Geoelectrical Surveys for Geo-Engineering Hazards Assessment in Faulted Areas Applying Genetic Algorithms and Advanced Inversion Method

Abstract

Summary Direct current resistivity (DCR) surveys play an efficient role for near-surface applications, such as engineering geology. However, the conventional interpretation methods still have a degree of the exact-data non-uniqueness problem leading to erroneous geological interpretations essentially in highly deformed urban areas. This study presents the efficient use of linear and non-linear inversion methods for preliminary geo-hazards assessment in a highly structured urban area, Badr city, Egypt. Genetic algorithms are applied to robust the DCR soundings interpretation considering the borehole data and conventional inversion results. Based on DCR soundings inversion results, some geotechnical properties are predicted considering the consequences of traditional engineering measurements. Although the electrical resistivity tomography (ERT) is a remarkable method for mapping the rock discontinuities, the resistivity artefacts at shallow depths due to soil lateral heterogeneities can increase the effects of ill-posed inverse problem with missing shallow subsurface layers and structures. Accordingly, advanced inversion method is applied using a decoupling line and a robust inversion option to attenuate the near-surface resistivity artefacts especially with high conductive layers presence. Consequently, the shallow subsurface structures and shale layers can be resolved. The results demonstrate that our protocol is cost efficient for preliminary geo-hazards assessment in highly faulted urban areas.