Geophysical Experimental Survey on Flood Protection Dikes - The Case Study of the Loire River Basin
M. Pareilh-Peyrou, P. Labazuy, K. Kelfoun and F. Chalus
Event name: Near Surface Geoscience 2015 - 21st European Meeting of Environmental and Engineering Geophysics
Session: Integration of Geophysics III
Publication date: 06 September 2015
Info: Extended abstract, PDF ( 4.68Mb )
Price: € 20
An electromagnetic induction (EMI) survey has been performed along the Loire River protection dikes (France), with a 60 km long, high speed and high resolution, field acquisition campaign. The main aim of this dikes diagnostic mission was to locate and identify potential local weakness or damaged zones inside the engineering structures. We used an EMI device (EM31) and a GPS receiver on board an experimental fiberglass cart support, designed for high yield acquisition surveys. This study allowed to provide the electrical subsurface image (conductivity) of the whole structure and allowed, in addition, for precise detection of the small-scale anomalies. The outputs consist of electrical images of both the inner dike structure and the subsurface geological environment. This fast first-phase study is efficient for detecting decametric local anomalies while giving information about the dike inner structure. Once EMI anomalous zones have been detected, further detailed investigations have been performed on selected areas, including electrical resistivity tomography (ERT) profiles and geotechnical drills. Thus, the objective of our experimental study was to scale down and optimize this second phase of the prospecting campaign, which will considerably reduce the cost and the time spent on the whole survey.