Electrical resistivity characterization and defect detection on a geosynthetic clay liner (GCL) on an experimental site

• Published in: Journal of applied geophysics 2013-03, Vol.90, p.19-26
• Main Authors: Sirieix, C., Fernández Martínez, J.L., Riss, J., Genelle, F.
• Format: Article
• Language: English
• Subjects: Electrical resistivity; GCL; Landfill cover; Particle swarm optimization; Tomography; VES
• ISSN: 0926-9851; 1879-1859
• DOI: 10.1016/j.jappgeo.2012.12.005

In this paper we analyze the onsite characterization of a geosynthetic clay liner (GCL) that serves to ensure the impermeability of a landfill cap by DC electrical methods. The imaging of the GCL geoelectrical properties is a challenging problem because it is a very thin (between 4 and 7mm thick) and resistive layer (from 100,000 to 2,000,000Ω·m) depending on meteorological conditions and aging. We compare results obtained using electrical resistivity tomography (ERT) using two different kinds of arrays (dipole–dipole DD and Wenner–Schlumberger) on an experimental site with engineered defects. To confirm these results and to find the real onsite GCL resistivity we have performed sampling of the posterior distribution of this parameter using vertical electrical sounding (VES) inversions. Different VES methods were extracted from ERT with DD array and converted into a Schlumberger array. As a main conclusion the dipole–dipole array provides a better resistivity resolution of the defects than the Wenner–Schlumberger array. On ERT images, the defect detection seems to be impossible if the GCL has very high resistivity, as it happened when it was put in place. Taking into account the equivalence rules, the inversions are in both cases (ERT and VES) compatible. The GCL resistivity estimated from PSO (particle swarm optimization) varies from 3.0 105 to 1.106Ω·m depending on saturation conditions during the twenty first months of its placing. Then, the resistivity dropped to 4.104–9.104Ω·m, indicating a probable chemical damage of the GCL due to aging. Finally the fact that the VES inversions are solved via PSO sampling allows for the detection of a very thin and resistive layer and opens the possibility of performing micro VES surveys along the landfill to detect possible GCL defects. ► Study of an experimental landfill cover by DC electrical methods. ► ERT profiles are compared to VES inverted by PSO. ► Estimation of the electrical resistivity of a geosynthetic clay liner. ► Measurement of evolution of onsite GCL electrical resistivity.