Abstract

Lateritic soils at the DALL Quarry in Ilorin metropolis (Sango area), southwestern Nigeria were investigated with respect to their geotechnical properties and their suitability as construction materials. The two samples collected fall within the basement complex and they overly the migmatite-gneiss complex rocks.

The grain size analysis shows that soil sample ADET 1 is silt-clayey, very gravelly sand while sample ADET 2 is gravelly, silt-clayey sand. Atterberg consistency limit test shows that ADET 1 has 40% liquid limit, 18.2% plastic limit, 21.8% plasticity index, 7.4% shrinkage limit and an activity of 0.95 (normal clay). ADET 2 has 46% liquid limit, 23.5% plastic limit, 22.5% plasticity index, 8.2% shrinkage limit and an activity of 0.63. The soil samples are above the activity (A) line in the zone of intermediate plasticity (CL) which means that they are inorganic soils. The samples contain inactive clay suggesting little or no swelling tendency and therefore good for construction material and this would prohibit foundation failure during foundation settlement. The California Bearing Ratio (CBR) values are 1-4 % (average = 2.5%) and 3-5% (average = 4%) in ADET 1 and ADET 2 respectively which means that they are good as sub-grade construction materials. The cohesion ranges from 60-100Kpa (average = 75%) and the angle of internal friction ranges from 31^o- 35^o with an average of 33^o.

The geotechnical analyses results show that the soils have high bearing capacity with little or no volume change and therefore can be used as construction materials in engineering works. Thus, the soil could support shallow foundation, dam construction, homogeneous embankments, slope stability and sub-grade materials in road constructions.

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