The NorthConnex Tunnel: DSI Underground supplies High Quality Products for Australia’s longest Road Tunnel

Once completed, the NorthConnex Tunnel will be one of the longest road tunnels in Australia. The approx. 9km long double tube tunnel north of Sydney connects the M1 motorway near Wahroonga with the M2 motorway in West Pennant Hills, thus connecting the city’s north to the 110km long bypass known as the Orbital Network. This will bring relief to Pennant Hills Road, which is being used by more than 5,000 trucks per day.

The tunnel tubes have a height clearance of 5.3m and are designed for a long-term capacity of three lanes, but will initially operate with two lanes and one breakdown lane in each direction. A tunnel section of approx. 22 km had to be excavated for the main and access tunnels of the NorthConnex project. More than half of the tunnel is located at a depth of over 60m; the deepest part is approx. 90m deep. To stabilize the advancement, DSI Underground Australia supplied 476 Types P-140-25-32 and P-200-32-40 Lattice Girders with arch lengths of roughly 20-23m. Furthermore, 190,000 post-groutable CT-Bolt^™ with double corrosion protection were used for immediate primary roof support that were produced by DSI Underground Australia in their Newcastle factory. As permanent ground support products, both systems are designed for a service life of 100 years. Furthermore, DSI Underground supplied soil nails, rock bolts and other ground support products consisting of 20, 25, 28, 32 and 40mm Ø, Grade St 500 DSI Bars and supplied the equipment needed for stressing and testing. Due to the limited time frame, the ground support products were installed in a 24 hour operation with up to 14 roadheaders and roofbolters. This required an optimal supply chain, product management, planning and cooperation between the project teams and DSI Underground Australia. The company’s local production was an advantage because the systems could be delivered to the jobsite just in time.