Investigation of soil contamination by iron pipe corrosion and its influence on GPR detection

It has been observed that the corrosion of iron pipes in soil can produce variations in ground conductivity around the pipe, and that the visibility of such pipes to GPR can be greatly reduced. This new investigation and measurement of the permittivity and conductivity of soil contaminated by iron pipe corrosion products produces more accurate knowledge of permittivity and conductivity data and their likely spatial variation with distance from the corroding pipe. The experimental data are the result of monitoring accelerated corrosion over a period of several weeks and using TDR and direct conductivity measurement schemes. FDTD simulations of GPR signals show how the corrosion induced variation in the visibility of the pipe varies with the thickness and shape of the new spatial variations permittivity and conductivity. The results indicate that in the earlier stages of pipe corrosion use of lower GPR frequencies will still detect the pipe, although at lower spatial resolution.