<abstract xmlns="http://www.w3.org/1999/xhtml"><p>Very low frequency (VLF) was used to assess variations in overburden composition, bedrock lithology and the concealed basement structures within the bedrock of Owena Dam in Igbara-Oke of the Precambrian Basement Complex of Southwestern Nigeria. Five VLF-electromagnetic (EM) traverses were occupied at 5 m intervals. The VLF normal and filtered real component anomalies identify major geological interfaces suspected to be faults/fractured zones. The points of crossover between the real and imaginary components delineate the fractured zones, which were identified as areas of possible seepage (piping and sloughing). The internal erosion (permeability) of soil mass eventually leads to the formation of an open conduit in the soil, which may lead to failure of the embankment/dam. The fractured zones are suspected to be present at all traverses. In total, 21 fractured zones were identified along the dam embankment, with the deepest occurrence at Traverse 5. These seepage zones cause heterogeneity in the subsurface composition, which could lead to dam failure. The result of the study suggests that VLF is an adequate method of monitoring seepages in embankment dams.</p></abstract>

Very low frequency (VLF) was used to assess variations in overburden composition, bedrock lithology and the concealed basement structures within the bedrock of Owena Dam in Igbara-Oke of the Precambrian Basement Complex of Southwestern Nigeria. Five VLF-electromagnetic (EM) traverses were occupied at 5 m intervals. The VLF normal and filtered real component anomalies identify major geological interfaces suspected to be faults/fractured zones. The points of crossover between the real and imaginary components delineate the fractured zones, which were identified as areas of possible seepage (piping and sloughing). The internal erosion (permeability) of soil mass eventually leads to the formation of an open conduit in the soil, which may lead to failure of the embankment/dam. The fractured zones are suspected to be present at all traverses. In total, 21 fractured zones were identified along the dam embankment, with the deepest occurrence at Traverse 5. These seepage zones cause heterogeneity in the subsurface composition, which could lead to dam failure. The result of the study suggests that VLF is an adequate method of monitoring seepages in embankment dams.

Electromagnetic profiling of Owena Dam, Southwestern Nigeria, using very-low-frequency radio fields

Department of Earth Sciences, Adekunle Ajasin University, Akungba-Akoko, Ondo State,

Materials and Geoenvironment

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Very low frequency (VLF) was used to assess variations in overburden composition, bedrock lithology and the concealed basement structures within the bedrock of...

Electromagnetic profiling of Owena Dam, Southwestern Nigeria, using very-low-frequency radio fields

Published Online: Feb 18, 2017

Page range: 237 - 250

Received: Aug 28, 2015

Accepted: Sep 14, 2016

DOI: https://doi.org/10.1515/rmzmag-2016-0021

Keywords
very low frequency (VLF), dam, Igbara-Oke, fault/fractured, embankment

© 2016 Cyril Okpoli et al., published by De Gruyter Open

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Electromagnetic profiling of Owena Dam, Southwestern Nigeria, using very-low-frequency radio fields

Published Online: Feb 18, 2017

Page range: 237 - 250

Received: Aug 28, 2015

Accepted: Sep 14, 2016

DOI: https://doi.org/10.1515/rmzmag-2016-0021

Keywordsvery low frequency (VLF), dam, Igbara-Oke, fault/fractured, embankment

© 2016 Cyril Okpoli et al., published by De Gruyter Open

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Keywords
very low frequency (VLF), dam, Igbara-Oke, fault/fractured, embankment