Evaluation of the Bearing Capacity of Near-Surface Soils Using Integrated Methods: A Case Study of Otukpa, Ogbadibo Lga, Benue State, North-Central Nigeria

Abstract

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/cm3. Permeability ranges from 7.8×10−6m/sec to 3.36×10−4m/sec while volume compressibility under 250kN ranges from 7.27×10−5m2/kN to 1.3×10−4m2/kN and the rate of consolidation under 250kN is within 12.43 m2/year to 1.33m2/year. MDD peaks at 1.85g/cm3 at an OMC of 12.11% and is lowest at 1.67g/cm3 at an OMC of 11.99%. UCS ranges from 31-45kN/m2 while shear strength is between 258.81kN/m2 to 338 kN/m2. 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.

Assessment of the Engineering Properties and Suitability of Some Tropical Soils as Backfill Materials

“…The consistency indices, which measures the degree of coherence between soil particles at a given water content, show values that are very close to negative; hence explaining why the soils couldn't behave as liquid, but only as soft to hard material. The observations also suggest that since the soilsgenerally have relatively similar consistency, they would all behave in a similar manner when extra water is added to them [1]. However, it is pertinent to note that excess water content (and some other external factors) can interfere their consistency.…”

“…5). Soils with similar specific gravity show similarity in textural and mineralogical makeup [1]. These soils are mainly medium-coarse grained materials (except for OKJ).…”

“…This attempt increases a soil's density, shear strength, stability, bearing capacity and factor of safety. Informed by these observations and facts, the samples, for the shear strength improvement, were compacted at optimum moisture contents to simulate the best possible field moisture compaction conditions [24] [1]. The compaction test defined the maximum dry density and the optimum moisture content (OMC) for the soils.…”

Assessment of the Implications of Geotechnical Properties of Soils in Otukpa Area of Ogbadibo LGA, Benue State, Nigeria

“…We expect a little pore pressure to build up as a result of the low permeability that will result. This pore pressure will not affect structures in the area because [14] showed that the water table in the area is at a depth of 201m. …”

“…The oedometer method of determining the 1D-consolidation of soil was done with one-directional drainage allowed [14]. The calculated consolidation values of C v and M v at a stress level of 250kN are presented as Table 6.…”