Determination of Both Liquid and Plastic Limits of Clays by the Fall Cone Test

Abstract

An investigation was made of the applicability of the Fall Cone Test for determining both liquid and plastic limits of clays. The test was carried out on various kinds of clays for a 60°, 0.6 N cone and for a soil container 100 mm in diameter and 50 mm in depth. The penetration vs water content of the clay relationships were found to become, generally, straight lines on a double logarithmic scale in the wide range of the water content.
The mean values of penetration at the liquid and plastic limit for the Casagrande method were 12.0 and 1.3mm, respectively. The back calculated water content for these values of penetration on the penetration vs water content straight line were compared to agree well with the corresponding values of limits for the Casagrande method.
The undrained shear strengths of clay at the liquid and plastic limit calculated for 12.0 and 1.3mm penetration were 1. 25 and 106. 86 kPa, respectively, and were in good agreement with the vane shear test results.