Improving the Diagnosis of Coastal Earth-Filled Dikes Combining Geophysical Methods by Data Fusion
Abstract
With 40% of the world population living on coasts and with climate changes extreme weather to be more frequent, the durability assessment of dikes is major concern, since structural failure might entail environmental catastrophes and human losses.
The diagnosis of coastal earth-filled dike (CEFD) using geophysical methods like seismic methods, ground-penetrating (GPR), and electrical resistivity tomography (ERT), are commonly used to detect and locate pipeline networks or defects, such as large voids. However, small-sized voids or low-density areas, which might eventually be filled by water, are usually undetected when using a single geophysical method. This study aims at improving the diagnosis and extend the capability of such geophysical characterization by combining the physical observables issued from any of these three techniques (aka data fusion). The performance of the proposed approach was investigated on three scenarios. First, a set of earth samples were produced in laboratory conditions by varying two physical states (or indicators): water content and dry bulk density at the optimal normal Proctor. The lime and salt contents were respectively fixed at 0 and 2%, and 30g.L-1. This parametric study established a collection of observables, which were divided in three groups: electrical (apparent resistivity), seismic (compressional and shear wave velocities), and electromagnetic (relative permittivity). Both, water content and dry bulk density were accurately predicted by using the data fusion algorithm. Second, synthetic electrical and seismic data were produced on a 2D finite element model using a commercial software. After post-processing the data, the resulting density map matches that set on the numerical model. And finally, third, seismic and electrical data was collected on field conditions, where defects, such as low-density areas and small voids were already present. This latter experimental campaign included information of temperature and moisture sensors. In the scope of the CPER FEDER Digue 2020 project, the proposed method shows promise for evaluating the mechanical integrity of CEFD.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMNS41A..02G
- Keywords:
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- 0915 Downhole methods;
- EXPLORATION GEOPHYSICS;
- 0925 Magnetic and electrical methods;
- EXPLORATION GEOPHYSICS;
- 0935 Seismic methods;
- EXPLORATION GEOPHYSICS;
- 0205 Archaeological geology;
- GEOHEALTH