Immersion techniques

Thanks to a laws of physics, a hollow concrete tunnel segment remains afloat in water. Strukton Immersion Projects takes advantage of this law to bring the object into optimum position before it is immersed. To ensure that once the segment has been correctly positioned, it can still be immersed, its ballast tanks are filled with water until there is a predetermined amount of excess weight. This makes the tunnel segment heavy enough to immerse in a controlled manner. The immersion commander uses winches to carefully lower the segment into a previously-excavated ditch. The ballast water is then replaced with ballast concrete, which ensures that the section stays in position.

Voorbereiden afzinken Venetië

Strukton Immersion Projects has gained experience with immersions around the world: from a 3.2-kilometre tunnel in South Korea to the tunnel under the IJ in Amsterdam, which connects the city’s Central Station with North Amsterdam, to, in 2014, caissons for the storm surge barrier in Venice, Italy.

Precision job

Immersion is a real precision job, since the tunnel segments need to end up in exactly the right spot. That is why the front end of each new segment is positioned over the edge of the previously-immersed segment. While this ensures that the front end is placed correctly, getting the rear end into position is a lot less easy. If the measured data show that the segment’s rear end is lying too much to the right or left, the segment needs to be ‘wagged’ a bit: by applying pressure to the front end of the segment with a jack and slightly lifting the rear end at the same time, the team can carefully shift its position. 

About Strukton Immersion Projects


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