ABSTRACT
In the last 10 years there has been a number of major deep gravity sewerage and drainage tunnels constructed. The projects provide a sustainable solution to increase the capacity of large sewer/drainage systems and include the DTSS in Singapore, the STEP in Abu Dhabi, the IDRIS in Doha, the Thames Tideway in UK and the Dubai Stormwater project. They are large tunnels, mostly in excess of 5 m in diameter, constructed with a segmental lining and in most cases a secondary in-situ lining. These tunnels need to have a long service life, thus the durability design of the concrete segmental or in-situ lining to resist the deterioration mechanisms associated with the ground conditions and sewerage is of primary importance. Clients and Consultants have adopted quite different strategies and solutions in order meet the service life requirements. These strategies together with the experience from a number of recent projects is presented.
