Georesistivity modelling and appraisal of soil water retention capacity in Akwa Ibom State University main campus and its environs, Southern Nigeria

Abstract

Soil water retention capacity is one vital hydraulic property that affects the productivity of soils and the environment. Soils with high water retention capacity can result in waterlogging, which is detrimental to engineering foundations or civil engineering structures. In this study, the surface resistivity method was used to investigate the cause of waterlogging, which is often observed in Akwa Ibom State University main campus and its environs. Ten vertical electrical soundings (VES) were carried out using the Schlumberger electrode configuration with a maximum current spacing AB/2 of 200 m. The one-dimensional (1-D) interpreted resistivity model curves revealed that the study area is made up of three to four geoelectric layers: motley topsoil, followed by sandy clay, fine sands and coarse sands. The soil water retention capacity was assessed through estimates of the resistivity anisotropy coefficient, resistivity reflection coefficient and longitudinal conductance for the first two layers. The estimated resistivity anisotropy coefficient varies from 1.00 to 1.78, resistivity reflection coefficient varies from − 0.89 to 0.61 and longitudinal conductance varies from 0.01 to 0.91 Ω−1. The resistivity anisotropy observed in some parts of the study area is attributed to alternating sequence of sand and clay, which is the major cause of waterlogging in these parts, especially during the rainy season. The anisotropy results show excellent correlation with the resistivity reflection coefficient and longitudinal conductance results and thus, demonstrate the potential of using georesistivity anisotropy for soil water retention capacity appraisal for a variety of geotechnical applications.