Latest revision as of 13:45, 6 June 2024

Abstract

In this paper, we discuss the results of long-term electrical resistivity tomography (ERT) monitoring of a critical slope located on an important high-speed railway gallery. Data were acquired by a customized ERT system from 24 March 2022 until 31 august 2023 and were analysed with the final objective of defining thresholds of attention for resistivity changes derived from water table fluctuations after heavy rainfalls. This helps the authorities in reducing the hydrogeological risk impacts related to potential slope instabilities triggered by extreme meteorological conditions. In order to continuously observe water level changes, five piezometers were also integrated with the ERT monitoring system which is also accompanied by a meteorological station. All datasets were inverted using a time-lapse algorithm that was optimized to minimize artifacts generated by the subsurface complex geology of the site. Due to the long period considered, seasonal temperature corrections on resistivity values were also explored by calibrating a seasonal model of soil temperature versus depth and evaluating the corresponding effects on the resistivity tomographic maps. Finally, the correlation between resistivity values and piezometric levels was studied by producing scatterplot graphs for a selected subzone of the ERT sections. Based on this analysis, a preliminary threshold of attention was defined.

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