Distributed optical fiber systems for monitoring the serviceability strain response of an Italian concrete arch dam and its foundation

Concrete arch dams are large constructions aiming at producing hydroelectricity, providing water for irrigation and controlling flooding. Although the maximization of the water level of the basin allows to optimize the management of the dam, an accurate monitoring of such large structures must be carried out carefully to evaluate the deformations in operational conditions. Traditionally, the monitoring of the dam body as function of the environmental temperature and reservoir water level is performed through visual inspections, periodic manual surveys or topographical measurements. Nevertheless, this monitoring is complex and time consuming due to the considerable spatial extension of dams. Recently, both traditional survey and innovative techniques for field monitoring have greatly improved, making these checks faster and more complete. In this context, the use of Distributed Optical Fiber Sensors (DFOS) as detector of strain and temperature can be considered a very attractive option, allowing the measurements of spatially dense and distributed data along large distances and with high resolution. The paper deals with the monitoring of a concrete double arch dam, namely Ponte Cola dam, located in Valvestino (BS) in North Italy. Between December 2020 and February 2021, two different types of DFOS both in the foundation and along the crown of the dam were installed. The DFOS are one for strain and one for temperature measurement. Several measurement campaigns were carried out. These measurements have been compared with the ones obtained from traditional monitoring techniques, to estimate the reliability and potentiality of such an innovative system in monitoring the very low strains developed in this type of structures.