Liquid Limit Results from Various Types of Grooving Tools

Abstract

Early in the development of soil mechanics, a need arose for a system for classifying soils according to their physical characteristics. To meet such a need, Atterberg, in 1911, established upper and lower limits of plasticity for soils and developed test procedures to determine those values. For the upper limit, Atterberg selected a soil-water mixture which had very little strength and flowed like a liquid; hence his designation “liquid limit.” His test was designed to measure the water content at which a soil-water mixture would flow together in a groove of specified dimensions under a specific number of applied impacts. The lower limit of plasticity, which he called the “plastic limit,” denotes the water content at which a soil-water mixture ceases to be plastic and crumbles or breaks when rolled out into threads. The numerical difference between the liquid and plastic limit values, called the “plasticity index,” was found by Atterberg to be a satisfactory measure of the degree of plasticity of a soil. Because of their simplicity and ease of performance, the Atterberg limits tests have become a valuable and widely used aid for quickly predicting soil behavior.

Practical Considerations when Using the Swedish Fall Cone

“…Many factors can explain the poor repeatability of the Casagrande method. Examples of such factors are the volume and mass of clay used in the cup, the tool used to make the groove (Mitchell 1960a) and the base hardness (Norman 1958).…”