Geoelectrical study of corrosivity and competence of soils within Uburu and Okposi areas of Ebonyi State, Southeastern Nigeria

Abstract

Purpose

The corrosivity and competence of soils within Uburu and Okposi areas of the Southern Benue Trough, Nigeria, were evaluated using the electrical resistivity method. This paper aims to provide information that will aid pre-design of subsurface iron/steel pipe networks for distribution of pipe-borne water and construction of subsurface structures for agricultural and environmental purposes.

Design/methodology/approach

In total, 22 vertical electrical soundings (VES) in the Schlumberger configuration were acquired with Allied Ohmega™ Terrameter with a maximum half current (AB/2) electrode spacing of 200 m. Layer parameters were determined using partial curve matching techniques, using the Schlumberger master curves, while processing and modelling were done with the IPI2win™ software. The VES results were interpreted qualitatively and quantitatively to obtain various curve types and layer parameters, respectively, which were used to categorize the area into different competence and corrosivity zones. The first layer isoresistivity and competence maps were used to delineate four zones (A,B,C and D) with varying apparent resistivities and competences.

Findings

Incompetent soils with resistivity values ranging from 24.3-88.7 Om are found in Zone A. The soils in Zone A are mainly expansive clays which swell on absorption of water. Zone B contains moderately competent soils with resistivity values ranging from 273-308.6 Om, while Zones C and D are underlain by sandstones and contain competent to highly competent soils with resistivity values ranging from 511-750 Om and 835-1,525 Om, respectively. Zone E contains highly corrosive (24.3 Om) to mildly corrosive (102 Om) soils; Zone F contains soils that are essentially non-corrosive with resistivity values ranging from 271-1,525 Om, while the corrosivity of soils within Zone G varies from corrosive to mildly corrosive, with resistivity values ranging from 44.3-114 Om.

Research limitations/implications

Some of the areas are not accessible because of community restrictions.

Practical implications

These findings are essentially very significant and should be taken into consideration when materials that are susceptible to corrosion are being considered for engineering, agricultural and environmental purposes in the area.

Social implications

The findings will aid water resource planners and developers on how to protect metal pipes from corrosion, when used for water reticulation and agricultural purposes.

Originality/value

This paper fulfils an identified need to study the corrosivity of soils in the study area with a view to providing adequate protection to metal objects when being considered for water reticulation for domestic and agricultural purposes in the area.

Citation

Ekwe, A.C., Opara, A.I. and Onwuka, O.S. (2018), "Geoelectrical study of corrosivity and competence of soils within Uburu and Okposi areas of Ebonyi State, Southeastern Nigeria", Anti-Corrosion Methods and Materials, Vol. 65 No. 6, pp. 637-645. https://doi.org/10.1108/ACMM-05-2018-1936