Electrical Resistivity Imaging and Seismic Refraction: Application for Residential Building Foundation at South East of Addis Ababa, Lebu Area, Ethiopia
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Date
2019-05-05
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Addis Ababa University
Abstract
In this study, geophysical method of seismic refraction and electrical resistivity measurements using electrical resistivity tomography and vertical electrical sounding (VES) technique was utilized for the acquisition of geotechnical information of the subsurface at a proposed site. The site is located in south East of Addis Ababa at a place locally called Lebu Mebrat Haile.
The study is aimed to image the subsurface geology and understand the soils and rocks characteristics in terms of site‟s suitability for civil engineering applications. Three lines of seismic refraction data, two lines of electrical resistivity tomography data and six vertical electrical sounding stations with AB/2 ranging from 150m-220m were conducted.
The geophysical results discovered that the study area can be characterized as five geologic layers. Layer filled by loose sand and gravel, layer filled by silt clay with some sand, layer filled by silt clay with some sand with less moisture content, layer filled by clay with considerable fluid content and highly weathered and fractured basalt. The study also characterizes the presence of weak zones in the subsurface. This geophysical data‟s were linked to the borehole log result near the study area and the outputs correlate each other.
Generally the result of the study shows that the area is filled by loose sediments and clay with variable degree of moisture content and mineralogical composition. Since the study area is found in a place susceptible to low and medium earthquakes, such formation can amplify even small amount of earthquakes and cause any damage in the buildings. Up to survey depth which is 40m the researcher not found bedrock and ground water in the study area. Therefore, great caution should be taken by the engineer when designing foundation for the residential buildings found in the study area.
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Electrical Resistivity, Imaging, Seismic Refraction, Application, Residential Building, Foundation at South East, Addis Ababa, Lebu Area, Ethiopia