ground improvement in transport geotechnics - from theory ... · s.f × m f m b × 100 void...
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Ground Improvement in Transport
Geotechnics - from Theory to Practice
Prof. Buddhima Indraratna Professor of Civil Engineering & Research Director
Centre for Geomechanics and Railway Engineering
Program Leader, ARC Centre of Excellence in Geotechnical Science & Engineering
University of Wollongong, NSW 2522 Australia
14th IACMAG 2014, Kyoto, Japan
A/Prof. Cholachat Rujikiatkamjorn Associate Professor, School of Civil, Mining & Environmental Engineering
University of Wollongong, NSW 2522 Australia
Dr. Sanjay Nimbalkar Research Fellow, Centre for Geomechanics and Railway engineering
University of Wollongong, NSW 2522 Australia
Dr. Ana Heitor Lecturer, School of Civil, Mining & Environmental Engineering
University of Wollongong, NSW 2522 Australia
Figures from “Road and rail freight: competitors or complements?” Bureau of
Infrastructure, Transport and Regional Economics, Australian Government Canberra.
Demand for freight and passenger transport has increased in the past decade.
Increased traffic tonnage necessitates use of ground improvement techniques in
Rail, Road and Port Infrastructure.
2
Part A
Part B
PART A:
Railways – Granular media stabilisation
• Effect of confining pressure on track design
• DEM - Particle degradation modelling
• Cyclic loading and FEM modelling
• Track Contamination and design implications
3
Particle degradation Track buckling Subgrade clay pumping
Prismoidal Triaxial Rig to Simulate a
Track Section
(Specimen: 800x600x600 mm)
Cylindrical Triaxial Equipment
(Specimen: 300 mm dia.x600 mm high)
Dynamic Process Simulation Test Facilities, Designed and Built at UoW
4
Effect of High Impact Loads and Track Degradation
Subgrade
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 0.055
Soft Below ballast 0.056
Soft Above & below ballast 0.028
Shock Mat
Nimbalkar, Indraratna, Dash & Christie (2012). JGGE, ASCE, Vol. 138(3), 281-294
5
Effect of Confining Pressure on Strain Behaviour of Ballast
(Indraratna, Lackenby and Christie (2005), Geotechnique, Vol. 55(4), 325-328)
0 5 10 15 20 25 30 35
Axial Strain (%)
6
5
4
3
2
1
0
-1
-2
-3
-4
Vo
lum
etr
ic S
tra
in (
%)
3 kPa
10 kPa
20 kPa
30 kPa
45 kPa
60 kPa
90 kPa
120 kPa
180 kPa
240 kPa
3
qmax = 500 kPa
compression
dilation
Cyclic Loading
0 5 10 15 20 25
Axial Strain (%)
4
2
0
-2
-4
-6
-8
-10
-12
-14
-16
Vo
lum
etr
ic S
tra
in (
%)
1 kPa
8 kPa
15 kPa
30 kPa
60 kPa
90 kPa
120 kPa
240 kPa
3
dilation
compression
Monotonic Loading
Peak friction angle, p, of fresh ballast
Dilatancy (+)
(-) Compression
Particle breakage
f (excludes particle breakage and dilatancy)
0 100 200 300 400
Effective confining pressure (kPa)
36
40
44
48
52
56
60
Fri
ctio
n a
ngl
e,
(de
gree
)
0 50 100 150 200 250
Confining Pressure (kPa)
Fri
ctio
n A
ng
le
()
f (excludes particle breakage and dilatancy)
fb (includes breakage but excludes dilatancy)
Compression
Dilation
p
44
6
Increasing Confining Pressure using: Intermittent
Lateral Restraints or Embedded Winged Sleepers
Rail
Lateral restraints
Intermittent lateral
restraints
Sleepers
Winged sleepers
Lackenby, Indraratna, McDowell and Christie (2007) Geotechnique, ICE, UK. Vol. 57(6), 527-536 7
Effect of Confining Pressure on Particle Degradation
(Cyclic Loading)
Sieve Size (mm)
0
1
Fra
ctio
n P
ass
ing
Initial PSD
Final PSD
Arb
itrar
y bo
unda
ry o
f max
imum
bre
akag
e
2.36
d95iA
B BAABBI
2.36 = smallest sieve size
0 63
PSD = particle size distribution
d95i = d95 of largest
sieve size
Shift in PSD caused by degradation
dmax
Ballast Breakage Index (BBI)
0 50 100 150 200 250
Effective Confining Pressure (kPa)
0
0.02
0.04
0.06
Ba
llast B
rea
kag
e In
de
x,
BB
I
qmax = 500 kPa
qmax = 230 kPa
(I) (II) (III)
Optimum Contact
0 50 100 150 200 250
Effective Confining Pressure (kPa)
0
0.02
0.04
0.06
Ba
llast B
rea
kag
e In
de
x,
BB
I
qmax = 500 kPa
qmax = 230 kPa
(I) (II) (III)
0 50 100 150 200 250
Effective Confining Pressure (kPa)
0
0.02
0.04
0.06
Ba
llast B
rea
kag
e In
de
x,
BB
I
qmax = 500 kPa
qmax = 230 kPa
(I) (II) (III)
Optimum Contact
Unsta
ble
Dila
tion
Zone
Optim
um
Degra
dation Z
one
Compressive Stable
Degradation Zone
Indraratna, Lackenby and Christie (2005)
Geotechnique, Vol. 55(4), 325-328
8
Constitutive Modelling Incorporating Ballast Breakage
– Energy Approach
245tan1
3
1
3
2
sin1/
245tan1
3
1
3
2
12
45tan1
2
1
1
2
1
2
1
fv
fB
fv
fv
d
dp
ddE
d
d
d
d
p
q
f = basic friction angle
p = Effective mean stress
q = Deviator stress
dEB = increment of energy consumption due to particle breakage
Indraratna and Salim (2002)
Geotechnical Engineering,
ICE Proceedings, UK.
Conventional theory
Stress-Strain behaviour Volume Change Behaviour
**912
1
*23912
2
)(
)(
Mp
BM
p
peM
dMMp
p
p
p
do
i
ics
io
csps
MM
M
p
B
MM
M
d
dps
pv
*239
*
*239
9
Model Parameters need to
be determined by large-
scale testing
Salim & Indraratna (2004), Canadian Geotechnical Journal, Vol. 41(4), 657-671
0.0 5.0 10.0 15.0 20.0 25.0
Distrortional strain, s (%)
0
400
800
1200
1600
2000
Dis
tort
ion
al str
ess,
q
(kP
a)
3 = 300 kPa
100 kPa
200 kPa
50 kPa
Test data for crushed basalt(Indraratna and Salim 2001)
Model prediction
Deviatoric Strain, εs (%) 0.0 5.0 10.0 15.0 20.0 25.0
Distrortional strain, s (%)
8.0
6.0
4.0
2.0
0.0
-2.0
-4.0
-6.0
-8.0
Vo
lum
etr
ic s
tra
in, v
(%
) 3 = 50 kPa
100 kPa
200 kPa
300 kPa
Dilation
Contraction
Test data for crushed basalt(Indraratna and Salim 2001)
Model prediction
Deviatoric Strain, εs (%)
Constitutive Modelling of Particle Breakage
10
Particle Breakage near the top plate
Model particle shapes and sizes
Hossain, Indraratna, Darve, & Thakur (2007).
Geomech & Geoengg, Vol. 2(3), 175-181
Distinct Element Modelling: Train Velocity vs Breakage
11
Constitutive model: Critical State capturing particle breakage Indraratna, B., Sun, Q. D. & Nimbalkar, S. (2014). Can. Geotech. J. in press.
0 1c cM M exp BBI
c ref a exp b BBI ln p'
Mc0 is critical state stress ratio for BBI = 0
12
DEM Modelling Geogrid-reinforced Ballast under Shearing Loads
Comparison of shear stress and displacements for
DEM simulation of reinforced ballast DEM particle shapes and sizes
Ngo, Indraratna, and Rujikiatkamjorn (2014). Computers & Geotechnics, Vol. 55, 224-231
DEM - geogrid
13
DEM Model for Geogrid-reinforced Ballast under Direct Shearing
14
Role of Ballast Fouling on Track Performance
Infiltration of coal
VCI = (1+ef)
eb
× Gs.b
Gs.f
× Mf
Mb
× 100
Void Contaminant Index (VCI) proposed by UOW eb = Void ratio of clean ballast
ef = Void ratio of fouling material
Gs-b = Specific gravity of clean ballast
Gs-f = Specific gravity of fouling material
Mb = Dry mass of clean ballast
Mf = Dry mass of fouling material
Slurried Clay infiltration
15
Bounding Surface Model for Fouled Ballast
(Indraratna et al., 2014; Geotechnique, in press)
Bounding Surface
0lnR
'p'pln( 'p M p'pαqF
N1
coa
p
v
e
vv dεdεdε
ηMdε
dεfp
q
p
v
Non-Associated Flow rule
Mf=f(VCI)
Hardening modulus h=hb + hf
σF
m'p
κλ
e1
p'pln'pN
lnR
p'plnp p'pMα
hp
co
cc
1
coa
b
N
cf p
c maxv
1 p'h
p εf VCI
16
Loading Surface
f=0ij
p'c
M
q
n
n
Bounding Surface
F=0
p'P’c/R
Impeded Track Drainage due to Ballast Fouling
Large-scale permeability test apparatus
Variation of hydraulic conductivity vs. Void Contaminant Index
kb = Hydraulic conductivity of clean ballast
kf = Hydraulic conductivity of fouling material
Hydraulic Conductivity (k) of fouled ballast
100
b f
f b f
k kk
VCIk (k k )
Tennakoon, Indraratna, Cholachat, Nimbalkar and Neville
(2012) ASTM Geotechnical Testing Journal, Vol. 35(4), 1-12
0 20 40 60 80 10010
-7
10-6
10-5
10-4
10-3
10-2
10-1
100
Sydenham Site
VCI=22%
Coal-fouled ballast: Experimental
Coal-fouled ballast: Theoretical
Sand-fouled ballast: Experimental
Sand-fouled ballast: Theoretical
Hyd
rau
lic C
on
du
cti
vit
y, k (
m/s
)
Void Contaminant Index, VCI (%)
Bellambi Site
VCI=33% Rockhampton Site
VCI=72%
hydraulic conductivity
of clayey fine sand
hydraulic conductivity
of coal fines
17
Cyclic loading (sinusoidal form) of Track
18
Initial static loading to reach the minimum cyclic deviator stress.
Frequency conditioning phase (f = 1 Hz, N = 10) to prevent any loss of actuator
contact with the specimen.
Cyclic loading phase ( f = 5, 10, 20 and 40 Hz, N = 500 000).
Effect of frequency on the axial strain of ballast
Sun, Q. D., Indraratna, B. & Nimbalkar, S. (2014). Géotechnique, doi: 10.1680/geot./14-T-015.
Range I: Plastic shakedown (5Hz ≤ f ≤ 20 Hz)
Range II: Plastic shakedown followed by Ratcheting (30 Hz ≤ f ≤ 50 Hz)
Range III: Plastic collapse (f = 60 Hz) 19
Field Trial on Instrumented Track in Bulli and Singleton
Geocomposite layer (geogrid+geotextile)
before ballast placement
Ballast placement over the
geocomposite
Geogrid layer placed
above the capping
Settlement pegs
placement in the track 20
Field Instrumentation - Bulli
Settlement pegs
installed at ballast-
capping interface
Displacement
transducers installed at
sleeper-ballast interface
Field Deformation Response
The recycled ballast performed well
because, it was broadly graded compared
to the relatively uniform fresh ballast.
Indraratna et al. (2010). JGGE, ASCE, Vol. 136(7), 907-917
Indraratna et al. (2014). ICE Proc. Ground Improvement, Vol. 167(1), 24-34
0 2 4 6 8 10 12 14 16 18
18
15
12
9
6
3
0
0 1x105
2x105
3x105
4x105
5x105
6x105
7x105
8x105
9x105
6.00
5.00
4.00
3.00
2.00
1.00
0.00
Fresh Ballast (uniformly graded)
Recycled Ballast (broadly graded)
Fresh Ballast with Geocomposite
Recycled Ballast with Geocomposite
Number of load cycles, N
Aver
age
ver
tica
l def
orm
atio
n o
f bal
last
, (S
v) av
g (
mm
)
Aver
age
ver
tica
l st
rain
of
bal
last
, (
1) av
g (
%)
time, t (months)0.0 5.0x10
41.0x10
51.5x10
52.0x10
52.5x10
524
18
12
6
00 20 40 60 80 100
8
6
4
2
0
Vert
ical
Str
ain
of
Ball
ast
, v
(%
)
Time, t (days)
Vert
ical
Defo
rmati
on
of
Ball
ast
, S
v (
mm
)Number of Load Cycles, N
Type of Section Aperture
Size (mm)
Geogrid 1 44 44
Geogrid 2 65 65
Geogrid 3 40 40
Geocomposite 31 31
Optimum aperture size of geogrids is
about 1.15D50 of ballast.
Bulli Track Singleton Track
22
Plane Strain FEM Analysis of Track Substructure
(Confining Pressure @ 50 kPa by geocells)
0 5 10 15 20 25
0
100
200
300
400
500
600
700
800
900
1000
Effective confining pressure 3
' = 50 kPa
Devia
tor
Str
ess
, q =
' -
' (kP
a)
Axial Strain, a (%)
E50
1 asymptote
23
Track transverse section deformation
Track longitudinal section deformation
PART B:
Road Embankments and Port Reclamation – Soft Soil
Stabilisation
• Concepts of vacuum consolidation
• Factor affecting vacuum consolidation
• 2D and 3D FEM modelling of vacuum
consolidation
26
Membrane-type Vacuum Application (Courtesy Austress-Menard)
Drain Installation
Horizontal drain
installation Peripheral bentonite
trench
Connection between horizontal
drainage and vacuum pump Membrane installation
Time
-150
-75
0
75
150
Str
ess/
Pre
ssu
re (
kP
a)
Time
-150
-75
0
75
150
Str
ess/
Pre
ssu
re (
kP
a)
p (preloading pressure)
p (preloading pressure)
p0 (Vacuum
pressure)
Time
-150
-75
0
75
150
Excess p
ore
pre
ssure
(kP
a)
Time
-150
-75
0
75
150
Exce
ss p
ore
pre
ssu
re (
kP
a)
Time
-150
-75
0
75
150
Ve
rtic
al e
ffe
ctive
str
ess (
kP
a)
Time
-150
-75
0
75
150
Ve
rtic
al e
ffe
ctive
str
ess (
kP
a)
Maximum excess pore pressure
Maximum excess pore pressure
Principle of Vacuum Consolidation
Consolidation: (a) conventional surcharge loading;
(b) idealised vacuum preloading (Indraratna et al. 2005).
2 2
2 2
1( )h v
u u u uc c
r r r z t
Governing Equation
VP directly adjusts the initial
pore pressure boundary
conditions.
Vertical consolidation term
can be ignored if Z is
very large.
28
Pore Pressure generation and retarded dissipation within the Smear Zone
Mandrel Driving INCREASES effective vertical stress, hence, the lateral permeability
decreases within the smear zone (Sathananthan, Indraratna, & Rujikiatkamjorn (2008),
ASCE J. of Geomechanics, Vol. 8(6), 355-365).
Excess Pore Pressure is
rapidly created during
mandrel intrusion
Excess PWP dissipates
very gradually after
mandrel withdrawal in
spite of the drain.
29
Analytical and Numerical Simulation Multi-drain Analysis and Plane Strain Conversion
Field condition: Axisymmetric
Reduce the
convergence time
and require less
computer memory
Must give the same
consolidation response
Maintain geometric
equivalence
2D plane strain FEM
30
Conversion of an Axisymmetric Unit Cell into Plane Strain
Indraratna et al., 2000 & 2005
Conversion must give
the SAME time-
settlement curve
w
h
wp
hp
q
kls
hkh
k
s
n
q
k
B
l
hpk
hpk
hk
hpk
3
275.0lnln
3
4
2
2
31
0.1 1 10 100 1000Time (days)
0
0.2
0.4
0.6
0.8
1
Ave
rag
e e
xce
ss p
ore
pre
ssu
re r
atio
ch=0.32m2/year
de=0.45m
Axisymmetric
Plane strain
2 graphs coincide
0
vach
o
vac
o u
uT8exp
u
u1
u
u
Normalized average excess pore pressure in axisymmetric
condition with vacuum (Indraratna et al., 2005), CGJ
= pore pressure at time t (average values)
= time factor
= undisturbed horizontal permeability
= smear zone permeability
0u = initial pore pressure
u
hT
w
h
h
h
q
kls
k
k
s
n
3
275.0)ln(
'ln
2
hk
h'k
vacu = average applied vacuum pressure kh ks
-p0
-k1p0
z
l
ds/2
de/2
Smear zone
Undisturbed zone
Vacuum pressure
distribution
C L
32
Sea wall and
development area
33
WD5A WD5BWD1
VC2
WD4
WD2 WD3
VC1
155m
35m
70m 41m 84.5m 84.5m
70m
70m
50m
169m
210m
MS15-1
MS17-1 MS18-1
MS16-1MS22-1 WD5B
VC1-2
VC2-1
Surface settlement plates
Piezometers
VWP2-WD1
VWP1-WD2
VWP4-WD4
MS20-VWP5
MS19-VWP5
MS28-VC1
MS27-WD3
Inclinometers
0 40 80
Liquid and plastic limit (%)
-30
-20
-10
0
10
Ele
va
tio
n (
m)
PL
LL
Water Content
0.4 0.6 0.8 1
Cc
2 4 6 8
Cv, Ch (m2/yr)
Ch
Cv
20 40 60 80
Su (kPa)
Dredged mud
Upper Holocene sand
Holocene Clay
Pleistocene
Plan view Soil Properties
PL w LL
Tough Luck! No Vertical Drains here
Applications at Port of Brisbane
3D modelling at corner of embankment or at marine boundary
Effect of vacuum application (negative movements) may extend more than 10 m
from the edge of the embankment
A
A
34
Time-Settlement, Pore Pressure & Lateral Yielding Response
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
11/0
5/0
7
08/0
6/0
7
06/0
7/0
7
03/0
8/0
7
31/0
8/0
7
28/0
9/0
7
26/1
0/0
7
23/1
1/0
7
21/1
2/0
7
18/0
1/0
8
15/0
2/0
8
14/0
3/0
8
11/0
4/0
8
09/0
5/0
8
06/0
6/0
8
04/0
7/0
8
01/0
8/0
8
29/0
8/0
8
26/0
9/0
8
24/1
0/0
8
21/1
1/0
8
Sett
lem
ent
(m)
Prediction
Field
UOW Predicted DOC (%)
0
10
20
30
40
50
60
70
80
90
100
11/05/07 19/08/07 27/11/07 06/03/08 14/06/08 22/09/08
De
gre
e o
f C
on
so
lid
ati
on
(%)
-80
-60
-40
-20
0
20
40
60
11/05/07 19/08/07 27/11/07 06/03/08 14/06/08 22/09/08
Excess p
ore
pre
ssure
(kP
a)
Dredged MudUpper Holocene SandUpper Holocene ClayLower Holocene ClayMeasurement
(a) Settlement and (b) excess pore pressure
for a typical vacuum site
35
0 1 2Lateral displacement/Total change in effective stress
(mm/kPa)
-30
-28
-26
-24
-22
-20
-18
-16
-14
-12
-10
-8
-6
-4
-2
0
2
4
6
8
10
De
pth
(m
)Section/Plate No.
VC1/MS28
WD3/MS27
PlatformPlatform
Dredged mud Dredged mud
HS Holocene sand
UHCUpper Holocene Clay
LHC
Lower Holocene Clay
(b) Reduction of lateral displacement for a
typical vacuum site
Part A + Part B: PVD Applications to Rail Embankment at Sandgate and FEM Analysis
Class A Prediction (Indraratna et al. 2010; ASCE, JGGE, Vol. 136(5), 686-696)
Soft Alluvial Clay
Stiffer Silty Clay
0 10 20 30 40 50Lateral displacement (m)
-20
-16
-12
-8
-4
0
De
pth
(m
)
No PVD
PVDs @ 1.5m spacing
Field
Reduction in
lateral displacement
0 100 200 300Time (days)
0.25
0.2
0.15
0.1
0.05
0
Se
ttle
me
nt
(m) Field Data
Prediction-Class A
36
• Geogrids increase confining pressure and reduce particle dilation
and breakage in rail tracks.
• Vacuum preloading effectively controls excess pore pressure and
lateral displacement of soft soil. VP is often the ideal choice, where
lateral movement at a marine boundary needs to be curbed.
• PVDs effectively mitigate the build-up of excess PWP under high
cyclic loading (e.g. applications to railways and airport runways).
• DEM models are most useful to analyse track degradation,
compared to current empirical assessments.
• Fully-instrumented Field trials are imperative to study complex
issues of track behaviour and for performance verification.
Conclusions
37
Australian Research Council (ARC) for substantial funding
Past and Present research students, Research Associates and
Technical Staff
Industry Organisations: RailCorp (NSW), ARTC, QLD Rail,
ARUP, Coffey Geotechnics, Douglas Partners. Roads & Traffic
Authority, Queensland Department of Main Roads, Port of
Brisbane Corporation
Acknowledgment
Thank You!
38