2051
Design and Construction of Inclined-Braceless Excavation Support Applicable to
Deep Excavation
Dimensionnement et Construction du Support d’Excavation Incliné Sans Butons Applicable à une
Excavation Profonde
Maeda T., Shimada Y., Takahashi S., Sakahira Y.
Obayashi Corporation
ABSTRACT: The inclined-braceless excavation support (IBES) construction method is characterized by allowing the reduction of
retaining wall rigidity and omission of shoring because it reduces the earth pressure acting on the wall, compared with construction
using vertical retaining walls. Thus, there are cases where inclined retaining walls are more beneficial in terms of workability and
economy than vertical retaining walls, depending on the excavation depth or ground conditions. For the inclined-bracelless excavation
support construction method applied at open-cut (excavation depth of 9.6m) construction site, this paper presents results of centrifugal
model experiments that reflected the actual excavation cross section, the design of the retaining walls in consideration of the
inclination of the wall, applied construction method, and measurement results at the site.
RÉSUMÉ: On peut s'attendre à ce qu'une paroi de soutènement inclinée subisse une pression du sol moindre qu'une paroi verticale
classique. Le Support d’Excavation Incliné Sans Butons (SEISB) pourrait donc offrir des avantages: un besoin de rigidité réduit et la
disparation des étrésillons ou des ancrages. Selon la profondeur d'excavation et les conditions de sol, il peut aussi être plus efficace
qu'un système vertical en termes de coût et de durée des travaux. Le présent document rapporte le cas d'un chantier où la méthode
SEISB a été utilisée pour une excavation de 9,6m de profondeur: test en centrifugeuse sur un modèle de la coupe d'excavation du
chantier, dimensionnement prenant en compte la pression du sol sur un support incliné, méthode de construction adaptée et réalisation
des travaux.
KEYWORDS: Inclined-braceless excavation support, steel sheet pile, centrifuge model experiment, earth pressure
1 INTRODUCTION
According to earth pressure theory, the earth pressure acting on
temporary earth retaining walls set up during excavation work is
reduced when the earth retaining wall is reclined. However,
earth retaining walls are generally installed vertically in
consideration of workability and construction site limitations,
and no earth retaining walls which utilized effect of reduced
earth pressure for inclined retaining wall were implemented.
Furthermore, deep excavation work requires shoring such as
bracing or ground anchors for vertical earth retaining walls with
high rigidity (Figure 1).
Figure 2. Inclined-braceless
retaining wall
Figure 1 Vertical retaining
wall
The inclined-braceless excavation support (IBES)
construction method is characterized by allowing the reduction
of wall rigidity and omission of shoring because it reduces the
earth pressure acting on the wall, compared with construction
using vertical retaining walls (Figure 2). Thus, there are cases
where inclined retaining walls are more beneficial in terms of
workability and economy than vertical retaining walls,
depending on the excavation depth or ground conditions.
The authors have previously conducted centrifugal model
experiments on inclined-braceless retaining walls using sand
ground to examine earth pressure distributions and deformation
behavior (Shimada et al. 2010, 2011) and quantitatively
confirmed that the earth pressure acting on the retaining walls
and deformation arising from excavation can be reduced by
inclining the retaining walls.
This paper reports on centrifugal model experiments that
reflected the excavation cross section at an actual scale
construction site for the inclined-braceless retaining wall
construction method to determine its suitability, the design of
inclined-braceless retaining walls using reduced earth pressure
by inclination of the wall, applied construction method, and
measurement results at the site.
2 SUMMARY AND ISSUES OF CONSTRUCTION
METHOD FOR INCLINED-BRACELESS RETAINING
WALL
Cantilever retaining walls have been widely adopted to retain
earth at relatively shallow excavation depths (3–4 m). Inclined-
braceless retaining walls are an attempt to switch from the
conventional concept of vertical retaining walls in order to
reduce earth pressure and make it possible to apply cantilever
retaining walls even at deeper excavation depths.
There are no application examples of temporary inclined
retaining walls; design issues for the inclined-braceless
retaining wall construction method include calculation of the
earth pressure while considering the inclination of the retaining
wall, and consideration of rollover not only to the excavation
side but also to the back side in calculation of embedding of
walls. Construction issues include the accuracy of the
inclination angle set during retaining wall installation and the
construction work cycle time. Centrifuge model experiments
conducted to examine these design issues, the applied design
