Four TBMs are now working in Melbourne to expand the sewer network in the Victoria state capital in two separate construction schemes being built by John Holland.
The contractor launched a Lovat EPBM early this month on one scheme while, elsewhere in the city, it had a Robbins double shield nearing completion on its second drive and two Herrenknecht EPBMs continuing to make progress.
The 2.92m diameter Lovat machine (RME115SE) is being used on Melbourne Main Sewer and has a mixed ground cutterhead with 15.5” discs. An almost 2.1km long tunnel is being bored through marine and estuarine deposits of sand, silt and clay, and possibly some basalt.
Melbourne Main Sewer is being developed by Melbourne Water to the east of the city on behalf of the state Government. The utility is also working, separately, with Yarra Valley Water, to build a total of 12.6km of sewer in the north of the city, also on behalf of the state, by 2012.
The utilities are handling Stage 1 (8km) and Stage 2 (4.6km) of the Northern Sewerage Project, respectively. In total, the seven new sewer tunnels will be excavated using the Robbins TBM and Herrenknecht EPBMs.
Robbins’ 3m diameter TBM (“Julia”) holed through last month after its first, 2.1km long drive. Geology comprised massive basalt to weathered basalt with clay filled seams, and roof conditions remained competent for installation of split set rock bolts, as planned.
The TBM is advancing on the final, 1.1km long bore and is due to hole through next month.
Herrenknecht’s 3m and 4m diameter TBMs – “Victoria” and “Gemma” – were launched earlier. The smaller machine was launched in May 2008 on a 1.6km drive and achieved the first programmed breakthrough on the project at the end of last year, driving at depths of 19m-37m.
