Railroad ballast plays an important role in supporting heavy rail loading, preventing the
deformation of track, and providing drainage of water from the track structure. However,
over time, ballast is fouled by the breakdown of ballast aggregate and=or the infiltration
of fines, which undermine ballast functions. This may result in damage to the rail system,
such as track settlement. Ground penetrating radar (GPR), a nondestructive method, can
be used to rapidly, effectively, and continuously assess railroad track substructure conditions.
Ballast under various fouling conditions generates various electromagnetic (EM)
scattering patterns. In this study, air-coupled 2GHz antenna was found to be sensitive to
the scattering pattern change. Appropriate data processing was used to remove the effects
of ties and rails to obtain clear GPR images of the subsurface layers. Then, the amplitude
envelope and time-frequency approaches were implemented to characterize the signal in
time and frequency domains simultaneously. Using these techniques, non-fouled ballast
thickness can be assessed and trapped water can be detected, along the track.
1. E. T. Selig and J. M. Waters. Track Geotechnology and Substructure Management. Thomas Telford
Ltd., London (1994).
2. I. L. Al-Qadi, S. Lahouar, K. Jiang, M. McGhee, and D. Mokarem. Accuracy of Ground Penetration
Radar for Estimating Rigid and Flexible Pavement Layer Thickness. In Transportation Research Record:
Journal of the Transportation Research Board, No. 1940, pp. 69–78 (2005). TRB, National Research
Council, Washington, D.C.
3. I. L. Al-Qadi and S. Lahouar. Measuring Rebar Cover-Depth in Rigid Pavements Using Ground
Penetration Radar. In Transportation Research Record: Journal of the Transportation Research Board
No. 1907, pp. 81–85 (2005). TRB, National Research Council, Washington, D.C.
4. I. L. Al-Qadi and S. Lahouar. Materials Evaluation Journal 63(9):921–925 (2005).
5. I. L. Al-Qadi and S. Lahouar. Construction and building materials. Special issue on nondestructive
testing 19(10):763–772 (2005).
6. I. L. Al-Qadi and S. Lahouar. Use of GPR for thickness measurement and quality control of flexible
pavements. Journal of the Association of Asphalt Paving Technologists 83:501–528 (2004).
7. I. L. Al-Qadi and S. Lahouar. Ground penetrating radar: State of the practice for pavement assessment.
Materials Evaluation Journal 62(7):759–763 (2004).
8. A. P. Annan. Ground Penetrating Radar Principles, Procedures and Applications. John Wiley & Sons,
Canada (2003).
9. T. R. Sussmann. Application of Ground Penetrating Radar to Railway Track Substructure Maintenance
Management, Doctoral Dissertation, University of Massachusetts, Amherst, May 1999.
10. G. Kantor, H. Herman, S. Singh, J. Tabacchi, and W. Kaufman. Automatic Railway Classification
Using Surface and Subsurface Measurements, Proc. 3rd Int. Conf. on Field and Service Robotics,
Helsinki, Finland, June 2001.
11. R. Roberts, I. L. Al-Qadi, E. Tutumluer, J. Boyle, and T. Sussmann. Advances in Railroad Ballast
Evaluation Using 2GHz Horn Antenna. International Conference on Ground Penetrating Radar,
June 19–22, 2006. Columbus, OH.
12. G. Gallagher, Q. Leiper, M. Clark, and M. Forde, Ballast Evaluation Using Ground Penetrating Radar,
Railway Gazette International, pp. 101–102, Feb. 2000.
13. M. Silvast, M. Levomaki, A. Nurmikolu, and J. Noukka. NDT Techniques in Railway Structure
Analysis. World Congress on Railway Research Conference, Montreal, June 2006.
14. A. V. Oppenheim, R. W. Schafer, and J. R. Buck. Discrete-Time Signal Processing. Pearson Prentice
Hall, (2005).