Giving freight rail tracks a boost

A booming industry in hydraulic fracturing has presented a new challenge: grains of sand can leak from rail cars, accumulate in rail bed ballast and, during a rainstorm, turn into mushy, track-loosening mud. Photos: Tuncer Edil/UW-Madison The big chunks of rock - crushed limestone or dolomite that engineers call ballast - that keep railroad tracks in place look like a solid footing even as freight cars rumble overhead. But temperature and vibration can destabilize ballast over time, keeping it from safely transferring the weight of a loaded train to the soil below, draining water and preventing vegetation from crowding the tracks. In Wisconsin, a booming industry mining sand used by oil and gas drillers in hydraulic fracturing has presented a new challenge: fine grains of sand can leak from rail cars, accumulate in rail bed ballast and, during a rainstorm, turn into mushy, track-loosening mud. "Some of these tracks have deteriorated so much that the trains travel at about 10 mph," says Dante Fratta , professor of civil and environmental engineering and geological engineering at the University of Wisconsin-Madison. "You have to lift up the track, remove the ballast, and put in new material. It's very expensive.