Bazin, Sara

Berre, Toralv

Donohue, Shane

Gribben, Shane

L’Heureux, Jean-Sebastien

Sivakumar, Vinayagamoothy

Quick clay has been involved in some of the largest landslides in Norway, Sweden, Canada,and Alaska. The transformation of marine and glaciomarine clay deposits is largely due tothe influence of local geology and hydrology. The main factor influencing the formation andextent of quick clay deposits is the post-depositional reduction in pore water salt content.This has been studied by numerous researchers and it is commonly accepted that the reduction in salt content causes a reduction in the remoulded shear strength due to leaching by freshwater and dispersing agents. Recently the use of geophysical techniques to locate and map the extent of areas prone to quick clay landslides has become more widespread, in particular the use of near surface resistivity, measured using Electrical Resistivity Tomography(ERT) or Resistivity Cone Penetration Tests (RCPTU).118 The primary aim of this research project is to investigate the factors that influence the sensitivity of quick clay, and how they impact upon the change in the geophysical properties of the clay in particular the resistivity of the clay. The testing is being carried out using a modified stress path cell that enables resistivity and shear wave velocity measurements to be made as the soil is leached by freshwater. The parameters that of interest include: the porewater salt content, void ratio, moisture content, the consistency limits, and the sensitivity.Testing to date has shown that the set up allows us to create a sensitive clay by leaching a naturally occurring unleached marine clay from Onsøy, Norway. A significant change in the electrical and mechanical geophysical properties were found to during the leaching process in these initial tests. Future testing will involve quantifying how the resistivity and stiffness of different unleached clays, with a range of different initial geotechnical properties, are impacted by the leaching process

Geophysical methods for assessing the geotechnical properties of sensitive clays

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