Upper West Side

Upper West Side
Brookfield Multiplex
Techniques Used: 
Bored Piles under Polymer Suspension Fluid in diameter 600 to 1500mm

Project Brief: The Upper West Side Apartments is located on Spencer St and Lonsdale St, opposite Southern Cross Station. This Melbourne CBD development is a new high rise landmark built at the location of the former main power plant. Built in the last century the old power plant was a masterpiece of engineering excellence. Large diameter pipelines running underneath the CBD from the Yarra river to the Port Phillip Bay supplied the water to generate energy for Melbourne’s centre and adjacent suburbs. The old façades and some remarkable structures from the power plant are incorporated into the Upper West Side apartment block.

Geological Conditions: The majority of the piles were installed from somewhat 6m below street level where the old basement level of the power plant is located. The old building was founded on Basalt ranging from medium to very high strength. The basalt is underlayered by clays and sands in varying thicknesses. Approximately 16 to 18m below the basement level medium to high strength siltstone was encountered.

Scope of Work: The conforming layout comprised approximately 200 piles in diameters ranging from 600mm to 1500mm. Loads of up to 47MN in compression and up to 13MN in tension had to be accommodated by Vibropile’s pile design. Restrictions by the existing underground structures did not allow an alternative pile layout. The challenge was an economical solution to carry huge loads into the lower Siltstone layer with minimal settlement. To achieve that, piles were socketed up to 6m into the Siltstone using the bored method. As the piles are penetrating through a sand layer with groundwater, a support medium was required. Vibropile decided to work the environmentally friendly polymer instead of using bentonite.

The so called Economizer building, a part of the old power plant located on Spencer St was integrated into the new structure almost completely. The confined space within the Economizer building allowed only the utilisation of a small E300 rig for the installation of 28m long piles with diameters up to 1500mm. The polymer supply into this area was managed from the basement area where another crew installed piles simultaneously. Additional pumps were required to transfer the polymer via pipelines to several locations all across the construction site.

Conclusion: The polymer mix set-up was initially supervised by an expert from the polymer supplier to confirm the adjustment to the given ground conditions. However, Vibropile’s experienced site crew handled the polymer fluid with confidence from the very start. Although the use of drilling fluid is a slow installation process and restricts the limited space on site, Vibropile managed to incorporate the piling activity smoothly within the client’s program.

The Upper West Side was the last job of the NCK crane with attached DB150 power drill and its operator Johnny Lee. For decades this powerful team was working together. With his over 60 years, Johnny Lee eventually made himself comfortable in a hydraulic rig of Vibropile’s fleet.