Alternative testing method for the measurement of ballast fouling: percentage void contamination

Economic constraints are driving the need for Queensland Rail (QR) to obtain more cost effective maintenance methods such as better planning of proactive ballast-cleaning cycles. One means to achieve this would be implementing testing methods that quantify the measurement of ballast fouling. Existing tests do not realistically represent the extent of contamination. A contributing factor is that they are based on a sieve analysis test that measures the mass of particles passing different sieve sizes. The Percentage Void Contamination (PVC) is a volume based test, which measures the extent of void fouling for the depth of the ballast profile, and takes into account the different densities of the contaminants. This paper validates the PVC test by evaluating test results and comparing to existing test methods. The PVC is a percentage value calculated by measuring the volume of contaminants (fouling material passing 9.5mm sieve) and dividing by the volume of voids within the existing ballast (retained on 9.5mm sieve). Within QR's coal systems, it has been noted that most of the ballast fouling is due to coal infiltration and ballast breakdown. The volume ratio range of contamination is in the order of 70% - 95% coal and 5% - 30% ballast. Ballast cleaning is an efficient recycling maintenance activity used by QR to maximise ballast life and decrease overall maintenance costs. However, as the extent of fouling is predominantly based on visual inspections by track staff, ballast cleaning is not programmed as effectively as might be possible if it was measured more quantitatively. The volume of voids within new/clean ballast constitutes approximately 45% of the total volume of ballast within track. As ballast becomes fouled its functions are minimised until the level of contamination reaches the bottom side of the sleeper. At this stage ballast loses its resilience, void storage and drainage capabilities and the total substructure then starts to fail. For minimal adverse effects on the superstructure, a minimum live ballast depth of 100mm is required and the maximum limit of contamination should reflect this. When the extent of fouling has reached this limit, the ballast cleaning process needs to be initiated to maximise the cost effectiveness of track maintenance. Therefore the Percentage Void Contamination test needs to be implemented in existing ballast cleaning procedures as a quantitative measure of ballast fouling.

Media Info

  • Pagination: 11p. ; PDF
  • Monograph Title: Cost efficient railways through engineering: CORE 2002: conference on railway engineering, November 10-13 2002, Wollongong, New South Wales, Australia

Subject/Index Terms

Filing Info

  • Accession Number: 01532043
  • Record Type: Publication
  • Source Agency: ARRB
  • Files: ATRI
  • Created Date: Jul 29 2014 11:52AM