Norfolk Southern Ballast Protection Improvement

Christiansburg, Virginia
Ballast Protection
Owner:
Engineer:
Contractor:
Technical Description:
  • Product: Tracktex™ High-Performance Geocomposite
  • Units: 3 rolls
  • Dimensions: 82' x 12.7'
Installation:
September 2014

In September 2014, three 82-foot rolls of Tracktex™ High-Performance Geocomposite were supplied to Norfolk Southern along a section of their track for a capability and assessment demonstration in the Whitethorne District of Virginia. The high-performance geosynthetic was installation along a section of track that ran through Narrows, WV through Roanoke, VA. One roll was also installed at a repeat mud spot in a 2˚ curve at MP V265.2. This section of track had been undercut the year before (2013), but the mud had returned.

The intent was to determine whether or not Tracktex would be able to provide an increased form of ballast protection in these known trouble areas. The initial sections were inspected repeatedly by the Norfolk Southern geotechnical engineering team to determine if there was an enhanced performance of the ballast and noticeable erosion control protection. The final inspection was performed roughly 2 and 1/2 years after the initial installation with successful results.

Tracktex is a multilayer composite with a unique microporous filter media guarded by specially engineered protective nonwoven geotextiles. The filter is an orientated microporous polymeric film with a series of microcells and interconnecting pores, characterized by its relative strength and ability to transmit water vapor and/or liquid under controlled conditions. This inherent characteristic allows the upward migration of liquid under load that will de-water the subgrade, improving load bearing capacity.

The initial sections were installed in 2014. By December 2016, several mud boils had developed in the low-side shoulder of the track which were then removed by an excavator. Photos were then taken during an inspection in April 2017 that showed the clean crib ballast.

It was determined after the two and half year inspection that the Tracktex that had been placed was very effective. It completely covered the limits of a very weak substructure. Within its 25 meters were a low spot and a saturated subgrade. East and west of the Tracktex, the track surface was good, ballast was clean, and there was no evidence of water seeping from the roadbed.

Brad Kerchof, Norfolk Southern Research & Tests, stated, "By preventing the subgrade from fouling the ballast section, and by more effectively distributing the vertical loads to that subgrade, the Tracktex has greatly extended surfacing cycles and the life of the ballast. The fact that the track needs only occasional shoulder cleaning and surfacing, despite resting on such a weak subgrade, is remarkable."

Tracktex was developed by geotechnical rail specialists and is extremely well-proven in applications across the world, over a number of years. This innovative solution has the ability to substantially extend maintenance intervals, by at least 25 times, generating significant cost savings in maintenance budgets for operators dealing with problem track sections, where ‘mud pumping’ contaminates the ballast.

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