BEARING CAPACITY ANALYSIS OF SUBSOILS, FOR SHALLOW AND DEEP FOUNDATION IN UYO TOWN, EASTERN NIGER DELTA, NIGERIA.

Abstract

The Geotechnical properties of soils in Uyo town were analysed to determine the bearing capacity and develop maps for shallow and deep foundation designs, which may serve as field models, for the planning of site investigation programmes for foundation purposes. Eleven boreholes were drilled to a maximum depth of 20 meters each across Uyo town. Standard penetration tests and cone penetration tests were also carried out on the field. Soil samples were retrieved during the field investigation for various laboratory tests including liquid limits, plastic limit, bulk density, shear strength and particle size distribution. The general soil profile consists of silty clays, sandy clays and sand from top to bottom. The silty clays are firm, low compressibility clays with liquid limit and plastic limit percentages between 32%-45% and 10%-45% respectively, cohesion averages of 4˚ to 12˚ and angles of internal friction between 48KN/m2-68KN/m2. Ultimate bearing capacities of this horizon range from 354.6kN/m2 to 866.7kN/m2.The sandy clays are also firm, low to intermediate plasticity clays with liquid limit and plasticity indexes of 29% - 42% and 9%-15% respectively. Their cohesion averages range between 50KN/m2-65KN/m2 and angles of internal friction between 6˚-12˚. The ultimate bearing capacities of this clay range from 482.5KN/m2 to 906.2KN/m2. The sand is a poorly graded, medium dense sand with standard penetration test N-values between 8 to 23. Pile bearing capacities of the sand gave ultimate and allowable bearing capacities between 10262.9KN-11510.2KN and 4105.2KN-4604.1KN respectively. The sand substratum is a suitable termination depth for piles.