The trench being built in downtown Auckland’s Albert Street for the City Rail Link (CRL) has now reached nine metres deep.
The CRL will use twin 3.4km long tunnels up to 42 metres below city centre streets. The tunnels will be constructed in this deep trench, which will be up to 18 metres deep.
The underground rail link will transform downtown Britomart Transport Centre into a two-way through-station that better connects the Auckland rail network.
The construction of twin cut and cover tunnels
The alignment of the tunnels generally follows the roads to minimise the amount of private property affected by the project.
Due to the gradient of the landscape between Britomart and the western line at Mt Eden and the limiting climbing capacity of the electric trains, the twin tunnels will vary in depth.
At each end of the tunnels (Albert Street and Mt Eden), it will be shallow enough to construct the tunnels using the ‘cut and cover’ method (building from the surface).
Cut and cover tunnels will be built by installing retaining walls to retain the soil and stop water from entering the site. Tunnels will be constructed, then the concrete floor, walls and roof will be cast and the completed structures backfilled.
The construction of twin cut and cover tunnels along Albert Street between Customs & Wyndham Streets will interface with the Fletcher Construction section of tunnels through Precinct Properties’ Commercial Bay development.
The $681 million development includes a new 39 level commercial office tower and a retail centre where the Downtown Shopping Centre used to be opposite Britomart at the foot of Queen Street.
The tower’s foundations, being built by Fletcher Construction, are being dug concurrently with the beginning of the tunnels.
See videos of the Albert Street construction at cityraillink.co.nz