Geotechnical Evaluation of Foundation Soils for a Building (Case Study of a Site in Jimma City, Southwestern Ethiopia)

This paper presents the findings of laboratory tests that were carried out on a soil sample collected from a site, in Jimma City, southwestern Ethiopia. The aim of the investigation is to determine the basic shear strength parametres of the soil, which is an important parametre to determine bearing capacity of the soil. Engineering tests such as direct shear, sieve size analyses, atterberg limits, and specific gravity were carrieid out on sample collected from 3m hund dug test pit. All analysis was carried out in line with the ASTM standards. Results obtained showed that the soil investigated contains 35.85% clay, 24.32% silt, 60.17% fine, and 28.70% sand and 11.13% gravel. The result of Atterberg limits analysis showed that the liquid limts is 81%, plastic limit is 55.57% and index of plasticity is 24.43. Clay activity of the soil is 0.68. Thus, the soil investigated is classified as inactive clay of high plasticity. The cohesion value of the soil is 40.2kPa and the angle of internal friction is 19.26 o . With these c and ɸ values, the soil will have good bearing capacity and will be good foundation materials for structures. Keywords: Bearing capacity, shear strength, sieve size analysis, specific gravity.