An Evaluation of the Effects of In-situ and Compaction Induced Structures on the Compression and Strength Characteristics of a Lateritic soil in the Laboratory

Laterite and lateritic soils are products of weathering under tropical conditions that is rich in the oxides of iron and aluminium. In-situ, the presence of these oxides leads to the creation of a structure which control most of the engineering properties. When compacted, however, a new compaction-induced structure is formed. In tropical environments, road and railway construction usually involve deep cuts in lateritic soils that is reworked and compacted into embankments. The analysis and modelling of stability and performance of these cuts and embankments require a good understanding of the mechanical behaviour of intact and of compacted lateritic soils. A laboratory experimental study was conducted to determine the differences in the effects of structure on behaviour of intact and of compacted samples. Samples of an intact lateritic soil were obtained and recompacted samples were prepared at the same insitu dry density and water content of 1.654Mg/m3 and 16.5% respectively. The intact and re-compacted samples were subjected to one dimensional consolidation in the oedometer test and also to the consolidated undrained triaxial tests at stress levels of stress ranging from 20kPa to 400kPa. The consolidation and shear strength behaviour are discussed in terms of the differences between the intact and compacted samples. The material parameters for modelling the behaviour are obtained and discussed.