From the magazine

Tunnelling the MMSR

The original Melbourne Main Sewer was built in the 1890s and needed replacing due to its age and capacity.

Enter John Holland, who constructed the project on behalf of Melbourne Water.

The tunnel boring machine (TBM) used was described at the time as “an underground factory – 110 m long, specially designed to cope with specific ground conditions.”

Trenchless Australasia asked John Holland Tunnelling General Manager Rob Muley about the issues that were faced during construction.

Mr Muley said the highly variable geology and hydrogeology were key challenges, one that was addressed by employing multiple construction methods on the project.

The construction methods included a hard rock TBM, and earth pressure balanced TBM, pipe jacking, drill and blast, roadheaders, and hand mining.

All the while these techniques were utilised under a heavily populated residential environment, working 24 hours a day, six days a week.

Reflecting on the technologies used, and whether the same methods would be used today, Mr Muley said “Technology continues to evolve including recent innovations, such as cast in gaskets for segments, which we have introduced to our project in Sydney – these would have been used on the project.

“We would also look at introducing deck-loading blasting techniques and an innovation introduced into our SIL 904 project in Hong Kong.”

Changes in industry

Mr Muley said that in 2009 the underground industry was at its peak.

“Projects like Eastlink, Airport Link and Melbourne Desal were all being constructed concurrently,” he said.

“The MMSR project commenced in 2007 and completed in 2011.

We continue to see projects packaged at a size we have not seen before, such as the East West Link in Melbourne, Bat tunnel in Queensland, WestConnex Tunnel in Sydney, and things of that nature.

“Today we’re also seeing significant growth in underground projects internationally.

Staff now more than ever have considerable opportunities in the underground industry and those who are portable will benefit most.

“We also see clients coming to contractors much earlier in the project development phase to embed innovation and optimisation of schemes well before coming to the market as part of ECI arrangements.

John Holland sees this as a positive initiative,” he said.

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