Geoelectrical and Geotechnical Investigations of Subsurface Corrosivity in Ondo State Industrial Layout, Akure, Southwestern Nigeria

  • Igbagbo Adedotun Adeyemo Federal University of Technology, Akure, Nigeria
  • Olumide Abiola Olumilola Federal University of Technology, Akure, Nigeria
  • Michael Adewale Ibitomi Kogi State Polytechnic, Lokoja, Kogi State, Nigeria
Keywords: Geotechnical, liquid limit (LL), plastic limit (PL), plasticity index (PI), clay plasticity, vertical electrical sounding (VES), natural moisture content (NMC) and CR-index corrosivity model map.

Abstract

Abstract

Fifty two vertical electrical sounding (VES) data and six subsurface soil samples were collected at Ondo State Industrial Layout, Akure, Southwestern Nigeria in order to determine the subsurface corrosivity. The VES results delineated 3 to 5 geoelectric layers across the area which corresponds to topsoil, weathered layer, weathered basement, weathered/fractured basement and the presumed fresh bedrock. The layer resistivity values range from 22 to 602 ohm-m, 7 to 2468 ohm-m, 17 to 436 ohm-m, 25 to 39 ohm-m and 203 to 10023 ohm-m in the topsoil, weathered layer, weathered basement, weathered/fractured basement and the presumed fresh bedrock respectively. The iso-resistivity maps at depth slices of 1 and 2 m shows that the northeastern, southeastern and the upper central part of the area are non-corrosive (above 350 ohm-m) to slightly corrosive (250 - 350 ohm-m), while the lower central, northwestern and southwestern parts of the area are moderately (150 - 250 ohm-m) to strongly corrosive (60 - 150 ohm-m).  Soil sample analysis shows liquid limit results that  vary from 37.6 to 59.7, while the plasticity limit results vary from 29.3 to 42.5 and all the plasticity index plots were below the A line indicating presence of non-plastic clay. The natural moisture content) values vary from 21.4 to 35.5 %. The 2 m depth slice isoresistivity map and clay plasticity factor were synthesized using additive model to generate subsurface CR-index corrosivity model map which indicates that the northwestern, northeastern and southern parts of the area are moderately (0.4 - 0.6) to strongly corrosive (0.6 - 0.8), while the upper central area and the flanks are slightly corrosive. The moderately and strongly corrosive zones correspond to the low elevation and water logged zones of the study area. The corrosivity model map was validated by the pH and corrosivity data.

Author Biographies

Igbagbo Adedotun Adeyemo, Federal University of Technology, Akure, Nigeria

Department of Applied Geophysics, Federal University of Technology, Akure, PMB 704 Akure, Nigeria

Lecturer I

Olumide Abiola Olumilola, Federal University of Technology, Akure, Nigeria

Department of Applied Geophysics, Federal University of Technology, Akure, PMB 704 Akure, Nigeria

Postgraduate Student

Michael Adewale Ibitomi, Kogi State Polytechnic, Lokoja, Kogi State, Nigeria
Department of Mineral and Petroleum Resources Engineering, Kogi State Polytechnic, Lokoja, Kogi State, Nigeria

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Published
2018-06-28
Section
Geological Eng. Article