Vol. 2, Issue 2 (2017)
Geo-Technical assessment of the Nekede old road borrow pit
Author(s): Obasi CL, Owuama CO, Uzoma HC
Abstract: The aim of this study was to assess the Geo- Technical characteristics of Nekede old road borrow pit. The study was focused on pit moisture content, specific gravity, direct shear strength, slope stability and slope factor of safety. The evaporation method and density bottle method was used to determine pit moisture content and specific gravity respectively. Shear strength was determined using box apparatus while slope stability was determined using Swedish method of slices. Results of the analysis showed that the moisture content range of 11.2 – 14.3% was obtained from the sample results. Also the test results showed specific gravity range of 2.68 – 2.71 across the soil layers of the pit. The shear test showed a shear strength range from 83.3 – 92.7KN/m2, with angle of friction range of 24 – 27o and low cohesion range of 3 – 5 KN/m2 across the pit walls making the soil susceptible to sliding at slightly steep slopes. Result of slope analysis for three failure planes of the pit slope at 20 meters depth gave a tangential component (T) range of 67.6 – 1018.6 KN within the three slides and a low critical safety factor (F) of 0.4 in the first failure plane and an average safety factor (F) of 0.7 for the three planes as a representative for unstable walls of the Nekede old road borrow pit. This shows that under saturated condition the pit walls collapses. Reconstruction of the borrow pits to suitable dimensions with proper sloping for easy draining was recommended so as to use the site as fish farms using the nworie river as source of water.