The influence of parent rock factor on some engineering index properties of three residual lateritic soils in Southwestern Nigeria

Abstract

Soils derived from sandstone, migmatite-gneiss and quartz-schist in the vicinity of sections of the Lagos-Ibadan expressway in Southwestern Nigeria were investigated. The investigation was meant to determine the extent to which the parent rock factor has controlled some basic engineering index properties of the derived soils. Field and laboratory investigations showed that the mineralogy and texture of the parent rocks show distinct variation from one rock type to another.

The study has proved that the influences of the parent rock factor on engineering index properties such as the specific gravity of grains, plasticity index and grain size distribution characteristics of the soils studied were significant. However, a rather weak influence of the genetic factor on the linear shrinkage of the studied soils was noticed. It is thus necessary to take proper cognisance of the parent rock characteristics prior to an adequate understanding of engineering properties and behaviour of residual soils.

Résumé

L'étude a porté sur des sols dérivant d'un grès, d'un gneiss migmatique et d'un schiste quartzeux prélevés le long de la route express Lagos-Ibadan dans le Sud-Ouest du Nigéria. Elle a montré l'influence des roches d'origine sur certaines caractéristiques géotechniques des sols telles que la densité des grains, l'indice de plasticité et la courbe granulométrique. On a par contre noté une faible influence du facteur génétique sur le retrait linéaire des sols étudiés.