Integrated Geophysical and Geotechnical Investigations for Building Foundation at Kotebe Metropolitan University North East of Addis Ababa, Ethiopia
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Date
2019-04-04
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Addis Ababa University
Abstract
This study was carried out within the premises of Kotebe Metropolitan University which is located north east of Addis Ababa with the objective to assess the suitability of the foundation condition for the new building is erected within the campus. To achieve this proposed objective systematic methodology was followed includes an integrated approach where both geophysical and geotechnical investigations were carried out. For geophysical investigations Electrical Resistivity Imaging (ERI) and seismic refraction methods were employed.
The collected data were interpreted using qualitative and quantitative methods of analyzing by integrating with borehole log data available from nearby areas. The results have revealed that the subsurface geology consisted of three distinct units whose geological interpretations correspond to a topsoil, weathered rock unit and bedrock which shows distinctive physical properties i.e. (resistivity and velocity). The topsoil is composed of reddish brown, medium stiff, moderately plastic silty clay soil. The second layer is a completely decomposed, weathered and fractured weak unit. The bottom stratum mapped in the survey, considered to be the bed rock in the area is a high resistivity, high seismic velocity unit which could be the response of basaltic layer. The geoelectrical section across the study area shows smooth characteristics of the bedrock morphology. From the combination of electrical resistivity imaging and the seismic refraction survey interpretations and from borehole log data this bed rock unit extends, from 7.5 to 21.5m. There are signatures of fractures and weathering within the bedrock, as deduced from reduced velocity within the bedrock unit which can affect the building foundations in some area of the site. From these assessments, the study area falls within a good to fair engineering property.
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Integrated Geophysical, Geotechnical Investigations, Building Foundation, Kotebe Metropolitan, University North East, Addis Ababa, Ethiopia