Three TBMs now excavating Melbourne's 26 km Suburban Rail Loop East tunnels

Three tunnel boring machines are now simultaneously excavating the twin tunnels for Melbourne's Suburban Rail Loop East, as underground construction expands across the Burwood, Glen Waverley and Clarinda sections of the project.

TBM Hacia, named after construction industry trailblazer Hacia Atherton, has joined TBM Alice on the drive from Burwood towards Glen Waverley, while TBM Aayushi, named after health advocate and medical student Aayushi Khillan, has started excavation from Clarinda in the opposite direction, also heading towards Glen Waverley. Since tunnelling began in September, the three machines have completed a combined 138 m of tunnel.

A fourth machine, Belinda, named after Puffing Billy steam train driver and medical student Belinda McKenzie, is currently being assembled at Clarinda and is expected to launch shortly. Additional TBMs will follow in 2027, with two machines planned to head north from Burwood towards Box Hill and further drives scheduled from Heatherton towards Cheltenham.

The tunnelling forms part of SRL East, which will comprise 26 km of twin tunnels linking six new underground stations at Cheltenham, Clayton, Monash, Glen Waverley, Burwood and Box Hill. On average, the tunnels will run approximately 26 m below ground level, equivalent to around six storeys.

One of the distinctive features of the current tunnelling programme is the way the machines are being launched. Restricted space at the construction sites has led crews to use an "umbilical" launch method, in which the front section of the TBM begins excavation before the entire machine has been assembled in its final underground configuration. The remaining sections and back-up equipment are progressively constructed and connected behind the advancing shield.

This approach allows tunnelling to begin from constrained launch sites where there is insufficient space to assemble the full machine before excavation starts. It also requires careful coordination between tunnelling, machine assembly, power supply, spoil handling and other supporting systems as the TBM advances away from the shaft.

Supporting infrastructure is being developed simultaneously above ground. At Clarinda, crews are constructing an acoustic shed over the launch site to reduce noise, light and dust impacts on surrounding properties. Systems are also being installed to remove excavated material and provide electrical power to the TBMs.

At Burwood, excavation is continuing for the future underground station as well as a second TBM launch site. The station will eventually provide a direct rail connection to Deakin University, with the project estimating that a student travelling from Cheltenham to Deakin will complete the journey by public transport in 19 minutes, saving around 40 minutes. The launch site will support the next northbound tunnel drives towards Box Hill.

All TBMs working on SRL East are planned to operate using 100% renewable electricity. More than 4,300 people are currently working across the wider project.

With three machines now underground and a fourth preparing to launch, the project is moving from individual tunnel starts into a broader multi-TBM construction phase. The simultaneous drives allow different sections of the 26 km alignment to advance in parallel, while placing increasing importance on the coordination of excavation, segment supply, spoil removal, power and activity at the project's multiple station and launch sites.