Malamocco navigation lock – PIANC paper 2018

 In Gate Design

This blog describes the project of the Malamocco navigation lock. After a severe storm in 2015, Consorzio Venezia Nuova (CVN) appointed SBE to carry out a full investigation of the damage phenomenon and to propose design solutions for both the sea side and lagoon side lock gates. 

As a part of the major storm surge barrier project to protect the Venetian lagoon from high tides, a large navigation lock (width of 54m) was built at Malamocco, Italy. Only months after commissioning, the sea side lock gate (type rolling gate) was severely damaged during a storm in 2015. During the storm the gate started to bounce on its vertical supports causing a breach in the technical rooms leading to the complete destruction of all the technical equipment.

The main conclusions of the investigation were:

  • The gate was subject to large waves with long wave periods. This means that the dynamic wave pressures resulting from long wave periods could penetrate deep enough to cause significant alternating uplift and down-lift forces on the ballast tank of the lock gate;
  • Technical rooms, positioned above the ballast tank, functioned as unintended additional floating body’s with high water levels causing a significant lowering of the operational weight of the gate;
  • Uncertain ballasting condition caused by inaccurate measurement devices;
  • Due to special circumstances at the lock, for the most of the time, the lock gates aren’t subjected to hydraulic head and therefore no vertical resistance due to friction forces is present.

In a next phase possible solutions/improvements where investigated. They included:

  1. Elimination of the technical spaces between the lowest and highest design water levels;
  2. Perforation of the ballast tank oo minimize pressure differences above and below the tank;
  3. Reduction of wave penetration into the lock gate (sea side skin plate, etc.);

By means of scale model tests the effects of improvements 2. and 3. where investigated.

Despite the mentioned improvements it was still necessary to significantly enlarge the net operational weight of the lock gate to provide sufficient resistant to uplift forces. It became clear that the existing gate and it’s supporting structures (hydrofeets) where not able to deal with large net weight.

Because of this a complete redesign of the sea side gate was made. The hydrofeet supports of the previous design were replaced by conventional rolling wagons on large steel wheels. Hereby it was necessary to install additional steel rails a both sides of the existing sliding tracks of the hydrofeet.

SBE submitted a paper and was selected to give a presentation at the 2018 PIANC-World Congress in Panama City. The full paper can be downloaded here:

pdf

For more information about the project, click here.

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Test set-up of the rolling gate