Liquid limit determination of low to medium plasticity Indiana soils by hard base Casagrande percussion cup vs. BS fall-cone methods

Atterberg limits of soils including the liquid limit are one of the oldest and most traditional tests conducted in geotechnical site investigations. The relationship between the liquid limits determined from the Casagrande percussion cup apparatus and the fall-cone device has been extensively studied. Despite the known convenience of the fall-cone method, it is scarcely employed for geotechnical site investigations in the USA. This paper presents the findings of investigations conducted on 65 soil samples from different parts of the Indiana State in the USA including their liquid limit tests. The results obtained by the Casagrande percussion cup method and the fall-cone method were compared. The comparison explains how the variations in the liquid limit effect the results of the two methods, and a correlation is also offered. Based on the results, a model is also presented for single-point determination of the liquid limit from the two methods. Finally, a modified plasticity chart for soil classification is proposed based on the fall-cone liquid limit and plasticity index results of these soil samples. The paper also includes the statistical analysis of the proposed relationships.