Why is the railroad track free of expansion joints now?
Seamless rail not thousands of kilometers without gaps, but the 25 meter long rail welding up into hundreds of metres long or even thousands of meters long, and then in the shop on the embankment, or the gap between 11 mm and a section of a seamless rail, now Shanghai Nanjing line is 303 km long ultra long seamless rail, seamless rail in order to solve the thermal expansion and contraction by slot number is not enough, now there are two methods of thermal expansion and contraction
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One is the long rail itself under all temperature stress, will be locked in the long rail sleepers, which is due to temperature change and contraction, this method is applicable to all the year round temperature of similar areas, for example in the south of Chinese. In some temperature difference regions should take another methods, namely the long rail itself does not bear the temperature stress, and stress or regular bleeding stress to automatic bleeding, make the long rail with temperature rise and free shrinkage, at the time of laying also try to choose the optimum temperature of the rail laying, the expansion value in the minimum range, so that regardless of temperature rise or fall, the rail expansion always control at a minimum.
