Comparison of Liquid Limit of Highly Plastic Clay by Means of Casagrande and Fall Cone Apparatus

The connection between the Liquid Limit found using the Casagrande and the Fall Cone Apparatus is tested for the Danish Eocene Clay that has Liquid Limits up to 350% and Plasticity Index up to 300%, which is well outside the normal range of Casagrande’s Plasticity Chart. Based on the high plasticity of the Danish Eocene Clay two new classification categories are introduces to the Plasticity Chart in order to fully describe the clay; super high plasticity Clay (CS) and extremely high plasticity clay (CE), covering the range up to Liquid Limits up to 200% and 350% respectively. A correlation between the Liquid Limit from the Casagrande and the Fall Cone Apparatus is for super high plasticity clay. For extremely high plasticity clay it was found that the Fall Cone method underestimated the Liquid Limit with up to 43 percentage points, making the Fall Cone an unreliable method of finding the Liquid Limit for extremely high plasticity clay