THE PHYSICO-CHEMICAL PARAMETERS RESPONSIBLE FOR ROAD FAILURES IN SOUTHERN NIGERIA

Road failure in the southern part of Nigeria is a phenomenon that scientists have shown much interest on. Diagenetic fabrics of compaction, dissolution, alteration and corrosion were common features. The reaction rims around grain margins indicating severe alteration and corrosion were seen growing from grain margins inward, leaving the sandstone, which many have been indurated with little or no cementing material, thus leading to the friability of the sandstone and its susceptibility to erosion. Apart from the friability of the soil in this area, mineralogical compositions of the underlying soil have made the area prone to some hazards.

Geotechnical tests were carried out, these include, Atterberg test, particle size, compaction test and plasticity index. Sieve analysis showed that the soils from this zone are within the medium to coarse grain range with low percentages of silt/clay, therefore the soil is non plastic. The compaction tests also showed that the optimum moisture content ranges from 13.50% to 15.20% while the maximum dry density ranges from 1.75mg/m³ to 1.98mg/m³. The plasticity index revealed that the soils are non-cohesive and non-plastic because it ranged from 1.2% to 5-2%. The maximum dry density values are generally low which indicated that the soil is not compact but loose.

There were presences of pockets of smectitic clay with high montmorillonite content. This has the most swelling potentials and accounts for the most of the damages resulting from expansive clays.