Time-frequency characteristics of ground penetrating radar reflections from railway ballast and plant

As increasing amounts of government and industry money are invested into the upgrading and maintenance of the European railway infrastructure, there is a growing demand for rapid and reliable non-invasive techniques for the characterisation of railway trackbed (ballast). Ground-penetrating radar (GPR) has been proposed as such a geophysical tool, employing pulses of high frequency electromagnetic radiation to characterise and profile the electrical properties (permittivity and conductivity) of the subsurface. Despite the popularity of this site investigation technique, scientific techniques and results have yet to be published presenting a systematic means to quantify and evaluate the GPR returns, correlating these with the degree of ballast deterioration. This study identifies a number of features extracted from time-frequency representations of GPR returns that are capable of accurately characterising the degree of ballast deterioration in accordance with a number of different ballast deterioration models.