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Mamu basin is a major tributary of Anambra drainage basin and a reservoir for wastewater from agricultural and runoff processes within the basin. Water quality of the Mamu basin was evaluated to determine its suitability for potable water and agrarian uses. This study utilized 24 water samples collected during the rainy and dry season from the upstream and downstream segments of the sub basins within River Mamu. Hdyro-geochemical analytical results were employed in the evaluation of several water quality criteria such as QWI, SAR, TH, SSP, MAR, PI, KR, Na% and %E of the water from the basin. The results suggested that the surface water is unfit for ingestion when compared with the WHO and Standard Organization of Nigeria (SON) standards. However, the QWI result showed that 66.7% of the water samples are good for consumption in the rainy season, while 75% of the samples are classified unfit for drinking in the dry season. Parameters such as Fe2+, Mn2+, TDS, temperature and total coliform (p < 0.001) exhibited temporal variation unlike pH, EC, Ce, Ca2+, Mg2+, Cl−, K + , NO3, PO43−, Na+, HCO3−, Zn2+, TSS, SO4, DO, BOD and turbidity which showed no response to season. Based on the results of SAR, TH, SSP, PI, KR, Na% and US salinity plots, the surface water is suitable for irrigation. Conversely, the MAR and %E results pointed out that water treatment is vital before use. The basin water is associated with permanent hardness due to CaCl2 coupled with the dominance of Mg2+ and SO42−. Gibbs plots and Stiff diagram showed that geology and dissolution process have an influence on the water chemistry via weathering and rock–mineral interactions, while chemical ratios and correlation coefficients (R2) point on anthropogenic activities.

This paper investigated the geotechnical properties of smectite-rich shale, and its implications as foundation material. Ten expansive shale samples were collected from foundation materials at Akpugo in Nkanu West L.G.A. of Enugu State, southeast Nigeria. Samples were subjected to grading, Atterberg limitscum-compaction tests, slake durability, specific gravity, permeability, undrained triaxial tests and x-ray diffraction scan. Fines and sand contents of the soil samples range from 51-97% and 3-49% respectively. Liquid limit, plastic limit and plasticity index have average values of 60.7, 19.1 and 43.3% respectively. Linear shrinkage and free swell showed average of 16.3% and 76%. These results are indicative of predominant clay soil with high plasticity, compressibility and water holding capacity. XRD scan established presence of smectite and illite clay minerals, confirming soil high plasticity, capable of causing instability in foundation soil. The shale achieved maximum dry density range between 1.79 and 1.94 kg/m 3 at optimum moisture content range of 6.9-12.8%, indicating poor to fair foundation materials. The shale cohesion ranges from 15 to 30 kPa while the angle of friction ranges between 10 • and 18 • , signifying an average strength soil material. Samples slake durability index and specific gravity fall within 24-55% and 2.50-2.58 respectively, suggesting non-durable and weak soil. Permeability of the samples ranges between 7.36×10 −6 and 4.77×10 −8 cm/s which suggested low drainage capable of causing water-log at sites. Therefore, the shale could be generally classified as poor to fair foundation material, which on moisture influx experience reduction in strength due to deterioration of its constituent minerals, especially clay and cement materials during the lifespan of engineering structures. Authors therefore recommend modification of foundation soil, appropriate foundation design and good drainage control as ways of improving stability of engineering structures underlain by expansive shale.

Over the years, the people of Akpugo community in Nkanu West L.G.A., Enugu State, South-East Nigeria have suffered from frequent building collapse without knowing the cause. This study integrates geotechnical and geophysical techniques to evaluate possible factors responsible for this anomaly. Areas with cracked and non-cracked buildings were studied to assess the geotechnical properties of the soils. Samples were taken at different locations and subjected to x-ray diffraction analysis, grain size analysis, specific gravity, Atterberg limits, permeability, compaction, and triaxial tests. Electrical resistivity method was also used to delineate the geo-electrical layers and to image the lateral variations of the subsurface. Results revealed that problematic zone (areas with cracked buildings) has lower permeability (4.018-7.016× 10 −7 m/s), lower angle of shearing resistance (10-14°), and medium to high plasticity index (25.1-38.33), while the nonproblematic zone (areas without cracked buildings) has higher permeability (1.55-1.925×10 −6 m/s), higher angle of shearing resistance (15-18°), and low plasticity index (18.1-19.4). The x-ray diffraction results of the problematic zone revealed a significant amount of smectite which has a very high swelling and shrinkage potential. The presence of substantial quantity of smectite in the soils of the problematic zone may be a strong factor in the structural problems. The electrical resistivity profiling delineated the boundary between the problematic zone and non-problematic zone and showed that the problematic zone has lower resistivity values (2-25Ωm) while the nonproblematic zone has higher resistivity values (20-170Ωm).

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