Construction Optimization in Arch Dams by Changing the Arrangement of Contraction Joints: a Proposal Based on Numerical Simulations

Abstract

In arch dams, significant volumetric deformations occur during construction - as a result of the heat released by cement hydration and the low thermal conductivity of the concrete -, which, if restrained, can lead to the occurrence of high tensile stresses. Consequently, arch dams are built through individual cantilever blocks, separated by contraction joints. This implies that, in each block, the concreting volumes decrease from the foundation to the crest, due to the reduction of the cantilever thickness, which diminishes the efficiency of the construction equipment installed on site for the first stages of the arch dam construction. This problem has been overcome in the past by interrupting some contraction joints at about 2/3 of the arch dam height, thus allowing to increase the concrete volume to be placed at each lift from then on, such as performed in Las Portas dam. Despite the benefits of this construction strategy, it is still not a current practice, due to the lack of numerical results that prove its efficiency. So, the present article aims to evaluate the possibility of modifying the arrangement of the contraction joints in order to reduce the construction time of arch dams. Using thermo-mechanical analyses, it is shown that the mentioned alternative arrangement of the contraction joints leads to a risk of concrete cracking identical to that obtained with the traditional arrangement normally adopted, which allows significant economic benefits, namely the reduction of the costs and time of construction.