NorthConnex Tunnel
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Overview

The NorthConnex project requires construction of twin nine kilometre tunnels joining the M1 Pacific Motorway and the Hills M2 Motorway. Excavation has been underway since May 2016 and is coming to an end.

The deepest part of the tunnel will be around 90 metres, passing under the Sydney Metro Northwest tunnel at Beecroft. More than half the tunnel is more than 60 metres deep – about the height of the Sydney Opera House. A map of the project alignment is available here.  

Tunnel construction progress

Construction activities are supported from four main work sites: 
      1. Southern interchange      
      2. Wilson Road tunnel support facility     
      3. Trelawney Street tunnel support facility      
      4. Northern interchange  

What work is underway?

Mainline tunnelling is coming to an end, with the project’s 20 roadheaders progressively being decommissioned. The following activities are being carried out underground.

Benching

Benching is the process of removing the lower part of the tunnel to achieve the desired final height. Two surface miners were commissioned to assist this work. A surface miner has a large cutting drum and can cut about 50 centimetres deep as they travel along the tunnel floor. Roadheaders are also used to carry out benching using the large cutting boom on the front of the machine.



Trenching

In sections of the tunnel where tunnel excavation and benching is complete, trenching is carried out. Trenching involves using a saw and hammer excavator to dig trenches for drainage infrastructure and electrical conduit.






Waterproofing

Waterproof membrane is installed along the tunnel either as a plastic or as a spray lining.









Final lining

A final layer of concrete is installed and smoothed to form a tunnel shell, ready for fit out with road pavement, panelling and electrical and mechanical equipment. The lining is sprayed on like shotcrete during the initial tunnel excavation phase.

A surface miner can cut 50cm deep
A hammer excavator then removes the trench
The waterproofing applied as a sheet of plastic
The final lining forms an empty shell ready for fit out works

Project Activities

Construction updates