ABSTRACT
In the existing metro tunnel in Rotterdam, failures of the immersion were encountered. The omega joint’s fixation was broken out of the concrete. After elaborate studies it was concluded that the Gina was pushed inwards due to the highly compacted soil column at the outer side of the Gina gasket and in between the end faces of both adjacent tunnel elements, whereby cyclic seasonal movements made the soil volume increase every winter and gradually push the Gina gasket inwards every following summer. This experience resulted in the contract requirement to foresee an anti-soil ingress measure in two simultaneously designed tunnels. The paper will enlighten how the mechanism was modelled and which mitigating measures were implemented in the execution of both tunnels. Numerical comparisons were made in between the two new tunnels and the existing Rotterdam metro tunnel to validate the design approach. Sensitivity analyses were made to assess the influence of soil cover, joint geometry, and the different behavior between the joint in the roof slab and the joint in the outer walls.
