Theoretical modelling of the compaction curve

Soil compaction is one of the major activities in geotechnical engineering involving earthworks. The compaction curve is used to find the optimum water content that maximizes dry density. Since its introduction by Proctor in 1933, several researchers have provided qualitative explanations for the inverted parabolic shape of the compaction curve. However, fundamental research on the compaction process and the evolution of compaction characteristics are limited, particularly from a quantitative sense. In order to understand the driving mechanisms of soil compaction, this paper investigates the effect of soil suction, stiffness and pore air pressure on the shape of the compaction curve, from an unsaturated soil mechanics standpoint. This paper presents an approach to predict the soil compaction curve during undrained loading. Particular attention is focused on the derivation of the compressibility coefficient due to net stress. Model predictions of the compaction curve are compared with some experimental results from the literature.