Guide to tunnel portals

The Cross River Rail project includes 5.9 kilometres of twin tunnels running under the Brisbane River and CBD, with a portal at either end providing access into and out of the tunnels.

The southern tunnel portal is being constructed between Dutton Park station and the new underground Boggo Road station, while the northern tunnel portal is being built near Victoria Park at Normanby.

When construction is completed and Cross River Rail is operational, these two portals will be the gateways into and out of the new underground rail network.

Excavation at the Northern Portal site - April 2021

Constructing the portals

The northern and southern portals are being built using a ‘cut and cover’ technique.

This involves installing piles – post-like concrete and steel reinforcement – to form a box, installing capping beams – concrete slabs – on top of the piles, excavating within the box, and then covering the box with concrete slabs to create a roof.

This box – the cut and cover structure – will then become the entrance through which trains will enter and exit Cross River Rail’s twin tunnels
 

Tunnel portal video

Watch the video below to see our tunnel portal progress to date.

Cross River Rail's tunnel portals

Cross River Rail's tunnel portals

Southern Tunnel Portal

The southern area of the project – between Park Road, Dutton Park and Buranda stations – includes the southern tunnel portal works as well as reconfiguration of existing rail infrastructure to integrate Cross River Rail into the South East Queensland rail network.

The project’s southern portal merges into one of the more complex areas in the South East Queensland rail network, at the intersection of multiple commuter rail lines and a freight line. In addition, the Eastern Busway and a number of other services and utilities run through the area.

This complexity makes the southern area one of the most technically challenging aspects of our project’s design, and Cross River Rail works closely with Queensland Rail, the Department of Transport and Main Roads and other key stakeholders in this area.

When complete, the southern tunnel portal will be 380 metres in length, inclusive of the open trough leading into the portal mouth and the covered trough leading into the tunnel.

In early October 2020, site establishment works commenced in the area including demolition of existing Queensland Rail buildings and installation of Cross River Rail site offices and facilities. Since then, a range of works have undertaken including realignment of the existing surface rail, relocation of services and utilities, and construction of the tunnel portal and twin tunnels.

Excavators will dig the portal trough at the Southern Area and continue digging from the southern portal to the tunnel which will lead to Boggo Road Station.

Construction of the southern tunnel portal is expected to continue until late 2022.

Fast facts

  • 533 piles will be installed for the portal
  • approximately 5,000 cubic metres of concrete will be poured for the installation of these piles
  • approximately 1,015 lineal metres of concrete will be poured for the capping beams
  • 242 precast deck units will be installed as part of the cut and cover portal roof
    approximately 12,000 cubic metres of concrete will be used to construct the southern portal

Northern Tunnel portal

The Northern Area of the project includes the northern tunnel portal works. Construction is taking place in the existing rail corridor at Normanby between the new underground Roma Street station and the upgraded Exhibition station.

The northern tunnel portal will be where trains will enter and exit the northern end of the Cross River Rail twin tunnels. When complete, the portal will be approximately 400 metres long, including 250 metres of open trough leading into the portal mouth and another 150 metres of covered trough leading into the tunnel.

In January 2021, site establishment works commenced including installation of Cross River Rail site offices and facilities, installation of fences around the portal site, and construction of temporary retention structures to allow the start of excavation.

Excavation and construction of the tunnel portal structure began immediately after these works were completed with the installation of all permanent piles completed by late August and commencement of roof installation works in September.

Construction is expected to continue until late 2022.

Fast facts

  • 130 temporary retention piles have been installed along the existing rail lines
  • 299 permanent piles have been installed for the portal
  • approximately 3,000 cubic metres of concrete have been poured for installation of these piles
  • 240 precast deck units will be placed on the capping beam prior to the full excavation of the portal
  • excavation of the TBM extraction box will generate a total 3,000 cubic metres of spoil
  • installation of the gantry crane will commence late September 2021.

TBMs on their way to the Northern Tunnel Portal

The northern portal is where Else and Merle, the two Tunnel Boring Machines (TBMs) being used to tunnel the of longest sections of the twin tunnels, will emerge later this year.

In preparation for the extraction of the TBMs, work has commenced on excavating an extraction zone approximately 15 metres deep as well as the construction of a portal TBM breakthrough face.

A gantry crane and supporting equipment will be installed to lift the TBM components out of the tunnel. An area will be constructed to wash and store the TBM components prior to their transportation away from the site.

You can see the progress of the TBMs via our TBM Tracker.