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WestConnex – M4 East Tunnel Design, Sydney, Australia

THe project

A critical part of the NSW Government’s integrated transport solution, WestConnex is the largest transport and urban renewal project in Australia. The M4 East Tunnel is the first underground stage of Sydney’s $6.8 billion WestConnex Project. It extends the existing M4 Motorway with two new three-lane tunnels linking Homebush to Haberfield. Each of the 5.5 km long tunnels has spans ranging from 15 m to 30 m. A further 8.5 km of ramp and access tunnels provide access and egress along the route. A joint venture between CPB Contractors, Samsung CT and John Holland (CSJ) was awarded the $2.7 billion contract to design and construct the M4 East tunnel.

PSM was engaged by CSJ to provide design and construction phase services.

engineering and technical OPPORTUNITIes

This high-profile project raised a high level of public concern and involved multiple stakeholders. It also involved complex interaction between numerous underground structures.

When complete, the caverns will include Australia’s widest civil road tunnel, with spans up to 30 m wide accommodating five traffic lanes.

approach AND innovation

Following rigorous assessment and geotechnical and hydrogeological modelling, PSM’s tailored approach included:

  • Prediction of ground settlement
  • Provision of geotechnical advice including retaining wall and cut slope design
  • Assessment of soil and groundwater salinity and material reuse
  • Validation of ground conditions
  • Provision of primary and permanent ground support designs
  • Provision of geotechnical and hydrogeological monitoring
  • Participation in permit to excavate (PTE) and provision of various construction-related geotechnical advice.


PSM successfully provided major aspects of the project within exacting timeframes including primary and permanent support design for 7.8 km of tunnel including all six caverns.




Services: #infrastructure #M4 East #Tunnelling #WestConnex

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