Identifying isolated defects in the ballast bed using a fractal analysis approach with reduced window length

Due to increasing demands on the availability of railway infrastructure, accurate estimates of safety-critical track condition as well as breakdowns of individual track components are crucial. This task can be supported by analysing track measurement data. Ballast breakdown can be determined by analysing the longitudinal level using fractal analysis. Typically, a window of 150 meters is drawn over the signal and an approximation of a fractal dimension of the signal is calculated for each position of the window. While a large window length can be used to describe the condition of ballast and substructure simultaneously, it fails to precisely localize isolated defects in the track (short-section ballast breakdown). To describe local effects in the ballast bed, this work analyses a set of 114 known weak ballast spots. By reducing the window length, the position of short-section ballast breakdowns can be reliably depicted. Using a smaller window size in modified fractal analysis allows for targeted maintenance of specific components. Ultimately, fractal analysis with reduced window sizes facilitates allocating maintenance resources and helps reducing unexpected downtime and saving on costs.