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The role of numerical modelling in the choice of the rehabilitation design solution to guarantee the long-term safety operation of Beauregard dam

pubblicazioni - Presentazione

The role of numerical modelling in the choice of the rehabilitation design solution to guarantee the long-term safety operation of Beauregard dam

La diga di Beauregard, soggetta a un movimento di versante in sponda sinistra che ha causato uno stato di fessurazione importante, è stata demolita parzialmente mediante esplosivo per garantirne l’esercizio in sicurezza nel medio lungo termine.

The Beauregard dam is a concrete arch-gravity structure 132m high, built between 1951 and 1958 on the Dora di Valgrisenche River (Italy). The design reservoir volume was about 70Mm3.The geological and geotechnical investigations carried out since the dam construction have underlined the presence of a Deep-Seated Gravitational Slope Deformation (DSGSD) on the left slope. Since the first fillings of the reservoir, the interaction between the DSGSD and the dam was recognized to have relevant implications on the dam structural safety.

For that reason, the Italian Dam Authorities in 1969 prescribed a limitation of the reservoir level with a corresponding reduction of its volume to 6.8Mm3, about 1/10 of the initial design volume.The interpretation of the effects of the slide movements against the dam, the forecast of the future possible trends and the choice of the design solution to guarantee the long-term safety operation of the dam – consisting in the demolition of the upper part of the structure in order to drastically avoid the foreseen occurrence of large deformations in the dam body associated to the DSGSD movement – have been performed making resort to complex numerical modelling activities carried out using ABAQUS Implicit.

The non-linear behaviour of the dam has been described by means of the Concrete Damage Plasticity model. Surfaces have been included into the mesh to model the interaction between the dam and the rock foundation/DSGSD as well as the sliding of the DSGSD on the rock foundation. The partial demolition of the dam has been simulated progressively removing groups of finite elements.

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