Development of a time–frequency approach to quantify railroad ballast fouling condition using ultra-wide band ground-penetrating radar data

Abstract

This paper discusses the use of ground-penetrating radar (GPR) to assess railroad track substructure conditions. An ultra-wide band (UWB) GPR system, having a centre frequency at or higher than 2 GHz, can be used to detect the scattering pattern and to predict air void volume in railroad ballast. A time–frequency technique was implemented to characterise the signal in time and frequency domains simultaneously. Because electromagnetic energy attenuation is highly frequency dependent, the frequency sub-bands of the reflected UWB GPR signal can be analysed separately to quantify the fouling material and quantify moisture content. Additionally, to validate the GPR system capability, a ground truth field survey was conducted. Using ballast samples collected from the field for validation, this paper shows that a time–frequency analysis may provide a new method to measure the thickness of clean ballast, detect the trapped water and assess the ballast fouling and moisture content along the track.

Keywords:

• ground-penetrating radar
• ultra-wide band radar
• scattering analysis
• railroad ballast
• fouling condition

Acknowledgements

The authors gratefully acknowledge the assistance of the staff at TTCI during data collection and cross trenching. The help provided by Erol Tutumluer, Chris Barkan, Jeff Boyle, Hai Huang and Zhen Leng is greatly appreciated. This research was partially funded by Federal Railroad Administration (FRA) Project DTFR53-05-D-00200. The contents of this paper reflect the view of the authors, who are responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the FRA or the Illinois Center for Transportation. Trademark or manufacturers' names appear in this paper only because they are considered essential to the object of this paper and do not constitute an endorsement of product by the FRA. This paper does not constitute a standard, specification or regulation.