La reacción sulfática de origen interno en presas de hormigón. Propuesta metodológica de análisis

Abstract

The main objective of this thesis is to analyse the behaviour of concrete dams affected by the expansive phenomena of internal sulfate attack (ISA) due to the oxidation of iron sulfide in the aggregate from the material level to the structural behaviour. As a result of that analysis, a comprehensive methodology of study was proposed to establish a decision-making policy in the management of such structures. The work has taken into account different complementary techniques including previous work, laboratory tests and analytical and numerical studies. The previous work, which includes both the analysis of the documentation and a visit to the dam and its zone, allows formulating a first hypothesis of the behaviour of these structures. A methodology of an experimental series on concrete and aggregate samples is presented. Using the results of the laboratory tests the main cause of the abnormal behaviour and the associated expansion can be confirmed. The next step was to analyse the behaviour of structural concrete dams affected by the ISA. On the one hand, a 2D linear analysis of the structural behaviour of cross sections under external loads and due to the expansive phenomena was made. On the other hand, a 2D non-linear numerical study in order to explain some cracks observed in the face of the dam is presented. It also presents an analysis of the displacement of the structure with an exponential mathematical model. The proposed methodology was applied and validated to real dam structures, mainly the Torán, Graus and Tavàscan dams located in the Catalan Pyrenees, all of which are an area with identical geological formation, with predominance of metamorphic rock with iron sulfide deposits. In addition, other dams with different typology and expansive phenomena have been presented: Belesar, Mequinenza, Portodemouros, in Spain and Isola and Roggiasca in Switzerland. As an important conclusion of the work it should be noted that the integration of different techn