PSI - Issue 64

Nicola Fabbian et al. / Procedia Structural Integrity 64 (2024) 1649–1656 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

1655

7

are detected by the DTS system. All these results indicate that DTS measurements well complement and enrich data acquired from the conventional monitoring system and together can better depict the temperature field and give a clear picture of the seepage development. 4. Discussion and conclusion The two-monitoring systems presented in this study integrate both conventional and innovative monitoring technologies to enhance the understanding of hydraulic behavior of levees and the identification of preferential water flow paths. While traditional sensors offer detailed temporal data on temperature and pressure at predefined points, DTS allows the reconstruction of continuous temperature profiles along vertical wells or horizontal trenches at specific moments. The great opportunity offered by the optical fiber system is the possibility to have information about the seepage condition over very long stretch (up to 10 km), overcoming the limits of the punctual sensors, which give information only in predetermined positions and have high costs in considerations to the amount of data given in the same stretch. Unfortunately, in the current installations, the DTS interrogation is carried out manually by an operator, with a reduced exploitation of the potential of DTS system. Certainly, this limitation could be addressed by installing the fiber interrogation unit in a secure location near the embankment and implementing an automated procedure for data recording. This approach would enable DTS to provide nearly continuous recording of temperature profiles. In this paper the authors present the experience performed with two DTS installation methodologies, since the installation plays a key role in exploiting the potential which this technology can offer. In any case, careful planning is essential to minimize soil disturbance and ensure long-term reliability. At Site A, where DTS cables were installed horizontally in a 350 m-long trench at the embankment toe, temperature changes during intense flood events were detected, indicating possible movement of water from the river to the landside. DTS data revealed temperature gradients suggesting upward seepage flow paths near the gravel lenses detected during geotechnical investigations. At Site B, the fibers placed in vertical boreholes facilitated a clearer observation of the depth-dependent temperature fluctuations during the flood events, and may providing insights into saturation or preferential filtration pathways at specific depths. The study underscores the importance of seasonal temperature fluctuations in shallow soil layers, underlining the necessity for periodic measurements to establish a reference measure. Of course, this problem could be well overcoming by having an interrogation unit working in automatic way. Moreover, since the obtained results show that the temperature variations caused by seepage in deep layers are minimal, for future installations it is advisable to concentrate on upper layers (such as the levee body and foundation layers up to 10-15 m). Undoubtedly, conducting additional measurements and analyses with different water river levels will significantly enhance the comprehension of DTS applications in monitoring embankment structures, leading to more precise evaluations. Furthermore, the advancement of artificial intelligence-based models for processing acquired measurements could enhance the efficiency and accuracy of data interpretation, thereby promoting the widespread adoption of this methodology. Acknowledgements The authors wish to thank the Mountain Water Authority of the Autonomous Province of Bolzano and Autostrada del Brennero S.p.a. for the economical contribution to this study. Author Contributions “Conceptualization, N.F. and S.C.; methodology, N.F.; software, N.F. , L.S. and L. B.; validation, N.F. and S.C; formal analysis, N.F.; investigation, N.F.; resources, N.F.; data curation, N.F. and L. X.; writing — original draft preparation, N.F.; writing — review and editing, N.F., and S.C.; visualization, N.F., and S.C.; supervision, N.F., and S.C.; project administration, P.S., F.D.P. and S.C.; funding acquisition, P.S., F.D.P. and S.C.”