In situ detection of sensitive clays – Part II: Results

Sensitive and quick clays are typically found in Norway, Sweden and Canada, and are characterised by a remoulded undrained shear strength considerably lower than the undisturbed shear strength. In geotechnical engineering, the presence of sensitive clays poses a major challenge. The landslides at Rissa in 1978, and more recently at the Skjeggestad bridge in Norway, are devastating reminders of the potential threats related to such soils. In a construction project it is hence important to 1) determine if there is sensitive clay present and 2) clarify the extent of the quick clay deposit. This is currently done based on interpretation of soundings and to some extent geophysical methods such as electrical resistivity measurements. However, for verification of quick clay, sampling and laboratory testing must be performed. Here, a set of updated and new guidelines for classification of sensitive clays from in-situ measurements are presented. The aim is to provide the geotechnical engineer with a practical classification tools where all available information is utilized and combined efficiently. The classification tools are based on results from methods such as conventional soundings, CPTU with measurement of total force, electrical field vane testing in combination with geophysical methods such as R-CPTU, 2D resistivity profiles (ERT) and airborne electromagnetic measurements (AEM). The methods, and how they are utilized in investigation strategies for detection of quick and sensitive clays, have been described in another paper to this conference. An extensive database of Norwegian test sites forms the basis for the work. The results from this study show that the above mentioned site investigation methods holds information that complements each other, to form a solid basis for detection of sensitive clays. In turn, this opens for more efficient site investigations where all available data are interpreted in a systematic manner to produce a reliable map of sensitive clay deposits.publishedVersio