BALLAST COMPACTION METHODS AFTER TAMPING

Technische Universität Graz // SS 2022 // Masterproject

Introduction

In order to achieve the global climate and environmental goals that have been set and thus minimize manmade global warming, there must be a global rethink. Shifting freight and passenger transport to rail matters an important role in measures to reduce greenhouse gases. However, more traffic on the rails means higher demands on the railway infrastructure. This requires a robust railway infrastructure that can meet these high demands. Since the invention of the railway, the principle of the ballast bed has not changed fundamentally. However, other important components of the superstructure have evolved, and track construction and maintenance work has been largely mechanised. Above all, the endless welding of rails has had a major impact on the system behaviour of the track. In the past, the rail was able to expand in the case of temperature expansion due to the joint gap between the individual rail strands and thus relieve stresses. This is no longer possible with endlessly welded track and additional stresses occur in the rail. [1] 

Therefore, technical solutions were needed to ensure that the track could be travelled at full speed after the tamping process. The push for ever higher speeds to be competitive with road and air transport is believed to be driving the developments fast forward. In 1974, the core technology of the Dynamic Track Stabiliser (DTS) was introduced by an Austrian Inventor and in 1976 the first Dynamic Track Stabiliser went into regular operation [2]. The principle is based on the compaction of the ballast by vibration after the tamping process and thus a uniform settlement can be achieved. Especially nowadays, the compaction of the ballast after tamping plays an important role, as more and more traffic rolls over the rails and therefore sufficient track position stability is of high importance. Ever shorter tamping pauses and the issuing of slow speed stops would hardly be tolerable or conceivable for today's system.

Structure

At the beginning of the Masterproject, Chapter 2 deals with basic terminology and definitions that are necessary for reading this thesis. Based on a literature review, Chapter 3 explains the historical milestones of ballast compaction and tamping. Chapter 4 explains the basic principle of tamping and compaction. A comparison between the two ways of compacting the track after tamping, that is with Crib Compaction or with the Dynamic Track Stabiliser, is given in chapter 5. In Chapter 6 there is a detailed description of the Dynamic Track Stabilizer. Chapter 7 provides a brief overview of the regulations and standards in the DACH-area (Germany, Austria, and Switzerland). In which countries are machines used for compaction after tamping? This question is answered in chapter 8. Chapter 9 deals with the possible developments of this method in the future and summarises the results and draws a conclusion of the insights and the resulting conclusion.

Conclusion and Outlook

In conclusion, it can be said that the key technology developed in the 1970s was an important milestone for ballast compaction after tamping. During this almost 50-year history, the technology has been continuously developed, improved or rather it was integrated into other track machines [24]. The Dynamic Track Stabilizer and the Crib and Shoulder Compaction increase RLatD after tamping. After both methods, the track can be travelled with full operation speed after tamping and subsequent compaction. Since this is the primary objective of both methods and is fulfilled almost equally well by both, both can be regarded as equivalent [40].

Ballast compaction after tamping is an invention of the second half of the 20th century and therefore has a very long history. What could the future look like? One promising development could be the integration of artificial intelligence (AI) and machine learning (ML). With integrated sensors in tamping machines and compaction machines, AI and ML can be used to analyse data and make predictions about the condition of the track. Particularly in tamping and compaction work, where the working tools plunge directly into the ballast, the data obtained in this way can be put to very good use and fed directly back into the work process until sufficient stability and compaction have been achieved. This can lead to a significant increase in the productivity of the DTS. 

Another trend in the future could be the integration of autonomous technologies, which, among other things, no longer require an operator and thus the compaction machine can act independently and make decisions. Overall, the future of DTS, like many other areas, will be characterized by a strong integration of AI and autonomous technologies.

[1] C. Esveld, Modern Railway Track, 2nd Edition. Zaltbommel: MRT-Productions, 2001.

[2] ‘Plasser & Theurer: Unternehmen - Über Plasser & Theurer: Geschichte’, Plasser & Theurer, 2022. https://www.plassertheurer.com/de/unternehmen/geschichte (accessed Oct. 23, 2022).

[24] ‘Geleisestopf-MaschineSystem  Scheuchzer’,  Schweizer  Bauzeitung,  Apr.  1938,  doi:  10.5169/seals- 49849.

[40] J.-F. Ferellec, R. Perales, V.-H. Nhu, M. Wone, and G. Saussine, ‘Analysis of compaction of railway ballast by different maintenance methods using DEM’,  EPJ Web  Conf., vol. 140, p. 15032, 2017, doi: 10.1051/epjconf/201714015032