CE5101 Lecture 9 - Case Histories and Consolidation Monitoring (OCT 2013) [Compatibility Mode]

8/14/2019 CE5101 Lecture 9 - Case Histories and Consolidation Monitoring (OCT 2013) [Compatibility Mode]

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5101 9 5101 9 5101 9 5101 9

201

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1

2 2

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Depth, m

+2.5m RLSoil Description c (kPa) kh (m/sec)

+0.5 CrustYellowish brown mottled red CLAY withroots, root holes and laterite concretions

110 -

-5.6

Upper

Clay

Light greenish grey CLAY with a few shells,very thin discontinuous sand partings,occasional near vertical roots and somedecaying organic matter (


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6


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Drainage

Length, l

(m)

Drain

Spacing, s

(m)

Equivalent

Diameter, dw

(m)

Influence Zone

Diameter, de

(m)

Smeared Zone

Diameter, ds

(m)

18.0 1.3 0.07 1.365 0.4

7

Triangular Layout


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8

Embankment constructed directly on thesubsoil

Fill compacted in 0.2m layers at a nominalrate of 0.4m per week until failure occurred

Coupled consolidation analysis was

performed


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9

Fill(15 Layers)

Crust

Upper Clay (OCR = 1.2)

Lower Clay (OCR = 1.2)

Sandy Clay

80 m

20 m2 m

6.4 m

10 m

4.1 m

GWT at 1.75m below

ground surface


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Material RL (m) sat(kN/m3)

c

(kPa)

(o) * *

kh(m/day)

kv(m/day)

UpperClay

+0.5 -6.0

15.5 1 20 0.13 0.05 1.3E-4 6.9E-5 0.15

Lower

Clay

-6.0

-15.915.5 5 22 0.11 0.08 9.5E-5 6.0E-5 0.15

10

Soft Soil Model

References include A.S. Balasubramaniam (1994) & B. Indraratna (2000)


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Material RL (m) sat(kN/m3)

unsat(kN/m3)

c

(kPa)

(o)

E

(kPa)

kh(m/day)

kv(m/day)

Fill - 20.5 20.5 19 26 5200 1.0 1.0 0.3

Crust+2.5

+0.516.5 14.5 20 26 14000 1.3E-4 6.9E-5 0.3

Sandy

Clay

-15.9

-20.0

16.0 16.0 10 22 2500 9.5E-5 6.0E-5 0.3

11

Mohr Coulomb Model

References include A.S. Balasubramaniam (1994) & B. Indraratna (2000)


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12Plan View Elevation View


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0

2

4

6

8

10

0 1 2 3 4 5 6

Thickness of Fill (m)

ExcessPorew

aterPressure(m)

Field Measurement

FEM Prediction

0

1

2

3

0 1 2 3 4 5 6


ExcessPorewaterPressure(m)

Field Measurement

FEM Prediction

13

Piezometer P2Piezometer P7


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-13

-11

-9

-7

-5

-3

-1

1

3

0 2 4 6 8

Excess Porewater Pressure (m)

ReducedLevel(m)

Field Measurement

FEM Prediction

-13

-11

-9

-7

-5

-3

-1

1

3

0 2 4 6 8 10


Reduce

dLevel(m)

Field Measurement

FEM Prediction

-13

-11

-9

-7

-5

-3

-1

1

3

0 2 4 6 8 10 12


Reduce

dLevel(m)

Field Measurement

FEM Prediction

14

Fill Height = 3mFill Height = 4mFill Height = 5m


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0

0.2

0.4

0.6

0 1 2 3 4 5 6


LateralDisplacement(m)

Field Measurement

FEM Prediction

-13

-11

-9

-7

-5

-3

-1

1

3

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

Lateral Movement (m)

Reduce

dLevel(m)

Field Measurement

FEM Prediction

15

Inclinometer I3

At Failure Height


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-0.6

-0.4

-0.2

0

0.2

0 5 10 15 20 25 30 35

Distance from Centerline of Embankment (m)

Vertical

Movement(m)

Field Measurement

FEM Prediction

-0.8

-0.6

-0.4

-0.2

0

0.2

0 5 10 15 20 25 30 35


VerticalMovement(m)

Field Measurement

FEM Prediction

-0.8

-0.6

-0.4

-0.2

0

0.2

0 5 10 15 20 25 30 35


VerticalM

ovement(m)

Field Measurement

FEM Prediction

16

Fill Height = 3mFill Height = 4mFill Height = 5m


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17

30m fromtoe


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18

30 m

Upper Clay


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StageFill Periods

(Days)

Fill Thickness

(m)

Rate of Filling

(m/day)

Rest Period

(days)

1 1 - 14 0.0 2.57 0.18 14 105

2 105 - 129 2.57 4.74 0.09 129 - present

20

Coupled Consolidation Analysis was performed


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135 m

FillCrust

Upper Clay (OCR = 1.2)

Lower Clay (OCR = 1.2)

Sandy Clay

PVD Stabilized

Zone

2 m

6.4 m

10 m

4.1 m

36 m

20 m

43 m

Soil Parameters were the same as

that of the embankment constructedto failure. GWT at 1.75m belowground surface


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(

)

22

w

h

r

h

q

klsk

k

s

n

3

2

4

3)ln()ln(

2

++= vv

h

e

ve kk

k

D

lk )

5.21( 2

2

+=

where l = Drainage lengthn =

w

e

d

d

de = Diameter of unit celldw = Diameter of drains =

w

s

d

d

ds = Diameter of smear zonekh = Horizontal permeability of natural soilkr = Horizontal permeability of smear zoneqw = Discharge capacity of PVDkv = Vertical permeability of natural soil

Verified by Tay, E.L

(2002)


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23

r

h

k

k

General

5 12 12

Spacing (m) 1.3

H(m) 18

Configuration Triangular

Axisymmetric

Radial Flow

Material Crust Upper Clay Lower Clay

kv (m/day) 6.9E-5 6.9E-5 6.0E-5

qw (m3/yr) 100

dw (m) 0.07de (m) 1.365

n 19.5

dm (m) 0.2

ds (m) 0.4s 5.714

Equivalent

Flow

Material Crust Upper Clay Lower Clay

kve (m/day) 5.99E-3 2.66E-3 1.97E-3

qw (m3/yr) 100

kh/ kr


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0

1

2

3

4

5

6

7

8

0 50 100 150 200 250 300 350 400 450

Time (days)

ExcessPorewa

terPressure(m)

Field Measurement

FEM Prediction (PVD)

PFEM Prediction (W/O PVD)

0

1

2

3

4

5

6

7

8

0 50 100 150 200 250 300 350 400 450

Time (days)

ExcessPorewa

terPressure(m)

Field Measurement


FEM Prediction (W/O PVD)

0

1

2

3

4

5

6

7

8

9

0 50 100 150 200 250 300 350 400 450

Time (days)

ExcessPorewaterPressure(m)

Field Measurement



25

Piezometer P2

Piezometer P3

Piezometer P6


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-1.4

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0

0 50 100 150 200 250 300 350 400 450

Time (days)

VericalMovement(m)

Field Measurement



-1

-0.8

-0.6

-0.4

-0.2

0

0 50 100 150 200 250 300 350 400 450

Time (days)

VerticalMovement(m)

Field Measurement



26

Ground Surface

5.5m Below Ground Surface


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-0.6

-0.4

-0.2

0

0.2

0 10 20 30 40 50 60 70 80 90 100

Distance from centerline (m)

VericalM

ovement(m)

Field Measurement



-0.8

-0.6

-0.4

-0.2

0

0.2

0 10 20 30 40 50 60 70 80 90 100


VerticalMo

vement(m)

Field Measurement



-1.4

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0 10 20 30 40 50 60 70 80 90 100


VerticalMo

vement(m)

Field Measurement



27

45 Days

105 Days

413 Days


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Located at Nong

Ngu Hao in theCentral Plain of

Thailand

Project area 8

km by 4 km

situated 25 km

east of Bangkok

MetropolisSoft clay strata

with low strength

and high

compressibility

Case 2 2nd BangkokInternational Airport

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Weathered Clay

Very Soft Clay

Soft Clay

Medium Clay

Stiff Clay

Dense Sand

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TEST EMBANKMENT TS3

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CONSTRUCTION SEQUENCE

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Conditions for analysis

Vertical closed consolidation boundary

conditions were set at centre of

embankment and 60.0 m from centre of

embankmentOpen consolidation boundary conditions

were set at ground surface and sand

layer at 22 m below stiff clay layer

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Method 1 Using interface element

Equivalent horizontal permeability of

soils, khpl, calculated

Different kh/ks ratio determined by thepermeabilities of different soil layers to

match instrumentation data

Method 2 Using an equivalent vertical

permeability

Treated as one-way drainage

Drainage length taken to be the length

of the vertical drain 35

FINITE ELEMENT MESH (METHOD 1)


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Analysis

Number of elements used for method 1

was 1268 and 1117 for method 2

Each element has 6 nodes and 3 stress

points

Line refinement used at improved zone

by vertical drains to increase theaccuracy of solution

FINITE ELEMENT MESH (METHOD 1)

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-1.8

-1.6

-1.4

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0

0 50 100 150 200 250 300 350 400 450 500

Time (day)

Settlement(m)

FEM (0-8m)

FEM (0-12m)

FEM (0-16m)

Measured (0-8m)

Measured (0-12m)

Measured (0-16m)

Method 1

SETTLEMENT GRAPHS

Method 1 - Using Interface Element as Vertical Drains

Consider Smear Effects Only

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-1.8

-1.6

-1.4

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0

0 50 100 150 200 250 300 350 400 450 500

Time (day)

Settlement(m

)

FEM (0-8m)

FEM (0-12m)

FEM (0-16m)

Measured (0-8m)

Measured (0-12m)

Measured (0-16m)

Method 1

SETTLEMENT GRAPHS

Method 1 - Using Interface Element as Vertical Drains

Consider Smear Effects and Well Resistance

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-2

-1.8

-1.6

-1.4

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0

0 50 100 150 200 250 300 350 400 450 500

Time (day)

Settlement(m

)

FEM (0-8m)

FEM (0-12m)

FEM (0-16m)

Measured (0-8m)

Measured (0-12m)

Measured (0-16m)

Method 2

SETTLEMENT GRAPHS

Method 2 - Using Equivalent Vertical Permeability


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-2

-1.8

-1.6

-1.4

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0

0 50 100 150 200 250 300 350 400 450 500

Time (day)

Settlement(m

)

FEM (0-8m)

FEM (0-12m)

FEM (0-16m)Measured (0-8m)

Measured (0-12m)

Measured (0-16m)

Method 2

SETTLEMENT GRAPHS

Method 2 - Using Equivalent Vertical Permeability

Consider Smear Effects and Well Resistance

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-2

-1.6

-1.2

-0.8

-0.4

0

0 100 200 300 400 500

Time (day)

Settleme

nt(m)

0-8 m (Method 1)

0-12 m (Method 1)

0-16 m (Method 1)

0-8 m (Method 2)

0-12 m (Method 2)

0-16 m (Method 2)

SETTLEMENT GRAPHS


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From the comparisons of settlementspredictions:

Difference in the 2 methods is large

when consider smear effects only, but forrealistic conditions of drain smearingand well resistance , difference is smaller

Difference between the two methods getslarger with increasing depths of

settlement measurements

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0

5

10

15

20

25

30

35

40

0 100 200 300 400 500

Time (day)

ExcessPorePre

ssure(kN/m2)

Method 1 (center of embankment, 8 m)

Method 2 (center of embankment, 8 m)

EXCESS PORE PRESSURE

44


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:

46


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Elevation view of a Typical Knoll

Zone A50 m

Zone C35 m

Zone B25 m

Zone B25 m

Zone C35 m

Reinforced Knoll

Sand Blanket

Geosynthetic Reinforcements

F il f K ll D8


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49

Failure of Knoll D8


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8

0

5

10

15

20

25

-145 -116 -87 -58 -29 0 29 58 87 116 145

Distance From Centerline (m)

Depth(m)

D8AL

SOFT CLAY

D8AR

STIFF CLAY

SAND

D8AC

50

Soil profile variedsignificantly

Obtained from CPTsresults and SoilClassification Chart

After Robertson and Campanella (1983)


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Type of Reinforcement Tensile Strength (kN/m) Elongation at Failure (%)

Rock G55/30

(Basal Reinforcement)50 10

PEC 50 (Side

Slope Reinforcement)50 10

TS 80 (Side

Slope Reinforcement) 30 10

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Zone DrainageLength (m)

DrainSpacing (m)

EquivalentDiameter (m)

InfluenceZone Diameter

(m)

Smeared ZoneDiameter (m)

A 15.0 1.25 0.0659 1.413 0.25

B 10.0 1.50 0.0659 1.695 0.25

C 5.0 1.50 0.0659 1.695 0.25

52

Equivalent Vertical Permeability was used to modelPVD stabilized foundation soil


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8

0.0

3.5

7.0

10.5

14.0

0 100 200 300 400 500 600

Time (Days)

HeightofKnoll(m)

53

Coupled Consolidation and Updated Mesh withPore Pressure Analysis was performed


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8

54

Fill (40 Layers)

Sand

CounterBalance

Soft Clay (OCR = 1.2)

Stiff Clay

60 m

SandBlanket

5 m

50 m25 m35 m

GWT at 1m below

ground surface

25 m 35 m 60 m

10 m 10 m


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Material sat(kN/m3)

unsat(kN/m3)

c(kPa)

(o)

E(kPa)

kh(m/day)

kv(m/day)

Backfill 22 22 3 30 7000 8.64E-2 8.64E-2 0.3

SandBlanket

22 22 6 30 7000 8.64E-1 8.64E-1 0.3

Sand 19 17 1 30 10000 8.64E-3 8.64E-3 0.3

Stiff Clay 20 18 15 30 10000 1.73E-3 8.64E-4 0.3

Material sat(kN/m3)

unsat(kN/m3)

c

(kPa)

(o) * *

kh(m/day)

kv(m/day)

ur

Soft Clay 16 16 1 16 0.187 0.019 3.46E-4 8.64E-5 0.15

55

Mohr Coulomb ModelSoft Soil Model

Reference from Tay (2002)


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-0.050

0.000

0.050

0.100

0.150

0.200

0.250

0.300

140 190 240 290 340 390 440 490 540

Time (Days)

Settlement(m)

Field Measurement

FEM Prediction

-0.200

0.000

0.200

0.400

0.600

0.800

1.000

1.200

200 250 300 350 400 450 500 550

Time (Days)

Settle

ment(m)

Field Measurement

FEM Prediction

-2.500

-2.000

-1.500

-1.000

-0.500

0.000

140 190 240 290 340 390 440 490 540

Time (Days)

Se

ttlement(m)

Field Measurement

FEM Prediction

-2.500

-2.000

-1.500

-1.000

-0.500

0.000

140 190 240 290 340 390 440 490 540

Time (Days)

Settlement(m)

Field Measurement

FEM Prediction

58

SP1

SP7

SP3

SP5


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8

59

Soft Clay


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60

Side slope reinforcements were ignored

Half geometry was modeled

Influence of the strength and stiffness of basalreinforcement on the allowable rate of loading

Comparison between the allowable rate of

loading for partial penetration of PVD and fullpenetration of PVD through the soft clay layer

Soil properties were based on Knoll D8

Coupled consolidation and Updated mesh withpore pressure anaylsis was performed


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Knoll Fill

(0.5m per layer)

Partial Penetration

of PVD

10 15 m

25 m 60 m35 m25 m


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62

Knoll Fill

(0.5m per layer)

Full Penetration

of PVD

10 15 m

25 m 25 m


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0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

4 6 8 10 12 14 16 18 20

Height of Knoll (m)

AverageLoadingRate(m/wk)

(1) Partial Penetration: Depth of Clay = 20m



Knoll 7 (Depth of Clay = 15m): Point of Failure



Knoll 12 (Depth of Clay = 10m): Point of Completion

63

Partial penetration of PVD and 50 kN/m Basal geogrid

(/) .


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()

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

4 6 8 10 12 14 16 18 20

Height of Knoll (m)





(4) Full Penetration: Depth of Clay = 20m


(6) Full Penentration: Depth of Clay = 10m

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

4 6 8 10 12 14 16 18 20

Height of Knoll (m)

Average

LoadingRate(m/wk)

(1) Patial Penetration: Depth of Clay = 20m






0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

6 8 10 12 14 16 18 20

Height of Knoll (m)

AverageL

oadingRate(m/wk)



(3) Partial Penetration: Depth of Clay = 10m(4) Full Penetration: Depth of Clay = 20m



0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

6 8 10 12 14 16 18 20

Height of Knoll (m)

Average

LoadingRate(m/wk)







64

50 kN/m Basal Geogrid100 kN/m Basal Geogrid150 kN/m Basal Geogrid200 kN/m Basal Geogrid

(/) .


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()

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

4 6 8 10 12 14 16 18 20

Height of Knoll (m)







(6) Full Penentration: Depth of Clay = 10m

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

4 6 8 10 12 14 16 18 20

Height of Knoll (m)

AverageLoadingRa

te(m/wk)

(1) Patial Penetration: Depth of Clay = 20m






0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

6 8 10 12 14 16 18 20

Height of Knoll (m)

Aver

ageLoadingRate(m/wk)







0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

6 8 10 12 14 16 18 20

Height of Knoll (m)

Ave

rageLoadingRate(m/wk)







65

50 kN/m Basal Geogrid 100 kN/m Basal Geogrid

150 kN/m Basal Geogrid 200 kN/m Basal Geogrid


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Depth of Soft Clay = 10 m Depth of Soft Clay = 20 m

49 kN/m 50 kN/m


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Strength of Geogrid

(kN/m)

Depth ofSoft Clay (m)

50 100 150 200

10 5.7m 7.2m 10.7m 17m

15 5.7m 6.9m 7.7m 8.5m

20 5.8m 6.7m 7.2m 7.3m

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Documents

CE5101 Lecture 9 - Case Histories and Consolidation Monitoring (OCT 2013) [Compatibility Mode]