chapter  44
Interpreting improved geotechnical properties from RCPTUs in KCl-treated quick clays
ByT.E. Helle, M. Long, S. Nordal
Pages 7

In January 2013, Potassium Chloride (KCl) wells were installed in a highly sensitive quick clay deposit at Dragvoll, Trondheim, Norway. The geotechnical properties significantly improved in the following years due to increased salt content and changed pore-water chemistry. Several Resistivity Cone Penetration Tests (RCPTU) were conducted around the wells to map the salt-plume extent, and to interpret improved geotechnical properties. The RCPTUs effectively mapped the salt plume extent around the wells, and the increased tip resistance clearly indicated improved properties in the salt-treated clay. Commonly used correlations for Norwegian clays are used herein for interpreting the geotechnical properties in the original quick clay and the salt-treated clay. The interpreted Over Consolidation Ratio (OCR) and shear strength (cu) are compared to laboratory determined geotechnical properties on high quality downsized Sherbrooke samples (mini-blocks). The tip resistance in the salt-treated clay increased significantly due to increased remolded shear strength and increased resistance to deformations. Improved OCR and cu in the salt-treated clay at Dragvoll are determined from the CPTU data applying existing correlations based on bearing factor for net tip resistance (Nkt). The existing correlations for Norwegian clays work reasonably well, but ideally specific local correlations should be developed.