Use of fall-cone flow index for soil classification: a new plasticity chart

Abstract

Use of the Casagrande-style plasticity chart to classify fine-grained soils using Atterberg's liquid and plastic limits is ubiquitous in geotechnical engineering. This classification is dependent on the thread-rolling and Casagrande-cup tests, which are both more operator dependent than the fall-cone liquid limit test. This paper shows that the slope of the data acquired during the fall-cone liquid limit test (the fall-cone flow index) can be used to redraw the plasticity chart, thus allowing classification of fine-grained soils to be achieved solely from fall-cone liquid limit data.

A Comprehensive Review of Soil Remolding Toughness Determination and Its Use in the Classification of Fine-Grained Soils

“…Moreno-Maroto and Alonso-Azcárate [11,31] developed their proposal according to objective criteria based on the quantitative measurement of properties, such as soil toughness, the bending capacity of formed soil threads, and the observation of adhesive consistency, whereas the Vardanega et al [32] system requires only fall cone w L test results to achieve the classification of fine-grained soils to an acceptable degree of accuracy, i.e., the approach does not require w P measurement, removing the dependence on the thread rolling w P test that can have high operator variability [25,33]. There is also greater awareness of the limitations of standard/conventional consistency limits test methods and fine-grained soil classification systems for investigations on unconventional soils, including (fibrous) peats [34] and diatomaceous soil [35]. In other words, the measured consistency limits of these soils do not provide reliable information on the soils' likely geotechnical properties as they are conventionally expected to do.…”