Abstract
As part of effort to examine the factors responsible for highway failure in the sedimentary terrain, geophysical survey involving Very Low Frequency Electromagnetic (VLF-EM), Schlumberger Vertical Electrical Sounding (VES), and dipole-dipole electrical resistivity techniques were carried out along Iruekpen-Ifon highway. This was aimed at using surface geophysics to characterize and identify the factors responsible the for road failures along Iruekpen-Ifon highway. ABEM WADI instrument was used to obtain electromagnetic-Very Low Frequency (VLF) field data, while ABEM resistivity meter was used to obtain electrical resistivity field data. The VLF-EM data were interpreted using the VLF Graphic software, VELFAN 1.0 double plot of filtered real and filtered imaginary against distance. The VES data obtained were interpreted using IP 2 Win software. Geoelectric parameters were used to generate the Dar Zarrouk second order parameters. 2-D inversion modeling of the dipole-dipole data was carried out using ZONDRES window software. VLF-EM result suggested varying degree of conductivity in the area and the wide spread of clay/metallic ore and water in the study area. Results show that the topsoil generally varies in composition from clay to clayey and laterite with resistivity values varying from 89 to 400 Ωm and thickness between 0.2 and 4.0 m. The fractured layers composed of clay and compacted clayey sand which represents the recent alluvial deposits with resistivity values of 2 to 89 Ωm and the thickness between 1.5 and 11 m. The fresh water zone is characterized by low resistivity ranging from 0.5 to 23 Ωm, which is diagnostic of saline water saturated with clay formation, fresh water ingression, and marls. The values of co-efficient of anisotropy (l) range from 1.03 to 2.19. The relatively higher values of λ (1.30 to 2.19) suggest that the subsurface rocks in these areas are likely to be more intensely fractured and more permeable. The saline water saturated with clay formation, fresh water ingression, fracture and marls clearly limit the lithological contacts and enhance high swelling potential which might be responsible for the road pavement failures in the studied area. Key words: Highway, resistivity, troubled roads, Dar Zarrouk, anisotropy.
Highlights
A road is a thoroughfare, way, or route on land between two places, which in general has been paved or otherwise, enhanced to allow travel by some transportation
This is evident in secondhand vehicles that are shipped from developed economies to Africa which are in most cases here considered as new vehicles
The geoelectric parameters were used to generate the concept of Dar Zarrouk second order (Maillet, 1974) parameters (transverse unit resistance, longitudinal conductance and resistivity ( -m) for the co-efficient of anisotropy ( ) in porous media). 2-D inversion modeling of the dipole-dipole data was carried out using ZONDRES window software
Summary
A road is a thoroughfare, way, or route on land between two places, which in general has been paved or otherwise, enhanced to allow travel by some transportation. Series of small polygons resembling an alligator’s skin (Figure 1a) This could result from the fatigue effect of repetitive heavy truck loads or ageing in combination with exponential loss of pavement thickness. A rut is a longitudinal deformation at wheel tracks mainly associated with shoving along the road (Figure 1b) This is caused by heavy loads and high tyre pressure, subgrade settlement caused by saturation, poor construction methods, or asphalt mixtures of inadequate strength. This is block cracking leading to chipping of pavement surfacing and/or upheaval outside the tyre cracks with associated cracking This could result from deficiency in cohesion and internal friction in pavement base structure due to ageing and fatigue (Figure 1e)
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