THE SAFETY ASSESSMENT OF FILL DAMS WITH GATED OR UNGATED SPILLWAYS

摘要

Hydroelectric developments with gated spillways and earthfill retention dams, quite vulnerable to overflowing, represent a large share of dam construction in Romania and raise major safety and risk problems. Usual regulatory principles and methods for gated spillway dimensioning take into account empirically the spillway peculiarities as compared to the ungated spillways from the safety point of view, but neglect significant aspects. There are suggested analysis and decision procedures based on determining the (binominal type) probabilistic distribution of the capable discharge of a spillway equipped with identical gates, starting from the unavailability probability (handling incapacity) of a gate and from the concept of checking the structure under limit conditions of breakdown induced by overflowing. Results show that value of. gate unavailability probability has a decisivej importance that leads to the necessity of providing a number of additional bays for taking over the discharges corresponding to the non-operating gates at any handling (opening) test. Reliability of spillway hydromechanical equipment (gates) is a primordial and decisive problem for work safety, much more important than that related to other elements, requiring a perfectly legitimate concern and financial effort.