Numerical 3-D Simulation of a Cathodic Protection System for a Buried Pipe Segment Surrounded by a Load Relieving U-Shaped Vault

A three-dimensional, multi-domain boundary element method approach was used to determine the performances of a cathodic protection system applied to a buried pipeline of limited longitudinal dimension, surrounded by a U-shaped vault of infinite resistivity (insulator). A Laplace model describing the potential problem was solved in combination with nonlinear boundary conditions that hold for the polarization behavior of the coated pipeline and coating holidays. The efficiency of this cathodic protection system was examined as a function of the soil conductivity, the position of the defects, and the presence of the U-shaped vault. The objective of these simulations was the quantitative determination of the reducing effect of this structure on the protection level of the outer pipe surface, as a result of its spatial obstruction for the protective currents that originate from the far-field anode beds.