Modeling the cracks opening-closing and possible remedial sawing operation of AAR-affected dams

A significant number of existing concrete dams are at present deteriorated by chemo-mechanical processes known as Alkali-Aggregate Reactions (AAR). This phenomenon is responsible for cracking and expansion of the material which lead to mechanical degradation of the structures operability and safety. Its chemo-mechanical modeling has been already dealt with by considering the influence of temperature, humidity, stiffness reduction and stress in the development of expansion. This modeling has first been developed as valid only for continuous media. In order to widen the field of modeling applicability, this paper describes a novel procedure for modeling displacement discontinuities in AAR-affected concrete structures, mainly to take into account two phenomena: firstly, the modeling of significant isolated cracks opening-closing that result from interactions between expansion and mechanical behavior of the structure; and secondly, the evaluation of the potential efficiency of stress release (e.g. sawing of dams), the procedure of which consists in the creation of slot cutting in the structure for release of excessive compressive stresses. The elaborated model, aimed to possibly combine contact elements and non-linear volume coupled models of durability mechanics related to AAR modeling, was applied to the 3D simulations of a simplified model ideally representing a part of a dam and also to a real gravity dam. Displacements and stresses at the contact elements zone were computed and compared with results of the dam computations without contact elements. The results show that the creation of the slot cutting leads to decrease of the compressive stresses in the structure, which confirms a favorable effect of this stress release technique in order to deal with AAR affected structures. (C) 2013 Elsevier Ltd. All rights reserved.