Monitoring of vertical deformations by means high-precision geodetic levelling. Test case: The Arenoso dam (South of Spain)

Abstract

Abstract The Arenoso reservoir is created by an embankment dam, with central clay core, slates and greywacke shoulders. This kind of engineering structure is subject of deformation due to factors such as changes of water level of the reservoir, seat structure, climate changes, etc. In general, dam monitoring involves measurements both outside (external shell) and inside the structure. A number of control points is established around the area of the dam and the measurements of the displacements of the control points take place at several epochs. In this study high-precision levelling techniques have been used to monitor the vertical deformations. In particular five high-precision levelling profiles were measured in five surveys: February and July 2008, March and July 2013 and August 2014. In this study the design, observations and results are presented. On the one hand the results put in evidence the precision of the observations that are always under 1-mm level. On the other hand these results indicate downstream (southeastward) motion of the thrust block center of the dam probably during the fall and winter. The subsidence reachs here the maximum with a value of −14 cm in 2014 (in respect of February 2008). The displacements observed at the berms of the dam exhibit a similar trend to the displacements observed at the crest but they are significantly smaller, as expected. The accumulative vertical displacements and the settlement index indicate the magnitude of the movements decrease in time, confirming the dam tends to stabilize.