Tessitore, Serena (2014) Application of DInSAR techniques to the monitoring of ground deformations. [Tesi di dottorato]

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Abstract

Subsidence is a natural hazard which affects wide areas in the world causing important economic losses annually. This phenomenon has occurred in the metropolitan areas of Murcia City (Spain) and of Telese Terme (Italy), causing relevant economic damage to structures and infrastructures. In Murcia city, subsidence is the result of groundwater overexploitation; due to the intensity of the phenomenon, institutions requested detailed studies since the ’90, to understand its cause-effect mechanisms. For this reason a monitoring network of extensometers and piezometers has been installed and implemented during the years. Telese Terme has been affected by subsidence due to its geological and hydrogeological settings. Here, in fact, the underground water circulation provokes piping phenomena in the surficial fine-grained soils and, because of chemical characteristics and physical properties of the water, may also activate processes of accelerated travertine’s corrosion. In this case, a monitoring network is not available and the only evidences of the phenomenon occurrence are the structural damage to buildings. These two study areas have been chosen to test the applicability of the innovative Advanced DInSAR techniques in the natural risk mitigation related to subsidence phenomena. In particular, these techniques can complete a monitoring network where available (as in the case of Murcia city) and partially replace it in case of its absence (as in the case of Telese Terme). In the first case, such techniques allowed to implement an integrated monitoring system based upon satellite DInSAR monitoring, in situ monitoring and geotechnical data. In particular, the correlation of the temporal evolution of ground surface displacement measures (radar and in situ) and the piezometric groundwater level variation have been analyzed to determine mechanisms and critical states of failure; this has permitted to implement a finite element model (FEM) of the phenomenon. The proposed numerical model will allow the prediction of possible future deformations and the consequences of any piezometric level variation in the study area. This is regarded as necessary to better plan the subsequent water resources exploitation and the land use management. In the Telese Terme case study, radar measured displacements allowed to understand the spatial extension of the phenomenon, its magnitude as same as its historical development. In fact, a remote sensing monitoring system allows the knowledge of unmonitored phenomena also in the past. This has permitted the individuation of the causes which provoked damage for some “test buildings”. For one of them, a structural model has been implemented; in this case, radar data have been used to verify whether its structural response to the displacements detected by SAR corresponds to the overpassing of the limit states. In conclusion, it has been argued that the proposed approaches could be applied to other scenarios affected by similar phenomena.

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