Investigation of Variation in Resistivity with Depth and Soil Dielectric Constant in Parts of Rivers State, Southern Nigeria

Abstract

The behaviour of the subsurface soil upon application of a low potential field has been investigated utilizing Schlumberger configuration of Electrical resistivity survey. The characteristics of three different soil types which include sandy clay, sand-clayey loam and loamy sand were also investigated through laboratory analysis. The aim was to determine the variation in the subsurface electrical properties such as resistivity and dielectric polarization with the soil texture and structure, density, soil moisture, and mineralogy. The results show variation in electrical resistivity for the different soil types at different depth range points as 1.33 Ω-m to 9.77 Ω-m for sandy clay, 2.09 Ω-m to 23.06 Ω-m for sandy clay loamy and 3.26 Ω-m to 128.0 Ω-m for loamy sand while apparent resistivity increases from 125 Ω-m for sandy clay to 1.448 x 103 Ω-m for loamy sand. The interpreted VES results indicate a variation of resistivity with depth and lithologic units. There is a general increase in both the electrical resistivity and dielectric constant with depth for loamy sand, sand clay loamy and sandy clay as the grain size of the soil mineral decrease with decreasing moisture content and pore space distribution with depth. However, the magnitude of variation of the dielectric constant with compaction are in the order Sandy Clays > Sandy Clay Loamy > Loamy sand. Soils with higher dielectric constants such as Sandy Clay should be more suitable for agricultural farming in tropical areas especially during dry season. The laboratory and field survey studies of rock electrical properties show that both the dielectric constant and soil resistivity increases with depth and density.