Influence Of Geology And Hydrogeological Conditions On The Performance Of A Road Pavement Between Shango And Chanchaga Along Minna –Lambata Road, Central Nigeria

Abstract

The dual carriageway along Shango – Chanchaga, in Minna, Central Nigeria, has continued to experience failure at a particular section, opposite the Public Works (PW) LTD yard, Tungan-Goro). This section of the road, which, unlike others, does not response to frequent and routine maintenance, is underlain by schist that is deeply weathered. Evidence shows that the failure experienced by the road is attributed to the geological/hydrogeological conditions underlying the road. This is because the frequently failed portion of this road is constructed on a fractured and deeply weathered schist as a subgrade material with low bearing capacity. The segment of this road is at a depression associated with concentration of groundwater discharge. Storage in the groundwater has increased as a result of blockage in most of the seepages culminating in fast disintegration of the base course materials. The schist under this portion of the highway is weathered to the depth of more than 10 meters into clay minerals with resistivity values as low as 21 Ohm. The clay minerals absorb water and swell in the wet season and compact at the dry season. The percentage of groundwater variation ranges between 154% - 2400% indicating medium to very high percentage of variation of groundwater fluctuation. These clay minerals absorb water and swell at the raining season and dries in the dry period. The road needs to be properly designed and provided with good drainage that will reduce the ingress of water.