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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!
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