Characterisation and engineering properties of Tiller clay

A detailed characterisation of the quick clay underlying the NTNU research site at Tiller, Trondheim is presented. The objective of the work is to provide guidance on quick clay parameters to engineers and researchers working with similar clays in Scandinavia and North America especially on landslide hazard assessment. The material is lightly overconsolidated and is characterised by its high degree of structure and very high sensitivity (quick clay). Clay and water contents are both about 40%. The plasticity index is low (5%). This relates to the low active minerals of the clay and silt fractions (illite/chlorite and quartz/feldspars respectively). Undrained shear strength is of the order of 30 kPa to 50 kPa (medium stiff) and increases with depth. The deposit is consistent across the site and its properties are similar to other Norwegian quick clays. Significant efforts have been made into examining sample disturbance effects on the material. It was found that thin walled steel fixed piston samples can yield results similar to those of block samples provided the work is carried out with extreme care and storage time is minimised. The piezocone (CPTU) test proved very useful in characterising the material.