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Sleeper, also known as sleeper, is also a kind of railway fittings. It's just that the materials used are not only wood, so it's more scientific to call sleepers. Although the sleeper looks monotonous and unremarkable, it plays a big role. Sleepers should not only support the rail, but also maintain the position of the rail and transfer the huge pressure of the rail to the ballast bed.
It must be flexible and elastic, neither hard nor soft. When the train passes by, it can be properly deformed to cushion the pressure, but it must be restored as much as possible after the train passes by.
Manufacturing material
At first, the sleeper was made of wood, with good elasticity, good insulation, little influence by the temperature change of the surrounding medium, light weight, simple processing and replacement on the line, and sufficient displacement resistance. The service life of the wooden pillow after anticorrosion treatment is also greatly prolonged, which is about 15 years. Therefore, 90% of the railways in the world use wooden sleepers.
According to statistics, in the heyday of wooden pillows, more than 3 billion wooden pillows were laid all over the world, most of which were pine. It is conceivable that how many forests will be destroyed? With the decrease of forest resources and the enhancement of people's awareness of environmental protection, and of course because of the development of science and technology, at the beginning of last century, some countries began to produce steel sleepers and reinforced concrete sleepers to replace sleepers.
However, due to the large metal consumption, high cost and bulky size, steel pillows have not been popularized, and only a few countries such as Germany are still in use. Since 1950s, reinforced concrete sleepers have been widely produced in many countries.
The utility model has long service life, high stability, small maintenance workload, and the damage rate and scrap rate are far lower than those of the wooden pillow. On jointless track, the stability of reinforced concrete sleepers is improved by 15~20% on average compared with wooden sleepers, which is especially suitable for high-speed passenger dedicated lines. For example, the Shinkansen in Japan and the high-speed trunk line in Russia.
Of course, reinforced concrete sleepers also have disadvantages, especially the weight is much larger than that of wooden sleepers. For example, mine cement sleepers, reinforced concrete sleepers in Britain each weigh 285 kilograms, those in the United States weigh 280 kilograms, and those in Germany also weigh 230 kilograms.