Пособие по техническому переводу, страница 22

In the majority of severe-curve environments, however, concrete has become the crosstie material of choice. This remains true in spite of the rail-seat abrasion problem that has occurred on a number of user railroads.

While there is still debate as to the cause of rail-seat abrasion, the problem is associated with an abrasive slurry made up of dust, silt, rail-grinding debris, locomotive sand, lubricating oils and water that works its way under the tie pads. Some of the components of the slurry are thought to be 10 times harder than the cement paste on the concrete tie. Researchers suspect that the slurry is moved beneath the pad as it is exercised by wheel loads passing over it.

An ad-hoc committee of railroaders, suppliers and researchers has been assembled to study the problem, and a number of repair methods are being tested on individual railroads and at the TTC (RT&S, July, p. 24). Research at the TTC is headed in two primary directions: Finding ways to prevent the problem from occurring and repairing the ties on which abrasion has already occurred. But as of yet, no definitive solution has been found.

«At FAST, all we can really say at this time is that by keeping the ties wet, we were able to get the abrasion started», says Rich Reiff, manager of the HAL project at the TTC.

One test designed to prevent abrasion was to glue the pads to the ties. This procedure appears to have failed in the sense that the glue no longer is holding the pad to the tie, he says. Some 50 to 60 other types of «fixes» on 300 ties are currently being evaluated.

In addition to the work being done at the TTC, the industry continues to look at various approaches to the rail-seat abrasion problem. Part of the solution may come from the protection of the concrete by a much higher quality pad, part of the solution may come from different, improved materials to enhance the quality of the concrete.

«It's going to be very difficult to improve hardness by a factor of 10-the amount necessary to overcome the abrasion effect of silica sand», says John White, president of CXT Inc.

The best multiplier the Bureau of Reclamation has been able to achieve is between three and four, adds Derek Firth, CXT vice president and general manager. «They don't believe anybody can find a multiplier of 10».

Harking back to a problem that the concrete tie industry has, for the most part, overcome, White says: «This industry still must be very careful about the choice of aggregates and cement used in concrete ties». Even if a company has been making concrete materials and never had any problems with them, the picture changes when a highly-stressed tie is put into a wet environment under cycling loads. Sometimes concrete that works well under normal situations does not work as a tie.

Manufacturers still have to watch very closely the quality of the aggregates and the alkalinity of the cement. Some people may say we're being over-cautious, but there have been occasions where there have been chemical reactions.

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