Direct current resistivity and time domain induced polarization methods in soil corrosivity assessment for buried infrastructure

Direct current resistivity and time-domain induced polarization (DC-TDIP) methods are promising proximal sensing tools that can be utilised in practice as part of initial screening of buried infrastructure such as pipelines within the scope of asset condition assessment and management. Such initial screening is greatly needed to focus attention and maintenance operations on pipe sections suspected of undergoing significant deterioration due to corrosion within a large pipe network. In this study, we report a previously collected and unpublished DC-TDIP dataset collected along an abandoned 123 m section of buried ductile iron pipe that was installed with plastic insulation material. Systematic analysis of the survey data with laboratory analysis of soil samples collected along the transect length suggests that the normalised chargeability parameter, MN, maybe a better parameter for delineating possible at-risk pipe sections suspected of undergoing relatively high levels of corrosion, in addition to the apparent resistivity parameter. The absence of strong electrode polarization signatures on the chargeability profiles suggests the response is mainly arising from the subsurface soil. The use of the normalised chargeability parameter as a screening variable is further supported through its correspondence with the dissolved salt contents, viz., sulphates and chlorides. As a first of its kind application, the use the of the DC-TDIP technique in the assessment of buried, ageing, and deteriorating metallic infrastructure looks promising and needs to be strongly explored further, especially in conjunction with pipeline coating inspection techniques. Future research that can enhance the technique in professional practice are identified.