Abstract
abstract Article history:Received 11 June 2013Accepted 7 September 2013Available online 19 September 2013Keywords:ERTRCPTConstrained inversionQuick clayCase histories Geotechnicalprojectsusuallyrelyontraditionalsoundinganddrillinginvestigations.Drillingonlyprovidespointinformation and the geology needs to be interpolated between these points. Near surface geophysical methodscan provide information to fill those gaps. Norwegian case studies are presented to illustrate how two-dimensional electrical resistivity tomography (ERT) can be used to accurately map the extent of quick clay de-posits. Quick clay may be described as highly sensitive marine clay that changes from a relatively stiff conditiontoaliquidmasswhendisturbed.Quickclayslidespresentageo-hazardandthereforelayersofsensitiveclayneedto be mapped in detail. They are usually characterized by higher resistivity than non-sensitive clay and ERT istherefore a suitable approach to identify their occurrence. However, our experience shows that ERT cannot re-solvethissmallresistivitycontrastnearlargeanomaliessuchasabedrockinterface.Forthisreason,aconstrainedinversion ofERTdata wasappliedtodelineatequickclayextent both vertically andlaterally.As comparedtotheconventional unconstrained inversions, the constrained inversion models exhibit sharper resistivity contrastsand their resistivity values agree better with in situ measurements.© 2013 Elsevier B.V. All rights reserved.
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