Polyurethane to the Rescue Rail research that pays off

Engineers at the University of Wisconsin-Madison are testing a method to stabilize rail ballast in a mere 15 minutes.

James Tinjum (left) , associate professor in the Department of Engineering Professional Development and Abdullah Alsabhan (right), a postdoctoral fellow in Civil and Environmental Engineering (CEE) lead this research project.

Tinjum and Alsabhan, along with CEE professors Dante Fratta and Tuncer Edil, anticipate that injecting liquid polyurethane into the rail bed could stabilize ballast.

This process could reduce the frequency and cost of track maintenance.

What is ballast?

The layer of crushed rock underneath the tracks.

Ballast can deform over time, which may compromise its load-bearing capacity, and could play a role in derailments.

When deterioration of the ballast, or “fouling,” occurs, repair crews have to lift the tracks to add or replace the damaged rock.

This process is often lengthy and expensive.

The UW researchers use small pipes to inject liquid polyurethane into the ballast.

The material turns into foam and then hardens within 15 minutes.

Polyurethane injections provide supplemental support to the rail substructure by filling voids in the ballast or strengthening ‘soft spots’ in the underlying subgrade.

Concern over ballast stability has grown in recent years as ‘fracking’ operations throughout the country have multiplied.

Transporting fracking sand has increased the weight and frequency of trainloads and sand spillages.

Though sand spills aren’t the only factor that contributes to diminish ballast quality, the demand for industrial sand has turned spillages into an important part of the equation.

In enough quantities, sand that pours through causes ballast to retain moisture, and this in turn increases the likelihood of ballast deformation.

Polyurethane stabilized ballast’s (PSB) effectiveness may translate into a faster, and potentially cheaper method to mitigate ballast fouling due to sand spills or heavier loads, or even preventing it before it happens.

PSB has shown promise.

Injections of the material have been effective in lab experiments.

Recently, the research team conducted tests on the UW-Madison campus, where preliminary results revealed a 90-percent improvement on the ballast layer, according to Tinjum.

The National Center for Freight and Infrastructure Research and Education, and Uretek USA provided funding for this pilot field demonstration. Wisconsin and Southern Railroad sponsored the field site.

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Created By
Alberto Orellana-Campos
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Alex Barutha, Alberto Orellana-Campos, James Tinjum, Advanced Google Image Search

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