Underground construction |
Tunnels, turbines, and transformations
From Australia’s Snowy 2.0 to Site C construction in Canada and Germany’s Forbach heritage conversion, India’s Vishnugad-Pipalkoti project and Scotland’s Cruachan 2 expansion – IWP&DC explores the underground construction work helping to shape these important projects
IN A SIGNIFICANT ACHIEVEMENT for Snowy Hydro and its Snowy 2.0 project, a major milestone was reached in July as one of the project’s three tunnel boring machines (TBM) marked its progress. TBM Lady Eileen Hudson crossed a pivotal milestone by commencing its second tunnel excavation after successfully completing the first phase. TBM Lady Eileen’s mission entails the excavation of a 6km tailrace tunnel that will connect the Talbingo Reservoir to an underground power station complex. This tunnel will play a crucial role in facilitating the flow of water for power generation, with the Snowy 2.0 project aimed at producing 2000MW of power. After completing the 2.8km main access tunnel
(MAT) in 2022, it has been a big task to disassemble and safely extract TBM Lady Eileen and reassemble her with new components before commissioning, said Snowy Hydro. The conveyor stacker, grout batch plant, and chiller plant were also relocated from the MAT portal to the Talbingo adit. Before embarking on its underground voyage, the
customary tradition of blessing was carried out for a safe journey under the watch of St Barbara, the patron saint of tunnelling and underground work. This ritual, observed at tunneling sites across the globe, took place in an onsite ceremony overseen by local parish priest Father Mark Croker, attended by Snowy 2.0 workers.
Following the blessing, TBM Lady Eileen was set
Below: Lady Eileen Hudson is one of three TBMs in use at the Snowy 2.0 project in Australia
into motion, its 378-tonne cutterhead making its mark on the rock face. This cutterhead, composed of 70 cutting discs, each weighing 290 kilos, has been designed to navigate the varying geological challenges of the 11m diameter tunnel. The TBM
itself, measuring 137m in length and weighing a staggering 2300 tonnes, operates as a mobile factory, orchestrating a synchronized dance of complex components.
A crucial aspect of this operation involves utilizing over 27,000 concrete segments manufactured at the Polo Flat, Cooma precast facility. These segments will line the tailrace tunnel, with the TBM housing essential equipment including a segment erector, segment feeder, segment cranes, and a sophisticated grouting system.
Incorporating advanced technology, the TBM is equipped with a guidance system that provides precise data to the machine’s pilot, ensuring meticulous accuracy down to the millimeter. This data is closely monitored by Snowy 2.0’s construction and engineering teams to ensure seamless progress. Last month, Snowy Hydro unveiled a new completion date of December 2028 and a revised total cost of $12 billion for the proejct, following an extensive review and reset process. In a statement, the company said that as of June 2023, $4.3 billion had already been invested in the project, with approximately 80% of these funds contributing to the Australian economy. It also said that first power generation from the project is now slated for the second half of 2027, with a subsequent target date for full commercial operation of all units set for December 2028. One of the key changes included in the reset is a
shift from the fixed-price Engineering, Procurement, and Construction (EPC) Contract to an incentivized target cost contract model. This transition is being carried out in collaboration with the Future Generation Joint Venture (FGJV), Snowy Hydro’s partner in the project. Additionally, Snowy Hydro is actively resolving all outstanding claims with FGJV. Through the project reset process, Snowy Hydro has successfully enhanced the project’s capacity by 10%, resulting in a total dispatchable generation capacity of 2200MW. Furthermore, Snowy 2.0 will provide energy storage of 350,000 MWh, equivalent to 160 hours of generation at maximum output. The cost revision reflects the cumulative impact of various external factors, including the challenges posed by the COVID-19 pandemic, labor shortages, disruptions in global shipping and supply chains, inflation in construction materials and labor costs, as well as design complexity. Despite these challenges, Snowy 2.0 remains economically viable, with strong market demand expected to support its services well into the future.
14 | October 2023 |
www.waterpowermagazine.com
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