Determination of liquid limit of a low swelling clay using different cone angles

Abstract

The fall cone test is one of the most popular methods used to determine the soil liquid limit. In this study, a series of laboratory tests were conducted on kaolin soil, which is considered representative of low-swelling clays, in order to determine the penetration depths for different cone parameters (angle and weight) under a liquid limit state. The required soil undrained shear strength of kaolin at liquid limit was determined using a hand-held vane shear device. Based on the analysis of the test results, the relationship between the angle of the fall cone and the ratio of undrained shear strength and fall cone penetration depth over cone weight was obtained and represented by a power function. The established relationship was then used to determine the penetration depth at liquid limit for different cone parameter values. A difference in liquid limit of less than 15% was recorded between tests using standard and alternative cone parameter values, respectively. Furthermore, a better and more reliable result was obtained when cone angles were below 90°, with a standard deviation of less than 2.5% from the standard method. Based on critical analysis of the test data, an equation with which to determine the penetration depth under a liquid limit state, as well as a one-point test method with which to determine the liquid limit for different cone parameter values are proposed for low-swelling clays.