Performance Evaluation of Shock Mats and Synthetic Grids ... · PDF fileTest data for crushed basalt (Indraratna and Salim 2001) -6.0-8.0 50 kPa ... The minimum and maximum aperture

Second International Conference on Transportation Geotechnics

10 - 12 September 2012 | Hokkaido University, Sapporo, JAPAN

Second International Conference on Transportation Geotechnics

10 - 12 September 2012 | Hokkaido University, Sapporo, JAPAN

Performance Evaluation of Shock Mats Performance Evaluation of Shock Mats and Synthetic Grids in the Improvement and Synthetic Grids in the Improvement

of Rail Ballastof Rail Ballastof Rail Ballastof Rail Ballast

P fP f B ddhiB ddhi I d tI d tProf. Prof. BuddhimaBuddhima IndraratnaIndraratnaProfessor of Civil Engineering & Research Director,Centre for Geomechanics and Railway engineering

ARC Centre of Excellence in Geotechnical Sciences and EngineeringUniversity of Wollongong, NSW 2522 Australia

Sanjay NimbalkarResearch Fellow, ARC Centre of Excellence,

Centre for Geomechanics and Railway engineering

Cholachat RujikiatkamjornSenior Lecturer, School of Civil, Mining & Environmental Engineering

Centre for Geomechanics and Railway engineeringCentre for Geomechanics and Railway engineeringUniversity of Wollongong, NSW 2522 Australia

Centre for Geomechanics and Railway engineeringUniversity of Wollongong, NSW 2522 Australia

ContentsContents

Introduction Introduction

Effect of Confining Pressure on Particle Degradationg g

Ballast Breakage and Impact Loads

Ballast Fouling and Improvement using Geogrids

From Theory to Practice: Bulli and Singleton Tracks

Finite Element Analyses of Rail Tracks

Conclusions

Problems in Rail Track SubstructureProblems in Rail Track Substructure

Foundation soil liquefactionBallast CrushingBallast Crushing Foundation soil liquefaction

Poor DrainagePoor Drainage

Coal fouling

Track Buckling

Differential settlement

Queensland FloodingQueensland FloodingSuiker, 2002Suiker, 2002

LargeLarge--scale Cyclic Triaxial Rigs Built at UoWscale Cyclic Triaxial Rigs Built at UoW

Prismoidal Triaxial Rig to Simulate a Track SectionSimulate a Track Section(Specimen: 800x600x600 mm)

Cylindrical Triaxial EquipmentCylindrical Triaxial Equipment(Specimen: 300 mm dia.x600 mm high)

Effect of Confining Pressure on Strain Behaviour of BallastI d t L k b d Ch i ti (2005) G t h iIndraratna, Lackenby and Christie (2005), Geotechnique

Cyclic LoadingMonotonic Loading

1

-2

-3-4

n (%

)

qmax = 500 kPa

-10

-12

-14-16

n (%

) 1 kPa8 kPa15 kPa30 kPa

90 kPa120 kPa240 kPa

3

2

10

-1

met

ric S

train

3

compressiondilation

-4

-6

-8

met

ric S

trai

60 kPa

6

543

Vol

um 3 kPa10 kPa20 kPa30 kPa45 kPa

60 kPa90 kPa120 kPa180 kPa240 kPa4

20

-2V

olum dilation

compression

0 5 10 15 20 25 30 35Axial Strain (%)

60 5 10 15 20 25

Axial Strain (%)

P k f i i l f f h b ll

60

Peak friction angle, p, of fresh ballast

Dilatancy (+)

48

52

56

le,

(de

gree

)

Angl

e

()

Dilation

p

(-) CompressionParticle breakage

f (excludes particle breakage and dilatancy)

40

44

48

Fric

tion

angl

Fric

tion

A fb (includes breakage but excludes dilatancy)

Compression

44

0 100 200 300 400Effective confining pressure (kPa)

360 50 100 150 200 250

Confining Pressure (kPa)

f (excludes particle breakage and dilatancy)

Effect of Confining Pressure on Particle Degradation (Cyclic Loading)( y g)

1d95iA ABBI

0.06qmax = 500 kPa

0.06qmax = 500 kPa

0.06qmax = 500 kPa

ng m brea

kageB BA

ABBI

2 36 = smallest sieve sizePSD = particle size distribution

dmax

0 04ex, B

BI

qmax 500 kPaqmax = 230 kPa

0 04ex, B

BI

qmax 500 kPaqmax = 230 kPa

0 04ex, B

BI

qmax 500 kPaqmax = 230 kPa

ne

mum

ra

datio

n Zo

ne

on P

assi

n

ary o

f max

imum2.36 = smallest sieve size

d95i = d95 of largest sieve size

0.04

eaka

ge In

de 0.04

eaka

ge In

de 0.04

eaka

ge In

de

e D

ilatio

n Z

on

Opt

imD

egr

Frac

tio

bitra

ry bo

unda

ry

Shift in PSD caused by degradation

0.02

Bal

last

Bre Optimum Contact

0.02

Bal

last

Bre

0.02

Bal

last

Bre Optimum Contact

Uns

tabl

e

Compressive Stable

0

Initial PSD

Final PSD

Arb

0 50 100 150 200 250

0

B

(I) (II) (III)

0 50 100 150 200 250

0

B

(I) (II) (III)

0 50 100 150 200 250

0

B

(I) (II) (III)

Degradation Zone

Sieve Size (mm)0 2.36

0 63

Ballast Breakage Index (BBI)

0 50 100 150 200 250Effective Confining Pressure (kPa)

0 50 100 150 200 250Effective Confining Pressure (kPa)

0 50 100 150 200 250Effective Confining Pressure (kPa)

Ballast Breakage Index (BBI)

I d L k b d Ch i i (2005)Indraratna, Lackenby and Christie (2005) Geotechnique, ICE, UK. Vol. 55(4), 325-328

Increasing Confining Pressure using: Increasing Confining Pressure using: Intermittent Intermittent Lateral Restraints or Embedded Winged SleepersLateral Restraints or Embedded Winged SleepersLateral Restraints or Embedded Winged SleepersLateral Restraints or Embedded Winged Sleepers

Intermittent lateral Lateral restraintsrestraints Winged sleepers

Rail SleepersSleepers

Lackenby, Indraratna, McDowell and Christie (2007) Geotechnique, ICE, UK. Vol. 57(6), 527-536

Constitutive Constitutive ModellingModelling of Particle of Particle BreakageBreakage

Before Loading After LoadingA itVoids Asperity wear

New hairline micro-cracks

Sharp corners broken off

Ballast Broken particles fill voids (fouling)

broken off

voids (fouling)

Decreased DrainageDecreased Shear StrengthDecreased Shear Strength

Track Modelling Incorporating Ballast Breakage Track Modelling Incorporating Ballast Breakage ––Energy ApproachEnergy Approach

dEB = increment of energy consumption due to particle breakage

2 fd

12

sin1/

12

12

45tan11

2

1 fB

fv

d

ddE

ddd

pq

245tan1

31

32

245tan1

31

32 2

1

2

1

fvfv

ddp

ddp

Conventional theory

p = Effective mean stress

q = Distortional / deviator stressIndraratna and Salim (2002) Geotechnical Engineering,

f = basic friction angle

q = Distortional / deviator stress g g,ICE Proceedings, UK.

Model validationModel validationSalim & Indraratna (2004) Canadian Geotechnical Journal 41: 657-671Salim & Indraratna (2004) Canadian Geotechnical Journal, 41: 657-671

2000

a)

Test data for crushed basalt(Indraratna and Salim 2001) -6.0

-8.0

50 kPa

Test data for crushed basalt(Indraratna and Salim 2001)

1200

1600

ress

, q (

kPa

3 = 300 kPa

200 kP

Model prediction

-2.0

-4.0

ain,

v

(%) 3 = 50 kPa

100 kPa

Dilation

( )

Model prediction

800

stor

tiona

l str

100 kPa

200 kPa

50 kP 4 0

2.0

0.0

lum

etric

stra 100 kPa

200 kPa

0 0 5 0 10 0 15 0 20 0 25 00

400Dis 50 kPa

8.0

6.0

4.0

Vo 300 kPa

Contraction

Stress-Strain behaviour Volume Change Behaviour

0.0 5.0 10.0 15.0 20.0 25.0Distrortional strain, s (%)Deviatoric Strain, εs (%)

0.0 5.0 10.0 15.0 20.0 25.0Distrortional strain, s (%)Deviatoric Strain, εs (%)

*23912)(

)(

dMMpp

pp

d ics

io

cspM d l P t d t

**91212

M

pBM

ppeM

do

i

s Model Parameters need to be determined by large-

scale testing

MM

MpB

MMM

dd

ps

pv

*239*

*2399

Effect of High Impact Loads and Track DegradationEffect of High Impact Loads and Track DegradationSubgrade Ballast BreakageSubgrade

type Location of shock mat Ballast Breakage Index (BBI)

Without shock mat

Stiff - 0.170

Soft - 0.080

With Shock mat

Stiff Above ballast 0.145

Stiff Below ballast 0.129

Stiff Above & below ballast 0.091

Soft Above ballast 0.055Soft Above ballast 0.055

Soft Below ballast 0.056

Soft Above & below ballast 0.028

Shock Mat

Nimbalkar, Indraratna, Dash & Christie (2012). JGGE, ASCE, 138(3): 281-294

Recommended New Railway Ballast Grading

100

80

Recommended Grading80

g

Australian Standards (AS 2758.7)

60

Pass

ing

40% P

Cu = 2.2 - 2.6

20

0

Cu = 1.5 - 1.7

1 10 100Particle size (mm) 12

Role of Ballast Fouling on Track PerformanceRole of Ballast Fouling on Track Performance

Infiltration of coal

Slurried Clay infiltrationSlurried Clay infiltration

Void Contaminant Index (VCI) proposed by UOWeb = Void ratio of clean ballast

VCI =VCI =(1+e(1+eff))

ee ××GGs.bs.b

GG ××MMff

MM×× 100100

Void Contaminant Index (VCI) proposed by UOW ef = Void ratio of fouling materialGs-b = Specific gravity of clean ballastGs-f = Specific gravity of fouling

eebb GGs.fs.f MMbb Mb = Dry mass of clean ballastMf = Dry mass of fouling material

Ballast Fouling AssessmentBallast Fouling Assessment

40

50

%

coal-fouled ballast sand-fouled ballast

Fouling Index (FI)Selig and Waters (1994)

20

30

Foul

ing

Inde

x, % clay-fouled ballast

FI =FI = PP4.754.75 ++ PP0.0750.075P4.75 = Percentage (by weight) passing the 4.75 mm sieveP = Percentage (by weight) passing the 0 075 mm sieve

0

10

80

100

F

Percentage Void Contamination (PVC) F ld d Ni (2002)

P0.075 = Percentage (by weight) passing the 0.075 mm sieve

40

60

80

PVC

, %

PVC =PVC =VVff ×× 100100

Feldman and Nissen (2002)

0

20

100

VVvbvbVvf = Total volume of fouling material passing 9.5 mm sieveV = Initial voids volume of clean ballast

Void Contaminant Index (VCI) proposed by UOW 40

60

80

VC

I, %

Vvb = Initial voids volume of clean ballast

VCI =VCI =(1+e(1+eff))

ee××

GGs.bs.b

GG××

MMff

MM××100100

( ) p p y

0 5 10 15 20 250

20

P f li %eebb GGs.fs.f MMbbPercentage fouling, %

Impeded Drainage of Track due to Ballast FoulingImpeded Drainage of Track due to Ballast Fouling

10-1

100

Coal-fouled ballast: Experimental Coal-fouled ballast: Theoretical Sand-fouled ballast: ExperimentalS d f l d b ll t Th ti l/s

)

10-3

10-2 Sand-fouled ballast: Theoretical

tivity

, k (m

/

Bellambi Site VCI=33% Rockhampton Site

VCI=72%

10-5

10-4

Sydenham Site VCI=22%

ulic

Con

duct

hydraulic conductivity of coal fines

10-7

10-6

10

Hyd

rau hydraulic conductivity

of clayey fine sand

0 20 40 60 80 10010

Void Contaminant Index, VCI (%)

Large-scale permeability test apparatusVariation of hydraulic conductivity vs. Void Contaminant Index

T k I d t Ch l h t & Ni b lk (2011)

kb = Hydraulic conductivity of clean ballast

Hydraulic Conductivity (k) of fouled ballast

b fk kk

Tennakoon, Indraratna, Cholachat & Nimbalkar (2011) ASTM Geotechnical Testing Journal.

b y ykf = Hydraulic conductivity of fouling material

100f b f

k VCIk (k k )

Improvement of Fouled Ballast behaviour with Improvement of Fouled Ballast behaviour with GeogridsGeogrids

Large scale direct shear test apparatusLarge-scale direct shear test apparatus

Modelling Modelling GeogridGeogrid--reinforced Fouled Ballast under Shearing Loadsreinforced Fouled Ballast under Shearing Loads

Computer modeling using discrete element method

Use of Use of geogridgeogrid for improving fouled ballasted trackfor improving fouled ballasted trackIndraratna et al. (2011). Geotextiles & Geomembranes, 29: 313-322

2 52 5 With geogrid p

n

Without geogridp n n= 15kPa

2.52.5 With geogrid

stre

ss , Without geogrid

stre

ss , p n= 27kPa

n= 51kPa n=75kPa

Maintenance

2.02.0

eak

shea

r

ak s

hear

s n

1.51.5

mal

ised

pe

alis

ed p

ea

1.01.0

Convergencerapid reductionNom

) e)

Nom

a

0 20 40 60 80 100 0 20 40 60 80 100p p) e 0 20 40 60 80 100 0 20 40 60 80 100VCI (%) VCI (%)

App

Ap

Beyond a VCI of 70%, the shear strength approachesh f f li i l i lfthat of fouling material itself.

Optimum Optimum GeogridGeogrid Aperture Size Aperture Size Indraratna et al. (2011). ASTM Geotechnical Testing Journal, 35 (2): 1-8

Geogrids Used for Testing

Unreinforced

Geogridtype

Aperture shape

Aperture size (mm)

Tult(kN/m)

Mi A/DOptimum A/D50

M A/D

UnreinforcedG1 Square 38 38 30

G2 Triangle 36 19Min.A/D50 Max.A/D50

G3 Square 65 65 30

G4 R l 44 42 30G4 Rectangle 44 42 30

G5 Rectangle 36 24 30

G6 Square 33 33 40

G7 Rectangle 70 110 20

The minimum and maximum aperture sizes of geogrid required to optimize theh t th 0 95D d 2 50D ti l

A/D50G7 Rectangle 70 110 20

shear strength are 0.95D50 and 2.50D50 respectively.

The optimum aperture size of geogrid can be treated as 1.15-1.3D50

From Theory to Practice: From Theory to Practice: GeosyntheticsGeosynthetics in Bulli Trackin Bulli Track

Details of instrumented track

Section of ballasted track bed with geocomposite layer

Field Trial on Instrumented Track near WollongongField Trial on Instrumented Track near Wollongong

Geocomposite layer (geogrid+geotextile) before ballast placement 8 October 2006

Ballast placement over the geocomposite

Geotextile

Bonded GeogridRecycled Ballast

from Chullora Quarry, Sydney

Fresh BallastBombo Quarry, Wollongong

Field Instrumentation Field Instrumentation -- BulliBulli

S l Di l tSettlement pegs installed at ballast-capping interface

Displacement transducers installed at sleeper-ballast interface

Deformation Response of Ballast at Deformation Response of Ballast at BulliBulli TrackTrackIndraratna et al. (2010). JGGE, ASCE, 136(7): 907-917

Number of load cycles, N

00 1x105 2x105 3x105 4x105 5x105 6x105 7x105 8x105 9x105

0.00

Fresh Ballast (uniformly graded) Recycled Ballast (broadly graded)v) av

g (mm

)

g (%)

6

3

2.00

1.00y ( y g )

Fresh Ballast with Geocomposite Recycled Ballast with Geocomposite

of b

alla

st, (

S v

balla

st, ( 1) av

g

9 3.00

efor

mat

ion

o

al st

rain

of b

15

12

5.00

4.00

ge v

ertic

al d

e

erag

e ve

rtica

0 2 4 6 8 10 12 14 16 1818 6.00A

vera

g

Ave

time, t (months)

The recycled ballast performed well, and this is because, it was broadly gradedcompared to the relatively uniformly graded fresh ballast.

Use of Shock Mats & Use of Shock Mats & GeogridsGeogrids: Singleton Track (NSW): Singleton Track (NSW)

Geogrid layer placed above the capping

Settlement pegs placement in the track

Mudies Creek Bridge pressure cells installation Placing of shock mat on bridge deck, Feb. 2010

Use of Shock Mats & Geogrids in Practice: Singleton (NSW)Use of Shock Mats & Geogrids in Practice: Singleton (NSW)

Use of geosyntheticsg y

Use of Shock mat above bridge deck

Vertical Deformation of Ballast Layer

00 20 40 60 80 100

0

Time (days)

)

Silty-clay Deposit BallastBallast with Geogrid

6 2 t (%

)

last

(mm

) Ballast with GeogridHard Rock

Ballast Ballast with Geogrid

6 2

of B

alla

st

on o

f Bal

l Bridge Ballast with Shock Mat

12 4

al S

train

o

efor

mat

io

18 6

Ver

tica

Ver

tical

De

0.0 5.0x104 1.0x105 1.5x105 2.0x105 2.5x10524 8

V

Number of Load Cycles

Geogrids can decrease ballast deformations by as much as 30%.

y

Effectiveness of reinforcement increases on softer subgrades.

Finite Element Analysis of Bulli Track: 2D Plane Strain Finite Element Analysis of Bulli Track: 2D Plane Strain

900

1000Effective confining pressure 3

' = 50 kPa

600

700

800

900

' -' (k

Pa)

E50

1 asymptote

300

400

500

600

Stre

ss, q

=

0

100

200

Dev

iato

r

0 5 10 15 20 25

Axial Strain, a (%)

Track transverse section deformationTrack transverse section deformation

Track longitudinal section deformation Class A Prediction of Rail Embankment with Class A Prediction of Rail Embankment with Cyclic LoadingCyclic Loading Indraratna et al (2010) JGGE ASCE 136(5): 686 696Cyclic Loading Cyclic Loading Indraratna et al. (2010) JGGE, ASCE, 136(5): 686-696

80

Pa) No PVD

With PVDs @ 1 5m spacing

40

60

pres

sure

(kP With PVDs @ 1.5m spacing

20

40

xces

s po

re p

Very Soft Alluvial Clay

0 100 200 300 400 500Ti (d )

0

Ex

Soft Silty Clay

Time (days)

0 05

0 0 10 20 30 40 50La tera l displace ment (m)

0

0.1

0.05

men

t (m

) Field DataPrediction-Class A

8

-4

m) Reduction in

la tera l displacement

0.2

0.15

Set

tlem

-12

-8

Dep

th(m

F ie ld

la tera l displacement

0 100 200 300Time (days)

0.25

-20

-16 No PVDPVDs @ 1.5m spacing

ConclusionsConclusions

Provision of sufficient lateral confining pressure improves trackperformance and reduces the cost of maintenance.

Geosynthetics can increase the track confining pressure toy g preduce particle movement at high train speeds.

The optimum aperture size of geogrid can be treated as 1.15– The optimum aperture size of geogrid can be treated as 1.151.3D50. Geogrids could decrease ballast deformations by asmuch as 30%.

Shock mats can mitigate ballast degradation under impactloads.loads.

The field trials near Wollongong and Newcastle demonstrate theimplications of track deterioration and the advantages of trackimplications of track deterioration, and the advantages of trackmodernization using synthetic inclusions.

Australian Research Council (ARC)

AcknowledgmentAcknowledgment

Centre for Geomechanics and Railway Engineering, Universityof Wollongong, Australia

Cooperative Research Centre (CRC) for Rail Innovation Cooperative Research Centre (CRC) for Rail Innovation

Past and Present research students, Research Associates andTechnical Staff

Industry Organisations: RailCorp (NSW), ARTC, QLD Rail,ARUP, Coffey Geotechnics, Douglas Partners.

Thank You!Thank You!