Evaluation of the bearing capacity of near-surface soils using integrated methods: A case study of Otukpa, Ogbadibo Lga, Benue state, North-Central Nigeria

摘要

The load bearing capacity of soils in Otukpa area of Benue state, Nigeria was evaluated by characterizing the geotechnical, geophysical and structural properties of the soil. The evaluation was necessary because aside the area holding good prospect for future increase in human population, sparsely distributed low-weight buildings in the area have cracks and other signs of failure. Remote sensing/GIS, geophysical and geotechnical approaches were integrated to achieve the objective. 2-D tomography and processed remotely sensed data confirmed the presence of areas of strength especially to the north. Stratigraphy of the northern portion consist of four layers; loose top soil (0-0.26m), compact clayey sand (0.26m-3.33m), dry clayey sand (3.33m-74.21m) and saturated clayey sands (74.21m-201.58m) While the stratigraphy in the south is slightly different; compact topsoil (0-1.2m), loose sand (1.2m-10.81m), compact sand (10.82m-19.71m) and compact clay sand (19.71m-56.03m). The plastic limit range from 11-17% with average specific gravity of 2.64g/cm(3). Permeability ranges from 7.8x10(-6)m/sec to 3.36x10(-4)m/sec while volume compressibility under 250kN ranges from 7.27x10(-5)m(2)/kN to 1.3x10(-4)m(2)/kN and the rate of consolidation under 250kN is within 12.43 m(2)/year to 1.33m(2)/year. MDD peaks at 1.85g/cm(3) at an OMC of 12.11% and is lowest at 1.67g/cm(3) at an OMC of 11.99%. UCS ranges from 31-45kN/m(2) while shear strength is between 258.81kN/m(2) to 338 kN/m(2). Due to the variability of engineering properties of soils, the southern part of the area is preferred for locating the buildings. Generally, careful foundation design in the area is necessary.