How are the sections of immersed tube tunnel joined together and made water tight?
A. The immersed tube units have temporary bulk-heads installed for their journey between the dry dock construction area and their permanent location. These have guiding mechanisms fitted to allow adjoining units to be located so that the sealing membranes engage. Once this has been successfully done the water between the two adjacent bulk-heads is pumped out to create a vacuum. The water pressure on the tubes then squeezes the tubes together to make the seal water-tight. The tubes are eventually locked into position at the two ends of the immersed tube tunnel where it meets structures produced by conventional construction methods.
