Tunnelling |
Tunnelling innovations
Recent research has unearthed innovative repairs, fire safety experiments, plus plans to utilise existing road tunnels for hydropower
Above: Full-scale fire experiments have been carried out at a hydropower station to investigate smoke propagation during tunnel construction
AES CORPORATION HAS BEEN carrying out work to extend the operating life of the 1000MW Chivor Hydropower Project which provides 6% of Colombia’s power demands. Chivor entered into service in 1977 with an initial life expectancy of 50 years and the company hopes this new work will extend operations for a further 50 years or more. In a paper published in Water, David del Rio and his co-authors discuss this one-of-a-kind renovation project which will use a modern lining to address the buckling of a headrace tunnel, all while the plant remains in operation. The problems can be traced back to the construction phase when two separate events occurred that directly affected the installed lining at one of Chivor’s two headrace tunnels. According to project records, the buckling occurred due to injection pressure during construction in the first case, and later due to the action of overpressure coming from a leak in the tunnels. Corrected in 1981, the first buckling section of the
14 | March 2024 |
www.waterpowermagazine.com
tunnel was addressed with the installation of a steel pipe with conical transitions at its ends. In December 2019 dewatering was scheduled to remove weak material around the second buckling area and to install a new pipe. AES had been assessing the state of the pipelines since 2000, and its condition assessment led to investigations to select one of four different design alternatives to renovate this important part of the plant’s infrastructure. The selected alternative considers a self-supporting lining capable of providing the appropriate structural resistance for different load conditions: material handling, internal pressure loads, temperature variation, and external pressure loads exerted by the water table over the empty tunnel. As the authors explain, the detailed design allowed obtaining the minimum wall thickness for handling, and the dimensions of straight pipe sections, transitions, and external stiffening rings. The material selected to build the new lining incorporates high-resistance technology and facilitates welding
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