During inspections of several immersed tunnels in the Netherlands, damage of immersion joints has been observed. In some cases the Gina seal has moved inwards from its original location, and in other cases a permanent elongation of the entire tunnel structure has been measured. For both cases it has been hypothesised that a seasonal expansion and contraction of the tunnel elements allows sand to enter the joint gap between elements during winter, where it is compacted during summer, leading to an increasing amount of sand in the joint gap over the years. In order to study this mechanism and assess its impact, a 1:3 scale model joint gap has been designed and constructed. This setup can simulate expansion and contraction cycles of the joint and measure stresses in the joint gap and deformations of the Gina seal. First test results are presented here and show that compaction of the sand entering the joint gap indeed occurs and leads to the observed large inwards
deformations of the Gina seals. ... Read more