1.5

2

2.5

3

3.5

settlement(m)

1 10 100fill height (m)

ESTIMATED SETTLEMENT DURING CONSTRUCTIONVERSUS FILL HEIGHT

ESTIMATED

MEASURED

0

2

4

6

8

10

12

FillHeight,m

-20

0

20

40

60

80

100

01-Oct-00

30-Nov-00

29-Jan-01

30-Mar-01

29-May-01

28-Jul-01

26-Sep-01

25-Nov-01

24-Jan-02

Excess

P.

P.

kP

a

EB L-m W BL -m Pr ed ic ted

February 2001

August 2001

Time Rate Predictions