I’m architecturally qualified by profession of course so my whole career has been involved working on mainstream projects with a strong bias towards large residential concrete-framed developments. I’ve long however been envious of the infrastructure engineers as they get to work on all the REALLY interesting structures like bridges and tunnels so it was a real treat to be invited to take some photographs of the new R210 million Durban Harbour Tunnel last week.
Forming a part of the larger Durban Harbour Entrance Widening project a necessity was borne for the existing services tunnel to be redesigned and rebuilt deeper and larger than the existing 50-year old one which has long served an important function here. The new 4.4m internal diameter tunnel is some 530m long dropping to some 30m below the new overhead widened and deepened harbour channel.
It is the first sub-aqueous soft-ground tunnel in South Africa, designed with some of the steepest grades and tightest vertical curves due to the space constraints. It is also the first time that a slurry boring machine has been used in South Africa with a refurbished Herrenknecht drilling machine (previously used on the Kai Tak Transfer Scheme in Hong Kong) being brought in specifically for the job.
Client eThekwini Water and Sanitation Department employed main contractor Concor-Hochtief Joint Venture and GOBA Engineering to have all the fun on this most sensational project. The UK’s Mott MacDonald also provided specialist advice on the tunnel design.