Passive Seismic and DC Resistivity Combined Acquisitions and Comparisons for the Assessment of a Pier

Cedric Sachet*1, Anaëlle Joubert2, Mathieu Le Feuvre2, Philippe Sentenac1, Philippe Cote2

1Department of Civil and Environmental Engineering, Glasgow, University of Strathclyde, UK (cedric.sachet@strath.ac.uk), 2Department of Geotechnics, Environment, Natural Hazard and Earth Sciences, French Institute of Science and Technology for Transport, Development and Networks (IFSTTAR), FR.

With the already visible effects of global climate change, Scotland is aware of its own local rise in sea levels, changes in rainfall patterns, with increased seasonality and more heavy downpours. Despite the current mitigation measures, these changes are projected to continue and intensify, shoreline at the forefront.

Without being inhospitable for geophysical acquisitions, the coastal environment remains a harsh environment where adaptions are ineluctable. The first steps of a work targeting the joint use of the Passive Seismic and Electrical Resistivity Imaging (ERI) to assess the coastal concrete infrastructures with a non-destructive multi-method approach is introduced here. A case study carried out on a pier affected by internal erosion is presented.

Passive seismic monitoring of the coastal shorelines using sea waves as a seismic source has already shown promising results for the characterization of the shoreline response to the tidal cycles. Sensors are preferentially installed linearly along the section auscultated. The analysis is based on delay measurements performed on reconstructed surface waves propagating along the array. Variations of velocity can be literally localized inside the structure body studied in response to water infiltration induced by changes in water level, which constitute precious information for the assessment of coastal concrete infrastructures.

Geo-electric measurements on concrete infrastructures with complex geometries and surrounded by water represent a challenge for both the technical equipment and the inversion routine. In such context, the latter has to consider the geometry of the infrastructure, the relative position of the tide and the resistivity distribution.

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