About the NorthWest Growth Centre
Comprising 16 Precincts, the North West Growth Centre is approximately 10,000 hectares and will contain about 70,000 new dwellings for 200,000 people. As part of early infrastructure works Lend Lease (then Abigroup) won Contract Packages 2 & 3A – The project has a value of $70M.
Work Lot 16 required microtunnelling 2 drives under a highly sensitive Aboriginal artefacts area. The length of the microtunnels were 205m and 180m long.
Pezzimenti Tunnelbore was awarded the contract by Lend Lease. Pezzimenti engaged RA Smith Contractors to construct the launch and receive shafts for the microtunnelling.
205m and 180m pipejcked
The 205m drive was completed in 3 weeks pipejacking a Ø508 steel sleeve through the saturated clay and gravels at the very flat grade of 0.29%. The 300 GRP pipes were supplied by LL from Flowtite. The pipes a SN10,000 pipe with a RRJ collared pipe were sliplined into the steel sleeves and the annulus grouted.
The 180m microtunnel encountered very hard cobbles at the 94m mark and slowed progress until the 120m mark when progress was halted after encountering a 120mm cobble. Because Pezzimenti carry multiple drilling rigs and microtunnel boring machines the microtunnel was completed using the intercept method drilling from the upstream end. Excavation of the surface in the Aboriginal sensitive area was not an option.
Typical site setup at the North West Growth Centre.
Steel Casing and rod being lowered into the shaft.
Preparing the next steel casing.
A steel casing is being aligned ready for pipejacking.
Large Boulders were a common feature of part of the works
High plasticity clay made microtunnelling difficult and slow on occasions. It’s always good to see the head poke through.
When pipejacking long distance the jacking frame is concreted in to provide stability and a clean work space.