Evaluation of highway failure of a portion of ibadan-iwo road, southwestern nigeria, using very low frequency electromagnetic and resistivity methods
Electronic Journal of Geotechnical Engineering
Department of Physics, University of Ibadan, Nigeria
About 1600 m portion of the Ibadan - Iwo road (southwestern Nigeria) which has suffered structural failures repeatedly was investigated using Very Low Frequency Electromagnetic (VLF-EM) profiling at 10 m intervals and five Schlumberger Vertical Electrical Sounding (VES). The results from the VLF-EM investigation showed the presence of near surface linear geologic structures of varying lengths, depths, and elevations which suggest probable conductive zones that are inimical to the foundation of the road subgrade. Also, the lateral resistivity profile showed low resistivity zones that coincided with most of the peak positive VLF-EM anomalies, indicating near surface clay materials and linear structures. The quantitative interpretation of the VES results established the presence of four geologic layers namely top soil, weathered layer, partly weathered layer and fractured basement with varying resistivity values and thicknesses. The unstable segment of the road was characterized by low resistivity of the near surface materials on which the road pavement was founded. The clayey subgrade soil below the highway pavement and identified geologic features are the major factors responsible for the highway failure. © 2012 ejge.
Fractured basement; Geologic features; Geologic layers; Geologic structures; Highway pavement; Ibadan-iwo road; Linear structures; Low resistivity; Major factors; Near-surface; Near-surface clay; Near-surface materials; Nigeria; Quantitative interpretation; Resistivity profile; Resistivity values; Road pavements; Schlumberger; Structural failure; Subgrade soil; Top soils; Vertical electrical sounding; Very low frequency; Vlf-em investigation; Electric prospecting; Electromagnetism; Fracture mechanics; Pavements; Surfaces; Transportation; electrical resistivity; electromagnetic method; failure analysis; motorway; pavement; subgrade; vertical electrical sounding; Ibadan; Iwo; Nigeria; Osun; Oyo