The Suburban Rail Loop (SRL) East project will create 26km of twin tunnels and six new underground stations from Cheltenham to Box Hill in Melbourne. Construction on the SRL East has begun, with tunnelling due to start in 2026.
A consortium of CPB Contractors, Ghella and Acciona Construction, known as Suburban Connect, will excavate 16km of twin tunnels between Cheltenham and Glen Waverley on the project’s southern section – the first to be built.
The consortium was selected for the A$3.6b (£1.9bn) contract by the Victorian Government in September of last year. The SRL project is being planned and delivered for the government by the Suburban Rail Loop Authority (SRLA).
Up to 10 tunnel boring machines (TBMs) were initially expected be used to dig the full 26km of twin tunnels for SRL East, with TBMs launching from Monash, Burwood and Heatherton.
Suburban Connect working with SRLA has now decided to use only four TBMs to build the southern section of the SRL East, instead of the six it originally proposed, to minimise construction impacts on the communities near SRL work sites.
The TBMs will also be launched from a new location – a recycling facility in Clarinda. This is to the east of the originally proposed location at the site of the future SRL East train stabling facility in Heatherton and further away from local homes.
SRLA has said that launching the TBMs from the new location better protects a critical state sewer pipeline which runs under the recycling facility.
Two TBMs will now be launched either side of the pipeline – which carries around 40% of Melbourne’s waste. This removes the need for TBMs to run over the pipeline during tunnelling and enables better protective measures to be built.
Two TBMs will travel north-east to Glen Waverley and will be retrieved from Monash once these works are complete. The other two TBMs will head west from Clarinda to the eastern tunnel entrance at the stabling facility in Heatherton. They will then be pulled above ground and transported to the western tunnel entrance, where they will be relaunched south-west to Cheltenham.
SRL East map
Suburban Connect will also use ground treatment techniques such as ground freezing from within the tunnels instead of at the surface. The technique will enable the consortium to excavate most of the cross passages from underground instead of from the surface, thereby reducing disruption to the public caused by the tunnelling programme.
SRLA has said this will eliminate dozens of construction sites on the surface, preventing significant disruptions for nearly 100 homes and businesses including local road closures, noise, dust and vibration.
A spokesperson for the Suburban Rail Loop Authority said: “Construction of SRL East is forging ahead, with construction underway at all six station sites and preparations well underway for tunnelling to start in 2026.
“We’ve been working with our tunnels south partner Suburban Connect to minimise impacts of construction and achieve even better outcomes for the communities near SRL work sites as we build the first section of twin tunnels.”
SRL East is expected to be operational by 2035. It is the first of three stages of the planned 90km orbital loop that will link every major rail line between Frankston and Werribee via Melbourne Airport.
The tunnels north contract for the Glen Waverley to Box Hill section of the SRL East project will be awarded later this year.
Ground Engineering UK
