The new Den Oever guard lock closes at high tide and when storms are forecast to protect the hinterland with the existing, renovated Simon Stevin locks, among others, from rising water. This new lock is part of the complete renovation and reinforcement of Afsluitdijk, which is an iconic water barrier in the north of the Netherlands. The miter gates of this new guard lock will in turn be protected from collision with a ship by a type of floating barrier.
The miter gates are made of steel and are operated by a hydraulic cylinder. They are composed of two main lines connected by posts. Both lines have steel pressure seats to transfer the hydraulic load to the civil structure. Sealing is done through rubber profiles that strike against embedded steel plates. Each gate is also equipped with a leveling device that consists of a vertical rising sluice gate that allows regulation of the water level between the new storm surge barrier and the existing guard lock.
Miter gates consist of two steel gate wings that lean against each other at an angle during the water retention process. Owing to their operation as a three-hinged arch, they are efficient in material use. Each gate wing is equipped with two hinge points that allow the gates to be moved using a hydraulic cylinder.
The collision protection is a separate structure that protects gates by means of a floating beam. When the miter gates close, this beam is pulled in front of the navigation channel on the Wadden Sea side. Combined with rubber fenders on the lock walls, the beam absorbs the kinetic energy of a ship in danger of hitting the gates.
The cross section, octagonal, was carefully selected. This strong and hollow section means that the beam can be locked by means of two toothed bars on the lock walls. The beam is therefore not pushed down during a collision
During normal weather conditions, i.e. when the guard lock is open to navigation and the navigation locks are operational, the beam rests outside the navigation channel. At rest, the floating beam is held in place by tubular piles connected by a coupling beam. At low water levels, they also provide support to ensure that the beam does not collide with the embankment.
The beam slides through a pontoon on which the main mechanical components are installed. An electric motor drives a chain attached to the floating beam to move the beam into position in front of the lock if needed.
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