189
EUROPA
the
Justus Lipsius
building the pressure from
the soil varied from 3 to 4 metres. The result
was that an entire series of support and
shoring measures were necessary.
It is obvious that this project required a host
of stability works, both complex and deli-
cate, which had to be completed in a certain
logical order over time, whilst taking into
account the simultaneous completion of the
railway tunnel.
As early as the draft project, a phasing plan
was elaborated for the works, translating
the duration of the various operations into
a general schedule. The latter stressed the
need to start the infrastructure works as
soon as possible, for fear of not being able
to meet the final deadline. It was rapidly
decided to launch the ADC undertaking,
which left time to finalise the entire main
project and to secure all of the necessary
approvals.
withstand the wind during the works as well
as the pressure from the soil on it during the
excavation of the basement in the Lantern’s
central zone.
The first solution considered was that of
erecting temporary external metal structures
to handle the stress, but assuming that they
were possible, these structures would be
very costly and wasted. It rapidly proved not
to be feasible, since the support to these
structures on the ground was impossible on
the west side, taken up by the tunnel works,
and also impossible on the south side, since
four underground levels had to be created.
In addition, the external roads had to remain
accessible to people and to construction site
equipment. The solution that was called for
was to precede the demolition phase by the
construction of three reinforced concrete
permanent newels, across the entire height
of the future project, and subsequently tear
down from top to bottom, by gradually
joining the section to be preserved to the
new newels, using temporary metal pieces.
The bracing during the works has therefore
been carried out by perennial structures,
in proportion with both the temporary and
permanent situation, with minimal additional
cost. Nonetheless, the need to install these
newels on the foundations, before demoli-
tion, was a major constraint both technically
and in terms of planning, added to the other
constraints already mentioned.
The stress from the wind on the bracing
structures was added to that due to the pres-
sure from the earth during excavation of the
four underground levels: on the west side,
from the lower level of the tunnel works, a
moderate pressure of 2.24 m was recorded;
on the oblique south side, a pressure of
3.50 m; on the south side, from the existing
level, major pressure of 12.27 m, impossible
to recover. The conclusion was that earth
works had to be carried out as soon as possi-
ble in this zone to reduce pressure to 5.26 m,
which was still considerable and required
special measures. The result was that said
zone, in addition to the railway tunnel works,
became a priority. On the east side, facing
– The extension of the four basements
under the lantern imposed multiple un-
derpinnings of preserved structures and
major supporting works, both internal to the
project and on the entire perimeter, adjoin-
ing or neighbouring constructions.
– Of the existing building, in zone 1, only the
listed façade and the first beam, approxi-
mately 5.5 metres wide, as well as two listed
stairwells remain.
– South side, in zone 2, a new underground
structure is built on four levels including
technical rooms, car parks and the circular
ramp to access the car parks.
– East side, along the
Justus Lipsius
building,
in zone 3, four levels of underground car
parks are constructed.
– Another constraint, the obligation to keep
in operation until mid-2009 the central
boiler room of the
Résidence
complex, situ-
ated on the south side, against zone 2. It is
only then that the asbestos can be removed
from this zone and major underpinning
works carried out. A ground area would be
discovered polluted by hydrocarbons, which
would pose detailed problems further on.
How to ensure the stability of preserved
listed constructions, during demolition,
excavation and construction works? It is the
first question that was posed. The exten-
sion from the 1960s, completely separated
from the historic building by an expansion
joint, will be torn down on the ground
floor, before the start of the railway tunnel
construction. The remaining structure to
be demolished will form part of the first
main contract, that of the civil engineering
company named ADC (Block A, Demolitions,
Conserving measures). The zones to be
demolished include the underground of
the 1960 extension, and part of the historic
building, both below and above ground.
Three reinforced concrete newels will
provide horizontal stability for the future
project.
Since some parts could not be torn down
without compromising the stability of the
preserved section, which is a thin sliver
of building ten floors high, which had to
WORK IN PROGRESS
