International Journal of Research Studies in Agricultural Sciences (IJRSAS) Volume 2, Issue 7, 2016, PP 14-21 ISSN 2454-6224 http://dx.doi.org/10.20431/2454-6224.0207003 www.arcjournals.org ©ARC Page | 14 Application of Atterberg Model on Surface and Sub-Grade Soils for Foundation Mechanics and Design Suitability I.D. Edem*, M.E. Nkereuwem *Department of Soil Science and Land Resources Management, University of Uyo, Nigeria. Department of Soil Science, Faculty of Agriculture, Federal University Dutse Jigawa State, Nigeria Abstract: The study location is within the coastal plain sand of Akwa Ibom State. The area lies within a sub- horizontal geomorphologic terrain with a measure of undulations arising from uneven surface area erosion. The study revealed that the soils are loose, coarse texture with 78 – 80% sandy fractions having single grain structure from unconsolidated materials of recent alluvial deposits. The soils are strongly acid in reaction with pH values between 4.8 and 5.8 which could be attributed to leaching of the basic cations to lower depth. Organic carbon content ranged from moderately low 1.50% to high 2.38% due probably to high surface litter and vegetation cover. Since the ultimate bearing capacity depends upon the angle of internal fraction (ф) and hence the penetration number (N), it was related directly to the N at profiles 1, 2, 3 and 4 from the existing surface, cohesion value of 25 kN/m 2 was applied and the allowable bearing pressure of 18.5 kN/m 2 , 17.1 k/Nm 2 , 54 k/Nm 2 , and 66 kN/m 2 were obtained for profiles 1, 2, 3 and 4 respectively by applying a factor of safety of 3.0. The higher the elevation, the higher the plasticity and the swelling potential; and the lower the bearing capacity and strength of the building sub-grade. Keywords: Soil mechanics, coastal plain, bearing capacity, ecological condition 1. INTRODUCTION Soil erosion is a phenomenon caused by multidimensional factors. Soil vulnerability to erosion focuses on climate and geotechnical soil characteristics as causatives. Soil erosion is a natural geological phenomenon resulting from the removal of soil particles by water or wind, and transporting them elsewhere. Some human activities can significantly increase erosion rates. Erosion is triggered by a combination of factors such as steep slopes, climate (e.g., long dry periods followed by heavy rainfall), inappropriate land use, land cover patterns (e.g., sparse vegetation) and ecological disasters (e.g., forest fires). Different indicators of soil erosion have been identified and it is a common opinion that the area actually affected by erosion is the best indicator for soil erosion. The factors which influence the rate of erosion are; rainfall, runoff, soil, slope, plant cover and the presence or absence of conservation measures (Muzik, 2002). Erosion and land use change are very closely related. Rates of soil loss accelerate quickly to unacceptably high levels whenever land is misused. Soil erosion threatens soil fertility due to nutrient and organic matter loss, while also decreasing water quality through increased turbidity (Bonilla and Vidal, 2011). Many authors have reported that soil erosion and sediment movement have important influences on Carbon (C) sequestration potential in soils and ecosystems (Smith and Skinner, 2002). Therefore quantifying the impacts of climatic parameters on soil erosion has important implications to the understanding of their environmental impacts as well as the feedback of soil carbon dynamics to global warming. The vulnerability of a piece of land to soil erosion depends on the physical and chemical properties of the soil. Different types of soil have different physical and chemical properties. The texture, structure, water retention capability, etc. play important roles in determining whether the soil is susceptible to erosion or not. Climate determines the precipitation levels and wind velocity. More precipitation means more surface flow, and more surface flow means more area vulnerable to erosion by running water. This research aimed at providing detailed assessment of the suitability of the soils of the area, the sub-soil conditions and suggests relevant soil improvements where necessary as well as recommend appropriate foundation type and design parameters