Journal de géologie et géophysique
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Joint Application of Geophysical Techniques for Engineering Site Characterization of Samara University Area, Ethiopia

Solomun Atsbahaa, Hindeya Gebrub, Tigistu Haileb and Anteneh Legessec

2D electrical resistivity imaging, vertical electrical sounding and magnetic methods have been conducted for site characterization for large building foundations at Samara University, one of the emerging institutions of learning in Ethiopia. The main objective of the study was to examine the suitability of the subsurface geological formations and structures for foundation on the on-going construction and future expansion of the university. From the results of the survey, it has been possible to map the stratification of the subsurface layers, areas of weakness in the subsurface and the vertical as well as lateral extents of the different lithologies. Moreover, the depth to the substratum suitable for foundation is determined. From interpretation of the geophysical survey results, the near surface geology of the study area includes three layers: a first layer, which is the top soil having considerably varying thickness over the area; a second layer which is interpreted as a layer of vesicular basalt which is the best lithology for the foundation purpose. This layer extends to depth of about 6 m on the north and eastern parts of the area whereas it goes up to 11 m depth on the south and south-western part of the survey area. The third layer which is characterized by very low apparent resistivity response is interpreted as weathered basalt and clay. From a combined interpretation of the geophysical data, three weak zones have been identified over the survey area. Out of these one is oriented N-S while the other two are oriented in a near NW-SE direction. From all the above interpretations, it was possible to suggest that the university must expand towards the northern part of the campus compound. Moreover, special considerations should be taken during designing and implementation of buildings in the eastern and southern part of the area, where the weak zones detrimental to foundation of large buildings are mapped.