Mapping of quick clay formations using geotechnical and geophysical methods

Quick clay has been involved in most serious, large clay slides in Sweden, Norway, and Canada. This paper describes geotechnical and geophysical methods that can be used to locate and map the extent of quick clay formations. Surface resistivity measurements and four different sounding methods have been tested. The results have been compared with sensitivities determined using fall-cone tests. The investigation shows that there is a correlation between sensitivity and electrical resistivity, which can be used to discriminate between marine clays that have been leached sufficiently to possibly form quick clay and those for which the salt content remains sufficiently high to prevent this. Although the most reliable evaluation of the variation in sensitivity was obtained by the CPT with additional measurement of total penetration force, this investigation suggests that any sounding method that uses a constant rate of advance into the ground and in which the penetration force applied on the top of the rods is measured may be used for quick clay mapping.