Foundation Evaluation of Subsoils in Parts of Finima, Bonny Island, Eastern Niger Delta.

Foundation evaluation of sub soils was carried out in Finima Bonny Island, Eastern Niger Delta to assess the particle size distribution and bearing capacity of the soils for shallow foundation designs using strip and square footings. The investigation involved the drilling of eight boreholes to a maximum depth of 30m each and the retrieval of soil samples at 1m interval, in situ cone penetration tests and laboratory analysis of the particle size distribution of the soil. The stratigraphy of the soil consists of fine to medium to coarse dense sand with intercalations of soft, dark grey clays at various depths between 11-14m and 25-28m. Particle size distribution of the soils show uniformly graded soils in all boreholes except BH06 and BH07 which are poorly graded. Analysis of the bearing capacities of the soils for strip and square footings showed that the soils in BH06 and BH08 had the highest ultimate and allowable bearing capacities at 1.5m depth, while BH02 and BH08 had the highest values at a depth of 3.0m. For the square footing, the ultimate and allowable bearing capacity values of the soil are highest in BH06 (Qu-4304KN/m, Qallow-1722KN/m) at 1.5m depth. While BH02 (Qu-9669KN/m, Qallow-3868KN/m) is highest at 3.0m depth. The results of the particle size distribution and bearing capacity reveal that the soils are suitable foundations for light and medium load structures like bungalows and one-storey building.