2485
Analysis of Floating Pile Capacity in Improved Ground for Thi Vai Port, Vietnam
Analyse de la capacité de Pile flottant dans un terrain Thi Vai Amélioration de Port, Vietnam
Hai N.M., Tuong N.K.
Faculty of Civil Engineering, Thu Dau Mot University, Vietnam
Long P.D., Nhon P.V.
Vietnamese Society of Soil Mechanics and Geotechnical Engineering, Vietnam
ABSTRACT: A static loading programme was performed to respond to total and effective stress analysis of floating pile capacity in
improved ground at Thi Vai Port approximately 90 km southeast of Ho Chi Minh City, Vietnam. The soil profile consists of an about
15 to 23 m thick deposit of soft, normally consolidated, compressible clay deposited on dense to compact sand. Scheme of soil
improvement was imposed, consisting of wick drains installed at a spacing of 1.5 m through the clay to the sand and placing to 4.7 m
thick surcharge. After removal of the surcharge, two square precast concrete piles, 400 mm diameter, were driven to depths of 16 and
22 m and the static loading tests were performed reaching the pile capacities after piles driven about 14 and 23 days, respectively. The
capacity of the 16 and 22 m pile measured are about 450 and 1,100 KN at maximum movements of about 5 and 6 mm, respectively.
The tests indicate a good agreement between measurements and analysis of total stresses, and the correlation coefficient, N
KT
,
between CPTU pore pressure adjusted cone stress and vane shear stress is about 18 instead of 12 through 16 as used for the Project.
RÉSUMÉ : Unprogramme de chargementstatiquea été réalisé pourrépondre àl'analyse des contraintestotale et effectivedela capacité
du pieuflottantdans un solamélioré au port deThiVai à environ 90 kmau sud-estde Ho Chi Minh-Ville, Vietnam. Leprofil de solest
constituéd'un dépôtde 15 à 23m d’épaisseurd'argile souplecompressiblenormalement consolidé, déposé sur un sabledenseet
compact.Le schéma d'amélioration des sols a été imposé, composé de drains verticauxinstallésà une distance de1,5 mà travers
l'argileau sableet à la miseà 4,7md'épaisseur en supplément. Après l'éliminationde la surcharge, deux pilescarréesen béton préfabriqué
de 400 mm de diamètreont été installés àdes profondeursde 16 à22 met lesessais de chargement statiqueont été réaliséspour
atteindreles capacitésde pieuxaprès ce quedes pieux sontmis en placeenviron 14et 23jours, respectivement. La capacitéde la pile16 et
22mmesuréeest d’environ 450et 1100KNaux mouvementsmaximum d'environ 5et 6 mm, respectivement. Lestests montrentun bon
accordentre les mesureset l'analyse descontraintes totales,et quele coefficient de corrélation, NKT, entrela pression
interstitielleCPTUajustéelacontraintecône et la contrainte de cisaillement est d'environ 18au lieu de 12à 16comme utilisés pourle
projet.
KEYWORDS: soil improvement, static loading test, total stress analysis, effective stress analysis.
0
5
10
15
20
25
0 2 4 6 8 10
ConeResistance,qt (MPa)
DEPTH (m)
0
5
10
15
20
25
0 20 40 60 80 100
SleeveFriction, fs (KPa)
DEPTH (m)
0
5
10
15
20
25
0 250 500 750 1,000
PorePressure (KPa)
DEPTH (m)
U2
U0
0
5
10
15
20
25
0 1 2 3 4 5
Friction Ratio, fR(%)
DEPTH (m)
1
INTRODUCTION
The Thi Vai Container Port is built on an improved ground over
a 470 m by 600 m area along the Thi Vai River approximately
90 km southeast of Ho Chi Minh City. The soil profile consists
of deltaic sediments of about 15 to 23 m of soft, normally
consolidated, highly compressible clay on a thick layer of dense
to compact sand. The highest water level is at Elev. +4.0 m,
which requires raising the ground elevation by about 2 m to
Elev. +5.0 m to avoid flooding. To reduce settlement after
construction, wick drains were installed with a spacing of 1.5 m
through the clay to the sand and a temporary surcharge was
added raising the surface to Elev. +7.6 m, an additional 2.0 m of
fill height. The surcharge was removed after 80 % to 90 % of
the consolidation settlements had developed and the expected
future ground settlement shall not exceed 200 mm over a period
of 20 years, which included secondary compression. After
removal of surcharge, two 400 mm square precast piles driven
into 16 and 22 m depth to serve for test and design of building
foundations.
This paper presents the methods used for analysis of the
pile capacity based on total and effective stress approaches,
details of the results from the tests on 16 and 22 m piles, and
discusses the merits of each method.
2
SOIL PROFILE
The soil profile is indicated in Figures 1 and 2. Figure 1 shows
the results of a typical CPTU sounding pushed at the site before
driving test piles.
Figure 1. Diagram of CPTU sounding pushed before
construction start
Figure 2 presents distribution of the grain size, water content,
consistency limits, and the distribution of the undrained shear
strength in the clay from a field vane. The field vane
demonstrates the clay to be very soft above 10 m depth and soft
below. Total saturated density is about 1,600 kg/m
3
throughout
the clay (from w
n
= 61 %). The density of the sand above and
below the clay is estimated to 2,100 kg/m
3
(from w
n
= 24 %)
and 1,800 kg/m
3
(from w
n
= 22 %), respectively.
Analysis of Floating Pile Capacity in I proved Ground for Thi Vai Port, Vietna
Analyse de la capacité de pile flottante dans un sol amélioré du port Thi Vai, Vietnam
Hai N.M., Tuong N.K.
Faculty of Civil Engineering, Thu Dau Mot University, Vietnam
Long P.D., Nhon P.V.
Vietnamese Society of Soil Mechanics and Geotechnical Engineering, Vietnam
ABSTRACT: A static loading programme was performed to respond to total and effective stress analysis of floating pile capacity in
improved ground at Thi Vai Port approximately 90 k southeast f Ho Chi Mi h City, Vietnam. The soil profile consists of an about
15 t 23 m thick deposit of soft, normally consolidated, compressible clay deposited on dense to compact sand. Scheme of soil
improvement was im sed, consisting of wick drains installed at a spacing of 1.5 m through the clay to the sand and placing to 4.7 m
thick surcharge. After removal of the surcharge, two square precast concrete piles, 400 mm diameter, wer driven to depths of 16 and
22 m and the static loading tests were perform d reaching the pile capacities aft r piles driven about 14 and 23 days, respectively. The
capacity of the 16 and 22 m pile measured ar about 450 and 1,100 KN at maximum mo ments of about 5 and 6 mm, resp ctively.
The tests indicate a good agree ent betwe n measurements and analysis of total stresses, and the correlation coefficient, N
KT
,
between CPTU pore pressure adjusted cone stress and vane shear stress is about 18 instead of 12 through 16 as used for the Project.
RÉSUMÉ : Un programme de chargement statique a été réalisé pour répondre à l'analyse des contraintes totale et effective de la
capacité du pieu flottant dans un sol a élioré au port deThi Vai à environ 90 km au sud-est de Ho Chi Minh-Ville, Vietnam. Le profil
de sol est constitué d'un dépôt de 15 à 23 m d’ép isseur d'argile souple compressible normalement consolidé, déposé sur un sable
dense et compact. Le schéma d'a élioration des sols a été imp sé, composé de drains verticaux installés à une distance d 1,5 m à
travers l'argile au s ble et à la mise à 4,7 m d'épaisseur en supplément. Après l'élimination de la surcharge, eux piles carrées en béton
préfabriqué de 400 mm de diamètre ont été installés à des rofondeurs de 16 à22 m et les essais de chargement statique ont été
réalisés pour atteindre les capacités de pieux après ce que des pieux sont mis n place environ 14et 23 jours, respectivement. La
capacité de la pile16 et 22 m mesurée est d’environ 450et 1100 kN aux mouvements maximum d'environ 5et 6 mm, respectiv ment.
Les tests montrent un bon accord entre les mesures et l'analyse des contraintes totales,et que le coefficie t de corrélation, NKT, entre
la pression interstitielle CPTU justée la contrainte cône et la contrainte de cisaillement st d'environ 18au lieu de 12 à 16comme
utilisés pour le projet.
KEYWORDS: soil improvement, static loading test, total stress analysis, effective stress analysis.
