Measuring the plastic limit of fine soils: an experimental study

Vinayagamoothy Sivakumar, Brendan C O'Kelly, Laura Henderson, Catherine Moorhead, Shiao Huey Chow

Research output: Contribution to journalArticlepeer-review

31 Citations (Scopus)


The Casagrande thread-rolling method for determining the plastic limit of fine-grained soil is heavily dependent on operator judgement and can often give inconsistent or unreliable results. This paper presents an energy-based approach used in the development of an improved testing procedure for the plastic strength limit. A 0.727 kg cone is allowed to fall freely through 200 mm before contacting the surface of the test specimen, with the plastic strength limit determined for a cone penetration depth of 20 mm. For ten mineral clays of intermediate to very high plasticity tested, the plastic limits deduced using the cone were in good agreement with the measured Casagrande plastic limits. The values deduced using an 8 kg contacting cone were consistently lower than the Casagrande limits.
Original languageEnglish
Pages (from-to)53-64
Number of pages11
JournalProceedings of the ICE - Geotechnical Engineering
Issue number1
Publication statusPublished - Feb 2015


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