case histories and consolidation monitoring

CE 5101 Lecture 9 – Case CE 5101 Lecture 9 – Case Histories and Consolidation Histories and Consolidation

MonitoringMonitoring

OCT 2010

Prof Harry Tan

11

OutlineOutline

• Consolidation Monitoring Principles

• Case 1 – Muar Tests Embankments

• Case 2 – Bangkok 2nd International Airport

• Case 3 – German Housing Project

22

Objectives of Back AnalysisObjectives of Back Analysis• Calibrate the soil properties by matching

FEM predictions with field measurements for the embankment constructed to failure

• Study the effect of PVD installation on the stability and performance of the embankment constructed on PVD stabilized foundation soil using the calibrated soil properties

33

Introduction – Muar TestsIntroduction – Muar Tests

44

Site ConditionSite ConditionDepth, m+2.5m RL

Soil Description ρc (kPa) kh (m/sec)

+0.5 CrustYellowish brown mottled red CLAY with roots, 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 (<2%)

40 4x10-9

-15.2

Lower Clay

Grey CLAY with some shells, very thin discontinuous sand partings and some decaying organic matter (<2%)

60 1x10-9

Peat Dark brown PEAT with no smell

-15.9-19.9

Sandy Clay

Greyish brown sandy CLAY with a little decaying organic matter 60 2x10-9

SandDark grey, very silty medium to coarse SAND (SPT>20) - -

55

Site ConditionSite Condition

66

PVD PropertiesPVD Properties

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

Triangular Layout

77

Loading Characteristics for Loading Characteristics for Embankment Constructed Embankment Constructed

to Failureto Failure• Embankment constructed directly on the subsoil• Fill compacted in 0.2m layers at a nominal rate of 0.4m per week until failure occurred• Coupled consolidation analysis was performed

88

FEM Model of Embankment FEM Model of Embankment Constructed to FailureConstructed to Failure

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

99

Soil Properties Used In Soil Properties Used In FEM AnalysisFEM Analysis

Material RL (m)γsat

(kN/m3)c’

(kPa)Ø’ (o)

λ* κ*kh

(m/day)

kv

(m/day)ν

Upper Clay

+0.5 –-6.0

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

Lower Clay

-6.0 –-15.9

15.5 5 22 0.11 0.08 9.5E-5 6.0E-5 0.15

Soft Soil Model

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

1010


Material RL (m)γsat

(kN/m3)

γunsat

(kN/m3)c’

(kPa)

Ø’

(o)

E (kPa)

kh

(m/day)

kv

(m/day)ν

Fill - 20.5 20.5 19 26 5200 1.0 1.0 0.3

Crust+2.5 –+0.5

16.5 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

Mohr Coulomb Model

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

1111

Instrumentation Plan of Instrumentation Plan of Embankment Constructed Embankment Constructed

to Failureto Failure

Plan View Elevation View 1212

Excess Pore Pressure VariationExcess Pore Pressure Variation

0

2

4

6

8

10

0 1 2 3 4 5 6

Thickness of Fill (m)

Excess P

ore

wate

r P

ressure

(m

)

Field Measurement

FEM Prediction

Piezometer P2

0

1

2

3

0 1 2 3 4 5 6


Excess P

ore

wate

r P

ressure

(m

)

Field Measurement

FEM Prediction

Piezometer P7

1313


-13

-11

-9

-7

-5

-3

-1

1

3

0 2 4 6 8

Excess Porewater Pressure (m)

Reduced L

evel (m

)

Field Measurement

FEM Prediction

Fill Height = 3m

-13

-11

-9

-7

-5

-3

-1

1

3

0 2 4 6 8 10


Reduced L

evel (m

)

Field Measurement

FEM Prediction

Fill Height = 4m

-13

-11

-9

-7

-5

-3

-1

1

3

0 2 4 6 8 10 12


Reduced L

evel (m

)

Field Measurement

FEM Prediction

Fill Height = 5m

1414

Lateral DisplacementLateral Displacement

0

0.2

0.4

0.6

0 1 2 3 4 5 6


Late

ral D

ispla

cem

ent

(m)

Field Measurement

FEM Prediction

Inclinometer I3

-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)

Reduced L

eve

l (m

)

Field Measurement

FEM Prediction

At Failure Height

1515

Surface Settlement ProfileSurface Settlement Profile

-0.6

-0.4

-0.2

0

0.2

0 5 10 15 20 25 30 35

Distance from Centerline of Embankment (m)

Vert

ical M

ovem

ent

(m)

Field Measurement

FEM Prediction

Fill Height = 3m

-0.8

-0.6

-0.4

-0.2

0

0.2

0 5 10 15 20 25 30 35


Vert

ical M

ovem

ent

(m)

Field Measurement

FEM Prediction

Fill Height = 4m

-0.8

-0.6

-0.4

-0.2

0

0.2

0 5 10 15 20 25 30 35


Vert

ical M

ovem

ent

(m)

Field Measurement

FEM Prediction

Fill Height = 5m

1616

Actual Failure Mode of Actual Failure Mode of EmbankmentEmbankment

30m from toe

1717

FEM Predicted Failure Mode FEM Predicted Failure Mode of Embankmentof Embankment

30 m

Upper Clay

1818

Cross Section of Embankment on Cross Section of Embankment on PVD Stabilized Foundation SoilPVD Stabilized Foundation Soil

1919

Construction Sequence of Construction Sequence of Embankment on PVD Embankment on PVD

Stabilized Foundation SoilStabilized Foundation Soil

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

Coupled Consolidation Analysis was performed

2020

FEM Model of Embankment FEM Model of Embankment on PVD Stabilized Soilon PVD Stabilized Soil

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 constructed to failure. GWT at 1.75m below ground surface

2121

PVD Modeling Technique PVD Modeling Technique (Equivalent Vertical Permeability)(Equivalent Vertical Permeability)

w

h

r

h

q

kls

k

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 cell

dw = Diameter of drain

s =

w

s

d

d

ds = Diameter of smear zone

kh = Horizontal permeability of natural soil

kr = Horizontal permeability of smear zone

qw = Discharge capacity of PVD

kv = Vertical permeability of natural soil

Verified by Tay, E.L (2002)

2222

PVD Modeling TechniquePVD Modeling Technique

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) 0.07

de (m) 1.365

n 19.5

dm (m) 0.2

ds (m) 0.4

s 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

2323

Instrumentation Plan of Instrumentation Plan of Embankment on PVD Embankment on PVD

Stabilized SoilStabilized Soil

2424


0

1

2

3

4

5

6

7

8

0 50 100 150 200 250 300 350 400 450

Time (days)

Excess P

ore

wate

r P

ressure

(m

)

Field Measurement

FEM Prediction (PVD)

PFEM Prediction (W/O PVD)

Piezometer P2

0

1

2

3

4

5

6

7

8

0 50 100 150 200 250 300 350 400 450

Time (days)

Excess P

ore

wate

r P

ressure

(m

)

Field Measurement


FEM Prediction (W/O PVD)

Piezometer P3

0

1

2

3

4

5

6

7

8

9

0 50 100 150 200 250 300 350 400 450

Time (days)

Excess P

ore

wate

r P

ressure

(m

)

Field Measurement



Piezometer P6

2525

Ground Settlement at 23m From Ground Settlement at 23m From Centerline of EmbankmentCenterline of Embankment

-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)

Verical M

ovem

ent

(m)

Field Measurement



Ground Surface

-1

-0.8

-0.6

-0.4

-0.2

0

0 50 100 150 200 250 300 350 400 450

Time (days)

Vert

ical M

ovem

ent

(m)

Field Measurement


FEM Prediction (W/O PVD) 5.5m Below Ground Surface

2626

Surface Settlement ProfileSurface Settlement Profile

-0.6

-0.4

-0.2

0

0.2

0 10 20 30 40 50 60 70 80 90 100

Distance from centerline (m)

Verical M

ovem

ent

(m)

Field Measurement


FEM Prediction (W/O PVD)45 Days

-0.8

-0.6

-0.4

-0.2

0

0.2

0 10 20 30 40 50 60 70 80 90 100


Vert

ical M

ovem

ent

(m)

Field Measurement


FEM Prediction (W/O PVD) 105 Days-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


Vert

ical M

ovem

ent

(m)

Field Measurement



413 Days

2727

1.4

1.5

1.6

1.7

1.8

1.9

2

2.1

2.2

0 50 100 150 200 250 300 350 400

Time Elapsed (days)

Fact

or

of

Safe

ty

With PVD Installation

Without PVD Installation

Factor of SafetyFactor of Safety

Height of Fill = 2.57 m

Height of Fill = 4.74 m

2828

Located at Nong Ngu Hao in the Central Plain of Thailand

Project area 8 km by 4 km

situated 25 km east of Bangkok Metropolis

Soft clay strata with low strength and high

compressibility

Case 2 – 2nd Bangkok International Airport

2929

Weathered Clay

Very Soft Clay

Soft Clay

Medium Clay

Stiff Clay

Dense Sand

3030

TEST EMBANKMENT TS3

3131

CONSTRUCTION SEQUENCE

3232

Conditions for analysis

Vertical closed consolidation boundary conditions were set at centre of

embankment and 60.0 m from centre of embankment

Open consolidation boundary conditions were set at ground surface and sand

layer at 22 m below stiff clay layer

3333

Conditions for analysis

Soft soil model is used for clay layers

Mohr-Coulomb model is used for embankment

PVD installation effects not modeled, PVD “wished-in-place”, followed by

stage construction of embankment

3434

Method 1 – Using interface element

Equivalent horizontal permeability of soils, khpl, calculated

Different kh/ks ratio determined by the permeabilities 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

3535

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 the

accuracy of solution

FINITE ELEMENT MESH (METHOD 1)

3636

-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)

Se

ttle

me

nt

(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

3737

-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)

Se

ttle

me

nt

(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

3838

-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)

Se

ttle

me

nt

(m)


Method 2

SETTLEMENT GRAPHS

Method 2 - Using Equivalent Vertical Permeability


3939

-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)

Se

ttle

me

nt

(m)


Method 2

SETTLEMENT GRAPHS

Method 2 - Using Equivalent Vertical Permeability


4040

-2

-1.6

-1.2

-0.8

-0.4

0

0 100 200 300 400 500

Time (day)

Se

ttle

me

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


4141

-2

-1.6

-1.2

-0.8

-0.4

0

0 50 100 150 200 250 300 350 400 450 500

Time (day)

Se

ttle

me

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


4242

From the comparisons of settlements predictions:

Difference in the 2 methods is large when consider smear effects only, but for realistic conditions of drain smearing and well resistance , difference is smaller

Difference between the two methods gets larger with increasing depths of

settlement measurements

4343

0

5

10

15

20

25

30

35

40

0 100 200 300 400 500Time (day)

Ex

ce

ss

Po

re P

res

su

re (

kN

/m2 )

Method 1 (center of embankment, 8 m)

Method 2 (center of embankment, 8 m)

EXCESS PORE PRESSURE

4444

ConclusionConclusion• Coupled consolidation in FEM can predict the

excess pore pressure and settlement variation reasonably well

• PVD stabilized foundation soil showed efficient drainage allowing for faster embankment construction

• Loading rate of embankment on PVD stabilized foundation can be much faster but is dependent on efficacy of PVD to accelerate consolidation

4545

Case Study:Case Study:Back Analysis of Back Analysis of

Reinforced Soil Knolls Reinforced Soil Knolls at Pulau Tekongat Pulau Tekong

4646

Objectives of Back AnalysisObjectives of Back Analysis• Calibrate the soil and drain properties by

matching FEM results with field measurements• Illustrate the need for finite strain analysis in

cases where there is relatively large displacement as compared to thickness of fill

• Identify the collapse mechanism involved• Study the performance of the reinforcements

and PVD proposed in the original knoll design• Proposed possible changes to original design

which may prevent future failure

4747

IntroductionIntroduction

Elevation view of a Typical Knoll

Zone A50 m

Zone C35 m

Zone B 25 m

Zone B 25 m

Zone C 35 m

Reinforced Knoll

Sand Blanket

Geosynthetic Reinforcements

4848

Failure of Knoll D8

4949

Site Condition of Knoll D8Site Condition of Knoll D8• Soil profile varied significantly• Obtained from CPTs results and Soil Classification Chart

After Robertson and Campanella (1983)

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

5050

Properties of Geosynthetic Properties of Geosynthetic ReinforcementsReinforcements

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

5151

Properties of PVDProperties of PVD

ZoneDrainage Length (m)

Drain Spacing (m)

Equivalent Diameter (m)

Influence Zone Diameter

(m)

Smeared Zone Diameter (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

Equivalent Vertical Permeability was used to model PVD stabilized foundation soil

5252

Loading Characteristics of Loading Characteristics of Knoll D8Knoll D8

0.0

3.5

7.0

10.5

14.0

0 100 200 300 400 500 600

Time (Days)

Heig

ht

of

Knoll

(m)

Coupled Consolidation and Updated Mesh with Pore Pressure Analysis was performed

5353

FEM Model of Knoll D8FEM Model of Knoll D8

Fill (40 Layers)

Sand

Counter Balance

Soft Clay (OCR = 1.2)

Stiff Clay

60 m

Sand Blanket

5 m

50 m 25 m35 m

GWT at 1m below ground surface

25 m 35 m 60 m

10 m 10 m

5454


Materialγsat

(kN/m3)

γunsat

(kN/m3)c’

(kPa)Ø’ (o)

E (kPa)

kh

(m/day)

kv

(m/day)ν

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

Sand Blanket

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

Mohr Coulomb ModelSoft Soil Model

Reference from Tay (2002)

Materialγsat

(kN/m3)

γunsat

(kN/m3)c’

(kPa)Ø’ (o)

λ* κ*kh

(m/day)

kv

(m/day)ν ur

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

5555

Instrumentation Plan of Instrumentation Plan of Knoll D8Knoll D8

5656


0.00

20.00

40.00

60.00

80.00

100.00

0 50 100 150 200 250 300 350

Time (Days)

Excess P

ore

Pre

ssure

(kP

a)

Field Measurement

FEM Prediction

Piezometer PP1

0

5

10

15

20

25

30

35

0.00 50.00 100.00 150.00 200.00 250.00 300.00

Time (Days)

Excess P

ore

Pre

ssure

(kP

a)

Field Measurement

FEM Prediction

Piezometer PP3

5757

Surface Settlement ProfilesSurface Settlement Profiles

-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)

Sett

lem

ent

(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)

Sett

lem

ent

(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)

Sett

lem

ent

(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)

Sett

lem

ent

(m)

Field Measurement

FEM Prediction

SP1

SP7

SP3

SP5

5858

FEM Predicted Failure Mode FEM Predicted Failure Mode of Knoll D8of Knoll D8

Soft Clay

5959

Parametric StudyParametric Study• Side slope reinforcements were ignored

• Half geometry was modeled

• Influence of the strength and stiffness of basal reinforcement on the allowable rate of loading

• Comparison between the allowable rate of loading for partial penetration of PVD and full penetration of PVD through the soft clay layer

• Soil properties were based on Knoll D8

• Coupled consolidation and Updated mesh with pore pressure anaylsis was performed

6060

FEM Model Used For FEM Model Used For Parametric StudyParametric Study

Knoll Fill

(0.5m per layer)

Partial Penetration

of PVD

10 – 15 m

25 m 60 m35 m25 m

6161

FEM Model Used For FEM Model Used For Parametric StudyParametric Study

Knoll Fill

(0.5m per layer)

Full Penetration

of PVD

10 – 15 m

25 m 25 m

6262

Validation of AssumptionsValidation of Assumptions

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)

Ave

rage L

oadin

g R

ate

(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

Partial penetration of PVD and 50 kN/m Basal geogrid

6363

Allowable Average Loading Rate Allowable Average Loading Rate (m/wk) v.s Height of Knoll (m)(m/wk) v.s Height of Knoll (m)

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)

Ave

rage L

oadin

g R

ate

(m

/wk)




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


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

50 kN/m Basal Geogrid

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)

Ave

rage L

oadin

g R

ate

(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)

Ave

rage L

oadin

g R

ate

(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

rage L

oadin

g R

ate

(m

/wk)








6464

Allowable Average Loading Rate Allowable Average Loading Rate (m/wk) v.s Height of Knoll (m)(m/wk) v.s Height of Knoll (m)

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)

Ave

rage

Lo

ad

ing

Ra

te (

m/w

k)






(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)

Ave

rage

Lo

ad

ing R

ate

(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)

Ave

rage

Lo

ad

ing

Ra

te (

m/w

k)








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

rage

Lo

ad

ing

Ra

te (

m/w

k)








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Velocity Field at FailureVelocity Field at Failure

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

6666

Tensile Force Distribution of Basal Tensile Force Distribution of Basal Reinforcement at FailureReinforcement at Failure

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

49 kN/m 50 kN/m

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Influence of Basal Influence of Basal ReinforcementReinforcement

Strength of Geogrid (kN/m)Depth of Soft 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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ConclusionConclusion

• Coupled consolidation and Updated mesh with pore pressure analysis is efficient in predicting the behaviour of large embankment

• Fully penetrated PVD can significantly increase the stability of an embankment as compared to partially penetrated PVD

• Weak and low stiffness basal reinforcement has minimal effect on the stability of an embankment

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Overall ConclusionOverall Conclusion

• PVD and basal reinforcement can significantly increase the stability of an embankment if they are properly designed

• When the displacement of the embankment is relatively large as compared to the height of fill, finite strain analysis is necessary in order to obtain reasonable results

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case histories and consolidation monitoring

Documents

failure embankment

lower clay ocr

mupper clay

mfill height

layerscrustupper clay

presentfem model of

cross section of embankment

calibrated soil properties