Structural diagnosis of a concrete dam with cracking and high nonrecoverable displacements

Expansions in concrete dams may be caused by chemical or physical sources; however, in certain occasions the evidences observed in the dam may not be attributed to a single cause. Mequinenza is an example of a concrete dam affected by expansions and high nonrecoverable displacements that cannot be explained by the most frequent pathologies. This paper presents new hypotheses that could justify such behavior by assuming the superposition of a global phenomenon of water induced expansion in concrete in the entire dam and a localized effect consisting in the opening of cracks in the construction joints located in one of the blocks. This is validated by conducting numerical analyses through 2D finite element models that consider the nonlinear behavior of the construction joints and use zero-thickness interface elements to simulate the potential cracking planes in the dam. The results confirmed the diagnosis proposed and the capability of the model to reproduce the behavior of the dam, revealing the significant contribution of the opening of the cracks to the non-recoverable displacements in the dam

Effects of an internal sulfate attack and an alkali-aggregate reaction in a concrete dam

The alkali-aggregate reaction and the internal sulfate attack are two chemical reactions that lead to expansions in concrete structures. The former is one of the main causes of expansions in concrete dams and has been extensively reported in the literature, whereas the latter is less common and, thus, less studied. The confluence of both reactions in one structure is highly unlikely but still possible as shown by the case of the dam studied in this paper. This gravity dam exhibits significantly high non-recoverable displacements that may only be justified by the superposition of both phenomena. This paper focuses on the study of a concrete dam whose diagnosis hypotheses have changed throughout the years according to evolution of the behavior observed. The hypotheses proposed in the study are validated by conducting numerical analyses through 3D and 2D finite element models. The results confirmed the diagnosis proposed and the capability of the model to reproduce the behavior of the dam