Geophysical Characterization of Abandoned Dumpsite Soil Properties for Pre- Foundation Delineation at Bowen University Campus, Iwo, Nigeria

Abstract

Geophysical investigation and microstudy of soil properties were carried out within Bowen University, for the characterization of the subsurface pattern in the area using vertical electrical sounding (VES) survey and evaluation of soil properties with a view to mapping subsurface geological features, such as weak and competent zones and to determine the overburden thickness of the area for pre-foundation studies for a proposed high-rise building. Four (4) VES was carried out in the study area employing schlumberger electrode configuration. The data collected were used to curve match and the results used for subsequent interpretation to reveal the depth,  thickness and resistivity of the study area. In addition, soil samples were collected from three (3) selected points located at the entrance, centre and the end of the study area at about a depth 0-60 cm. Consequently, the VES results were presented as resist graph, which revealed the range of values for the depth (1.3 – 24.5), thickness (1.3 – 15.4 m) and resistivity (357.4 - 6311.6 ohms), which was later used to generated the geoelectric maps of the study area. It was also observed that the result of the soil properties
revealed that all the samples taken from the study area have low bulk density (1.41 g/cm³, 1.26 g/cm³, 1.36 g/cm³), high particle density (2.81 g/cm³, 2.94 g/cm³, 3.16 g/cm³), and high porosity (49.64%, 57.22%, 57.03%). In conclusion, it was observed that erection of high-rise building is not advisable within the study area since the results showed that the
overburden (depth to basement) is generally thick mostly greater than 15 m. Also revealed from the microstudy of soil properties is that foundation stability should be properly managed, since a porous soil does not  accommodate engineering activities except when an artificial basement is put in place.

Keywords: Geophysical Investigation, Soil Analysis, Foundation Studies, Subsurface Competency