All Around #12

"The precision engineering it has taken for this machine to tunnel eight kilometers, through varying and sometimes challenging soil types, to break through in exactly the right spot, is truly remarkable.” With these words, Western Australian Transport Minister Rita Saffioti expressed her admiration for an outstanding project achievement. She was speaking in February 2020 on the occasion of the first TBM breakthrough in Perth for the Forrestfield-Airport Link.

The new subway with its two parallel tubes will connect the eastern parts of the city and the international airport to the city center. With three new stations (Redcliffe, Airport Central, Forrestfield) and the connection to the Midland Line near the Bayswater station, the Forrestfield-Airport Link will significantly increase the capacity of local public transport in the Western Australian city. The journey to the city center will take only 20 minutes by subway instead of 45 minutes by car.

Herrenknecht assembled two Variable Density TBMs (Ø 7,050mm) at its facility in Guangzhou, China, for Perth. In July and October 2017, the two specialists for tunnelling in complex and changeable ground began their work. On the journey from east to west, the two machines passed under both Perth airport in full operation and the Swan River, here up to 26 meters below the river bed.

In April 2020, on the occasion of the second and final breakthrough, Western Australian Premier Mark McGowan paid tribute to the achievement of miners and machines: “The completion of the tunnelling marks an important milestone for Western Australia's infrastructure.”

Carapateena is considered one of the largest copper deposits in Australia. Considerable amounts of gold are also thought to be located here. A gigantic underground mine is being built around 160 kilometers north of Port Augusta in South Australia. The infrastructure requirements for developing the mine and extracting the mineral resources include a series of shafts for the ventilation of galleries and drifts.

Herrenknecht supplied two powerful RBR400VF and RBR600VF Raise Boring Rigs for the construction of four ventilation shafts for the Carapateena Mine. Thanks to their compact design, the RBRs offer high flexibility, even under space constraints. They have proven their worth with their modular design and efficient center-free drive.

To begin with, the rig is installed above a starting point for the shaft using a transport system. The Raise Boring Rig then sinks the pilot drill – depending on the drilling depth, more drill rods are gradually installed until the target in an existing heading is reached.

Subsequently, the pilot drill bit is removed and the reamer attached to the drill string. Once assembled, the rig pulls the reamer upward on the drill string. The rotation of the rods is transferred to the cutterhead, thus excavating the rock. The muck falls down and can be easily removed. In this way, from bottom to top, the entire shaft is expanded to the diameter of the reamer.

With the two RBRs from Herrenknecht, four ventilation shafts with depths of 100 to more than 400 meters were created for the Carapateena Mine. After the pilot holes had been sunk, the reamers successfully extended the boreholes to 5 or 5.5 meters.

Further information about RBR technology:
> Raise Boring Rig (RBR) by Herrenknecht

The Army Bay Wastewater Treatment Plant Outfall Replacement project, on the Hibiscus Coast near Auckland, is creating a new sea outfall with a total length of 2.9 kilometers. As a replacement for the existing obsolete pipe, the pipeline connects the pump station with the discharge point – about one kilometer off the coast – and increases the pipeline capacity of the wastewater treatment plant fourfold.

For this modernization measure, Herrenknecht’s innovative Direct Pipe® technology was used. With a drive of 1,930 meters, the crew set a distance world record with this method – the first time the method was used in New Zealand. The previous longest pipe string installed with Direct Pipe® was 1,496.48 meters long.

A special focus of the project was on environmental protection: neither the surrounding recreational and fishing area nor the local flora and fauna were to be affected. The Direct Pipe® method is ideal for such sensitive installations. Pipeline installation takes place in a single step. In this way, the environmental impact is kept low and the landscape remains largely intact. In Herrenknecht’s patented method, an AVN machine excavates a tunnel while the pipe string attached to the TBM is simultaneously inserted during the tunnelling process. The required thrust force is provided by the Pipe Thruster, two of which were used in New Zealand.

Just under four months after launch, the successful breakthrough of the microtunnelling machine “Blanche” was reported in New Zealand’s Whangaparaoa. After reaching the target location on the seabed, the AVN machine was recovered from the sea and towed back to land.

Success story, part 2

In 2019, the utility tunnelling specialists rely on the same Direct Pipe® system only a couple of kilometers to the north close to Mahurangi. For the underground installation of the Snells Algies Outfall Pipeline another record-breaking tunnel drive is tackled. Watercare Services, the Auckland region’s water and sewage company, has commissioned a new and more efficient sewage tunnel for the communities on the Mahurangi peninsula.