References
Port 2000 quayside 1 to 4
FRANCE, 2001-2005
Realisation of the first 4 quayside berths for Port 2000 operation (1,602m of length)
Within the construction of Port 2000 launched by the Port Autonome du Havre to increase its operating capacity, Soletanche Bachy was awarded as main contractor the first phase of these works. This consists of the construction, under the cover of a new breakwater, of four berths (over a length of 1,602m) in an operation called External Harbour. These works, which started in May 2001 and were delivered to the Port Autonome du Havre in April 2005, included all the various operations necessary for the construction: foundations, dewatering, earth moving and dredging, civil works, sheet pile wall and anchors, furniture and container crane tracks.
Description of the works
The structure designed for this quay comprises a diaphragm wall constructed beneath the future container crane front rail, footed in the Villerville chalk. This structure is capped with a L shaped concrete beam linking the panels of the diaphragm wall and permitting the installation of future fittings to the quay wall (fenders, bollards, ladders and container crane track). On completion, the quay wall will be retained by an anchoring system to the rear made of a sheet pile wall and two layers of inclined passive anchors, installed during backfilling of a 17m deep excavation behind the quay wall. At the end of these works (including the backfilling to the rear of the quay wall) the dredging to the front of the quay wall is then made to its final level. The attached figure shows a typical cross section of the structure.
Programming and particular items of the works
Due to the hydraulic constraints of the site, the works had to be undertaken in a strict sequence of operations.
Phase 1: preparatory works, scraping and clearing of the working and warehousing zones. This phase included in particular the setting of the logistics to the site, including steel assembly areas, erection and certification of concrete ready-mix plant, delivery of the steel, anchors and sheet piles by rail.
Phase 2: installation of the diaphragm wall with Hydrofraise to more than 40m deep with 2 service cranes for the handling of reinforcement cages each weighting over 60 tons.
Phase 3: dewatering in front and behind the quay; this dewatering enabled the continuation of the works and needed slurry walls to more than 40m deep. It was necessary to mobilise 4 KS 3000 excavation rigs working 24 hours a day to construct these walls.
Phase 4: earth moving following the dewatering in front of the quay and undertaking of the civil works for the capping beam on the top of the diaphragm wall.
Phase 5: earth moving behind the quay wall under the continuous dewatering.
Phase 6: installation of the sheet piles and the lower layer of anchors.
Phase 7: 1st phase backfilling and installation of the upper layer of anchors.
Phase 8: 2nd phase backfilling up to almost the finished level.
Phase 9: cease dewatering, the quay now being safe.
Phase 10: dredging in front of the quay wall of Port 2000.
Phase 11: installation of the quay wall furniture and construction of the rear rail for the container crane.
Phase 12: finishing works: dredging the harbour to profile, re-profiling the breakwater, 3rd phase backfilling behind the quay and completing works.
Techniques
Regardless of site size, and providing it involves a significant proportion of works in the ground, Soletanche Bachy will handle the complete project, and all aspects of the works, including site supervision, excavations, foundations, civil engineering and all construction operations.
A diaphragm wall is a reinforced concrete wall that is made in situ. The trench is prevented from collapsing during excavation, reinforcing and casting by the use of supporting bentonite slurry. The slurry forms a thick deposit (the cake) on the walls of the trench which balances the inward hydraulic forces and prevents water flow into the trench. A slurry made of polymers can also be used.
A ground anchor is a load transfer system designed to transfer the forces applied to it to a competent stratum. An anchor is said to be temporary if it has a lifespan of under two years and permanent if the lifespan is over two years.
Groundwater is one of the most complex issues to be resolved in geotechnics. During the start phase of a project, the proper techniques have to be chosen for building any cut-off walls that might be required, pumping (wells, filter points, etc.) and monitoring (piezometers) resources.
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