Reservoir assessment using non-invasive geophysical techniques

Philippe Sentenac,Helen Keenan,Vojtech Benes

doi:10.1007/s12665-018-7463-x

Philippe Sentenac, Helen Keenan + Show 1 more

Open Access

https://doi.org/10.1007/s12665-018-7463-x

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Journal: Environmental Geology	Publication Date: Apr 1, 2018
Citations: 14	License type: open-access

Affiliation: University of Strathclyde

Abstract

This paper describes the use of three geophysical techniques to detect potential seepage that could jeopardise the integrity of reservoir embankments, could induce partial or total collapse and pose a risk to the population nearby. A fast-scanning geophysical technique using two dipole electromagnetic (EM) profile apparatus GEM2 provided the first step to detect the weakest points on the selected dams in order to proceed to a more detailed analysis and visualisation of the soil erosion (fissuring or piping) using electrical resistivity tomography (ERT). Finally, self-potential surveys were carried out to relate to the EM and ERT anomalies that could be pathways for seepage and changes of the water displacement inside the embankment. The three geophysical techniques used were evaluated in one case study of reservoir in a location relevant to flooding issues in Czech Republic. A risk approach based on the geophysical results was undertaken for the reservoir embankment. The three techniques together were compared for the same problematic section and confirmed seepage by showing similar results. Conclusions were also drawn on the efficiency of using these three techniques as a package to give a comprehensive non-invasive assessment to be used as common practice by local authorities and environment agencies whereby remedial action could be recommended to protect assets and civilians.

Highlights

When coupled with the predicted increase in precipitation, the importance of maintenance and inspection of reservoir dams is of increasing public importance in the UK
The common approach to assess reservoir embankments is by visual surveying, requiring the surveyor to walk the entire length of the structure to observe any possible weaknesses
Other geophysicists preferred the use of ground-penetrating radar (GPR) for the monitoring of river embankments (Di Prinzio et al 2010) and detection of

Summary

Introduction

When coupled with the predicted increase in precipitation, the importance of maintenance and inspection of reservoir dams is of increasing public importance in the UK. An examination of the literature discussing geophysical techniques applied to surveying flood embankments have shown the use of electrical resistivity tomography (ERT) to be common, due in part to the suitability of the construction materials (normally compacted, fine grained soils) and its sensitivity to changes in moisture as well as its ability to detect discontinuities in the material (Fargier et al 2014; Seokhoon 2012). In association with ERT, geophysical techniques such as electromagnetic scanning and self-potential have been suggested as non-invasive methods for examining internal embankments conditions (Sentenac et al 2013, 2017; Jones et al 2014; Utili et al 2014; Ikard et al 2014; Bolève et al 2011). The potential of the conventional electrical, electromagnetic, and self-potential methods to detect severe erosion and to confirm seepage was assessed against one reservoir in South Bohemia (Czech Republic)

Methodology

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Conclusion