Geotechnical Analysis of Lateritic Soil from Selected Borrow Pits in Minna Metropolis

Abstract

Laterite is a construction material widely used in roads, embankments, fill materials, building constructions and many more; its basic engineering properties especially geotechnical characteristic is still being explored. Eighteen soil samples were collected from three locations and subjected to geotechnical tests; Specific gravity, Sieve analysis, Consistency tests, Compaction and California Bearing Ratio (CBR) Tests. The results show that specific gravity ranges from 2.57 – 2.71 for Maikunkele, 2.52 – 2.62 for Maitumbi and 2.62 – 2.69 for Birgi. According to AASHTO classification, the soil samples are classified as Maikunkele: A – 2 group (granular materials), Maitumbi: A – 4, A – 6 group (Silty – clay materials) and Birgi: A – 4, A – 6, A – 2 – 5 group (Silty – clay materials) and USCS classification as mostly CL-ML, ML and CL. CBR values at 2.5mm and 5.0mm for Maikunkele sample ranges from 6.21 to 21.65% and 19.32 to 40.58%. Maitumbi sample ranges from 14.25 to 18.93% and 20.66 to 26.79%, while Birgi sample ranges from 10.27 to 23.36% and 24.61 to 30.64% respectively, indicating that most of the soils are suitable for sub-grade materials. Compaction results using different energy level for these areas varied with depth: MDD of 1.96 to 2.92 g/cm3, OMC of 7.20 to 14.60% for Maikunkele laterite, MDD of 1.85 to 2.19 g/cm3, OMC of 10.9 to 16.00% for Maitumbi laterite and MDD of 1.95 to 2.11 g/cm3, OMC of 8.40 to 14.70% for Birgi laterite. At 5mm penetration, Maikunkele laterite has the highest CBR value of 40.58, while Maitumbi and Talba Farm are 26.79 and 30.64% respectively. Based on these results, all the laterite samples obtained around Minna can be used as sub-base, sub-grade and fill materials in road constructions.