Strength and structure of laterites and lateritic soils

Abstract

Ten soils from Puerto Rico representing various states of weathering were subjected to engineering index tests, strength and density measurement, mineralogic analyses, and scanning electron microscopy. Engineering classification systems used for temperate soils tend to underestimate the engineering behavior of these undisturbed lateritic soils and in the undisturbed state the soils exhibit low densities and high strengths. The engineering properties of the undisturbed soils show systematic trends in relation to the degree of weathering and the parent rock. For a given rock, the void ratio is decreased and cohesion increased as weathering proceeds. This is the result of increasing crystallization and cementation by the sesquioxides. The specific gravity of the solid particles is a promising index property to characterize these lateritic soils insofar as it reflects iron oxide content. The decrease in void ratio and increase in cohesion with increasing specific gravity suggests a model for the engineering classification of tropical soils.