RAILWAY EMBANKMENTS
The Pangea Experience (Compacted)
Shah-Habshan-Ruwais Railway Project
Shah – Abu Dhabi (own photo)
Giulio Vitale
Pangea S.r.l.
giulio.vitale@fastwebnet.it
+39 0229406830
11/05/2015
RAILWAY EMBANKMENTS
The Pangea Experience (Compacted)
Shah-Habshan-Ruwais Railway Project
ROAD MAP to the TALK
1.
DEFINITIONS & OBJECTIVE
2.
MATERIALS & CONSTRUCTION
3.
ISSUES & SOLUTIONS
4.
MAINTENANCE
5.
CONCLUSION
Shah – Abu Dhabi (own photo)
Giulio Vitale
Pangea S.r.l.
giulio.vitale@fastwebnet.it
+39 0229406830
11/05/2015
1. DEFINITIONS & OBJECTIVES
EMBANKMENT : Man-made earthwork which has length > height, sloping sides, and a
flat top hosting a transportation structure (e.g. railway).
(Pangea)
Practical purpose of embankments is to:
provide a stable foundation to the railway line
Secondarily, to protect the railway line from flooding/sand burial (assisted by sand
mitigation facilities)
ADEQUATE STRENGTH (failure criterion c, f)
ADEQUATE RIGIDITY (Elasticity E)
1. DEFINITIONS & OBJECTIVES
Different parts shall accomplish different tasks to guarantee the integrity and functionality.
•
Sub-ballast: body absorbing and
distributing loads downward. Filter
against uprise of fine materials.
•
Sub-grade: body supporting the
track structure with low deflections.
•
Core
embankment:
structure
distributing the load to the sub-soil.
•
Subsoil: material laid down into the
box-out
and
supporting
the
overlying parts.
•
Box-out: the excavation carried out
beneath the existing ground level
•
Bank grade: body forming the
lateral slopes which confine the
core and contribute to protect it
from erosion.
Sub-ballast
Sub-grade
Core embankment
Bank grade
Subsoil filling the Box-Out
1. DEFINITIONS & OBJECTIVES
Construction materials are borrowed from areas nearby the project to limit costs.
Physical and mechanical properties are unknown but must meet the design specification.
Accordingly TRIAL EMBANKMENTS (TE) are executed in advance to:
•
•
test diverse combinations of available materials with construction methods,
identify and solve unexpected technical issues.
TE have a large relevance as the more data are available the better will be the
optimization of the construction.
GEOTECHNICAL PERFORMANCE + EXECUTION TIME + EXECUTION COSTS
1. DEFINITIONS & OBJECTIVES
The Shah-Habshan-Ruwais Railway Project is 264 km long and crosses different
geographic areas. One TE is performed for each area using materials which will be
presumably encountered along the route.
MIRFA (GMB): The area is mostly
flat (2,1 m a.s.l.) and crosses
coastal sabkha areas.
SHAH: The area is completely
formed by low/high dune sands.
2. MATERIALS & CONSTRUCTION
Construction materials are borrowed from areas nearby the planned line (when possible).
MATERIAL
SITE
@ SHAH
@ MIRFA
Water
Water
Site Sand
Site Sand
Gatch
(Red @ Ruwais,
Gray @ Habshan,
Light Gray @ Mirfa)
Gatch
Dune Sand
Dune Sand
(Habshan, Mirfa)
Granular Material
Granular Material
(from Oman border)
(from Oman border)
-
Recycled Material
Overall the available materials are
similar. Variations occur, at least visually.
Physical and geotechnical properties
shall be investigated.
2. MATERIALS & CONSTRUCTION
Water supply @ SHAH test site
WATER
@ SHAH
@ MIRFA
Depth BGL (m)
n.a.
0,9 – 1,1 (*)
Cl (ppm)
26,000-28,000 (**)
176,000 (**)
SO3 (ppm)
3,300 – 4,000
4,600
pH (-)
7.3
6.9
Presence and composition of water are different.
Possible issues:
Groundwater monitoring @ MIRFA test site
(*) Threat of capillary rise ?
(**) Threat of high Cl ?
2. MATERIALS & CONSTRUCTION
FOUNDATION SOIL (Sand)
@ SHAH
@ MIRFA
2,65
2,72
1,32÷2,24 (*)
1,94÷2,4 (*)
0,1÷12
9,8÷21
1,32÷2,24 (*)
1,68÷2,03
Maximum Dry Density (t/m3)
1,75÷1,81
1,77
Minimum Dry Density (t/m3)
1,52÷1,54
1,47
1,65÷1,68
1,77÷1,80
(sweet water)
1,84÷1,86
(salty water)
(**)
Optimum moisture content (%)
13÷15
12÷14
CBR in laboratory (%)
9÷12
16
21
0,7÷3,1
Friction angle f‘(°)
31÷36
32
Cohesion c’ (kPa)
0
0÷1
Particle Density (t/m3)
Bulk Density (t/m3)
Moisture content (%)
In situ Dry Density (t/m3)
CPTU at the base of Box-out @ SHAH site
Maximum Dry Density
(modified Proctor) (t/m3)
CBR in situ (%)
Box-out @ MIRFA site
(*) Anomalous values. Carefull interpretation of in site and laboratory tests.
(**) Note the effect of salt deposition.
2. MATERIALS & CONSTRUCTION
GATCH
Spread of Gatch @ SHAH site
MIRFA
MIRFA
(Red)
(Gray)
(Light Gray)
2,65÷2,66
n.a.
n.a.
n.a.
Bulk Density (t/m3)
1,79÷2,00
1,84÷2,13
1,88÷2,15
1,92÷2,18
8,4÷23
5,6÷24
6,7÷16
7,6÷18
1,51÷1,75
1,58÷1,88
1,70÷1,92
1,66÷1,87
Passing to 0,075 mm sieve (%)
23÷33
12÷14
16÷17
43
Liquid Limit (%)
27÷36
n.a.
n.a.
n.a.
Plasticity Index (%)
4÷10
5÷7
5÷6
15
1,66÷1,70
1,84
1,94÷1,96
1,95
Optimum moisture content (%)
14÷19
12
12
14
CBR in laboratory (%)
10÷18
15
15
15
CBR in situ (%)
2÷41
6,8÷43,9
3,3÷49,1
4,6÷33,3
Friction angle f‘ (°)
27÷33
29÷37
28÷35
29÷38
Cohesion c’ (kPa)
5÷10
2÷9
0÷9
2÷10
Moisture content (%)
Maximum Dry Density
Gray Gatch @ MIRFA site
MIRFA
Particle Density (t/m3)
Dry Density (t/m3)
Red Gatch @ MIRFA site
SHAH
(modified Proctor) (t/m3)
Gatch with Fines > 15% should be discarded according to
technical specifications. BUT what is the performance ?
2. MATERIALS & CONSTRUCTION
Particle Size Distribution
SHAH - Gatch
clay
silt
sand
6R min
1B max
gravel
100
90
80
Spread of Gatch @ SHAH site
Total passing [%]
70
60
50
40
COBBLE-GRAVEL BOUNDARY
1B min
SILT-SAND BOUNDARY
SAND-GRAVEL BOUNDARY
CLAY-SILT BOUNDARY
28/21/25/-4/GAT/PSD
29/14/55/5/GAT/PSD
29/22/25/-5/GAT/PSD
27/35/55/-11/GAT/PSD
15/31/55/-17/GAT/PSD
6E-6R min
Serie12
6E-6R max
6R max
30
6E-6R min
20
1B min
10
0
0,0001
100
90
Red Gatch @ MIRFA site
80
Total passing [%]
70
60
50
40
0,001
clay
0,01
Particle
1
Size0,1Distribution (BS
1377)
GMB
- Gatch
Particle
size [mm]
silt
sand
6R max
10
100
1B max
gravel
COBBLE-GRAVEL BOUNDARY
1B min
SILT-SAND BOUNDARY
SAND-GRAVEL BOUNDARY
CLAY-SILT BOUNDARY
S/10/GAT/PSD
S/9/GAT/PSD
S/3/GAT/PSD
S/12/GAT/PSD
S/15/GAT/PSD
6E-6R min
Serie12
6E-6R max
1000
6R max
30
6E-6R min
20
1B min
10
Gray Gatch @ MIRFA site
0
0,0001
0,001
0,01
0,1
1
Particle size [mm]
10
100
1000
2. MATERIALS & CONSTRUCTION
DUNE SAND
MIRFA
HABSHAN
2,65
2,65
2,65
1,32÷2,24
1,68÷1,91
1,46÷1,87
0,1÷12
2,3÷13
0,9÷16
1,32÷2,24
1,61÷1,74
1,46÷1,74
Passing to 0,063 mm sieve (%)
1÷3
2÷3
1÷2
Plasticity Index (%)
n.p.
n.p.
n.p.
Maximum Dry Density (t/m3)
1,75÷1,81
1,77
1,76
Minimum Dry Density (t/m3)
1,52÷1,54
1,49
1,46
1,65÷1,68
1,70÷1,80
1,66÷1,68
Optimum moisture content (%)
13÷15
13
11÷14
CBR in laboratory (%)
9÷12
-
7÷16
21
-
1,6÷10,4
Friction angle f‘ (°)
31÷36
34-36
28÷35
Cohesion c’ (kPa)
0
0
0
Particle Density (t/m3)
Bulk Density (t/m3)
Moisture content (%)
In situ Dry Density (t/m3)
Dune sand above Gatch @ SHAH test site
SHAH
Maximum Dry Density
(modified Proctor) (t/m3)
(as Sand)
Laying of Dune sand @ MIRFA test site
CBR in situ (%)
2. MATERIALS & CONSTRUCTION
Shah - Dune sands - Particle size distribution
clay
silt
sand
gravel
1B max
100
COBBLE-GRAVEL
BOUNDARY
1B min-max
90
SILT-SAND BOUNDARY
80
SAND-GRAVEL BOUNDARY
Total passing [%]
70
CLAY-SILT BOUNDARY
15/18/25/-9/DS/PSD
60
11/17/25/-11/DS/PSD
19/20/25/-9/DS/PSD
50
23/22/55/-2/DS/PSD
40
27/22/25/-8/DS/PSD
7/16/55/-12/DS/PSD
30
S1/EFS/MDD
Dune sand above Gatch @ SHAH test site
20
1B min
A8/5/10/0/DS/MDD
B6/3/10/0/DS/MDD
10
B9/5/20/0/DS/MDD
0
0,0001
0,001
clay
0,01Particle
Size
1377)
0,1Distribution (BS
1
Dune
sands
Particle
size [mm]
silt
10
100
1000
grav
el
sand
100
1B max
90
80
Laying of Dune sand @ MIRFA test site
Total passing [%]
70
60
COBBLE-GRAVEL BOUNDARY
1B min
SILT-SAND BOUNDARY
SAND-GRAVEL BOUNDARY
CLAY-SILT BOUNDARY
Mirfa
Habshan
50
40
30
20
1B min
10
0
0,0001
0,001
0,01
0,1
1
Particle size [mm]
10
100
1000
2. MATERIALS & CONSTRUCTION
GRANULAR MATERIAL
SHAH
SHAH
for SUB-BALLAST
(no cement)
(plus cement)
-
-
-
-
2,34÷2,36
2,19÷2,24
2,15÷2,18
2,07÷2,25
4,4÷4,5
4,9÷5,4
1,5÷2,9
8,8÷13,0
2,24÷2,26
2,08÷2,14
2,10÷2,13
1,88÷2,03
4
6
2
5
n.p.
n.p.
n.p.
n.p.
2,2
2,14
2,23
2,05
7,3
8,5
2
10
161
254
-
-
28÷51
108÷111
23,2÷>100
22,4÷50,4
Friction angle f‘ (°)
-
-
-
-
Cohesion c’ (kPa)
-
-
-
-
Particle Density (t/m3)
Bulk Density (t/m3)
Moisture content (%)
In situ Dry Density (t/m3)
Sub-ballast without cement on the left
(compacted), with cement on the right
(spreading) @ SHAH test site
Passing to 0,063 mm
sieve (%)
Plasticity Index (%)
Maximum Dry Density
(modified Proctor) (t/m3)
Optimum moisture
content (%)
CBR in laboratory (%)
CBR in situ (%)
Sub-ballast natural on the left, recycled on
the right @ MIRFA test site
MIRFA
MIRFA
(recycled)
2. MATERIALS & CONSTRUCTION
Subballast - Gravel and sand - Particle size distribution
clay
silt
sand
1B max
gravel
100
90
80
6E min
Total passing [%]
70
60
50
6E max
40
30
20
1B min
10
0
0,0001
0,001
0,01
0,1
1
10
100
1000
Particle size [mm]
Subballast - Gravel and sand + cement 2% - Particle size distribution
clay
silt
sand
1B max
gravel
100
90
80
6E min
Total passing [%]
70
60
50
6E max
40
30
20
1B min
10
0
0,0001
0,001
0,01
0,1
1
Particle size [mm]
10
100
1000
2.
TE
simulate
the
characteristic dimension.
MATERIALS & CONSTRUCTION
larger
Dimensions
L: Lenght (m)
SHAH TE
MIRFA TE
80
80
Different
materials
and/or
compaction methods at diverse
sectors and grades/elevations are
adopted.
W1: Base Width (m)
47,1
27,6
W2: Top Width (m)
19,5
12,0
H: Height (m)
6,9
3,9
Finished layers are tested in situ
and by laboratory tests to verify
accomplishment
to
design
geotechnical parameters.
BWG: Bank grade Width (m)
1,5
1,5
S: Slope factor (-)
1v:2h
1v:2h
Box-out depth (m)
0,2 and 0,4
0,2 and 0,4
2.
MATERIALS & CONSTRUCTION
Sketch of Box-out escavation depth and Subsoil filling
In site CBR test
In site Density test
2.
MATERIALS & CONSTRUCTION
Sketch of Core embankment and Bank grade
Spreading of Core Embankments
Wetting of Core Embankments
Plate Load Test on Core
Embankment
2.
MATERIALS & CONSTRUCTION
Sketch of Sub-grade and Bank grade
Spreading of Sub-grade
Gatch - Subgrade - Incremental Static Plate load test (n450mm)
0,00
-0,50
29/3/25/-5/GAT/PLT
Plot of Plate Load Test
data of Sub-grade
Settlement (mm)
-1,00
29/9/55/-5/GAT/PLT
-1,50
29/6/25/5/GAT/PLT
29/6/25/5/GAT/PLT
-2,00
-2,50
-3,00
0
50
100
150
Applied pressure (kPa)
200
250
In site Density test of Sub-grade
2.
MATERIALS & CONSTRUCTION
Sketch of Sub-ballast and Bank grade
Dune Sand - Main Embankment Western Half - Layers 25 cm
Density Index Id(%)
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
0,00
Depth from top of the embankment (6,3 m)
1,00
2,00
3,00
FromISD
CPT-28-13-25-5GAT
CPT-28-14-25-5GAT
CPT-C9
CPT-28-19-40-0
4,00
5,00
Rolling of Sub-ballast
6,00
7,00
8,00
9,00
Existing soil (dune sand)
Plot of In site Density and CPT results
2.
MATERIALS & CONSTRUCTION
Practical purpose of embankments is to provide a stable foundation to the railway line.
Beside the geotechnical assessment of the materials, TE are used to evaluate the best
construction method (spreading, lifts, compaction) for the selected materials.
2.
MATERIALS & CONSTRUCTION
Gatch with Fines > 15% should
be discarded according to
technical specifications. BUT
what is the performance ?
GATCH
Passing to 0,075 mm sieve (%)
MIRFA
MIRFA
MIRFA
(Red)
(Gray)
(Light Gray)
12÷14
16÷17
43
2.
MATERIALS & CONSTRUCTION
Gatch with Fines > 15% should
be discarded according to
technical specifications. BUT
what is the performance ?
GATCH
Passing to 0,075 mm sieve (%)
MIRFA
MIRFA
MIRFA
(Red)
(Gray)
(Light Gray)
12÷14
16÷17
43
HIGH COMPACTION DEGREE IS
ACHIEVED
AT
MOISTURE
CONTENT
LOWER
THAN
OPTIMUM.
THAT IS GOOD GEOTECHNICAL
PERFORMANCE at LOWER TIME
and $ COSTS
2.
MATERIALS & CONSTRUCTION
Gatch with Fines > 15% should
be discarded according to
technical specifications. BUT
what is the performance ?
GATCH
Passing to 0,075 mm sieve (%)
MIRFA
MIRFA
MIRFA
(Red)
(Gray)
(Light Gray)
12÷14
16÷17
43
2.
MATERIALS & CONSTRUCTION
Subgrade Reaction K is derived by empirical relationships with CBR values (NAVFAC)
Coefficient of Subgrade Reaction K
4
K value for CBR
15% (Navfac, DM
5.4)
3,5
SUBGRADE
Embankment elevation (m)
3
2,5
Red gatch
Grey gatch
Light grey gatch
K for CBR=15%
2
BANKGRADE
1,5
1
0,5
0
SUBSOIL
-0,5
0,0
50,0
100,0
150,0
200,0
K (MPa/m)
250,0
300,0
350,0
400,0
2.
MATERIALS & CONSTRUCTION
CPTU are used to define the mechanical properties (f, c, E) of the compacted materials:
• to check whether they meet the required values,
• to define the modification of properties in the foundation soil due to the embankment
surcharge (comparison of CPTU at PRE and at POST construction stage).
Cone resistance CPTU 2a-2b
0
10
20
30
40
50
60
70
0
1
2
Depth from embankment top (m)
3
4
2a
2b
5
6
7
8
9
10
11
12
MPa
3.
ISSUES and SOLUTIONS
Are there anomalous values based
on common engineering judgement
and personal experience ?
NO
Well done,
Keep going !
YES
Are the results reliable ?
Repeat tests.
Cross check with other related
parameters.
NO
Understand the possible
causes.
Propose
alternative
testing procedure.
YES
Understand the possible causes
and effects on the project. Verify.
Take action to optimize material
characteristics or construction.
3.
ISSUES and SOLUTIONS
EXAMPLE 1:
Anomalous
HIGH
DENSITY is observed
BULK
FOUNDATION SOIL (Sand)
Bulk Density (t/m3)
@ MIRFA
1,94÷2,4
3.
ISSUES and SOLUTIONS
EXAMPLE 1:
Anomalous
HIGH
Are the results
reliable BULK
?
DENSITY is observed
YES
3.
ISSUES and SOLUTIONS
EXAMPLE 1:
Understand
the
possible
causes and effects on the
project.
Density higher than usual is attributed to
capillary rise. Capillary rise may produce
unexpected settlement. Hazard for Sub-grade.
3.
ISSUES and SOLUTIONS
EXAMPLE 1:
Verify.
Capillary rise test
3.
ISSUES and SOLUTIONS
EXAMPLE 1:
FOUNDATION
(Sand)
Density
higherSOIL
than
usual@ MIRFA
is attributed to
Understand
the
possible
Anomalous
HIGH
BULK
YES
Are the results reliable ?
Capillary
may produce
1,94÷2,4
Bulk Densityrise.
(t/m3) Capillary
causes
Verify.
effects on the capillary
riserise
test
DENSITYand
is observed
unexpected settlement. Hazard for Sub-grade.
project.
Sand is compacted in cylinders with diameter = 17 cm
and height = 178 cm.
3.
ISSUES and SOLUTIONS
EXAMPLE 1:
FOUNDATION
(Sand)
Density
higherSOIL
than
usual@ MIRFA
is attributed to
Understand
the
possible
Anomalous
HIGH
BULK
YES
Are the results reliable ?
Capillary
may produce
1,94÷2,4
Bulk Densityrise.
(t/m3) Capillary
causes
Verify.
effects on the capillary
riserise
test
DENSITYand
is observed
unexpected settlement. Hazard for Sub-grade.
project.
Sand is compacted in cylinders with diameter = 17 cm
and height = 178 cm.
The specimen is placed in salty water (water head = 1027 cm) to monitor eventual capillary arising over the time
(6-8 days).
3.
ISSUES and SOLUTIONS
EXAMPLE 1:
FOUNDATION
(Sand)
Density
higherSOIL
than
usual@ MIRFA
is attributed to
Understand
the
possible
Anomalous
HIGH
BULK
YES
Are the results reliable ?
Capillary
may produce
1,94÷2,4
Bulk Densityrise.
(t/m3) Capillary
causes
Verify.
effects on the capillary
riserise
test
DENSITYand
is observed
unexpected settlement. Hazard for Sub-grade.
project.
Sand is compacted in cylinders with diameter = 17 cm
and height = 178 cm.
The specimen is placed in salty water (water head = 1027 cm) to monitor eventual capillary arising over the time
(6-8 days).
Fractures are clearly visible supporting the hypothesis of
further compaction and settlements.
3.
ISSUES and SOLUTIONS
EXAMPLE 1:
FOUNDATION
(Sand)
Density
higherSOIL
than
usual@ MIRFA
is attributed to
Understand
the
possible
Anomalous
HIGH
BULK
YES
Are the results reliable ?
Capillary
may produce
1,94÷2,4
Bulk Densityrise.
(t/m3) Capillary
causes
Verify.
effects on the capillary
riserise
test
DENSITYand
is observed
unexpected settlement. Hazard for Sub-grade.
project.
Sand is compacted in cylinders with diameter = 17 cm
and height = 178 cm.
GOOD AGREEMENT between EXPERIMENT and EMPIRICAL FORMULA
The specimen is placed in salty water (water head = 10= capillary rise,
27 cm) to monitor
capillary
arising over the time
c eventualhc
c = empirical coefficient (shape of the grains and surface impurity),
( m) 
(6-8hcdays).
e = void ratio,
D10supporting
= Hazen’s effective
size
10 visible
Fractures are eD
clearly
the hypothesis
of
further compaction and settlements.
Capillary rise ~ 70 cm. That is negligible with respect to the position of the Sub-grade
3.
ISSUES and SOLUTIONS
EXAMPLE 1:
FOUNDATION
(Sand)
Density
higherSOIL
than
usual@ MIRFA
is attributed to
Understand
the
possible
Anomalous
HIGH
BULK
YES
Are the results reliable ?
Capillary
may produce
1,94÷2,4
Bulk Densityrise.
(t/m3) Capillary
causes
Verify.
effects on the capillary
riserise
test
DENSITYand
is observed
unexpected settlement. Hazard for Sub-grade.
project.
Sand is compacted in cylinders with diameter = 17 cm
and height = 178 cm.
GOOD AGREEMENT between EXPERIMENT and EMPIRICAL FORMULA
The specimen is placed in salty water (water head = 10= capillary rise,
27 cm) to monitor
capillary
arising over the time
c eventualhc
c = empirical coefficient (shape of the grains and surface impurity),
( m) 
(6-8hcdays).
e = void ratio,
D10supporting
= Hazen’s effective
size
10 visible
Fractures are eD
clearly
the hypothesis
of
further compaction and settlements.
Capillary rise ~ 70 cm. That is negligible with respect to the position of the Sub-grade
Take action to optimize
Material or Construction.
NO ACTION REQUIRED
3.
ISSUES and SOLUTIONS
EXAMPLE 2:
Anomalous HIGH DRY DENSITY observed in Trials
3.
ISSUES and SOLUTIONS
EXAMPLE 2:
Are the results reliable ?
NO, not supported by improvement of CBR. Plus
Anomalies appear systematically at DRY SAND layers
3.
ISSUES and SOLUTIONS
EXAMPLE 2:
Understand
causes.
the
possible
Sand is cohesionless and has the tendency to fill
the excavated volume, thus resulting in high
density.
3.
ISSUES and SOLUTIONS
EXAMPLE 2:
Sand
is cohesionless
and
the tendency to fill
NO,
PLUS
Anomalous
DRY DENSITY
observed
inhas
Trials
Are the results
?HIGH Anomalies
Understand
thereliable
possible
appearprocedure.
systematically
DRY SANDinlayers
the excavated
volume,
thusat resulting
high
Propose alternative
testing
causes.
density.
Use of Nuclear Density Gauge
Allowed by national Laws ? To be investigated accordingly.
3.
ISSUES and SOLUTIONS
EXAMPLE 2:
Sand
is cohesionless
and
the tendency to fill
NO,
PLUS
Anomalous
DRY DENSITY
observed
inhas
Trials
Are the results
?HIGH Anomalies
Understand
thereliable
possible
appearprocedure.
systematically
DRY SANDinlayers
the excavated
volume,
thusat resulting
high
Propose alternative
testing
causes.
density.
Drive a CBR mould in the Use
sandofand
subsequently
dig out the sand. That preserves
Nuclear
Density Gauge
the volume to be filled with calibrated sand.
Dry Density values are scattered
on a wide
range. Presumably
the mold was to thick
Not allowed
by national
laws.
and modified the density of the sand.
3.
ISSUES and SOLUTIONS
EXAMPLE 2:
Sand
is cohesionless
and
the tendency to fill
NO,
PLUS
Anomalous
DRY DENSITY
observed
inhas
Trials
Are the results
?HIGH Anomalies
Understand
thereliable
possible
appearprocedure.
systematically
DRY SANDinlayers
the excavated
volume,
thusat resulting
high
Propose alternative
testing
causes.
density.
Drive gently
a CBRsome
mouldwater
in the
sand
and
subsequently
dig
sand.
That preserves
Pour
inUse
the of
testing
Nuclear
siteDensity
and digGauge
out out
thethe
sand.
Apparent
cohesion
the volume
to stabilizes
be filled with
develops
and
the calibrated
volume to sand.
be filled with calibrated sand.
on a wide
range.
mold was
to thick
Dry Density
Density values
valuesare
arescattered
concentrated
on
smallPresumably
range. Thisthe
method
appears
to
Not allowed
by a
national
laws.
and modified
the density
of the sand.
provide
reasonable
and reliable
results.
3.
ISSUES and SOLUTIONS
TE construction follows general guidelines but may be considered as short-term research
projects rather than a routine operation.
Tests on TE shall be planned in advance to verify front-end construction hypothesis, but not
limited to that.
Flexibility should be allowed accordingly to the encountered site conditions in order to
otimize the instruction for the definitive embankments.
Are there anomalous values based on
common engineering judgement and
personal experience ?
Are the results reliable ?
Repeat tests.
Cross check with other related
parameters.
Well done,
Keep going !
Understand the possible
causes.
Propose alternative testing
procedure.
Understand the possible causes
and effects on the project. Verify.
Take action to optimize material
characteristics or construction.
Adequate construction specifications reduces delays and costs in the execution phase, as
well as in the following maintening phase.
4.
MAINTENANCE
The scientific study of TE through front-end planning and in site optimization allows
the construction of high quality embankments.
However that is not conclusive.
Despite any engineering effort, maintenance is needed to guarantee the durability and
integrity as per the designed life of the railway.
A Maintenance System is prepared giving:
• a list of processes which can degrade the work,
• the evidences of the acting process,
• the severity of the degradation,
• the action to take.
5.
CONCLUSION
1. Trial Embankments have the potential to greatly improve the Engineering &
subsequently the construction when geotechnical engineers can and are
allowed to explore soil parameters and preparation, as well as construction
strategies.
2. For the specific case study a large geotechnical database provided a deep
general knowledge of materials and behaviours. This circumstance enabled to
make appropriate decisions even when the site conditions were adverse
(heterogeneous material, lack of water).
3. Pangea has a solid background in geotechnical engineering (32 years) and
has also acquired a wide experience in construction and testing
embankments, including complementary structures in Railway engineering
(e.g. pile foundations and concrete work).
THANK YOU FOR YOUR ATTENTION
Hoping to be together in the next project !
Pangea S.r.l.
Via Pinturicchio, 5
20100 Milano
giulio.vitale@fastwebnet.it
+39 0229406830