Geotechnical Properties of Lateritic Soils Derived from Various Geologic Formations in Ohafia Area, Southeastern Nigeria

Some lateritic soils collected and used for road construction in Ohafia Area, Southeastern Nigeria are not suitable. The purpose of this paper was to evaluate the quality of lateritic soils derived from various geologic formations in Ohafia, Area, as road construction materials using their geotechnical properties (Atterberg limits, grain-size distribution and CBR). Eight representative samples derived from various geologic formations in the study area (including 2 from Mamu Formation (Asaga and Akanu); 3 from Nsukka Formation (Ebem, Ozu Abam and Ndi Uduma); 1 from Nkporo Formations (Ndiorioko); 1 from Ajali Formations (Ndi Uduma Ukwu); and 1 from Imo Shale (Amagbu), was used in the study. Results of the laboratory tests indicate that the liquid limits range from 26.0 to 33.0%, while the plasticity indices range from 2.8 to 10.0%. The % fines range from 18.6 to 64.9%. The CBR (Soaked) range from 17.0 to 39.0%, while CBR (unsoaked) range from 35 to 79%. On the basis of Federal Ministry of Works Specifications for highway pavement materials, only soils derived Ajali Formations, Nsukka Formation and Nkporo Formation are fairly suitable materials. They satisfy the specification in all areas LL<36%, P1 < 12% and % fines < 30%), though they have low CBR values (soaked and unsoaked). Soils derived from Mamu Formations and Imo Shale are not good because of their particularly very high % fines. Treatment of any of or all the soils with either cement or lime will improve the poor quality aspect (low CBR and high % fines) and hence make the soils suitable to be used as road construction materials.