Assessement of Geotechnical Properties of Soil Underlying o Collapsed Structure Along Iman Street, Uyo, Nigeria

Abstract

Samples of soil were obtained from two pits, about 1.8m from a collapsed location along Iman Street in Uyo, Akwa Ibom State, Nigeria. These soil samples were analysed in a laboratory using different sieve sizes to separate dried grains with the help of a sieve shaker. Microsoft Excel was used for the processing of this information and computations. The paint package of Windows 7.1 software was also used to deduce the necessary parameters for gradation result. The result of the grain size distribution yielded the uniformity coefficient, coefficient of gradation and sorting coefficient as 2.71, 0.91 and 1.64. This information classified the soil as poorly graded and more susceptible to soil liquefaction; most of the particles are approximately of the same size; they are not suitable for construction as they may not be compacted better like well-graded soil. The average percentage of natural water content was achieved as 23.99%. However, from the Atterberg limit investigation, the water content where the liquid limit corresponds to the number of blows as 25 is 45.56%. The plasticity index obtained is 18.58%. For better assessment information, some indices results were necessary which include Activity Index = 0.4494%, Liquid Index = - 0.61609, Consistency Index = 1.1609, Flow Index = 1.4390, Toughness Index = 12.9117 and Group Index =  3.7042. The plasticity index is high. This may show a marked reduction in bearing capacity with increase moisture content. The soil (laterite) clay mineral is Kaolinite which has low shrink-swell potential. It can hold large amount of water and still stay in plastic state. It is medium compressible since its liquid limit is within 30% to 50%. It is cohessionless and with the value of the group index obtained, the soil subgrade may be predicted as belonging to a fair class.