Application of ground-penetrating radar to railway track substructure maintenance management

Railway track substructure maintenance management is the process of utilizing railroad resources to maintain and upgrade the track substructure. The process begins with a measure of the track condition to evaluate the substructure performance, determine locations along the track that require maintenance, and identify appropriate solutions. Ground penetrating radar (GPR) has been proposed as a potentially valuable tool for this purpose. The objective of the research was to develop GPR testing and data interpretation techniques suitable for use by railroad personnel in this application. The principle of GPR operation is the transmission of short electromagnetic waves into the subsurface and recording the resulting signal of the reflected waves. Electromagnetic waves are influenced most significantly by the dielectric constant of the soil. The dielectric constant is most affected by moisture content making GPR a valuable tool for locating trapped water that will cause increased track deterioration rates. GPR has the potential to evaluate the thicknesses and properties of the substructure layers on a continuous, non-destructive basis to improve the process of diagnosing substructure causes of track performance deterioration. GPR railroad research at UMass started with the construction of a test track. Different track structure components were tested to determine their effects on the GPR data. Approximately 200 tests were conducted. Subsequently, about 275 miles of data were collected on several U.S. railroads including Amtrak, Conrail, New England Central, and Burlington Northern Santa Fe, and in England on AMEC Rail. The data were studied to determine how well GPR can define substructure conditions, identify track problem areas, and provide an indication of the cause of the problem. The analysis included comparison of the GPR data to track geometry, subsurface stratigraphy, and ballast condition (fouling and moisture). GPR processing techniques were developed to simplify interpretation of the data. The results showed that GPR could locate zones of increased substructure degradation at over 75% of the sites