ABSTRACT
An immersed tube tunnel is buried in a marine environment, and gaining access to the outside surface for inspection or repair is impractical. The costs associated with excavation are likely to be prohibitive, and the ability to perform reliable inspections and remedial works underwater would be questionable. Therefore, it is necessary from the outset to ensure that the tunnel structure is inherently durable and will require little or no maintenance over its life, and that any maintenance work that is required can be carried out from within the tunnel without disruption to its operation.
