Geotechnical characterization of lateritic soils for road construction in guinea: case study of dabola

The rapid deterioration of roads across the Republic of Guinea has become a major concern, as their service life remains relatively short. In this work, the focus is placed on the road network of the town of Dabola, where the road infrastructure is in very poor condition. The subgrade soils at the study site, developed on the lateritic weathering crust, exhibit a low-plasticity clay behavior according to the Casagrande classification. To propose effective improvement solutions, laboratory tests were conducted, including particle size analysis, Atterberg limit determination, standard and modified Proctor compaction tests, and the CBR immersion test. The results show that the soil is a slightly clayey gravelly sand, classified as Class B, subclass B2S according to the GTR. The deformation modulus obtained (120 MPa) places the platform in category PF3 (very slightly deformable), so no subgrade removal is required. However, the CBR value obtained at 95 % of the modified Proctor optimum (CBR = 24) remains below the threshold required for direct use as a subbase layer (CBR = 30), whereas at 98 % of the optimum the CBR (38) satisfies this requirement. Based on the measured plasticity index, chemical treatment with lime and/or cement is recommended to bring the material’s bearing capacity up to the level required for the base and subbase layers.