Geophysical and Geotechnical Examination of Structural Failure in Federal University Otuoke, Nigeria

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Abstract

The cause of foundation based structueral failure of some buildings in the premises of Federal University Otuoke, Nigeria was investigated using electrical imaging technique and geotechnical test involving moisture content, bulk density, specific gravity, free swell and texture determinations. The apparent resistivity data collected with ABEM SAS 300C Terrameter along three profiles, respectively laid in the vicinity of the affected buildings were processed using RES2DINV Software to produce the 2-D electrical resistivity tomograms. The results showed that the electrical resistivities of the subsoil at shallow depths underlying the buildings in the areas range from 2 to 1100  and this range encompasses the range for Sandy Silty Clay, Coarse Sand and clay respectively. The geotechnical test showed that the soils in the area are predominantly Sandy Silty Clay, Clay and Coarse Sand, fine aggregates, probably sandfill. The ranges of the moisture content (4.40 – 36.25%), bulk density (1.11 – 2.08 gcm^(-3)), specific gravity (1.69 – 2.71) and free swell (0.0 – 106.3%) of the soil layers directly underlying the buildings suggest that the structural failures are most likely initiated by differential settlement caused by significant variation laterally in the compaction of the soils and clay swelling. Therefore, to minimise structural failure in the university and its environs, building engineers in the area should ensure that each building is directly underlain laterally by the same type of soil having no significant difference in compaction.

Keywords: Structural failure,Electrical resistivity imaging,Geotechnical test, Compacted soil, Clay

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