From the magazine, Microtunnelling, Pipe jacking, Tunnelling

Pipe jacking in the west

The Pilbara Region is located in the North Western corner of Australia in what is known as one of the hottest and at times wettest parts of the world. The Pilbara Region was first inhabited by the ancestors of today’s Indigenous Australians some 40-50,000 years ago. In the 1950s, it was discovered that the Pilbara area was home to one of the world’s largest iron ore deposits. Since this time the region has been an integral contributor to the Australian economy with the help of mining companies such as Rio Tinto.

Upgrading the Cape

Today, the Pilbara region is home to the rail and port infrastructure needed to transport ore from this remote region. With most of the ore being exported, large ports have been built to accommodate the ore transport; one of the largest of these ports is Rio Tinto’s Cape Lambert. Trains travel in from Rio Tinto mines throughout the region, carrying around 80 million tonnes of iron ore per year into Cape Lambert for processing and ship loading.

At present, the port is undergoing an infrastructure upgrade that will see the transportation capacity of Cape Lambert port more than double by mid-2015. Included in the infrastructure upgrades are additional rail lines, ore dumpers, stockyards and jetty. At the project completion, an estimated 200 million tonnes of iron ore will be exported per year from this port alone.

Trenchless installation; the obvious choice

An integral part of the of the overall upgrade are the “÷Sam’s Creek’ stormwater drainage lines, which run under the existing rail lines and allow the release of stormwater during the wet season. Any upgrades to these drainage lines needs to allow the existing rail lines above to stay in constant operation to maintain continual loading of ships. The rail lines are a critical piece of the mining infrastructure and stopping the productivity across this rail for drainage upgrades was not an option, making trenchless installation the only choice. The design of the new drainage culvert specified two rows of 2,100 mm internal diameter pipes at approximately 100 m long, each with an additional row of 2,100 mm internal diameter pipe for services.

Sinclair Knight Merz (SKM), who were contracted to design and manage the project, finalised the upgrade plans specifying HOBAS jacking pipe with an outside diameter of 2,250 mm. The top of the culvert sits approximately 3 m below the rail line, being installed in hard rocky ground. Pipes with a stiffness of SN32,000 were chosen by SKM, given the initial calculations expected a jacking force of up to 800 tonnes would be applied. Intermediate jacking station pipes were also supplied.

HOBAS reduces risk and installation time

With the rocky ground conditions, the smooth outer surface of the HOBAS pipes, coupled with the use of bentonite and the much smaller outside diameter of HOBAS jacking pipe, resulted in a significant reduction in the expected jacking forces required to jack the pipes, compared to the alternative option of using concrete pipe. The substantially smaller outside diameter had the additional benefit of allowing increased ground cover beneath the rail line, reducing both risk and installation time.

Both the client and contractor were surprised to learn that the lead-time for HOBAS was substantially shorter than that of locally supplied concrete pipe. Given the tight timeframe for the project, the decision to use HOBAS was easy. Credit must be afforded to SKM, NRW-NYFL and Tunnel Boring Australia for adopting worldwide proven technology to ensure their project is completed with minimal risk, quickest installation time and most cost effective pipe option.

NRW-NYFL Joint Venture is the head contractor for the works and with the guidance of SKM they have employed Tunnel Boring Australia to undertake the installation of the Sam’s Creek culvert. This installation will set new records in terms of the largest diameter HOBAS jacking pipe installed in Australia, paving the way for similar projects in the ever growing mining industry in Australia.

Promoting awareness of traditional land owners

The NRW-NYFL Joint Venture was established to promote understanding and cultural awareness of the traditional owners of Cape Lambert, as well as to develop employment opportunities within the project for local indigenous workers. The joint venture had the ground breaking idea to use this fascinating project as an opportunity for cultural awareness. The joint venture partner Ngarluma Yindjibarndi Foundation Limited (NYFL) invited local artists Loreen Samson, Katherine Samson, Pansy Hicks and Wendy Warrie to paint the HOBAS pipes in the artistic style of the traditional owners. The images bring good fortune to the land and the HOBAS pipes are now truly part of the local landscape.

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