Geophysical Investigation of Road Pavement Failure along the Mubi Bypass Road, Jambutu, Jimeta, Yola, Adamawa State

Abstract

The electrical resistivity method, utilizing Wenner configuration, was conducted along the failed and stable portions. Five (5) soil samples along the electrical resistivity measurement points were collected for ex-situ geotechnical tests. The geophysical results show that resistivity range of the failed sections FS1, FS2, FS3 and FS4 are respectively 23.5 – 82.7 Ωm, 9.81 – 29.7 Ωm, 7.84 – 21.9 Ωm and 11.8 – 22.8 Ωm while those of the stable sections SS1, SS2, SS3 and SS4 are respectively 38.9 –138 Ωm, 28.2 – 121 Ωm, 13.7 – 20.3 Ωm and 14.5 – 21.9 Ωm. Lithologies of the stable sections (SS) 1 and ( SS) 2 were inferred as very hard clay, sandy clay, and sandstone, which are moderately competent, whereas those of stable sections (SS) 3 and 4 were inferred as dry clay, silty and sandy clay though overlying a weak/saturated zone.  Failed section sample 1 (FSS) 1 was inferred as saturated clay and sandy clay, all of which are incompetent, whereas failed section samples (FSS) 2, 3, and 4 were inferred as weak zones of saturated moist clay, silty sand, and sandy clay with exposed clay deposit. The study has therefore shown that the integrity and stability of the road pavement is under heavy threat by the incompetence of the silty clay and silty sand subbase and subgrade course material, as well as poor drainage network and flood-prone nature of the study area. This failure can be ameliorated via operational drainage system and efficient soil stabilization measures.