Client:
Cross Yarra Partnership (CYP)
Cross Yarra Partnership (CYP) link opens in a new tab
Project Owner:
Rail Projects Victoria (RPV)
Rail Projects Victoria (RPV) link opens in a new tab
Borehole geophysical surveys, accurately locating raking piles to protect live infrastructure during excavation for Melbourne’s Metro Tunnel
The Metro Tunnel Project
The $11 billion Metro Tunnel will create a new end-to-end rail line from Sunbury in the west to Cranbourne/Pakenham in the south-east, with high capacity trains and five new underground stations.
The project scope includes twin nine-kilometre rail tunnels from the west of the city to the south-east as part of a new Sunbury to Cranbourne/Pakenham line, and five new underground stations: North Melbourne, Parkville, State Library, Town Hall and Anzac.
The problem
Between the Western Portal and the future North Melbourne Station, the tunnels will be excavated beneath the existing West Melbourne electricity terminal station, in Kensington (VIC). Several abandoned or working foundations are expected at the location of a decommissioned transmission tower and of an existing tower. SIXENSE were appointed to develop a borehole geophysical survey solution to determine the length and the location of existing foundations.
The downhole geophysical survey
The expected clearance between the existing foundation and the future tunnel excavation is less than 1m for some of the piles. Three geophysical methods – seismic, magnetic & electromagnetic – were successfully used to accurately locate the raking piles and precisely determine the clearance.
Finally, the clearance between the existing structures and the future works was confirmed to be very small and a new design was developed to mitigate the risks and avoid encountering issues during excavation.
Images of the project
6 boreholes
Downhole seismic, magnetic, EM,
Acc. +/-30cm on pile location
