An accurate and direct approach for sample-free in-situ detection of quick clay

¹ Department of Civil and Environmental Engineering, Norwegian University of Science and Technology, Trondheim, Norway
² Norwegian Water Resources and Energy Directorate, Norway
³ Norwegian Public Roads Administration, Norway
⁴ Trondheim County, Trondheim, Norway
⁵ Bane NOR, Norway

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

The objective of the research presented in this paper is to develop prototypes or concepts for new in-situ tests aiming to detect quick clays. Existing in-situ geophysical and geotechnical methods can indicate that a clay may be quick. But the only reliable method for detecting a quick clay is by sampling, followed by fall cone tests in a laboratory. This approach is time-consuming and costly, thus often with limited information over the depth. Attempts have been made on identifying quick clays from side friction measured by conventional CPTUu. However, the clay is not sufficiently remoulded during penetration of the CPTu rod, and the sensors of the sleeve do not have sufficient accuracy to detect the low shear strength of a remoulded quick clay. A new approach aiming to obtain both complete remoulding and accuracy for in-situ measurement of remoulded strength at round 0.3 kPa has been tested. It consists of a mixing module mounted on a total sounding rod and a T-bar on a conventional CPTu probe. Field tests prove that it is possible to fully remould quick clays and measure its remoulded shear strength with sufficient accuracy in the field applying the new concept.