Safety starts below the surface measuring subballast and subgrade

The Issue:

MxV Rail’s Facility for Accelerated Service Testing (FAST®) is the industry’s proving ground for new rail technologies. Before construction began on the new FAST loop, MxV Rail experts were working with Zetica Rail and Rhomberg Sersa to capitalize on opportunities for learning by studying the lifecycle of this new infrastructure.

Non-destructive track inspection technologies have developed at an impressive rate over the past decade, including ground penetrating radar (GPR) for characterizing trackbed material condition. A novel approach combining non-intrusive measurements of formation stiffness and material change, with trackbed and track asset condition measurements, was deemed appropriate for the size and scale of MxV Rail’s FAST track. Going forward research will cost effectively explore interrelationships between elements of the whole track ecosystem.

With a better understanding of the subbase, and trends in track geometry, railroad engineering teams have more clarity on why a section of track would behave in a certain way. These insights support ongoing safety across the railways and help the industry address challenges more efficiently.

View showing geo-referenced point cloud (main image) with 2D linescan camera image (top left) with highlighted ties, and elevation color-coded point cloud (bottom left).

The Solution:

A combination of electrical, P-wave seismic refraction, and multi-channel analysis of surface waves was used to characterize the subgrade pre- and post-build. The quality of track construction was assessed using multi-frequency ground penetrating radar, 2D linescan camera vision, and mobile terrestrial laser scanner methods.

“Keeping a strong foundation is vital to the safety and maintenance of railroad infrastructure,” said Stephen Wilk, PhD, Principal Investigator at MxV Rail. “We have a unique opportunity for insights here in a controlled environment, where we do a lot of component and performance testing in wide ranging conditions. Having a uniform and strong foundation is imperative so we can conduct research over the long term with consistency and rigor.”

MxV Rail, Zetica and Rhomberg Sersa are innovating by measuring every level of the track and how components affect one another. As the team continues monitoring FAST loop changes below the surface, they will also collect data and produce findings about the entire ecosystem while the FAST loop accumulates 140 million gross tons or more of heavy axle load traffic per year.

Geophysical survey output examples. Clockwise from top left - GPR radargrams showing layer thickness categories, seismic refraction P-wave model, electrical resistivity imagin model, and apparent conductivities.
Geophysical survey output examples. Clockwise from top left - GPR radargrams showing layer thickness categories, seismic refraction P-wave model, electrical resistivity imaging model, and apparent conductivities.

Moving Forward:

The collaboration builds on work that started in 2010 inspecting ballast with ground penetrating radar. “We’re often interested in the same technical questions, and we have overlapping projects for interested parties, which keeps us in close contact,” said Asger Eriksen, PhD, CEO at Zetica. “When MxV Rail announced that they were moving, we saw the opportunity to do more than inspect as-built track. This is a rare chance to see how the foundation evolves over time and its potential impact on the lifecycle of track assets.”

Future non-destructive surveys during the life of the FAST loop will compare any changes in trackbed and subgrade material properties and link these to trackbed performance. Watch for future academic work to be published in Technology Digest or within MxVRail’s website Knowledge Interchange.

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