Tunnelling starts on Melbourne Suburban Rail Loop

Tunnelling has started on Melbourne’s Suburban Rail Loop (SRL), with Terra Verde JV launching the first of four CREG TBMs that will excavate the northern section of the SRL East tunnels. TBM Alice has started its drive from Burwood towards Glen Waverley, while a second machine, Hacia, has been lowered into the launch site and is expected to begin the parallel drive in the coming weeks. Terra Verde, comprising Webuild, GS Engineering & Construction and Bouygues Construction Australia, was awarded the A$1.7bn Tunnels North contract to construct the twin tunnels between Glen Waverley and Box Hill. Its scope includes almost 10km of parallel tunnels, 39 cross passages, two station boxes, two TBM launch sites and an intervention and ventilation shaft. Alice and Hacia are the first two of four TBMs being supplied by China Railway Engineering Equipment Group (CREG) for the northern tunnelling package. Manufactured in Zhengzhou, China, the machines have 7.25m-diameter cutterheads and are approximately 103m long in their initial configuration. The complete machines will extend to around 120m once assembly underground has been completed. Because of the restricted space at Burwood, the machines are being started using an umbilical launch method, in what SRL says is a first for Victoria. The approximately 500t front shields were assembled at surface and lowered into the launch shaft before excavation began. During the initial drive, the front section of each TBM operates connected to the surface by long cables and hoses providing power and support services. Once sufficient tunnel has been excavated, the remaining gantries and equipment are installed behind the shield to complete the machines. The two machines will drive south from Burwood towards the Glen Waverley station box. Two further CREG TBMs will subsequently be launched from Burwood in 2027 to excavate north towards Box Hill. Collectively the four machines will excavate more than 10km for the northern section. Meanwhile, the southern tunnelling package between Cheltenham and Glen Waverley is being delivered by the Suburban Connect consortium of CPB Contractors, Ghella and Acciona Construction. Four 7.24m-diameter Herrenknecht TBMs will excavate approximately 16km of twin tunnels on this section. Two of the machines are new, while two are being refurbished following their use on Sydney Metro. Different machine configurations will be used to deal with changing ground conditions, including slurry operation and machines capable of conversion to EPB mode in softer ground towards Cheltenham. The first southern machine, Aayushi, is currently being assembled at Clarinda and is scheduled to begin tunnelling towards Glen Waverley later this year. Further machines will subsequently drive towards Cheltenham via the Heatherton stabling facility. In total, eight TBMs will excavate the 26km of twin tunnels forming SRL East between Cheltenham and Box Hill. The tunnels will run at an average depth of around 26m and reach approximately 60m below ground at their deepest point. Major construction is underway at all six SRL East station sites – Cheltenham, Clayton, Monash, Glen Waverley, Burwood and Box Hill. The Victorian Government said tunnelling had started on schedule. It has identified A$1bn in project savings and commissioned an independent technical review aimed at finding a further A$1bn. SRL East is scheduled to open to passengers in 2035 and will form the first section of Melbourne’s planned orbital rail network. Comments: