Geotechnical mapping of lateritic gravels for efficient road construction in Cameroon’s intertropical zone

The study shows that the effective and timely construction of roads in the intertropical zone is hindered by the lack of geospatial data on the distribution of lateritic gravels (LG). This study uses a multicriteria geographic information system (GIS) mapping of elevations, relief curvature, slope classes, and rock types to determine the distribution of LG north of Mount Bangou in Cameroon. The California Bearing Ratio (CBR), maximum dry density, fines content, and plasticity index are used to assess the geotechnical quality of these materials, with CBR values ranging from 17 to 32%. LG with good geotechnical characteristics covers an area of 50 km2 north of Mount Bangou, with a CBR ≥ 30%, maximum dry density > 1.80, gravel content exceeding 64%, fines content < 30%, and plasticity indices < 30%. LG with moderately good geotechnical characteristics cover an area of 79 km2, with a 25 ≤ CBR < 30% and a gravel content between 53 and 59%. LG with poor geotechnical characteristics cover an area of 61 km2, with CBR values below 25%, gravel content between 38 and 50%, maximum dry density < 1.80, gravel content exceeding 64%, fines content > 30%, and plasticity indices > 25%. Altitude has the greatest influence on the spatial distribution of LG in the landscape. The LG with good geotechnical characteristics were found in areas with high slopes of ≥7° and at altitudes of ≥1700 m. Those with moderately good geotechnical characteristics are located in areas with average slopes of 5° and at average altitudes of 1570 m. LG with poor geotechnical characteristics are observed in areas of low slopes of ≤3° and at altitudes of ≤1600 m. These soils can be used in road layers, especially in foundations and sub-base layers, particularly for very low to moderate traffic. The application of an integrated GIS approach for geotechnical mapping of LG, taking into account genetic and geoenvironmental constraints, is promising. This method can be used to assess larger-scale studies on the spatial distribution of lateritic soils for road construction in the intertropical zone.