Preliminary identification of the structural effects of concrete swelling in Chicamba dam (Mozambique)

Abstract

This paper presents the relevant results of the monitoring data analysis of the Chicamba dam (Mozambique), which confirmed the existence of an ongoing concrete swelling process in the dam’s body. The performed analysis was based in the qualitative evaluation of the monitoring results complemented with the quantitative interpretation of some physical quantities. The Chicamba dam is a concrete dam, 75 m high, composed by two independent arch structures linked by an artificial abutment, built in two stages in the decades of 50 and 60 of the last century. The monitoring system had the last large rehabilitation and strengthening in 2010 and 2011. The safety control of the dam is based on the data provided by the monitoring system and on regular inspections. About ten years ago, the first signs of alkali aggregate reactions were identified by tests performed in concrete samples extracted from the dam’s body for the installation of rod extensometers in the foundation. The available monitoring results, namely the displacements measured through plumb lines and by geodetic methods, were properly treated to estimate the swelling structural effects in the last 10 years. These effects are moderate and the apparent cracking is limited to specific areas of the structure, but the accumulated swelling effects over time are not known. To evaluate the development of this pathology, an experimental study using cores to be extracted from the dam’s body is planned to be carried out.