BEARING CAPACITY AND FOUNDATION QUALITY OF SUBSOILS IN PARTS OF THE MAIN CAMPUS OF AKWA IBOM STATE UNIVERSITY, IKOT AKPADEN, AKWA IBOM STATE, NIGERIA

The study of the Foundation quality of Subsoils in parts of the main campus of Akwa Ibom State University, Ikot Akpaden, Eastern Niger Delta, Nigeria was carried out with the aim of determining the bearing capacity of the subsoils and designing suitable foundations for the construction of structures. Through field and laboratory investigations carried out, the geophysical study revealed four geo-electric layers namely; the top soil, silty clay, sand, and clayey sand. Six geotechnical boreholes were drilled in the field to a maximum depth of 15m each, with standard penetration tests and cone penetration tests carried out. Soil samples were extracted at 1meters each for different laboratory tests including; moisture content, liquid limit, plastic limit, bulk density, specific gravity, particle size distribution, shear box test, undrained shear strength and Consolidation test. The subsurface stratigraphic profile consists of clayey silty sand (0-7m), sandy silty clay (2-14m) and sand (10-15m) from top to bottom. The clayey silty sand are soft to firm, low to medium compressibility clays with liquid limit, plastic limit and average cohesion values of 23% to 41.5%, 14% to 24% and 14KN/m2 to 64KN/m2 respectively. Ultimate bearing capacity values of the clayey silty sand range from 152.65KN/m2 to 667.94KN/m2. The sandy silty clays are soft, intermediate to high compressibility clays with liquid limit, plastic limit and average cohesion values of 44% to 83%, 25.5% to 51% and 10KN/m2 to 32KN/m2 respectively. Ultimate bearing capacity values of the sandy silty clay range from 269.43KN/m2 to 582.4KN/m2.The sand is poorly graded, medium dense with standard penetration N- values ranging from 13-16. The ultimate bearing capacity ranges from 7878.12KN/m2 to 11423.36KN/m2 respectively. Standard penetration tests and pile bearing capacity analysis indicate that the sands are suitable foundation materials for construction. A Pile foundation terminated within the sand substratum is recommended for large structures.