Tunnel boring machines to churn through 26km of rock and soil for Suburban Rail Loop

The longest tunnel project in Victoria’s history will use up to 10 mega borers at once to help fast track the Suburban Rail Loop.

Up to 10 tunnel boring machines could be used to churn through 26km of rock and soil for the first stage of the Suburban Rail Loop.

The TBMs for the project, which plans to connect Cheltenham to Box Hill to begin a new orbital rail network through middle Melbourne, would be selected based on local ground conditions.

A decision to send multiple machines into the ground at the same time would also speed up the build time, allowing construction to start in 2026 and the tunnel to open in 2035.

It is not unusual for mega projects to use such a system, with London’s Crossrail project employing eight TBMs for a 21km dig.

Expressions of interest are now open for two tunnelling packages for the project, which is likely to cost a total of $30-34.5 billion.

The first package is for the longest tunnel project in Victoria’s history, burrowing through almost 14km of rock and soil between Cheltenham and Glen Waverley.

It is hoped that contract would be awarded next year, with project chiefs aiming for one of the unsuccessful consortia to take on a second tunnel package between Glen Waverley and Box Hill.

Industry sources have raised questions about this process given it requires at least three strong bids, given the lack of suitable tier 1 rail tunnel builders in the mix.

Suburban Rail Loop will need up to 10 tunnel boring machines just for stage 1.

An artist’s render of how the machines will operate underground.

However, an international search is underway to maximise the number of companies vying for the lucrative jobs.

The primary package of works includes cross passages between tunnels, station boxes at Clayton and Monash, and tunnel entrances and exits at a stabling facility in Heatherton.

Suburban Rail Loop Minister Jacinta Allan said the SRL was a “city-shaping project on a scale we haven’t seen before in Victoria”.

“With early construction about to start, we’re preparing to put tunnels in the ground,” she said.

“Up to 10 tunnel boring machines built specifically for Melbourne’s underground conditions beneath our middle suburbs will soon be ploughing through more than 50 kilometres of rock and soil to build the twin tunnels for SRL East.”

An Environment Effects Statement is still being assessed for the project, which the government hopes to finalise mid-year, before major tunnelling works are signed next year.

The state opposition has promised an audit of the project if it wins the November election, to ensure it represents value for money before contracts are signed.

Originally published as Tunnel boring machines to churn through 26km of rock and soil for Suburban Rail Loop