| Construction
Left, top: The Kemano T2 tunnel boring machine, named tl’ughus by the Cheslatta Carrier Nation after a legendary giant monster snake, broke through on 11 October 2021
Left, bottom: Employees stand in front of the head of the 1300-tonne tunnel boring machine after it completed its 7.6-km journey through Mt. Dubose
Right: A completed section of the second tunnel in Kemano, British Columbia
and ventilation tunnel, inclined pressure shaft and 2km of the headrace tunnel – more than 6km of tunnelling. Approximately 1400 people are working on Snowy 2.0, with 150 local businesses involved and 4000 jobs expected to be created during the life of the project. Built by Future Generation – a joint venture between
Webuild, Australian partner Clough, and Lane Construction, a US subsidiary of Webuild – Snowy 2.0 will link the existing Talbingo Reservoir with Tantangara Reservoir through a network of tunnels. Set in the Snowy Mountains, it will provide 2000MW of fast-start, dispatchable energy and provide 350,000MWh of large-scale storage, enough to power the equivalent of 500,000 homes for over a week during peak demand. It will reduce volatility in the power market, support reliability and bring down power prices for families and businesses.
Tunnel spillway research High-velocity air-water flows commonly occur in
hydraulic structures such as spillways and low- level outlets at reservoir dams. The entrained air induces strong changes in the flow properties of the air-water mixture, and engineers must take this into consideration when designing such infrastructure. However, existing design guidelines primarily take
into account laboratory scale tests as experiments that measure high-speed air-water flows at prototype scale are challenging, due to access difficulties and high costs, and are therefore scarce.
As Benjamin Hohermuth, Robert M. Boes and Stefan
Felder recently explained in a paper published in the Journal of Hydraulic Engineering, researchers have undertaken further study into this at the Luzzone Dam in Switzerland. In spring 2019, researchers at Switzerland’s Laboratory of Hydraulics, Hydrology and Glaciology (VAW) together with partners from the Water Research Laboratory at the University of New South Wales in Australia, developed a two-phase flow instrumentation for measurements at prototype outlets and spillways. They installed the system in the tunnel spillway of the 225m high dam in Ticino. Probes had to be custom-made for the research and, for the first time, air-water flows with velocities exceeding 40m/sec were measured. The study confirms good agreement with existing empirical design equations for some bulk air-water flow properties such as mean air concentration, while more detailed properties such as droplet size are significantly influenced by scale effects. Furthermore, the research is described as being an important step toward better understanding scale effects of air-water flows and will help to improve design recommendations for hydraulic structures. ●
References High-Velocity Air–Water Flow Measurements in a Prototype Tunnel Chute: Scaling of Void Fraction and Interfacial Velocityvertical_align_bottom by Benjamin Hohermuth, Robert M. Boes & Stefan Felder. Journal of Hydraulic Engineering (2021), doi: 10.1061/(ASCE) HY.1943-7900.0001936
Speed record for measurements of water-air flows by Iris Mickein. ETH Zurich, Dept. of Civil, Environmental and Geomatic Engineering. 29.10.2021
https://baug.ethz.ch/en/news-and-events/news/2021/10/speed-record-for- measurements-of-water-air-flows.html
www.waterpowermagazine.com | January 2022 | 13
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