Stabilization of dredged spoils for pavement construction in the Niger Delta, Nigeria

Natural soils underlying the East-West road are mainly clay and silt of poor quality as subgrade and subbase materials. However, dredged fine grained sandy soils stockpiled at river banks along the road as wastes may be modified for strength gain to replace the excavated natural soil during road construction. The optimum stabilization conditions of the dredged soils were determined in this study to evaluate the strength improvement for beneficial use as road construction materials in view of their large quantity and nearness to the point of use. The laboratory tests carried out on the dredged soils included particle size distribution, compaction and California Bearing Ratio. Cement stabilization was performed on the dredged spoil. Results of the particle size distribution analysis showed that about 80 % of the natural soils, but less than 2 % of the dredged spoil particles are finer than 0.075mm. The moisture content and plasticity indices of the natural soils are 37 to 57 % and 21 to 33 % respectively. They are A-7-6 to A-6-7 soils which indicate poor quality as subgrade materials. Tests on the dredged sand revealed the following range of geotechnical properties: coefficient of uniformity, 2.21 - 2.89; coefficient of gradation, 1.11 - 1.28; maximum dry density, 1.79-1.84 g/cm3; optimum moisture content, 14-15 %; and CBR of 17-20 %. To improve the engineering properties and hence suitability in pavement construction of the spoils, 4 to 7 % addition of cement for stabilization resulted in significant strength increase, with optimum results obtained on addition of 6 % cement. The natural soils constitute very poor pavement construction materials based on their index properties. They may be excavated and replaced with the dredge spoils which must be stabilized before use.Keywords: Stabilization, dredge spoil, pavement, Niger Delta, cemen

Challenges and opportunities in the design and construction of a GIS-based emission inventory infrastructure for the Niger Delta region of Nigeria

© 2017, Springer-Verlag Berlin Heidelberg. Environmental monitoring in middle- and low-income countries is hampered by many factors which include enactment and enforcement of legislations; deficiencies in environmental data reporting and documentation; inconsistent, incomplete and unverifiable data; a lack of access to data; and technical expertise. This paper describes the processes undertaken and the major challenges encountered in the construction of the first Niger Delta Emission Inventory (NDEI) for criteria air pollutants and CO2 released from the anthropogenic activities in the region. This study focused on using publicly available government and research data. The NDEI has been designed to provide a Geographic Information System-based component of an air quality and carbon management framework. The NDEI infrastructure was designed and constructed at 1-, 10- and 20-km grid resolutions for point, line and area sources using industry standard processes and emission factors derived from activities similar to those in the Niger Delta. Due to inadequate, incomplete, potentially inaccurate and unavailable data, the infrastructure was populated with data based on a series of best possible assumptions for key emission sources. This produces outputs with variable levels of certainty, which also highlights the critical challenges in the estimation of emissions from a developing country. However, the infrastructure is functional and has the ability to produce spatially resolved emission estimates

Engineering-geological properties of subsoil of Yenegoa in Niger Delta, Nigeria

The major aim of this research work is to determine the stratigraphy and engineering geological properties of foundation subsoils of Yenagoa, the fast growing capital city of Bayelsa state in the Niger Delta, which can be used as reference database for future infrastructure and environmental development of the area. A total of six (6) boreholes were drilled to depths of about 20m and soil samples were subjected to several geotechnical tests (including natural moisture content, particle size distribution, plasticity, bulk density, specific gravity, organic content, shear box test, consolidation, etc). The study revealed that the subsoil profile from 0 - 20m, essentially consists of an organic clayeysilt top layer, a middle sand stratum and a gravelly-sand at the bottom. There are great variations in the values of the geotechnical index properties of the soils hence the geotechnical data of one location cannot be used as a basis for design of foundation in other locations. The top organic silty clay horizon can only be considered as foundation substratum for very small/light civil engineering structures whilst the sand and gravelly- sand horizons constitute the best foundation substratum for medium and large civil engineering structures

Statistical analyses of variability in properties of soils in gully erosion areas of Agulu-Nanka-Oko, Southeastern Nigeria.

The study involved the statistical analyses of variability of soil with depth and its influence on gully development. The soil data were obtained from field study and laboratory analyses. The statistical analyses of soil data were performed on soil index properties using Statistical Package for Social Sciences. Results of the analysis of variance and Duncan Multiple Range Test (DMRT) indicate that there are significant differences (