7. 2-DIMENSIONAL SUBSURFACE IMAGING OF AUCHI-IGARRA ROAD USING ELECTRICAL RESISTIVITY METHOD

Abstract

We conducted a 2D Electrical Resistivity Imaging (ERI) survey along a section of the Auchi-Igarra Road, opposite the proposed Momoh University, to investigate the cause of existing road failures. Four ERI profiles, two on each side of the road, were acquired to cover both the failed and relatively stable sections. The profiles had lengths of 60 m, 72 m, 48 m, and 36 m. The ERI results revealed anomalously low resistivity values beneath the failed road sections, suggesting the presence of highly conductive subsurface materials. Profile 1: Showed extremely low resistivity (down to 395 Ωm), indicating high conductivity. Profile 2: Resistivity values ranged from 352 to 1758 Ωm, significantly lower than the surrounding material. Profile 3: Featured a low resistivity zone between 5.81 and 31.8 Ωm. Profile 4: Resistivity varied between 15.6 and 3133 Ωm. The road failure is likely due to the presence of moisture-sensitive, highly conductive clay materials beneath the pavement. The consistently low resistivity zones across the failed areas were interpreted as evidence of conductive clay minerals in the subsurface. These materials are susceptible to freeze-thaw phenomena (swelling during the rainy season and shrinking in the dry season), which compromise the road's structural integrity. We recommend that the suspected clay mineral under the failed section be excavated and replaced with competent, engineered materials or crushed rocks geo texiles capable of withstanding the highway's vehicular load. Keywords: Auchi-Igarra Road, Imaging, Assessment, Surveying, Public Infrastructure