Concrete dam AAR numerical modelling and stress relief measures

In Switzerland, the peak period for the construction of large hydropower plants dates back than 50 years ago. Only in the '80s a reaction was discovered, which generates internal swelling of the concrete and causes permanent damage to the structures. The reaction, known as the alkaliaggregate reaction (AAR), is aecting more and more concrete structures, especially dams, both in Switzerland and around the world. Given that the reaction is highly inhomogeneous and its propagation is often extremely uncertain current simulation methods are unable to provide an unequivocal description of the internal stress state. Such methods, which are calibrated with in-situ deformation measurements, do not allow a single plausible stress distribution. The present study, based on the numerical modelling of AAR using thermal analogy, is carried out using the nite element program ANSYS Mechanical. Three expansion cases are proposed which expressly generate identical macro-deformations but present a dierent stress distribution. Through the application of the diamond wire cutting method, often used for rehabilitation, an investigation method has been developed that allows the identi- cation of the corresponding swelling model, according to the parameters measured in the cut. This allows the validation of the good expansion model and therefore the continuation of the most suitable rehabilitation measures.