ABSTRACT

This study investigates the influence of two main geotechnical properties of soils in the town of Ikole-Ekiti on civil engineering construction. The strength and compaction characteristics of the natural soil were determined. The investigation was carried out through laboratory tests on disturbed and undisturbed soil samples obtained from four trial pits (Samples A, B, C & D) in the town, across Ilotin, Ijemo-Titun, Yeye-Oba and Asin respectively. The samples were collected between depths of 1.5m and 2.0m. The soils were mostly lateritic ( except Sample C) and were all coarse-grained. The consistency limits indicate Liquid Limit of 29- 52 %, Plastic Limit of 12- 29%, Plasticity Index of 17- 28% and Shrinkage Limit of7.1- 12.1%. The average specific gravity ranges from 2.31- 2.63, these make all the soils suitable as subgrade material. According to AASHTO, the soils were respectively classified as A-2-7, A-2-7, A-2-6 and A-2-7. While in the USCS, the soils were also classified as SW, SP, SW-OL and SW-SC. Standard Proctor compaction tests indicated Maximum Dry Densities of 1.73 g/cm3 , 1.71 g/cm3 , 1.79 g/cm3 and 1.56 g/cm3 at optimum moisture contents of 19.05%, 19.80%, 14.90% and 15.40% for soil samples obtained from Trial Pits A, B, C and D respectively. While modified Proctor compaction tests indicated Maximurn Dry Densities of 1.95g/cm3 , I.92g/cm 3 , 1.99 g/cm3 and 1.87 g/cm3 at optimum moisture contents of 18.20%, 20.20%, 15.70% and 16.90% for soil samples obtained from Trial Pits A, B, C and D respectively, Sample A, B& D are suitable as landfill barrier mate1ials. The direct shear tests indicate undrained cohesion within the range (11- 74.41) kN /m 2 and corresponding range for the tmdrained angle of internal friction 15.26°- 18.44°. Triaxial (Consolidated Drained) and Unconfined compression tests were carried out on Samples A, B & D. Triaxial results showing range of(50.l - 52.2) kN /m 2 , at an angle of internal friction of 18°. These soils can be used for shallow foundations for loads of the order of 20- 53 kN /m 2 • While for Unconfined Compression, the undrained shear strength range from (21.73 - 47.43) kN /m 2 . These values are also important in the construction of finite& infinite slopes, of which the critical height of the slope is yet to be detennined. Factor of safety can also be derived, in tl1e design process of such slopes to avoid failure later on, before/ during/ after construction process.