Geophysical Mapping of Quick Clay – A Case Study from Smørgrav, Norway

Marine clay deposits in coastal, post-submarine areas of Scandinavia and North America may be subjected to quick clay landslides. Quick clay may be described as highly sensitive marine clay, deposited in a marine environment during the last glaciation. In Norway some of the most densely inhabited areas, such as the areas around Oslo and Trondheim are located in potential quick clay areas and hence significant efforts are being taken to map its occurrence and extent. In this paper Electromagnetic (EM-31), Electrical Resistivity Tomography (ERT) and Multichannel Analysis of Surface Waves (MASW) methods were tested on a site known to contain quick clay. The site under investigation, Smørgrav, has a history of quick clay sliding, the most recent event occurring in 1984. A number of these approaches have proved promising, in particular ERT, which delineated a zone of quick clay that had previously been confirmed by rotary pressure soundings and borings.