Probing Soil Corrosivty Potential Using Barnes Geo-Electric Method in Shagamu, Southwestern Nigeria

ABSTRACT Corrosion of pipeline and other underground infrastructures are notable soil structure interaction process that have resulted in material and underground structural failures posing serious threat to the integrity of structures and safe movement of petroleum products. This paper presents the results of soil corrosivity evaluation using the Electrical Resistivity Test (Barnes Layer Analysis) and conventional Vertical Electrical Sounding (VES) deploying Wenner and Schlumberger array systems respectively along buried pipelines routes in Shagamu, Southwestern, Nigeria. The investigation was carried out along six traverses in twenty different locations in N–S and E–W directions using resistivity meter. The resistivity distribution style at the probed depths pinpointed three distinct groups. Group 1, 2 and 3 have resistivity values which ranges between 50 – 100 ohm-m, 100 – 200 ohm-m and above 200 ohm-m respectively. The VES results however reveals three to five geo-electric layers which varies from topsoil, clay, clayey sand, sandy clayey sand and lateritic clayey sand. Interpretation of the ERT results and the generated iso-resistivity maps denote that the resistivity values of soils at depth range of 2.25 – 4.5m are lower compared to the resistivity at depth range of 0.75 – 1.5m which make depth range 2.25-4.5m a more corrosive environment. The iso-resistivity maps also reveal the order of resistivity signatures as [email protected]<[email protected]<[email protected]<[email protected]. Further analysis of the results shows that about 12.5% of the ERT points conducted reveals high corrosive probability, 35.5% indicates low corrosive probability and 51.0% reveals negligible corrosive probability across the study area in both N–S and E–W directions. Comparing the resistivity distribution styles along the various traverses indicate that the degree of vulnerability to corrosion can be arranged as traverse 3>traverse 4>traverse 5>traverse 6, thereby pinpointing focus areas for possible treatments and rehabilitation. The capability of the Barnes analysis approach to delineate probable corrosion stretch along buried pipeline route demonstrate its effectiveness as a non-invasive corrosion evaluation tool. KEYWORDS: Soil Corrossivity, Barnes Analysis, Electrical Method, Shagamu, Nigeria, Tomography, Iso-Resistivity