Influence of hydromorphic conditions in the variability of geotechnical parameters of gneiss-derived lateritic gravels in a savannah tropical humid area (Centre Cameroon), for road construction purposes

- Lateritic gravels of dry savannah and humid savannah were studied.
- Lateritic gravels of humid savannah have a low bearing capacity.
- Lateritic gravels of dry savannah are usable as base layer after lithostabilisation.

The influence of the water table on the geotechnical properties of lateritic gravels found in a Savannah area in the Centre Cameroon used for road construction was studied. The descriptive statistical analyses show that the values of the geotechnical parameters are more dispersed in humid savannah area than in dry savannah area. The results of the Principal Component Analysis (PCA) and through Agglomerative Hierarchical Clustering (AHC) reveal the existence of three groups of materials, the lateritic gravels of a humid savannah (<75 μm = 32.9%, PI = 27%, MDD = 1.9 g/cm3, CBR = 31%), intermediate lateritic gravels (<75 μm = 24.0%, PI = 22%, MDD = 2.0 g/cm3, CBR = 44%) and lateritic gravels of dry savannah (<75 μm = 18.9%, PI = 19%, MDD = 2.1 g/cm3, CBR = 51%). The lateritic gravels of humid savannah are characterised by the granulometry and plasticity parameters while those of the dry savannah are characterised by physical and compaction parameters. The lateritic materials of humid savannah are gravels and fine clayey sand, averagely plastic and used as sub-base layer while those of dry savannah are more coarse, less plastic and used as sub-base layer and as base layer after lithostabilisation.