Applications of 2D resistivity measurements for quick-clay mapping in mid Norway

Abstract

During the last 10 years, several Norwegian projects have explored the possibilities of using 2D resistivity measurements for quick-clay mapping in combination with traditional geotechnical methods. Experience has shown that an effective first-order interpretation of 2D resistivity profiles can be performed by using the following classification: unleached clay deposits (1–10 Ωm); leached clay deposits, possibly quick (10–100 Ωm), and dry crust clay deposits and coarse sediments (>100 Ωm). However, resistivity values are influenced by local conditions and there is an overlap between the classes. The 2D resistivity method can prioritize areas for further investigation using other geophysical methods or drilling to refine the interpretation of the subsurface. Through several case-studies, the 2D resistivity method has proven useful for detecting potential layers of quick clay, for outlining the extent of these layers and their positions in slopes (also near the shoreline), and for engineering applications such as construction planning. To this end, the method has shown to be applicable for adjusting the extent of hazard zones to improve stability evaluations. Another important application is landslide investigations, to identify barriers that may deter further landslide propagation.