Sower's Lecture Atlanta May 8, 2012 - Geosystem Gatechgeosystems.ce.gatech.edu/abstracts/Bengt_H_...
37
Wick Drains and Piling for Cai Mep Container Port, Vietnam Bengt H. Fellenius Sower's Lecture Atlanta May 8, 2012
Transcript of Sower's Lecture Atlanta May 8, 2012 - Geosystem Gatechgeosystems.ce.gatech.edu/abstracts/Bengt_H_...
1
Wick Drains and Piling
for Cai Mep Container
Port, Vietnam
Bengt H. Fellenius
Sower's Lecture
Atlanta
May 8, 2012
The Mekong
3
The General Area Saigon/HoChiMinhCity
4
Thi Vai Port
Cai Mep Port
5
Artist View
6
CFSCG
The site of the new container facility extends over an 800 m by 600 m area along the Thi Vai River
7
Locations of Buildings, Boreholes, and Settlement Points
0
200
400
600
800
1,000
1,200
0 100 200 300 400 500 600 700 800 900 1,000
EAST-WEST
NO
RT
H-S
OU
TH
TCM and CPTU
SS
BH
Piezometers
Extensometers
N
CFS
C-Gate
M-Shop
Substation
BH-14
8
Soil Profile
0
5
10
15
20
25
30
35
40
45
50
0 20 40 60 80 100
WATER CONTENT (%)
DE
PT
H (m
)
0
5
10
15
20
25
30
35
40
45
50
0.0 1.0 2.0
CONE STRESS, qt (MPa)
DE
PT
H (m
)
0
5
10
15
20
25
30
35
40
45
50
0 20 40 60 80 100
GRAIN SIZE DISTRIBUTION
DE
PT
H (m
)
CLAY SILT
SAND
wn BH-14
SILTCLAY
GRAVEL
wP wn wL
wn BH-14wn BH-76
CPTU-26
+ 3.5 m
GW & GL
CONE STRESS, qt (MPa)
9
CPTU Sounding Results
0
5
10
15
20
25
30
35
0 2 4
Cone Stress, qt (MPa)
DE
PT
H (m
)
0
5
10
15
20
25
30
35
0 20 40 60 80 100
Sleeve Friction, fs (KPa)
DE
PT
H (m
)
0
5
10
15
20
25
30
35
0 500 1,000 1,500
Pore Pressure (KPa)
DE
PT
H (m
)
0
5
10
15
20
25
30
35
0 1 2 3 4 5
Friction Ratio, fR (%)
DE
PT
H (m
)
10
Results from a large series of consolidation tests show the soil to be
very compressible, normally consolidated
1.00
1.20
1.40
1.60
1.80
2.00
2.20
2.40
10 100 1,000
Stress (KPa)
Vo
id R
ati
o (-
-)
m = 5
mr = 55
e0 = 1.92
Cc = 1.40
DEPTH: 9 m0
5
10
15
20
25
30
35
0 2 4 6 8 10
Modulus Number, m
DE
PT
H (m
)
From consolido-
meter Test
From CPTU
Sounding
Typical example of results
CR = 0.48
11
The highest water level expected at the site is Elev. +4.0 m, which level is about 0.5 m
above the ground surface. Therefore, the ground elevation will be raised by about 2.0 m
to Elev. +5.5 m in order to avoid flooding and to create a suitable foundation surface.
Risk for flooding in the area is real and the inundation can be severe,
as illustrated by the flooding of the Fall of 2011. The above shows an
areal photo of a Honda factory parking lot in Bangkok (October 2011).
12
Because of the thick very compressible clay and silt layer, the
2+ m thick fill placed to raise the land will cause significant
settlement, which would continue for a very long time. To
shorten that time, vertical drains (wick drains) were installed
to 37 m depth across the site (in some places into the sand,
in other places a bit of the clay was left between the drain tip
and the sand). Moreover, a temporary surcharge was added
raising the surface to Elev. +8 m through Elev. +10 m, i.e., an
additional 2.5 m to 4.5 m of fill height.
13
FIL
L H
EIG
HT
TIME
SE
TT
LE
ME
NT
Surcharge removed
when 80% – 90%
consolidation is
achieved
For case of surcharge
not removed
For case of surcharge
removed
For case of surcharge
not removed
Paving and
roadways
For case of surcharge
removed
80 % to 90 % of
total consolidation
settlement
ORIGINAL GROUND SURFACE
ORIGINAL GROUND SURFACE
Amount of fill placed
FILL
SETTLEMENTInitial compression and
consolidation settlement
Principle of the wick drain and surcharge
soil improvement scheme
14
The wick drain used for the project is a 100 mm wide
and 3 mm thick and consists of a corrugated, 0.15 mm
thick, plastic core wrapped with a synthetic filter.
15
Fill height and ground surface settlement until one month before
start of driving piles for the building foundations
16
Fill height and pore pressures measured June 24, 2009, through
September 17, 2010 (Days -527 and -77) at the CFS building
The tip elevations are
per original installed
depth. The settlement
of the piezometer tips
is not included.
17
0
5
10
15
20
25
30
35
40
0 50 100 150 200 250 300 350 400D
EP
TH
(m
)
June 24, and Sep 18, '09 just before adding surcharge (Days -504 and -447).
Sep 17, '09 last reading (Day -77).≈U0
+ 5.0 m
PORE PRESSURES JUNE 24, 2009 THROUGH SEP 17, 2010 (KPa)
Dec 1, '09 maximum reading (Day -365).
Distribution with depth of the pore pressures at the CFS building
FILL ELEVATION
18
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
-800 -700 -600 -500 -400 -300 -200 -100 0
DAYS
Se
ttle
me
nt
(mm
)
Container Freight Station, CFS
and Container Gate, CG
SS-32
SS-39
SS-30
SS-108
SS-29
SS-28SS-104
SS-38Surcharge
removal
Ground surface settlements 10-12-01
Start of pile
driving for
the CFS and
CG buildings 09-01-01
19
View on October 4, 2011, taken from the south-east end of CFS building
showing some of the about 1,680 piles driven for the CFS.
20
The building foundations were placed on precast, ordinary reinforced, concrete piles with a
square 400 mm cross section made up by 10-m segments spliced in the field by welding steel
end-plates together. For Buildings CFS and CG, the piles were driven to 28 m and 18 m depth,
respectively. The intended working loads were 347 KN for the CFS building and 265 KN for the
other buildings. One pile at each building was subjected to a static loading test. The test piles
were not instrumented, and the test schedule included unloading/reloading cycles and varying
load hold durations. Therefore, the test results have very limited use for the design.
Load-movement curves from static
loading tests at CFS and CG buildings
The static loading tests (CFS and CG) were carried
out in September 2010, nine months after pile driving
21
22
23
The below figure shows the settlements measured by the SS-plates at or near the buildings
until November 15, 2011. The zero date is December 1, 2010, the day of the start of the pile
driving for the CGS building. Driving was completed on January 24 at the CG building.
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
-800 -700 -600 -500 -400 -300 -200 -100 0 100 200 300 400 500
DAYSS
ett
lem
en
t (m
m)
Container Freight Station, CFS
and Container Gate, CG
SS-32
SS-39
SS-30
SS-108
SS-29
SS-28
SS-108
SS-104
SS-38
Surcharge
removal
Pile
driving
24
2,000
3,000
4,000
5,000
6,000
7,000
8,000
9,000
10,000
-800 -700 -600 -500 -400 -300 -200 -100 0 100 200 300 400 500 600
DAYS
EL
EV
AT
ION
(m
m)
ORIGINAL GROUND SURFACE
MEAN WATER LEVEL
MAXIMUM WATER LEVEL
ELEV. +5.5 m
SS-28
SS-29
PILE
DRIVING
AS-PLACED FILL HEIGHT
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
-800 -700 -600 -500 -400 -300 -200 -100 0 100 200 300 400 500 600
DAYSS
ett
lem
en
t (m
m)
Red heavy lines are
SS-28 and SS-29
All values are normalized to
the 2,900 mm average
settlement at Day 0
Start
placing fill
End placing
surcharge Removing
surcharge
Pile
driving
AT CFS and CG
400 mm
25
0
50
100
150
200
250
300
350
400
500 550 600 650 700 750 800 850 900
EAST-WEST
NO
RT
H-S
OU
TH
SS-29
SS-34
SS-234
SS-22
SS-28
SS-33SS-233
SS-230
SS-24
SS-30
SS-23
SS-108
SS-36
SS-37
SS-236
SS-235
SS-227
SS-102
SS-228
CFS
C-Gate
CONTAINER FREIGHT STATION, CFS
AND CONTAINER GATE
Ext-09
Pz-09
Pile head settlements and benchmark
settlements at the building locations
Container Freight Station (CFS) and Container Gate (CG)
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
-800 -700 -600 -500 -400 -300 -200 -100 0 100 200 300 400 500
DAYS
Se
ttle
me
nt
(mm
)
Container Freight Station, CFS
and Container Gate, CG
SS-32
SS-39
SS-30
SS-108
SS-29
SS-28
SS-108
SS-104
SS-38
Surcharge
removal
Pile
driving
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
-800 -700 -600 -500 -400 -300 -200 -100 0 100 200 300 400 500
DAYS
Se
ttle
me
nt
(mm
)
Container Freight Station, CFS
and Container Gate, CG
SS-32
SS-39
CFS Average of
Piles added to
SS29
SS-30
C-Gate Average of
Piles added to
SS108
SS-108
SS-29
SS-28
SS-108
SS-104
SS-38
Surcharge
removal
Pile
driving
26
Settlements measured for SS-plates and piles at the
CFS and CG buildings until November 15, 2011
2,500
2,600
2,700
2,800
2,900
3,000
-100 -50 0 50 100 150 200 250 300 350 400 450 500
DAYS
Se
ttle
me
nt
(mm
)
CFS Average values of pile head
settlement added to SS-29
CG Average values of pile head
settlement added to SS-108
SS-108
SS-29
27
0
5
10
15
20
25
30
35
40
0.0 0.5 1.0 1.5 2.0 2.5 3.0
SETTLEMENT (m)
DE
PT
H (m
)
July 17, 2009 — January 14, 2011
+ 5.0 m
Zero Reading of was taken on July 17, 2009. The
settlement plates located within the CFS footprint then
showed that 0.6 m settlement had already occurred
(since February 20, 2009). Total plate settlement on
January 14, 2011, was 3.08 m. The curves show
readings spaced about one month apart.
First Fill
Surface
June 29, 2010, after the
temporary surcharge
had been removed
Relative
settlement
between anchor
points during
last five months
of monitoring
R≈4 mm/m
R≈6 mm/m
R≈30 mm/m
R≈12 mm/m
Settlement distribution measured in an extensometer station (multi-anchor points) outside the CFS
building during 18 months: from July 17, 2009 (one to three months after start of placing fill) through
January 14, 2011, one month after piles were driven near the location of the extensometer station.
28
0
20
40
60
80
100
120
140
0 5 10 15 20 25 30 35 40
MONTHS
ST
RE
SS
(K
Pa
)
Stress from
as-placed fill
(approximated)
Removal of Surcharge
Stress reduction due to
settlement and buoyancy
Stress from fill adjusted for
settlement and buoyancy
Stress from fill elevation
From measured fill height and settlement to input to analysis
31
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
0 6 12 18 24 30 36 42MONTHS
SE
TT
LE
ME
NT
(m
m)
Measured
settlement
Settlement calculated with
the drains assumed not to
function below 20 m depth
Settlement calculated
with the drains
assumed functioning
along the full depth
Piles
driven
Surcharge
removed
Immediate
Compression
Secondary
Compression
Full fill height
reached
32
28 m
CFS
Pile
CLAY
SAND
DEPTH
SETTLEMENT
Settlement
of the CFS
Building for
28 m Pile
Neutral
Plane
28 m
CFS
Pile
40 m
CFS
Pile
CLAY
SAND
DEPTH
SETTLEMENT
Settlement
of the CFS
Building for
28 m Pile
Neutral
Plane
Neutral
Plane
33
View on October 4, 2011, taken from the south end of CFS building
showing some of the about 750 piles driven for the CFS building. In
the background, lengthened piles are being driven for the CG building.
39
Photos from the driving
of piles with extension
40
41
CONCLUSIONS
The most probable cause to the continued consolidation below about 20 m depth is that large soil
stresses have squashed the wick drains preventing the drains from functioning properly.
The consequence is that the overall area and the piles will continue to settle even if no new loads
are placed. But there will be new loads, so ...
The problem with the piled foundations can be (and was hopefully) resolved by lengthening the
piles to bring the neutral plane (the depth to the settlement equilibrium) into the non-settling sand
below the clay.
It is not realistic to install new and better drains or arrange, say, for vacuum treatment to get the
consolidation to occur quickly. The site will have to live with continuing to add fill to compensate
for excessive settlement, which will in turn add consolidation, and to suffer the maintenance
actions that regularly will be required for non-piled foundations.
The monitoring scheme was designed to confirm that the wick drain method worked. When the
measurements showed that the method did not work, the method became very much inadequate,
and it could not be of any assistance for selecting a solution to the problem. Every monitoring
programme should have redundancy and be designed to resolve issues should the design show to
be unsuccessful. How to resolve the question "what if we're wrong?" should always be kept in
mind and in the planning of a monitoring programme.
42
The Lotus — Vietnam's National Flower
Thank you for your attention
