Integrated Analysis of Geophysical Data for Road Networks Sub Base Lithology Integrity Assessment Case Study in Crystalline Basement Complex, Southwestern Nigeria

Abstract

Magnetics and Electrical resistivity methods were used in the evaluation of the subsurface integrity of a 2500 m segment of Ipinsa road off the Ilesha-Akure expressway adjacent to the Federal University of Technology, Akure, Ondo State, Nigeria in order to provide guidelines for the authority whenever the road is to be constructed. The road was investigated using geophysical prospecting methods involving Magnetics profiling and Vertical Electrical Sounding (VES) technique. The magnetic data were analysed first by taking care of diurnal variation and the results were presented as relative magnetic. The VES results were presented as geoelectric sections. The results from the two methods were stacked for easy correlation. The results from the Magnetics method study shows the presence of near-surface linear geologic structures and of varying length, depth, and altitude at different distances (350, 550, 650, 840, 870, 900, 1080 and 1160 m) and depths (5, 12, 13, 15, 15.5, 16, 17 and 19 m) respectively, which suggest the probable fracture zones that are inimical to the foundation of the road subgrade. The vertical electrical sounding survey were conducted at points of anomaly and non-anomalous zones based on the magnetic survey results. This is done to further delineate the fracture zones and correlate the results to get enough information of the subsurface. The corresponding geoelectric results delineated weathered/fractured bedrock with resistivity range of 222 - 412 Ωm at distances 650, 800 - 900 and 1080 - 1160 m along Traverses A and B. Likewise at distances 1380 - 1600 m, 2040 m, 2240 m, 2260 m and 2540 m along traverses’ C and D. The integrity assessment of the Ipinsa road network sub base lithology was successfully assessed using the geophysical modeled results and possible fractured bedrock and saturated/clayey sub soil material zones that are inimical to road stability were delineated. The research findings are valuable for precise decision in road infrastructural design.

Subsurface Geotechnical Competence Evaluation Using Geoelectric Sounding and Direct Cone Penetrometer Test at Plural Garden Estate, Ilaramokin Southwestern Nigeria

“…Presence of expansive clay minerals (such as illite, chlorite, montmorillonite, halloysite among others) in the subsoil materials can results in differential settlement in the subsoil materials leading to foundation failure (Egwuonwu et al, 2011;Das & Roy, 2014;Okoro et al, 2014). Other geologic conditions capable of precipitating foundation problems are shallow depth to bedrock, poor soil strength and shallow static water level (Ugwu & Ezema, 2013;Adeyemo et al, 2020).…”

Application of TOPSIS and AHP models in subsurface layers’ competence evaluation - case study of Ilaramokin, Southwestern Nigeria

“…All structures erected on the earth have their own substructures (foundation). Foundation design depends on the characteristics of both the subsurface geologic structures (voids, joints, fractures and faults) and the subsurface soil or rock Abiola, 2011, Oluwakuuse et al, 2019;Oluwakuuse et al, 2020 andAdeyemo et al, 2020).…”

“…TOPSIS being a data-driven approach is widely adopted in the field of engineering site investigation as well. In attempt to evaluate geotechnical competence at different geologic setting in the world, several works have been done by integrating geophysical and other relevant parameters using one MCDA technique (Adiat et al, 2017;Olayanju et al, 2017;Adeyemo et al, 2020). In this study, foundation competence was evaluated using parameters obtained from geophysical and geological sources.…”

“…Poor building design, substandard materials, faulty design of foundation are all scientific factors believed to be responsible for many of the collapse buildings in the south west Nigeria (Osaghale et al, 2015). Apart from the aforementioned factors, it is believed that there are other factors such as geologic structures (fault, joint and void), degree of weathering, static water level, soil strength among others can also be responsible for the failure of engineering structures and building collapse (Adeyemo et al, 2020). All structures erected on the earth have their own substructures (foundation).…”

“…None destructive technique such as geophysical method which gives the response of the soil particles through some physical parameters that are related to subsoil competency are often considered. Cost effective geophysical method has been found suitable for engineering site investigation (Olorunfemi et al, 2002;Adeusi, 2009 andAdeyemo et al, 2020). Electrical resistivity technique which measure the resistivity or conductivity contrast has proven to be a major tool in engineering studies (Adepelumi and Olorunfemi 2000;Soupious et al, 2007;Akintorinwa and Abiola 2011;Adeyemo and Omosuyi, 2012;Salami et al, 2012;Fatoba et al, 2013 andSiddiqui andOsman 2013).…”