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

Abstract

The rocks and soils underlying Lambata-Minna road and the neighbourhood 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 profile of the road. The geoelectric studies revealed that the soil profiles of the road are composed of laterite, sand and clayey soils. Road traffic statistics revealed that the traffic density of the road is within the 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 road was observed to determine the variation in seasonal groundwater variation. 35 water samples were collected from wells along the road and subjected to hydrochemical. A total of 47 soil samples were collected and subjected to geotechnical analyses. The field mapping, thin section and XRD revealed the road is underlain by migmatites, gneiss, granites, marble, granodiorite and schist. The groundwater occurring within migmatite has higher ionic concentration and physical properties. The soils are gravely soils. Low permeability ranges from 4.73 x 10-4cm/s to 9.78 x 10-3cm/s were obtained. Optimum moisture content ranges from 18 to 27%. The soaked CBR of soils ranges from 0.9 to 70% while the unsoaked CBR ranges from 5 to 70%. The soils underlying the granites 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 soils occurring within those terrains have poor geotechnical properties to serve as either sub-grade, sub-base or base material in their natural state.