The French Waterways Authority (Voies Navigables de France), manages in the North of France a particularly active territory in terms of river traffic. The Seine Nord Europe canal project, as a future link between Belgium and France, needs to improve two large-gauge waterways. One of these two itineraries, the canalized Deûle, presents a problematic lock on its route, the Quesnoy-sur-Deûle lock.
The lock is located in France, closed to the city of Lille, less than 5 km from the Belgian border. The problem stands in the fact that this lock has only one lock chamber of 110 m long, while all the others have a lock chamber of 144 m. It does not allow the navigation of the Large Rhine boats of 135 m, which are very widespread in the Nederlands, Belgium and on the Rhine River. For that reason, BRLingénierie was selected by VNF in 2013 to study the design of the extension of this lock to extend it at its new dimensions of 144.6 x 12 meters. The main difficulty for this operation is that the river traffic can only be stopped during very short closure period, which do not exceed 2 weeks per year. The second difficulty is that the lock is located in a geological context of Flandria Clay with weak and very particular characteristics.
The proposed solution consists of constructing the walls of the new lock head set back from the chamber lock, under the shelter of two cofferdams and then putting them at their final location by a lateral slide operation. This operation offers the great advantage of providing, in fine, a conventional, reinforced concrete lock, without requiring long closure. However, it induces a certain number of problems to be solved, such as the construction of modular evolutive cofferdams, the placement of tracks and slide bearings capable of bearing loads around 3 000 t, the construction of homogeneous foundations, a phasing of works allowing to work isolated from water, the connection to the existing lock.
The manner in which each of these difficulties has been solved will be developed in the article. The aim of the article is to propose an unusual solution to the problem of the extension of locks with a limited cut-off of the river traffic.