BHP Hot Briquetted Iron Plant

BHP Hot Briquetted Iron Plant
BHP Pty Ltd
Techniques Used: 
Concrete Injected CFA Piles

Project Brief: BHP’s Hot Briquetted Iron Plant was located on Australia’s north west coast in the west of the Pilbara region.  It was one of the largest of its kind in the world at the time and was the first to be constructed in Australia.

With massive iron ore deposits and close proximity to the main port (Port Hedland), this was the logical site for such a plant. Iron ore would be railed to the port, offloaded and transported via conveyor belt through and undersea tunnel to the processing plant (8km away). The completed product, compressed iron briquettes would be returned via the same route, loaded onto ships for exporting.

Geological Conditions: The Pilbara is a very flat mass covering hundreds of kilometres; a semi-desert area shaped over many years by seasonal torrential rain and strong cyclonic winds and is part of the Antecambrian shield.

The dense soil condition together with high uplift loadings from the structure precluded the use of driven systems, while the standing groundwater level at 4.5m depths and the presence of the unstable strata to be penetrated made conventional bored piling difficult and expensive.  Extensive soil investigation was carried out for the project including boreholes, numerous SPTs and extensive pressuremeter testing was undertaken. 

Scope of Work: The project comprised the design and construction of various modules supported on approximately 1500 CFA piles of 600 and 750 diameters with lengths ranging from 9 to 18 metres.

In the Briquetting and Reactor structures, up to nine piles per column were employed to rest a maximum load of 30,297kN compression and 13,447kN tension. Due to the height of the process reactor bins (up to 100m high) settlement and stiffness criteria for the structures was critical.

A detailed global settlement analysis was undertaken by Vibropile using a combination of hand calculations, computer modelling and load testing. Subsequent settlement monitoring proved Vibropile’s analysis to be robust and accurate.

Conclusion: Both the pile type and design methods selected for this significant project were proven to be the most appropriate. The novel design approach was vindicated by both testing and ongoing settlement monitoring.  Despite the remoteness and harshness of the project site, all obstacles had been overcome and a high performance foundation system was installed in Australia’s first iron production plant