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Dam breach
Published in Willi H. Hager, Anton J. Schleiss, Robert M. Boes, Michael Pfister, Hydraulic Engineering of Dams, 2020
Willi H. Hager, Anton J. Schleiss, Robert M. Boes, Michael Pfister
A fuse plug corresponds to an erodible, pre-determined separate section of an earthfill dam designed to wash out if the approach discharge exceeds the spillway capacity discharge, and the reservoir reaches the design crest elevation. Fuse plugs are progressively eroded within a certain duration thereby releasing a surplus discharge without endangering dam safety. An uncontrolled auxiliary spillway would serve the same purpose but its length would have to be excessive to keep the overflow depth small. In contrast, the fuse plug provides identical discharge capacity with a much reduced width because it is gradually washed away.
Fuse Plugs and Fuse Gate Spillways
Published in R. M. Khatsuria, Hydraulics of Spillways and Energy Dissipators, 2004
Fuse plug, or a breaching section, is an erodible predetermined separate section of an earth dam designed to wash out when the inflow is in excess of the spillway capacity and the reservoir behind it reaches a specified level. The fuse plug collapses gradually over a reasonable time frame when overtopped, releasing surplus flood without endangering the safety of the main dam and lowering the reservoir level. An uncontrolled auxiliary spillway with a higher crest elevation would also serve the same purpose, however, the length of such a spillway would be very large in order to keep the depth of overflow as small as desired. A fuse plug can be provided in a shorter length by envisaging development of a deeper channel in downstream as the fuse plug embankment gets washed away.
A review of Piano Key Weir as a superior alternative for dam rehabilitation
Published in ISH Journal of Hydraulic Engineering, 2022
Piano key weirs are themselves extremely hyper-static structures that are solid and very simple (Sharma and Tiwari 2013). They have a specific flow range varying from 3 to 1000 m3/s/m. Overall stability and anchorage of PKW have been studied for like Goulors dam, Gloriettes dam, Saint-Marc and Etroit dam (Vermeulen et al. 2011), in Malarce dam (Pinchard et al. 2011), upgrading of Dartmouth dam (Phillips and Lesleighter 2013), Hazelmere dam and Tzaneen dam in South Africa (Botha et al. 2013), Charmines dam (Valley and Blancher 2017) etc. The detailed report in the erection of PKWs has established them to be structurally safe, and load analysis can be done just like a gravity dam. Fuse devices have also been studied in association with PKW. Fuse devices are spillway structures that open only once and then are lost or permanently displaced. Such devices may be very cost-effective, delivering the benefits of a gated spillway with lower material and construction costs. Labyrinth fuse gates have been used in over 55 dams around the world (Le Blanc et al. 2011). Optimization of fuse gates can lead to economical and versatile solutions for flood routing of common floods. Lempérière and Vigny (2011) have suggested that the PKW solution is the best solution for discharges up to 5000 m3/s. For higher discharges, PKW, in association with fuse plugs, can give interesting and cost-effective solutions (Ouamane et al. 2017). The primary drawback of using Fuse plugs is the cost of replacement and lost reservoir storage if the fuse device does deploy. Typically, these types of spillways are used for floods having an annual probability of 1 in 100 or less. Concrete fuse plugs are relatively inexpensive to build, but they require a large amount of space. Further problems persist as to their long-term reliability (in particular, changes over time in the cohesion and compaction of the earth) and the downstream consequences of their deployment. Structural costs of Fuse plugs, though being lower, the complex design and hard currency required for patents are more difficult than a PKW. Moreover, operators are reluctant to the use of fuse gates because of costing and negative public image in case of gate loss.