Plastic limit and compaction characteristics of finegrained soils

Laboratory determination of the compaction characteristics of soils is important for use in earthwork constructions. The purpose of compacting earth fills such as earth dams and embankments (highway, railway and canal) is to produce a soil mass that will satisfy the two basic criteria: reduction in settlement and increase in shear strength. For preliminary design and assessment, correlations with the liquid limit have been attempted by various investigators. However, from the present study it is seen that the correlations are not up to a satisfactory level. In this paper the results of detailed investigations carried out are examined to find which of the index properties correlate well with the compaction characteristics. In the analysis, apart from the authors' experimental results, results from the available literature have also been considered. It is found that the plastic limit bears a good correlation with the compaction characteristics, namely optimum moisture content and maximum dry unit weight, much better than liquid limit or plasticity index.