Dry dock
Diaphragm wall - Sheet piling - Ground anchors - Civil works - Equipment
CONCARNEAU DRY DOCK
CONCARNEAU - FRANCE
Design and construction as main contractor of dry dock,
length 130m, width 27m, depth 10.80m
he target contract for
construction
of
the
Concarneau dry dock was
performed by a consortium of
Soletanche Bachy and Le Pape
(excavation and fill). The site
was a lagoon fed by a stream
and open to the sea. The dock
was needed to suit modern
requirements, to supplement a
boat hoist and slipway already
in operation at Concarneau.
Design
The dry dock is 130m long, 27m
wide and 10.80m deep, controlled on the seaward side by a
trolley-mounted sliding gate.
The remote end has a spiral
access ramp for more efficient
operational use by the commercial companies operating there.
A pump room is provided to
control washwater and gate
leakage. Three pumps can discharge up to 4000 m3 per hour
to dewater the dock in four
hours when a ship is being docked. There are all the usual
fittings conventionally found
in harbours works such as
bollards, capstans and winches.
A390
Dry dock and port
OWNER:
CHAMBRE DE COMMERCE ET D'INDUSTRIE DE QUIMPER
ENGINEER:
CHAMBRE DE COMMERCE ET D'INDUSTRIE DE QUIMPER
MAIN CONTRACTOR:
SOLETANCHE BACHY / LE PAPE
CLASSIFICATION SOCIETY:
BUREAU VERITAS
PERIOD:
APRIL 2000 TO DECEMBER 2001
CONSTRUCTION COST:
11.5 MILLION EUROS
MAIN WORKS QUANTITIES:
Diaphragm wall: 4800 m2
Earthmoving: 220,000 m3
2
Sheet piling: 1200 m
Strip drains: 60,000 m
Ground anchors: 106
Drained raft: 4000 m2
Tie beams: 228t
Civil works: RC raft (4000 m3), spiral access ramp, capping beam, pump room,
L walls, etc.
Facilities: Control building, perimeter road, services (water, electricity, gas)
Equipment: Sliding dock gate, bollards, winches, pumps (35-4000 m3/hr), capstans, keel blocks, etc.
Typical section
Works
One of the challenges facing the
weight of the fill gradually expelled
consortium was how to deal with the
the water from the mud through
mud covering the lagoon bed to
sumps collecting the water in the
The floor is a drained raft to prevent
depths of up to 7 metres, considering
free-draining layer. Settlement of
the build-up of uplift. Works on the
that the finished dock was to be
approximately one metre was obser-
dock entrance proceeded behind a
surrounded by earth platforms for
ved before construction work proper
watertight cofferdam built in the port:
normal harbour operations, with a
could commence.
pump room, floor under the gate, gate
Sinking strip drains
specified bearing capacity of at least
recess (rock excavation with shotcrete
3 tonnes per square metre. Excavation
and nail support). The contract requi-
of the mud would have been difficult
red a turnkey graving facility, and
and disposal even more problematical,
ancillary works included a perimeter
and it was decided to consolidate it in
road around the dock, drinking water,
situ by preloading. Apart from the
electricity and gas supply, fire-figh-
excavation for the dock itself, there-
ting system, two-storey control buil-
fore, all the mud has been left in
ding and all fittings for ship docking
place. An interceptor channel was dug
(keel blocks, winched cradles, etc.).
to divert the river around the lagoon,
One of the last operations was assem-
then the lagoon was emptied to
Diaphragm wall and sheet pile driving
bly of the dock gate, by assembling
four caissons to form a single unit
expose the mud. A geotextile was laid
over the whole area and covered with
The dock sidewalls were built as
28m long, 11m high and 4m thick,
the same thickness of free-draining
diaphragm walls, tied back at the
weighing 170 tonnes. The gate was
gravel. Strip drains were sunk from
top with passive anchors to sheet
launched by a nearby boat hoist,
this platform down to bedrock in a
piling and fixed at the bottom by the
towed to station and sunk onto its trol-
1-metre square array. The subsequent
concrete floor of the dock.
leys, standing ready on their rail tracks.
Capping beam and sidewalls
A390
Dock after pouring reinforced
concrete floor
