Assessment of Quality of Some Laterites in Northeastern Nigeria by Multivariate Analysis of their Geotechnical Index Properties

The index properties of lateritic soils derived from sandstone, limestone, gneiss, granite, basalt, and migmatite in northeastern Nigeria were assessed for selecting the type with the best engineering potentials. The laboratory test results indicate that the tested samples comprised predominantly sand-sized particles (58-88%), with clay fraction (2-12%) of low to moderate plasticity (liquid limit, LL 35-49 and plasticity index, PI 12-24). Other geotechnical properties are as follows: natural water content (W-n), specific gravity (SG) 2.51-2.68, maximum dry density (MDD) 1.69-2.05 mg/m(3), and unconfined compressive strength (UCS) 20-43 kPa. Principal component analysis reveals three significant factors. The first factor has loadings from clay, LL, PI, W-n, and SG, indicating impacts that are mineralogical and particulate constituent related. The second has loadings from gravel, MDD, and UCS and indicates textural influence, while the third factor has loadings from silt and sand, thus, reveals textural impact. The analysis of variance result reveals a significant difference in dataset, while cluster analysis indicates three different sample clusters, with a granite laterite sample representing the central object of the first cluster and sandstone and limestone laterite samples representing central objects of the second and third clusters, respectively. Comparatively, the second cluster samples would likely perform best in engineering projects having recorded comparatively the least clay content, lower plasticity, highest SG, MDD, and UCS. Thus, a combination of index properties and multivariate analysis proves a useful tool in the geotechnical prospecting for lateritic soils.