Design Changes during Construction of the Coatzacoalcos Immersed Tunnel

Abstract: During the construction of the Coatzacoalcos Immersed Tunnel there have been several design changes. In the paper, the following changes are addressed: - poor soil conditions in the casting basin and extended construction time caused settlements of the segments during casting. This resulted in an unknown bottom geometry of the elements; - incorporation of crack inducers in the outer walls of the tunnel segments to cope with shrinkage cracks; - partial preload of the tunnel elements just after immersion and prior to finishing of the immersion joints to avoid overloading of the shear keys in these joints; - installation of an `immersion joint` (Gina gasket) in the casting basin; - an alternative foundation with grout bags instead of a gravel bed for the tunnel part in the embankment; - ship traffic restrictions just after immersion and prior to installation of the locking fill; and - interfaces with the installations.