Investigation of Some Unpaved Highways in Awka Metropolis, Southeastern Nigeria Using 2D Electrical Resistivity Tomography and Geotechnical Methods
Publication Date: 12/05/2020
Author(s): Egwuonwu Gabriel N., Ebom Emmanuel C..
Volume/Issue: Volume 3 , Issue 1 (2020)
Abstract:
Shallow subsurface two-dimensional Electrical Resistivity Tomography (2DERT) and geotechnical surveys were carried out at some unpaved highways in Awka, Anambra State, Nigeria. The surveys were aimed at investigating and analyzing shallow subsurface formations along the roads on which future construction of pavement is expected. The 2DERT was carried out from five survey lines-oriented W-E, N-S and SE-NW directions respectively. Also, soil samples were collected from depths of sub-grade evaluation of maximum dry density (MDD), California bearing ratio (CBR), plastic index (PI), particle size distribution (PSD) and specific gravity of (Gs) respectively. Results of the 2DERT inverse models were characterized by apparent resistivity range of 0.200 to 5601 Ωm. Results from the geotechnical analyses showed ranges of MDD (1.94-2.09 mg/m3), CBR (48.30-51.7%), PI (14-19%), PSD (34-38%) and Gs (2.57-2.61 mg/m3) respectively. Interpretation of the results from the two methods showed that at shallow depths along the unpaved roads; sand, clayey-sand and clay are predominant. Non-homogeneity of the top soils suggests impending danger of expansive soil, non-homogenous subsurface formation, dipping and fractured layers at sub-grade depths in the area. Hence, the findings suggest the need for embankment of the unpaved roads at some portions before construction of durable highway pavements could be attained in the area.
