Mignano Dam Rehabilitation
(pubblicato in: Atti del convegno internazionale “9th ICOLD European Symposium – Sharing experience for safe and sustainable water storage” organizzato da ITCOLD – Comitato nazionale italiano per le grandi dighe, 10 – 12 aprile 2013, Venezia)
Marco Belicchi, Denis Cerlini, e Ugo Majone
SUMMARY: Mignano dam on Arda river is subjected from several years to water level restrictions until the finish of some rehabilitation works (now completed) finalized to reach the complete dam efficiency, safety and the maximum utilization of the reservoir.
Mignano dam rehabilitation required:
– an exhaustive hydrological study to define the design discharge (800 m3/s, T=1000 years) for the overfall spillway extension and new stilling basin;
– physical modeling (1:40 geometric scale, according to Froude similarity) to check the hydraulic behavior of the designed structures.
Some cases of damage experienced on spillways chute and stilling basins (e.g.: Malpaso, Tarbela and Karnafuli dams), operating under flood conditions, showed that conventional design methods proposed in literature had been correctly applied but they were not sufficient to avoid damages in the linings. So, Mignano dam physical modeling was focused on stilling basin concrete slabs stability design criteria, measuring directly forces and pressures (using force and pressure transducers) acting on the slabs at the bottom of the stilling basin in the hydraulic jump region. The experimental results allowed to define a design criteria of the equivalent thickness that should be assigned to the concrete slabs to assure the stability of the lining in the stilling basin.
Keywords: dam rehabilitation, stilling basin, pressure fluctuations