2015
Case Studies of Complicate Urban Excavation from Design to Construction
Études de cas d’excavations complexes en site urbain: de la conception à la construction
Jang Y.S.
Dept. of Civil & Env. Eng., Dongguk Univ., Seoul, Korea
Choi H.C.
Architectural Structure Team. SK E&C
Shin S.M., Kim D.Y.
Saegil Engineering & Consulting. Co. Ltd., Seoul, Korea
ABSTRACT: Various types of retaining walls, e.g. H-Pile with Timber, C.I.P (cast in place pile) and subsurface continuous walls, are
domestically used for excavation sites in Korea depending on the site conditions, architectural structure and geotechncial conditions.
Ground Anchor, strut and permanent slab are used as support methods. The wall displacements and axial forces of the struts are
variable depending on the excavation depth, groundwater level and construction methods, etc. In this study, case studies are
performed for the excavation sites, where the modified slab methods, e.g S.P.S, and S.T.D are used and the ground anchors as
temporary supports. The wall displacements and the axial forces predicted at the design stage and monitored in the actual excavation
stage are analyzed. The advantage of construction time using the permanent slab method is discussed.
RÉSUMÉ : Différents types de murs de soutènement, par exemple pieu en H avec du bois, CIP (Pieu en béton coulé en place) et des
parois continues ancrées dans le sol, sont à usage domestique pour les sites d’excavation en Corée suivant les conditions du site, la
structure architecturale et les conditions géotechniques. Ancrage au sol, entretoise et dalle fixe sont utilisés comme méthodes
d’étaiement. Les déplacements du mur et les forces axiales des entretoises sont variables en fonction de la profondeur de l'excavation,
du niveau des eaux souterraines et des méthodes de construction, etc. Dans cet article, des études de cas sont réalisées pour les sites
d’excavation, où les méthodes de dalle modifiées (SPS, MST) sont utilisées et aussi les ancrages au sol comme des appuis
temporaires. Les déplacements du mur et les forces axiales prévus au stade de la conception sont examinés et analysés dans la phase
réelle d'excavation. L'avantage de la durée de construction en utilisant la méthode de dalle permanente est discuté dans cet article.
KEYWORDS: S.P.S, S.T.D, C.I.P, Ground Anchor, Strut, Slab, Displacement, Axial force, Construction time
MOTS-CLÉS : S.P.S, S.T.D, C.I.P, Ancrage au sol, entretoise, dalle, déplacement, force axiale, durée de construction
1 INTRODUCTION
Recent urban building construction has trends of deep
excavation and the methods of excavation are diversified. In
addition, various types of structures, e.g. the subway tunnels
and utility lines and pre-existing buildings are located around
the excavation sites. Therefore, when the excavation is done in
the metropolitan area, the excavation plans must be made
considering the safety, constructability and cost effectiveness
synthetically.
In this paper, the retaining wall displacements and the axial
forces of the excavation sites which are constructed using the
various supports, e.g. C.I.P. with ground anchor, and the
permanent slab methods, i.e. S.P.S and S.T.D., are monitored
and analyzed using the related case histories.
2 EXCAVATION METHODS
In the case studies, two new excavation methods, i.e. S.P.S
and S.T.D, are used and the concepts of each methods are
introduced. In the S.P.S(Strut as Permanent system) method, the
subsurface steel frame and beams are designed strong enough to
endure the temporary and permanent external pressures. They
are used as temporary retaining walls while the excavation is
going on. They can also be used as the walls of main structures
without dismantling of strut after the excavation is finished. Fig.
1 shows the conceptual diagram and the field example.
S.T.D (Strut Top Down) method can use the struts which
increase the resistance to horizontal pressures. It can also use
various types of basement slabs such as beam & girder as well
as one or two way wide beams (Sho et al. 2004). Fig. 2 shows
the conceptual view of S.T.D construction and the field
example.
Figure 1. Conceptual diagram and field example of S.P.S
Figure 2. Conceptual diagram and field example of S.T.D
