Earth Sciences Pakistan (ESP)

The purpose of this study was to investigate the geotechnical properties of the brackish shoreline of Abonnema, Niger Delta, Nigeria using both in-situ and laboratory means. The study aimed to provide essential information for development planning and design of structures in the area. The study utilized borehole drilling, particle size analysis, oedometer tests, and triaxial tests. Five boreholes were drilled, and four lithostratigraphic layers were identified, with silty peaty clay at the top and medium-coarse sand at the bottom. The analysis was carried out using approved methods, and the in-situ results were compared with laboratory geotechnical properties. The study found that the clay had a very high proportion of fines, with atterberg limits ranging from 21.0 to 22.9% for the plasticity index and corresponding liquidity index values of 0.49 to 0.63, respectively. The clay had an average moisture content of above 35%, which is expected to vary with the season. The coefficient of permeability (k) averaged at 1.39 x 10-4, while the coefficient of the volume of compressibility (Mv) and coefficient of consolidation (Cv) ranged from 1.65 x 10-4 to 1.98 x 104m2/MN for Mv and 1.84 to 2.48m2/yr for Cv. The strength parameters showed cohesive clay with values from 21kPa to 24kPa with an average frictional angle of 4o. The bearing capacity values increased from 75.154kPa at the top clay layer to 207.733 kPa at the bottom medium-coarse sand. The settlement values averaged 157mm for Immediate settlement and 815mm for consolidated settlement. The study provides crucial information about the geotechnical properties of the brackish shoreline of Abonnema, Niger Delta, Nigeria. The results suggest that the area has a high percentage of fine particles, and the clay is cohesive with low shear strength. The bearing capacity values increased towards the bottom medium-coarse sand, and the settlement values were significant. These findings are vital for development planning and the design of suitable structures in the area.