How to solve the problem of thermal expansion and cold contraction of railway rail?
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 solve the thermal expansion and contraction in two ways, 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 suitable for a year four small temperature difference areas, for example in the south of China. In some temperature difference regions should take another approach, namely the long rail itself does not bear the temperature stress, and stress or regular bleeding stress to automatic bleeding Method, 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 the temperature rising or falling, the rail expansion always control at a minimum.
In order to solve this problem, the railway department within a certain distance, playing a few holes in the rail waist to release the energy generated by thermal expansion and contraction, and within a certain distance (about 1500m) retaining rail joint, to assist in releasing the energy generated by the thermal expansion and contraction, in order to solve the problem of rail expansion and contraction.
The railway line to solve the rail expansion and contraction method is generally used for fastening the way, is the shrapnel into spring fastener fastener (also called spring bar fastener), rail tightly in the sleepers, forcibly will produce thermal expansion and contraction of the energy to digest, but the existence of such a problem is generated when the thermal expansion and contraction energy is greater than the distance unit of sleeper rail adhesion, makes up the phenomenon of rail, rail sleeper unit length twist.
