2067
Establishing a high risk construction pit in a hurry
L'établissement d'une excavation profonde à risque élevé en court temps
Philipsen J.
Ramboll, Denmark
ABSTRACT: In order to establish a cut & cover road tunnel in Copenhagen, a deep construction pit is established. The future tunnel
will run below four railway lines and alongside a fifth, the latter being in poor condition. Since all five railway tracks are vital for the
infrastructure in the region, it was not possible to close down all lines during the construction period simultaneously. In fact only two
fixed and extremely short closures were allowed for in the construction schedule. This paper presents the thought processes and
considerations of the parties involved during the design and planning phase and contains a description of the outcome, that is, the
chosen solutions and structural elements.
RÉSUMÉ : Afin de construire un « cut & cover » tunnel routier à Copenhague, une excavation profonde est réalisée. Le futur tunnel
est construit sous quatre lignes de chemin de fer et à côté d'une cinquième, cette dernière étant en mauvais état. Étant donné que les
cinq voies ferrées sont vitales pour l'infrastructure de la région, il n'était pas possible de fermer toutes les lignes au cours de la période
de construction en même temps. En fait, seulement deux fermetures fixes et extrêmement courtes ont été accordées par les autorités.
L´article présente les considérations faites par les acteurs concernées lors de la conception et la phase de planification du projet et une
description des résultats et les solutions choisies.
KEYWORDS: Construction pit, Temporary retaining structures
1 INTRODUCTION
In Copenhagen a cut & cover tunnel is being established as a
part of the new road Nordhavnsvej connecting an existing
motorway with the city center of Copenhagen. The construction
period is 2011-2015.
The tunnel is a traditional concrete twin tube box tunnel with
two road lanes in each tube, build bottom up in a dry
construction pit. The length of the tunnel is about 650m.
The alignment of the future tunnel runs below four railway
lines at ground level, along a fifth railway line in an old fragile
tunnel, below a busy main road and into a narrow path between
existing buildings. Figure 1 shows the horizontal alignment and
some of the key structures
Figure 1. Horizontal alignment and key structures.
The existing railway lines connect a large part of northern
Copenhagen and Zealand to the City centre of Copenhagen, the
capital's airport and subsequently to Sweden via the fixed link
across the Øresund, which means that they are vital for the
infrastructure in the region. Consequently it was not possible to
close down all lines during the construction period
simultaneously. Only two extremely short main closures were
allowed for at each end of the construction schedule.
Figure 2 shows a photo of the 5 railway lines taken from east
towards west.
Figure 2. Picture taken prior to project start up showing the 5 railway
lines.
The client (the Municipality of Copenhagen) chose Ramboll
to be the client’s consultants, preparing the detailed design of all
permanent works, while the design of the temporary structures
was chosen to be split in two parts with different premises and
responsibilities.
In the central and most complex part of tunnel alignment -
which means at the railway crossing - the client chose a contract
form whereby the contractor (Pihl-Zueblin JV) and Rambøll
should sit together and optimize the temporary structures at the
railway crossing with due consideration, of course, to economy
and safety, but most of all with reference to the time schedule.
In the remaining parts of the alignment (the ends) the
contractor designed the temporary structures, which e.g.
included retaining walls and temporary bridges across the
construction pit to facilitate the main road to be open during the
complete construction period.
