Efficacy of 2D induced polarization in detecting fractures in foundation soils

Abstract 2D Electrical Resistivity Imaging (ERI) has become quite popular for determining near-surface inconsistencies that can cause serious problems in foundation soils and, as a result, may lead to failure of engineering structures laid on them. The usefulness of deploying another geophysical technique, the Induced Polarization Imaging (IPI) technique, in detecting similar near-surface heterogeneity was the target of this investigation. The cost effectiveness, availability and easy usability of the technique is a major attraction. Using identical field configuration for the ERI and IPI techniques, studies were executed at a failed engineering structure with known foundation challenges within the Southeastern Nigeria—Nsukka area. Four Electrical Resistivity Imaging (ERI) and four Induced Polarization Imaging (IPI) surveys were performed on the same survey plan, utilizing the same Wenner Array electrode configuration and electrode spacings for both approaches. Electrical Resistivity Imaging results for survey line one (ERI 1 ) and the opposite segment, that of survey line three (ERI 3 ), demonstrated an NNW- SSE fault trend. This anomaly was seen at the same offset distances on Induced Polarization Imaging for survey line one (IPI 1 ) and survey line three (IPI 3 ), outlining the same fracture zone. The results of Electrical Resistivity Imaging for survey line two (ERI 2 ) and Electrical Resistivity Imaging for survey line four (ERI 4 ) were used to map a second fault trending in the NE-SW direction. The Induced Polarization equivalents (IPI 2 and IPI 4 ) also captured the defect. Field validation following delineated patterns revealed apparent foundation fissures that followed the same trend as the IPI and ERI.