Pages: (46-59 )
Abstract
Geoelectrical surveys were conducted at a site across river Shasha, Edunabon, Southwestern Nigeria in order to determine its suitability for an earth dam. The investigation employed Schlumberger vertical electrical sounding (VES) and dipole-dipole horizontal profiling to delineate the subsurface strata, determine depth to the bedrock and overburden thickness, and identify subsurface geological structures which might compromise structural integrity along the dam and its vicinity. The study area is underlain by three geoelectric layers representing the topsoil, saprolite and bedrock. The resistivity and thickness of the topsoil range from 10 Ωm to 1431 Ωm and 0.2 m to 2.7 m respectively. The saprolite is mainly clay/sandy clay with resistivity ranging from 11 Ωm to 242 Ωm and thickness varying from 0.3 m to 10.2 m. Resistivity of the bedrock ranges from 377 Ωm to 28,304 Ωm. The bedrock is shallow, at depth ranging from 1.6 m to 12.2 m. The clay-rich saprolite is suitable material for dam embankment. The suspected bedrock fractures are not extensive and may pose no threat with geotechnical remedial measures put in place, to prevent seepage and structural failure. Based on the findings above, the study area is suitable for siting an earth dam.
Keywords: Geoelectric layers, Dam embankment, Dam foundation, Bedrock fractures, Structural integrity.,