INVESTIGATING THE EFFECTS OF SOME GEOTECHNICAL PROPERTIES ON EXPLOITATION OF SELECTED LATERITE DEPOSITS IN SOUTH WEST, NIGERIA.

Abstract

Investigation was carried out on the stability of lateritic soildue to some geotechnical properties in selected burrow pits in Akure, Ibadan, Ewekoro and Iperu areas, south western Nigeria for predicting their slope stability. The geotechnical properties of laterite soils slopes were determined on the field and in laboratory in accordance with American Society for Testing and Materials (ASTM) Standards. The conventional slope stability analysis was based on the linear Mohr – Coulomb failure criterion utilizing the notion of safety factors with respect to shear strength, where their average results of cohesion, angle of friction, bulk density and moisture content from the locations are 82 kPa, 18 degree, 1700 kg/m3, and 22 % respectively. The results of geotechnical properties of the laterite soil at various locations where their average specific gravity for the six locations was 2.73 were computed. The degree of permeability of the laterite soils from the locations was very low except for location 6 which is medium. The grain size distribution for the locations was classified into SC – SM (silt clayey sand) based on unified classification of soil sample. From the compaction test, the average moisture content, average wet density and dry density for all locations are 23 %, 1849 kg/m3 and 1512 kg/m3 respectively while the average compaction curve deduced 24 % optimum moisture contents and 1639 kg/m3maximum dry density. The Atterberg limits test results indicate that locations 1 to 5 were recorded as plastic soil while location 6 was recorded as a non-plastic soil due to its sandy nature. Also, the linear shrinkage degree of expansion for location 1 to 5 indicates critical while location 6 indicates non-critical. Finally the statistical mathematical model equations relating the failure slope of the lateritic soil was developed. The factor of safety for locations 1 to 5 was satisfactory for routine extraction and loading operations while location 6 was unsafe due to loading conditions of the terrain.