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Geogrid could extend ballast life span
By Tim Carpenter
Musician Johnny Cash gave voice to travel lust by pointing an acoustic guitar at the country’s spider web of railroad tracks.
“Oh, the clickety clack of the railroad track is callin’,” he sang. “One more ride, one more ride.”
Researchers at The University of Kansas are leaving songwriting about railroads to others, but they are testing a new concept for improving integrity of rock ballast sitting beneath the country’s 150,000-mile network of wood ties and steel rails.
Investigators in the School of Engineering are interested in making ballast more durable using polypropylene netting commonly used to reinforce soil. If the geogrid option is effective, ballast life could be extended and railroad companies would save time and money dedicated to replacing rock foundations and rerouting trains during maintenance.
“Ballast helps to redistribute the load from the trains,” said Bob Parsons, KU professor of civil, environmental and architectural engineering. “Ballast is composed of large rock, but over time it gets contaminated from finer particles from rock dust, natural dust and coal dust from coal trains.”
He said dust infiltrating ballast prevented water from draining properly from rock.
“If the water is allowed to stand there and soak in, the soils under the railroad are going to get soft and weak,” Parsons said. “Then the ballast sinks down, and the track moves and gets out of alignment.”
Currently, railroad companies remove, clean and replace ballast in a time-consuming and expensive process necessary to maintain track alignment.
KU researchers built a test segment of track reinforced with geogrid netting. The mesh has triangular openings that trap larger rocks in a layer to reduce fouling by dust.
“By providing a framework, and making it more rigid and fixed and stronger in general, it prevents the ballast from breaking down,” Parsons said.
The research was funded by $75,000 by the Mid-America Transportation Center, with BNSF Railway Co. providing ballast and track sections and Tensar Corp. providing the geogrid.