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Project Updates Mar 12, 2024


Rozelle Interchange is one of the most complex underground motorways constructed in Australia, and is the final stage of WestConnex. Rozelle Interchange, constructed by John Holland and CPB Contractors (JHCPB) Joint Venture and delivered for Transport for NSW, has been completed and was opened to the traveling public in November 2023.

Delve Underground provided design and construction phase services (CPS) to JHCPB for Rozelle Interchange. Our services included mainline carriageways, ventilation arrangements, cross passages, portals, shafts, and temporary declines that formed part of a network of crisscrossing curved tunnels. The design and construct contract was signed on December 14, 2018; detailed design commenced in late January 2019; and construction began in November 2019.

Rozelle Interchange comprises a 23-kilometer-long (14.3 mi) network of road and ancillary tunnels. Its unique multilevel underground interchange created engineering challenges in the way tunnel excavation and rock deformation interact with the ground support. There are 16 caverns on the project, up to 29 meters (95.1 ft) wide and 24 meters (78.7 ft) high. The complex geometric alignment of the project results in more than 50 tunnel interactions, with rock bridges between crossing tunnels as narrow as 4 meters (13.1 ft).

Ventilation Facility 4 under construction

Excavation was completed using the sequential excavation method (SEM), with up to 23 roadheaders at peak production. Most of the tunnels were supported using permanent double corrosion protected rock bolts and shotcrete with a design life of 100 years. Difficult ground conditions associated with complex geological structures, high in situ stresses, and proximity to the Sydney Harbour created significant challenges for excavation and support, including rock bolt shearing.*

As a part of the contract, Delve Underground provided CPS to JHCPB, giving our team extensive involvement in construction. CPS includes an on-site presence to assess encountered ground conditions and ensure appropriate ground support is selected. CPS support also includes a design element in the form of responses to Requests for Information, Nonconformance Reports, and Hold Points.

“The last bit of rock” at Site B was excavated in May 2022, commemorated with a special banner. After more than 18 million work hours and 5 years of construction, Rozelle Interchange opened to the public in November 2023. The project was delivered on time and within budget.

For additional information, the Rozelle Interchange interactive construction portal website provides flythroughs above and below the surface on the Rozelle Interchange project, including the parklands and main tunnels.

*See Bai et al., “Rock bolt shearing during construction of multi-level tunnels in Sydney,” Proceedings of the Australasian Tunnelling Conference, November 2023, Auckland.

“The last bit of rock” at Site B, Rozelle Interchange