Impact of Geology on the Stability of Minna-Lambata Road, North-Central Nigeria

Abstract

The rocks and soils underlying lambata – minna road and the neigbourhood in central Nigeria were mapped and subjected to various analyses in order to determine their impact on the stability of the road they underlay. Vertical electrical soundings were done along the road to determine the soil profie of the road. The geoelectric studies revealed that the spil profiles of the road are composed of laterite, sand and clay soils. Road traffic statistics revealed that the traffic density road is within permissible limit. A total of 5 rock samples were collected and each subjected to thin section, XRD and XRF analyses. Groundwater table of wells along the roadwas observed to etermine to determine the variation in seasonal ground water variation. 35 water samples were collected from the wells along the road and subjected to hydrochemical. A total of 47 soil samples were collectedand subjected to geotecthnical analyses. The field mapping, thin section and XRD revealed the road is underlain by migmatites, gneiss, granites, marble, granodorite and schist. The ground water occurring within migmatite terrain has higher ionic concentration and physical properties. The soils are gravely soils. Low permeability ranges from 4.73×10-4 cm/s to 9.78×10-3cm/s were obtained. Optimum moisture content ranges from 18 to 27%. The soaked CBR of soil ranges from 0.9-70% while the unsoaked CBR ranges from 18-27% the soil underlying the granite are generally more competent than those underlying the migmatite. The consistent failure of the Lambata-Minna road portion underlain by migmatite gneiss and granite is because the soil occurring within those terrains have poor geotechnical properties to serve as eigher sub-grade, subbase or base material in their natural state