Terrestrial CSEM for buried steel infrastructure

Summary Maintenance of buried steel infrastructure is an important problem in civil engineering practice. Corrosion, for example, can lead to damage and excessive repair or replacement expenses. Soil corrosivity is one of the main physical factors that determines the corrosion rate of pipelines and other steel infrastructure. Methods that can reliably estimate soil corrosivity by non-invasive and inexpensive means would be of great benefit to the civil engineering community. Soil corrosivity is well-known to depend on multiple interacting physical factors such as moisture content, aeration, pH, organic matter content, microbial activity, etc. However, in most cases a dry and/or sand-dominated soil is electrically resistive and generally less corrosive in comparison with a wet and/or clay-dominated soil characterized by lower bulk resistivity. In this paper, with the objective of evaluating terrestrial CSEM as a potential tool for mapping possible corrosion of buried steel infrastructure, we examine synthetic responses from a terrestrial CSEM layout and report the magnitudes and characteristics of secondary signals that are caused by the presence of a zone of anomalous soil resistivity surrounding a uniform steel pipe. Further consideration of development of a practical slingram-type terrestrial CSEM system for steel infrastructure investigation is recommended.