Prediction of Compaction Characteristics of Fine-Grained Soils Using Consistency Limits

Abstract

Evaluation of laboratory compaction parameters, i.e., maximum dry unit weight $${(\gamma_{{\rm d}{\rm max}})}$$ and optimum moisture content (OMC) of a soil, is an essential task in controlling field compaction for all earthworks construction. Laboratory determination of compaction parameters requires considerable time and effort which can be saved through the use of empirical correlations during early stages of a project. In this paper, correlations between consistency limits, compactive effort (CE) and compaction parameters, i.e., $${\gamma_{{\rm d}{\rm max}}}$$ and OMC, for fine-grained soils have been proposed. In order to develop the correlations, 105 soil samples of fine-grained soils representing various classification groups were collected from different areas of Punjab province of Pakistan. Besides classification tests, standard and modified proctor compaction tests were performed on the selected samples. Based on the classification test results, the selected samples are classified as CH, CL, CL-ML, ML with gravel fraction in the range of 0–12 %, sand fraction from 2 to 48 % and silt clay fraction from 50 to 95 %. The laboratory standard and modified compaction tests on the selected samples indicate the $${\gamma_{{\rm d}{\rm max}}}$$ in the range of 15.8–19.7 kN/m3 with OMC varying from 9 to 19.5 %. Multiple regression analyses were performed on the experimental data, and correlations have been proposed to predict the compaction parameters ( $${\gamma_{{\rm d}{\rm max}}}$$ and OMC) in terms of LL, PI and CE. In order to validate the proposed equations, an independent data set of 37 samples was used for the validation purpose. The comparative results showed that the variation between experimental and predicted values of $${\gamma_{{\rm d}{\rm max}}}$$ is within ±2.5 % and that of the OMC (%) is within ±9.5 % at 95 % confidence interval. Based on the correlations developed, predictive curves corresponding to standard and modified proctor energy are proposed for quick estimation of $${\gamma_{{\rm d}{\rm max}}}$$ and OMC based on LL and PI without performing the laboratory compaction tests.