Volume 23, Issue 2 (June 2000)
Percussion and Cone Methods of Determining the Liquid Limit of Soils: Controlling Mechanisms
The mechanisms controlling the liquid limit of montmorillonitic and kaolinitic soils are different. The observation that the liquid limits obtained by both the conventional percussion method and the cone penetration method differ quite appreciably from each other at low and high plasticity ranges indicates that the mechanisms dominating the two testing procedures are different. The analysis of the results obtained from the present experimental investigation, and the results available in the literature prove that the viscous shear resistance primarily controls the percussion method of testing, and that the frictional shear resistance dominates the cone method of testing. Since the viscous shear resistance is primarily due to the double-layer held water, which is characteristic of montmorillonitic soils, and the liquid limit of montmorillonitic soil is primarily governed by the diffuse double layer thickness, the percussion method is well suited to montmorillonitic soils. Likewise, as the interparticle frictional resistance is due to the mode of particle arrangement in addition to mineral frictional characteristics, and the same primarily controls the liquid limit of kaolinitic soils, the cone method suits kaolinitic soils better.