Converting optimum compaction properties of fine-grained soils between rational energy levels

Abstract

This study introduces a practical energy conversion (EC)-type modeling framework capable of converting the optimum compaction properties of fine-grained soils between any two rational compaction energy levels (CELs). Model development/calibration was carried out using a database of 242 compaction test results — the largest and most diverse database of its kind, to date, entailing 76 fine-grained soils (covering liquid limits of 16–256%), with each soil tested for at least three different CELs. On establishing the framework, an independent database of 91 compaction test results (consisting of 34 fine-grained soils tested for varying CELs) was employed for its validation. The proposed EC-based models employ measured optimum water content (OWC) and maximum dry unit weight (MDUW) values obtained for a rational CEL (preferably standard Proctor) to predict the same for higher and/or lower compactive efforts (covering 214–5416 kJ/m3). The 95% lower and upper statistical agreement limits between the predicted/converted and measured OWCs were obtained as 2.16 wc % and +2.25 wc %, both of which are on par (in terms of magnitude) with the ASTM D1557 allowable limit of 2.1 wc %. For the MDUW predictions, these limits were calculated as 0.71 and +0.66 kN/m3, which can also be deemed acceptable when compared against ASTM’s allowable limit of ±0.7 kN/m3 (= ±4.4 lb/ft3). The proposed framework offers a reasonably practical procedure to accurately convert the optimum compaction parameters across different CELs (without the need for any soil index properties), and thus can be used with confidence for preliminary project design assessments.