New technique assessment of plastic limit of soft clay particularly peat soils

Rashidah Adon, Noriyuki Yasufuku, Ryohei Ishikura, Devapriya Wijeyesekera

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


Plastic Limit (PL) is considered as the moisture content at which soil becomes too dry to remain plastic. Both the British Standards Institute (BS 1377 (1990)) and American Society for Testing and Materials (ASTM D4318 (2001)) are consistent with their proposition of determining PL as the moisture content when the soil crumbles upon rolling it to thread of 3 mm diameter. However for challenging soils such as peat which is naturally organic substance derived from the remains of plants, the "rolling method" is not appropriate, particularly in the area of fibrous peat. Very little information is available in the public domain for satisfactory techniques to define PL. Huat (2004) reported that west Malaysia Peat has a PL of 100-200% and Liquid Limit (LL) of 190-360% Therefore, the aim of this paper is to make a critical evaluation of this and alternative method to determine PL particularly for peat. The authors have investigated the extended adoption of the standard cone penetration (300 apex angel, 80g of mass, 20mm penetration) method used in the liquid limit determination recommended in BS 1377 and ASTM 4318. As early as 1978 (Wood and Worth) and as research on 2000 (Feng) the modified cone penetration method has been proposed for the determination of PL but only focusing on cohesive soil. This paper presents the "full range" penetration -water content data obtained at intervals of 5 percent moisture content for four different soils (laterite soil, kaolin, local clay (RECESS) and Peat). The results indicated that the standard method and new techniques give very satisfying result. It is apparent that the author's analysis using the cone penetration method will be more feasible means of measuring Plastic Limit of soil especially for peat soil.

Original languageEnglish
Pages (from-to)47-55
Number of pages9
JournalMemoirs of the Faculty of Engineering, Kyushu University
Issue number1
Publication statusPublished - 2013
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Energy(all)
  • Atmospheric Science
  • Earth and Planetary Sciences(all)
  • Management of Technology and Innovation


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