Assessment of some geotechnical properties of Nigerian coastal soil: A case-study of Port-Harcourt beach mud

Soils naturally exhibit variable engineering properties and thus make the geotechnical characterization of soil for sustainable design and construction of infrastructure imperative. This study was undertaken to investigate the geotechnical properties of the underlying soils of the Port-Harcourt Beach Mud, Rivers State, Nigeria. Five boreholes namely BH1, BH2, BH3, BH4 and BH5 were drilled using hand auger at different depths of 300mm, 350mm, 400mm, 450mm and 500mm respectively. Basic geotechnical tests were then performed on the samples in the laboratory to determine their properties. Results obtained showed that the area is underlain predominantly by poorly graded sands based on the Unified Soil Classification System (USCS). The soil material had an average Moisture Content of 71%, Liquid Limit of 13%, Plastic Limit of 11%, Plasticity index (PI) of 2% and Hydraulic Conductivity (K)of 2.88 x 10-1 cm/s. The high values of K show that the aquifer system in the area is prolific. The soil material however met the requirements of the Nigerian General Specifications for use as subgrade in the construction of roads.Keywords: geotechnical properties, hydraulic conductivity, California Bearing Rati