637
Geotechnical Challenge for Total Cost Reduction related to Construction
of Connecting Bridge with Pile Foundations
Défi géotechnique pour la réduction totale des coûts liés à la construction du pont de liaison
avec les fondations sur pieux
Yasufuku N., Ochiai H.
Kyushu University, Fukuoka, Japan
Maeda Y.
West Nippon Expressway Company Limited, Osaka, Japan
ABSTRACT: Changes of geotecnical engineering profile are briefly mentioned based on the density of in-situ investigations and
laboratory tests. Then, the method used for evaluating the vertical bearing capacity of driven piles in the actual design is presented..
The applicability is also verified by comparing the predicted results with the results from the full-scale pile load tests, whose results
were linked with the reduction of the safety factor for design. Finally, the significance of geotechnical investigations including in-situ
and laboratory tests and full scale pile load tests are discussed in terms of the cost performance of the construction of pile foundations
for supporting the connecting bridge.
It is concluded that in-situ and laboratory investigation with reasonable geotechnical
considerations can reduce the total cost of the construction of the bridge with pile foundations for New-Kitakyushu airport.
RÉSUMÉ : Dans ce papier, la politique de base et des concepts pour des études géotechniques et de conception fondation sur pieux du
pont qui relie pour la Nouvelle-Kitakyūshū sont introduits. Les changements de profil géotechnique sont brièvement mentionnés basés
d’après la densité du terrain (in-situ) et des essais au laboratoire. Ainsi, la méthode utilisée pour l’évaluation de la capacité portante
des pieux battus conçu selon la méthodologie actuelle est présentée sur la base des considérations géotechniques. L'applicabilité est
également vérifiée en comparant les résultats prédits avec les résultats des essais en vraie grandeur de chargement de pieux. Les
résultats ont été comparés en termes de réduction du facteur de sécurité utilisé au dimensionnement. . Enfin, l'importance des études
géotechniques y compris les essais in situ et en laboratoire et les essais en vrai grandeur de chargement de pieux sont discutés en
termes de performance des coûts de la construction des fondations sur pieux pour soutenir le pont de liaison.
KEYWORDS: cost reduction, field investigations, pile foundations design, bearing capacity
1 INTRODUCTION
Connecting Bridge
（
2.1km, 24 piers
）
Aug. 2002
Airport site
Figure 1. Overview of connecting bridge under construction
A connecting bridge has been constructed on the sea as an
access road for New Kitakyushu airport, which will be opened
in 2005. The length of the bridge is about 2km and 24 piers are
mounted for supporting the bridge. An overview of the
connecting bridge under construction is shown in Figure 1. In
order to clarify the geological and mechanical characteristics of
the ground for supporting the bridge and the manmade airport
island, a large number of in-situ and laboratory tests had been
performed for five years from 1991 to 1995.
In this paper, the basic policy and concepts for geotechnical
investigations and design of this project are introduced. The
changes of geotecnical engineering profile are briefly
mentioned based on the density of in-situ investigations and
laboratory tests. The process of producing a model ground for
design is also made clear, which is used for estimating the
bearing capacity of driven piles. Further the method used for
predicting the vertical bearing capacity of driven piles is
presented based on the geotechnical considerations. The
applicability is also verified by comparing the predicted results
with the results from the full-scale pile load tests, whose results
are linked with the reduction of the safety factor for design.
Finally, the significance of in-situ investigations and full scale
pile load tests are discussed in terms of the cost performance of
the construction of pile foundations for supporting the
connecting bridge.
Design of foundation
Assessments based on
Geotechnical considerations
Investigation
design
Select of possible
models
Decision of sort and
number of field & lab.
tests
Modeling of ground
• Careful selection of soil parameters
• Determination of adequate model
Reconsideration of
safety factors et al.
Implementation of rational and
Economical design in total
Verification by
site investigations
• Full scale load tests
• Field observations
(
Collaboration
)
Implementation of
site investigation
(
Feedback
)
(
Reassessment
)
Figure 2. Collaboration of geotechnical investigations with design
2 GEOTECHNICAL INVESTIGATIONS AND DESIGN
Figure 2 shows the policy and concept of geotechnical
investigation and design for constructing the connecting bridge
