Shear strength of an unsaturated laterite soil under different compaction conditions

Compacted soils are a common component of engineering structures worldwide. In tropical regions, lateritic soils exhibit distinct characteristics due to soil aggregation from iron and aluminum hydroxides and their bimodal structure. However, the compaction process can alter soil structure and mechanical behavior. This paper aims to assess the effects of soil structure on the saturated and unsaturated mechanical behavior of a lateritic soil under different compacted energies. The methodology involves porosimetry, retention curve and saturated and unsaturated triaxial tests, using appropriate standards and references. Under saturated conditions, these structural variations affected the volumetric behavior at the critical state, particularly in samples compacted on the dry side of the compaction curve. Additionally, a unique Critical State Line (CSL) could be traced for all samples in the p’ x q space. Under unsaturated conditions, the effects of soil structure were evident, with both the volumetric response and shear strength increase being influenced by suction. Samples molded with no compaction energy, or non-proctor energy, resulted in higher macropore void ratio leading to more pronounced volumetric contraction during shear and less gain in shear strength. Therefore, this work contributes to the understanding of the behavior of compacted laterite soils, providing valuable information for projects involving compacted laterite soils in the field, such as dams, embankments and pavement subgrade.