Spatial variability of geotechnical parameters of lateritic gravels in an Olama–Ngomedzap road section in a humid tropical area (Cameroon)

Abstract Searching for borrow pits often used during civil engineering constructions is an important step that requires a lot of time and money. The nature of the parent rock, climate, topography, vegetation and time influence the formation of lateritic gravels with different geotechnical properties within the same region. The present study aims at finding the spatial variability of geotechnical parameters of lateritic gravels from two different deposits using a variogram and statistical analysis. Out of 122 lateritic gravel samples collected, 69 were from underdeveloped lithic ferrallitic soils (LFS) and 53 from under developed non-lithic ferrallitic soils (NLFS). The mean values of the coefficient of variation (CV) shows that the geotechnical parameters of LFS-derived lateritic gravels are more dispersed than those developed on NLFS. The fines content, plasticity index (PI) and Californian bearing ratio (CBR) variograms observed mainly in the North and NNE parts of the study area, suggest that, the lateritic gravels in this area have average to good geotechnical characteristics. The principal component analysis (PCA) indicates that the CBR and the maximum dry density (MDD) are inversely related to the optimum moisture content (OMC). The discriminant factor analysis (DFA) coupled to the ascending hierarchical classification (AHC) shows three families of lateritic gravels: (1) class 1/3, lateritic gravels characterized by MDD, CBR, consistency index (CI), gravels content, and plastic limit (PL); (2) class 2/3, lateritic gravels characterized by fines content, and maximum grain diameter (D max ) and, (3) class 3/3, lateritic gravels characterized by OMC, liquid limit (LL), PI, PL, and fines content, that fit for road construction.