Abstract:

This study on in-situ assessment of three genetically different lateritic derived soil was carried out to investigate the strength reduction rate of different lithological-derived lateritic soils. The in-situ (DCP) sounding was performed at thirty-seven investigation points and soil samples were collected along soil’s profile for moisture content analysis. The studied route was underlain mainly by porphyritic granite (OGp), medium to coarse-grained granite (OGe), and charnockite (Ch). The mean moisture content values ranged from 13.67 – 24.96%, 7.52 – 15.67% and 11.38 – 17.21% for Ch, OGp and OGe derived soils respectively, with corresponding FCBR values of 7 – 19%, 13 – 53%, and 7 – 37% for Ch, OGp, and OGe respectively. The results of the CBR reduction coefficient were 1.85, 1.47 and 1.67 for Ch, OGp, and OGe-derived soils respectively. This implies that all the derived soils are susceptible to ingress of water with a consequential reduction in strength, which is characteristic of the lateritic soils. Meanwhile, the degree of CBR reduction is an expression of the lithological differences in the three rock types. Geological factors such as lithology should be taken into consideration whenever lateritic soils are being considered for construction.