Abstract
A geophysical survey involving the electrical resistivity method utilizing the Vertical Electrical Sounding (VES) and Electrical Imaging Techniques was conducted around the premises of an area within south-western Nigeria with the aim of studying structural defects which may be responsible for future problems and characterizing the soil conditions of the site. A total of 15 VES stations were occupied using Schlumberger Configuration with AB/2 varying from 1 to 65 m. In the electrical imaging, dipole-dipole array was adopted and the two traverses were occupied in the S-N and E-W directions close to where wall cracks and subsurface problems were manifested. Five main geoelectric sequences were delineated within the study area; these include the topsoil (clay and sandy clay), lateritic clay, weathered bedrock (clay, sandy clay and clayey sand), fractured bedrock and fresh basement. A major discontinuity (fracture zone) was discovered along the S-N direction, while a weak zone was also discovered along E-W direction. The result of this research has shown that the causes of the cracks and distress on the walls within the site may have been influenced by the differential settlement resulting from the incompetent subsoil materials and the fractured bedrock on which the foundation of the building was laid.
Highlights
With the growing demand for site development and unpleasant experience of building failure, there is increasing number of necessary site investigations to reveal possible subsurface problems
It was observed that a nearby stream that flows beneath a local bridge gradually seeps through the sandy clay compartments on the western flank towards the eastern flank to the weak zone observed between stations 6 and 11
A major discontinuity was identified by the electrical imaging on bedrock along the S-N direction. This would have been the reason for differential settlement, since it was confirmed that the foundation of the structure was placed on this weak bedrock
Summary
With the growing demand for site development and unpleasant experience of building failure, there is increasing number of necessary site investigations to reveal possible subsurface problems. Geophysical investigations are important in evaluating the physical properties of the subsurface in terms of its soil type, soil competence, soil corrosivity, depth to bedrock and lithologic sequence. For reasons of cost and other considerations such as assumptions in structural design, sometimes fail to incorporate pre-construction investigations in their job schedule. A geophysical investigation is necessary for the site to reveal possible future subsurface problems and proffer possible solutions before the erection of buildings
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
