Prediction of maximum dry unit weight and optimum moisture content for coarse-grained lateritic soils

Abstract

Laboratory compaction of soils is an important aspect in the selection of materials for earthwork construction. Owing to time constraints and concern for depleting resources, it becomes imperative that empirical relationships would be developed to predict compaction parameters, maximum dry unit weight (MDUW) and optimum moisture content (OMC) from easily measured index properties. The aim of this note is to develop empirical relationships between MDUW /OMC and logarithm of compaction energy (E)/fines content: sand content ratio (FC/S_dC) for some lateritic soils. Index property tests were carried out on twenty (20) lateritic soils to classify them and obtain the FC/S_dC. The soils were compacted at three compaction energies; British Standard Light (BSL), West African Standard (WAS) and British Standard Heavy (BSH). Two models were developed from relationships based on slopes and intercepts derived from MDUW/OMC versus log E plots; one model employs ‘FC/S_dC’ and one compactive effort (BSL) while the other model employs only ‘FC/S_dC’. The models were validated for robustness with soils used in the development of the models and six (6) other soils not used to develop the models. For the prediction of BSH, the model employing FC/S_dC and one compactive effort showed typical errors of ±0.63 kN/m³ and ±0.76% for MDUW and OMC respectively. The model employing only FC/S_dC showed typical errors of ±0.4 kN/m³ and ±0.83% for MDUW and OMC respectively. The typical errors are within allowed variations for projects and standards for MDUW and OMC, thus the models are quite robust.

Keywords
Compaction; Compactive effort; Lateritic soils; Fines content-sand content ratio; Maximum dry unit weight; Optimum moisture content