City Rail Link Stage 1 - Auckland

Allied Concrete provide technical expertise to Downer Soletanche Bachy JV for construction of City Rail Link Stage 1.

The CRL project involves constructing an extension to the existing passenger rail network from the current termination point within the Britomart Transport Centre and through to Mt Eden Station, Auckland.

Downer Soletanche Bachy JV (DSBJV) are responsible for the Contract 1 works at Britomart Station, the Chief Post Office (CPO) building and across Lower Queen Street (LQS).

Separate works are being undertaken to continue the CRL tunnels from this point under the former Downtown Shopping Centre site (which is being redeveloped by Precinct Properties), and then up Albert Street.

Significant works beneath the CPO are required, including diaphragm wall construction (complete), underpinning of the CPO and the new rail tunnel construction. In LQS works include secant piling across the road corridor, excavation undertaken to form the rail tunnels followed by reinstatement of LQS as public space following the completion of works.  During construction, existing ticketing and retail functions and pedestrian access to the station has been accommodated in the new temporary station building, east of the CPO and Glasshouse buildings.

"All pumped pours (58 in total) were successful thanks to quality concrete"

In regard to the concrete for the DWall works, 64 panels were poured using a tremmie concrete with design strength of 40 MPa at 28 days and 50 MPa at 56 days. The average concrete volume for each panel was 45 m3, which were completed in approximately 2- 3 hours.

Given that most of the pours were constructed inside the Britomart building (6 in LQS and 58 inside the CPO) it was not possible to use the traditional DWall method pouring straight out of the truck. Also due to a Head room of 6.5 m only inside the CPO building, DSBJV and Allied Concrete worked on a pumped tremmie concrete mix design with 3-4 hours workability. This was all done via various technical exchanges and trial mixes all supervised by DSBJV concrete specialist to the satisfaction of CRLL and the Engineer.

The concrete supply fully complied noting the average concrete strength of 60 MPa at 28 days and 70 MPa at 56 days.

All pumped pours (58 in total) were successful thanks to the quality of concrete, delivery team and concrete pumps team (Ian Howe). Allied Concrete also provided a good performance in term of supply flexibility in order to assist DSBJV to cope with site unexpected events.

Article care of Downer Soletanche Bachy JV.