Premature failure of a major highway in southwestern Nigeria: the case of Ipele–Isua highway

Abstract Mineralogical, geochemical and geotechnical analyses were carried out to evaluate the contributions of geological and geotechnical properties of subgrade soils to the incidence of failure of the Ipele–Isua road, south-western Nigeria. Field observations showed that the road is in a very poor state of disrepair as major portions of the road alignment have failed. The road alignment is underlain in places by Quartz Schist, Banded Gneiss and Granite Gneiss. The results of the laboratory tests revealed that the natural moisture content ranges from 6.5 to 23.3%, liquid limit from 20.1 to 55.1%, plasticity index 5.2 to 22.2%. The grain size analysis showed that the amount of fines ranges from 13 to 60.8%. Others are linear shrinkage between 2.9 and 11%, free swell between − 16.67 and 41.94%, maximum dry density from 1520 to 1792.1 kg/m3 and CBR between 2 and 17%. The specific gravity ranges from 2.51 to 2.63. The major clay minerals present are kaolinite and dickite with dominance in 50% of the samples. Major oxides present are SiO2, Al2O3, Fe2O3, K2O. Na2O, MgO and CaO are generally less than 1%. Based on AASHTO classification, 19% of the samples are classified as A-2-4, 33% classified as A-2-6 while 44% classified as A-7. Dominance of low California bearing ratio, low maximum dry density, high linear shrinkage and A-7 soil group expectedly contributed to poor geotechnical properties of the subgrade. Absence of drainage is suspected to have worsened the failure as exhibited on the road

Improvising border security: 'a situation of security pluralism' along South Sudan’s borders with the Democratic Republic of Congo

This article compares two cases of securitization along South Sudan’s border with the Democratic Republic of the Congo. By comparing how a security concern – the presence of the Lord’s Resistance Army – was interpreted and responded to, the article shows that border security practices in two borderscapes are improvised, contradictory and contested, and serve to establish authority rather than actually securing the border. This is apparent on three levels: (a) through the multiplicity of security actors vying for authority; (b) in how they interpret security concerns; and (c) in terms of what practice follows. The article argues that by allowing authority at the border to be taken by actors that are not under direct control of the central government, the South Sudanese state is developing as one that controls parts of the country in absentia, either by granting discretionary powers to low-level government authorities at the border or through tactical neglect. Processes of securitization by both state and non-state actors in the borderland are largely disconnected from the South Sudanese central government, which does not claim authority over this border and thus seemingly does not consider the lack of security for its citizens, and the parallel authorities, as a threat to central stability