Airborne TEM Measurements Used As Reconnaissance Tool for Mapping Areas with Quick Clay in Sweden

An airborne transient electromagnetic (ATEM) survey was carried out over four test areas to evaluate the method for mapping potential quick clay areas in Sweden. The first results from an area located in southwestern Sweden are presented here. Previous geotechnical investigations confirm the presence of both quick clays and un-leached marine clays in the area. Based on the results from the ATEM survey, additional geotechnical investigations (including CPTU-R) and ERT measurements were also carried out. Comparison between ATEM results and the geotechnical investigations show that, over low resistivity areas (around 1 Ohmm) the clay is generally low sensitive, while in areas with resistivities higher than 5 Ohmm, high sensitive quick clay is identified. The resistivities obtained from the ATEM survey also correlates well with the results from ERT and CPTU-R measurements. The results show that the ATEM method can be used as an effective tool in mapping potential quick clay zones. Geotechnical sampling is always needed for comparison and confirmation of results from ATEM measurements.