Characterizing cyclic and static moduli and strength of compacted pavement subgrade soils considering moisture variation

Compacted soils are widely used as the subgrade layer for pavements. Knowledge of the mechanical properties of subgrade soils under cyclic and static loading conditions and their variation under the influence of environmental factors is required for the rational design of pavements based on mechanistic methods. This paper presents an experimental investigation of the cyclic and static moduli and the strength properties of seven different compacted Canadian subgrade soils considering the variation in the post-compaction moisture content. Cyclic triaxial tests were performed to reliably determine the resilient modulus (MR). Unconfined compression tests, which allow an unloading-reloading loop at 1% strain, were performed to determine the deviator stress (Su1%) at 1% strain, the reloading elastic modulus (E1%) at 1% strain and the unconfined compressive strength (qu) at failure. The physical properties, the chemical and mineralogical compositions, and the soil-water characteristics of these soils were also determined. Relationships were developed to predict the MR from the Su1%, E1%, qu and soil physical properties for the investigated subgrade soils because the experimental determination of MR is both expensive and time-consuming. The studies presented in this paper provide useful information and approaches that can be used to promote the implementation of mechanistic pavement design methods using simple techniques.