An Assessment of the Geotechnical Properties of the Subsoil of parts of Federal University of Technology Minna, Gidan Kwano Campus, for Foundation Design and Construction

Abstract

The subsoil conditions of parts of Federal University of Technology, Minna permanent site (Gidan Kwano campus) northwestern Nigeria was investigated by excavating six trial pits from the existing ground level to between (1.00 to 1.5) meters. Twenty disturbed and undisturbed samples were collected and sent to Julius Berger Nigeria Plc. laboratory, Minna and National Steel Raw Material Exploration Agency, Kaduna for relevant geotechnical analysis. Prior to the excavation, lithological and structural mapping was undertaken to reveal the presence of any geologic features that might affect the foundation of buildings and anticipated construction difficulties. The soil is heterogeneous. The liquid limit ranges from 18% to 43%, the plastic limit varies from 13.8% to 28.0%. The plasticity index is of the order of 2.1% to 18.1%. The pH is neutral, sulphate (SO42-) and chloride (Cl-) contents are negligible. The soil cohesion (C) ranges from 130 KN/m2 to 164 KN/m2 while the angle of internal friction (?) is 8. The coefficient of consolidation (Cv) varies from 1.47 m2/yr to 2.57 m2/yr. The coefficient of volume compressibility (Mv) ranges from 0.20 m2/MN to 1.15 m2/MN and the compression index (Cc) is of the order of 0.32 to 0.38. Based on the field and laboratory results, shallow foundation (reinforced strip, pad or raft) can be adopted for lightly loaded structures. Greater bearing capacity can be obtained by founding pad or strip on the bedrock within the southeastern part of the study area. Deep foundation in form of driven or bored pile should be adopted for heavily loaded building. A pile founding depth of about 33m depth anchored on the bedrock is recommended for the other areas.