Ground Penetrating Radar - a useful tool to assess the track substructure condition

The ballast fouling index is a way of expressing the state of ballast fouling ([Selig] 1998). A very high fouling index (e.g. > 80%) indicates that ballast sieving is required to prevent deterioration of the track geometry, especially in the wet season. GPR can be used effectively to determine both the ballast thickness and the fouling index continuously along the line. Figure 2 shows the correlation between the laboratory fouling index and the GPR fouling index obtained in the pilot study.