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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Continuosly welded track with compensation rails for railway bridges

In rail tracks on long bridges, spanning over 100 m, the temperature stresses are equalized currently by using special devices – compensators.

It has been proved however that in most cases compensators are not required, provided three or four pairs of compensation rails, 12.5 m long, are included in the continuously welded track spanning the bridge. In this case temperature displacement of the rails is taken up by adjusting the gaps in rail joints within 1 to 22 mm. Further, in the spring-summer period one of the 12.5 m long compensation rails is substituted by a shortened rail, 12.46 or 12.42 m long; in the autumn-winter period the rails are switched back. To ensure the durability of the bridge beams split bolt connections are used for fixing down these compensation rails.

The use of seasonal compensation rails in a continuously welded track makes it possible to give up completely the costly compensators. The advantages are a considerable cut in the track laying and maintenance expenses in large bridges, decrease of metal consumption and of labour rates, higher traffic safety, lower dynamic loads, lower noise level.

Бесстыковой путь с уравнительными рельсами на железнодорожных мостах

Для компенсации температурных деформаций рельсового пути, уложенного на больших мостах с пролетами более 100 м, в настоящее время применяются специальные устройства – уравнительные приборы.

Однако исследования показали, что в большинстве случаев можно отказаться от применения уравнительных приборов, заменив их тремя или четырьмя парами уравнительных рельсов длиной 12,5 м с укладкой на остальном протяжении моста бесстыкового пути. При этом компенсация температурных перемещений рельсового пути достигается изменением величины раскрытия зазоров в стыках уравнительных рельсов в пределах от 1 до 22 мм. Кроме того, в весенне-летний период один из уравнительных рельсов длиной 12,5 м заменяют на укороченный длиной 12,46 или 12,42 м, а в осенне-зимний период – наоборот. Эти сезонные уравнительные рельсы для обеспечения должной сохранности мостовых брусьев прикрепляют к ним с помощью раздельных болтовых скреплений.

Использование сезонных уравнительных рельсов и бесстыкового пути позволяет полностью отказаться от дефицитных уравнительных приборов, что значительно снижает затраты на укладку и содержание пути на больших мостах, понижает металоемкость и трудоемкость, повышает безопасность движения поездов, уменьшает динамическое воздействие поездной нагрузки, понижает уровень шума.