Towards geophysical and geotechnical integration for quick-clay mapping in Norway
S. Sauvin, I. Lecomte, S. Bazin, J.-S. L’Heureux, M. Vanneste, I.-L. Solberg and E. Dalsegg
Journal name: Near Surface Geophysics
Issue: Vol 11, No 6, December 2013 pp. 613 - 623
Special topic: Geotechnical Assessment and Geoenvironmental Engineering
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Quick clay is a known hazard in formerly-glaciated coastal areas in e.g., Norway, Sweden and Canada. In this paper, we review the physical properties of quick clays in order to find a suitable, integrated and multi-disciplinary approach to improve our possibilities to accurately identify the occurrence of quick clay and map its extent both vertically and laterally. As no single geophysical method yields optimal information, one should combine a variety of geophysical methods with geotechnical data (in situ measurements using Cone Penetration Testing (CPTU), Seismic CPTU (SCPTU) and Resistivity CPTU (RCPTU); laboratory tests) for an in-depth quick-clay assessment at a given site. In this respect, geophysical data are used to fill the gaps between geotechnical boreholes providing ground-truth. Such an integrated and multi-disciplinary approach brings us closer to 2D or pseudo-3D site characterization for quick clays and as such, an improved assessment of the potential hazard they pose. The integrated approach is applied in practice on two Norwegian quick-clay sites. The first site, Hvittingfoss, was remediated against potential landslides in 2008 whereas the second one, Rissa, was the scene of a major quick-clay landslide in 1978, quick clays being still present over a large area. The collected data and preliminary site characterizations illustrate the high diversity as well as the complexity and clearly emphasize the need for higher resolution, careful imaging and calibration of the data in order to accomplish the assessment of a quickclay hazard.