New lock of immense dimensions in Terneuzen
The “Nieuwe Sluis Terneuzen” project comprises the design, realization and subsequent maintenance for 2 years of a new lock with dimensions 427 m x 55 m with a depth till NAP-16.44 m (length between the outer lock gates is 457 m) within the Terneuzen lock complex, including 2 bascule bridges with a span of 55 m, adapting the primary and regional flood defense and excavating and maintaining the outer harbor and the navigation route to the lock at a depth of approximately 16.5 m below reference level (Normaal Amsterdams Peil or NAP). There is also a service port and a number of buildings that had to be realized and the demolition of the adjacent central lock must also be carried out. The excavation pits for the outer lock gate with a bascule bridge and the inner lock gate with a bascule bridge were both approximately 80 by 130 meters in size and 25 m deep!
Geoconstruct was involved in the project from the Tender where the combination Sassevaart made the winning offer. In the tender Geoconstruct’s activities consisted of the design of the lock gates, whereby a very surprising concept was chosen, namely an anchored diaphragm wall construction and an underwater concrete floor without tension anchors but with deep well drainage underneath the water-sealing and ancient Boomse Clay layer present here.
During final design Geoconstruct was involved in the further development of the construction pit, including the part closest to the adjacent west lock. The (temporary) diaphragm wall that forms the barrier to the excavation pit, together with the front wall, forms an immense cofferdam. The front wall had to be completed before the storm season of 2018 and therefore had to be accelerated in design, as failure to achieve this milestone would mean that the entire project could only be completed half a year later. Geoconstruct, together with 2 other geotechnical advisors from the companies Arcadis and Fugro made the final design within a short period of time, to get the client ready for the next phase, engineering the buiding pits.