Abstract:
Geoelectric soundings are combined with static Cone Penetration Tests (CPT) in this study for the
purpose of evolving a comprehensive site evaluation methodology for foundation designs. Five
locations were selected for study within Ondo state. Cumulatively, forty-five (45) Schlumberger
Vertical Electrical Sounding (VES) and sixty-four (64) CPT points were occupied. The geoelectric
sounding curve types obtained from these locations are A, AA, H, KH, K and Q. The apparent
resistivity values obtained vary between 66 and 4044 Ω-m. The cone penetration resistance values
obtained vary between 2 and 170 kg/cm2. The cone penetrometer resistances were plotted against
depth and blocked into litho-units. The quantitative interpretation of the sounding curves and CPT
values showed that the area is generally underlain by subsurface lithological sequence consisting
of the topsoil, weathered bedrock and the resistive basement. Empirical equations were generated
for each location by plotting the results of cone tip resistance against the formation resistivity using
logarithm-linear graphs. The empirical equations were used to generate CPT values from
resistivity measurements at each VES station. The resistivity derived CPT values obtained from
the logarithm-linear regression for each locality is compared with the field CPT values and
correlation values ranging from 0.283 at Ifon to 0.643 at Oka-Akoko were obtained. Thus the
combined results of integrated geophysical and geotechnical site studies have enhanced the
understanding of predictable performance of soils and rocks when subjected to structural loadings
