Application of Geophysical Methods for Engineering Site Characterization of Wachamo University Referral Hospital Building Foundation in Hossana Town, Southern Ethiopia.

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Addis Ababa University


Application of the electrical resistivity and multichannel analysis of surface wave geophysical methods provide information on engineering site characterization of Wachamo University referral hospital site, in Hossana, southern Ethiopia. Often, existing hospital buildings and other large civil engineering structures found in Hossana town were constructed with limited point observation data, without continuous assessment of the site for foundation work and without knowledge of the possible subsurface discontinuities and structures through and without considerable understanding of earthquake effects on such structures. Vertical Electrical Sounding (VES), Electrical Resistivity Imaging (ERI) and Multichannel Analysis of Surface Wave (MASW) survey methods were employed on the site to get a better understanding of the site condition in a continuous manner. The VES, electrical resistivity imaging and MASW were processed by using winRsist, Res2Dinv and Seisimager software‟s respectively to get the desired information. The geo-electrical data haves shown that the depth of bedrock /competent rock is in range 5-13.1m beneath the subsurface having resistivity value roughly in between 39.5 and 75Ω-mfor shallow foundation of low rising buildings design while for deep foundation of high rising buildings design, the depth to the bedrock/competent rock is in the range of 13.1-21.5m beneath the subsurface having resistivity value roughly between 49.1-125Ω-m in the northern and central parts of the study area considering the presence of weak zone within the bedrock formation. In the case of southern part of the survey lines of the study area, the geo-electrical data has shown that the depth to the competent /bed rock is in range 5-13.1m and it is suitable for both shallow and deep foundation of the building design of the study area. The average shear wave velocities of the upper 30m depth of the study area are 219.7 and 239.7m/s. According to the NEHRP (National Earthquake Hazard Reduction Program) and IBC (International Building Code) standards the soil can be classified as D. Also based on the average shear wave velocity of up to 36.43 and 34.74m depth of the site are 216.84 and 240.91 m/s respectively and period (T0) the site is classified as D1 and D2 according to new site-soil classification scheme. The Gmax of the study area in the two multichannel analysis of surface wave are 105.74 and 169 pa. Therefore, both electrical resistivity and multichannel analysis of surface wave methods revealed that the material that lie between the third and the fourth layers over the site to be having with fair- good geotechnical properties.



Application, Geophysical Methods, Engineering Site, Characterization, Wachamo University, Referral Hospital Building Foundation, Hossana Town, Southern Ethiopia