3D Electrical Resistivity Imaging (ERI) for subsurface evaluation in pre-engineering construction site investigation

Abstract

Three Dimensional (3D) Electrical Resistivity Imaging (ERI) was carried out for pre-construction foundation investigation of a proposed engineering construction site within the University of Ibadan Campus, southwestern Nigeria, where some distressed structures (offices and hostels) have been reported to show stress induced cracks attributed to incompetent foundation support from rocks upon which they were constructed. The 3D grid of resistivity data generated along parallel and equally spaced profiles stations presented the resistivity distribution of the subsurface as well as delineated zones of relatively high resistivity values (450-4500 Ω m) in the east and lower resistivity zones (15-300 Ω m) in the west. The study also delineates zones of isolated low resistivity values (10-50 Ω m) at the mid and west end of the field. The generated resistivity distribution sections, maps and 3D model indicate spatial variation in resistivity value which varies both laterally and vertically. The variation which is attributed to differences imposed by underlying rock's structural and geological rock composition resulted from complex rock coexistence as schist (quartz-and amphibolitic-schist) and quartzite coexist as underlying rocks of the proposed construction site, especially since these rocks respond to weathering differently. The generated subsurface resistivity model guided selection of geotechnical investigation points which captures spatial variation in subsurface physical properties as recorded by the measured subsurface resistivity. Better guided geotechnical investigation provided needed information required to design appropriate foundation support for the proposed engineering structure.

Effectiveness of 2D Induced Polarisation & Electrical Resistivity Tomography in Mapping Fracture Heterogeneity in Foundation Soils.

“…Although Sitharam (2013) listed the presumed allowable bearing pressure for cohesionless soilscoarse grained sandstone (440 kPa) and medium grained sandstone (240 kPa) which are favourable, the presence of fractures in foundation soils can cause great harm to engineering structures placed directly on them. (Terzaghi et al, 1996;Osinowo and Falufosi, 2018). Figure 1 gives an overview of the geology in the study area.…”

“…In other words, the success of any engineering structure directly placed on the earth's surface would depend on the support provided by the foundation materials that bear the load of the structure alongside other factors. (Terzaghi et al, 1996;Osinowo and Falufosi, 2018). Apart from geo-structural factors, other factors that can threaten the stability of engineering structures include poor building design, poor materials, and inexperienced personnel (Adewuyi and Philips, 2018), with a number of such failures recorded (Ayedun et al, 2012;Oyedele and Olorode, 2011;Soupois et al, 2007).A case of a failing foundation of a massive auditorium nearing completion at the University of Nigeria Nsukka is being investigated.Fractures or cavities within the earth materials bearing the structure have been proposed as likely contributors to this failure.…”

“…The use of Electrical Resistivity Tomography is a well-known technique for detecting subsurface inhomogeneity associated with fractures. (Chieh-Hou et al, 2000;Samouelian et al, 2005;Nguyen et al, 2005;Han-lun et al, 2010;Reynolds, 2011;Ugwu and Ezema, 2013;Oyeyemi, 2016;Coker, 2017;Osinowo and Falufosi, 2018). Also, Time domain Induced Polarisation is another technique capable of detecting cavities and fractures, though it is yet to be deployed for this purpose in this region.…”

Granite Exploration by using Electrical Resistivity Imaging (ERI): A Case Study in Johor

“…As discussed by [6] and [7]- [9], Geophysical investigation offers a faster, cheaper and has the ability to cover greater areas more thoroughly as stated by [10]; [11] by getting credible and detailed information about the subsurface [12]. Various researchers from all over the world especially in geophysics and geotechnical field have exposed that the integration of geotechnical data and geophysical survey can provide a useful data and interpretation for sub-surface profile characterization [13]- [16].…”

Integrated Geophysical and Geotechnical Methods for Pre-Foundation Investigations

“…The electrical resistivity of material can be reduced by subsoil porosity and moisture contents. Therefore, the need to understand the use of electrical resistivity as indices to define subsoil competence and their engineering characterises [9,[22][23][24].…”