The Sydney Harbour Tunnel - Design Aspects of the Immersed Tube Structure

This paper examines the major design issues relating to the immersed tube structure, which comprises eight pre-cast reinforced concrete units. The principal design considerations are safety, structural integrity and durability. Detailed investigations have been made of various cement blends and concrete mixes to minimise heat of hydration, thermal and shrinkage cracking, and permeability. Water-tightness is being further achieved through specially designed joints and waterproofing membranes. In addition to an extensive range of service and extreme load cases, forces imposed during the towing and sinking operations were also important considerations.