Assignment
The Condor Tower in the Perth Central Business District has been built on top of the existing Oakleigh Building. The existing structure was re-engineered and strengthened to support 18 additional levels.
A building extension of this magnitude is rare, and required re-engineering of the existing structure and strengthening the foundations.

Our Role
Golder's geotechnical investigations indentified sand and clay layers beneath the building. A 2m deep raft foundation would be adequate, but the existing pad footings were only 914mm deep and would therefore have been significantly undermined during construction.

Golder designed a partially piled concrete raft 1400mm thick to provide support at the foundation level. Geotechnical advice also included using Micro-cement grouting and Micropiling. Microcement grouting was used to stabilise the soil under existing pad and strip footings, allowing them to be cut back and undermined by 400mm to provide space for the raft and Micropiles 300mm in diameter and 12m long to reduce differential settlement and internal forces within the raft slab. The raft was dowelled to existing pad footings.

Golder also provided excavation support analysis and specification of the construction sequence for the project.

Condor Tower won the Engineers Australia 2010 Sir William Hudson Award for the most outstanding project of the Australian Engineering Excellence Awards.

Completed in 2008, Condor Tower measures approximately 100m in height and comprises a carpark, two commercial floors and 25 residential floors. The results of the project will contribute to more efficient building restructuring designs.