Blowout is a serious threat to rail transport. Passengers may be hurt. And in the event of such an incident, traffic on the section of the canvas is closed. So what is it and what does it have to do with it?
Official statistics
According to official data from the Department of Tracks and Structures of the Ministry of Railways of the Russian Federation, from 1998 to 2001, nine train wrecks on the Volga, East Siberian, North Caucasian, Moscow and South-Eastern roads occurred due to the ejection of a section of the track under the trains. All crashes occurred between noon and 4 pm from April to September.
Deformations occurred with typical designs of seamless track, R65 rails. Under the canvas lay reinforced concrete sleepers, crushed stone ballast. Accidents occurred on straight sections of the road, and there were only two cases on circular curves with a radius of 400 to 650 m.
For a complete analysis of the causes of the crash, information is needed on the technical condition of the track and the derailed rolling stock. There is no such data in the materials of the Ministry of Railways of the Russian Federation. However, it is important that the track ejection occurred at the end of the train, and not in front of it, and all the derailments of the cars occurred precisely for this reason.
The above examples show that train crashes because of this may happen in the future. Measures must be taken to prevent track emissions under trains.
Path ejection - what is it?
There are several types of railway track failure: blowout, skew, splash, hijack.
The ejection of the track is the result of an increase in voltage in the rails and its spontaneous discharge. Thermal stress is one of the types of mechanical stress that occurs when the temperature is unevenly distributed. In a solid body, such stress arises due to the limitation of the possibility of expansion or contraction from other bodies. In particular, the lengthening or shortening of the rail is hindered by the joint pads and resistance in the supports.
When heated, the length would increase by a certain amount in accordance with the coefficient of thermal expansion of steel. Accordingly, it would decrease with a decrease. For such changes, structural gaps between the rails are provided. If the deformation is greater, the latter are stretched or closed. Thus, in winter, shearing of butt bolts is possible, in summer - violation of the stability of the rail-sleeper grid.
Temperature surge of the track - a sharp, for a time of about 0.2 seconds, the curvature of the rails in several waves from 30 to 50 cm, which occurs in a horizontal plane at a distance of up to 40 m. At the same time, crushed stone is scattered, part of the sleepers are split. The rails become unsuitable for further operation, asbecome permanently deformed.
How to avoid?
To prevent the ejection of the seamless track, it is necessary to observe the temperature regime when laying the railway tracks. So, the size of the butt gap must be set in strict dependence on the heating of the web. In a seamless track, the middle part of the rail lash is motionless. Only the ends can be shortened or lengthened. The stress that occurs in the fixed part of the rail does not depend on the length or type of rail.
Its change causes temperature. For this reason, rail lashes must be fixed taking into account the temperature range. The latter is calculated depending on the stability of the track and the strength of the rail. The allowable compressive and tensile stresses correspond to temperature differences. There are special formulas by which you can determine the minimum and maximum temperatures. Work must be carried out at a rail temperature that corresponds to the upper third of the calculated interval. If the conditions are different from the optimal, the length of the rail string is forced by a hydraulic tensioner. Thus, the rail is introduced into the desired temperature regime.
Unfavorable conditions
If the calculated temperature range is less than 10 °C or negative, the subsequent use of the railway track is possible only with periodic voltage discharges.
To do this, it is necessary to fix the leveling whips. Suchrails can be periodically replaced with longer or shorter rails. Equalizers can also be used.
Research
In the world, only a few have seen the outburst of the path. People are already facing the consequences. In Russia, at one of the departments of the Samara GUPS, a stand was built and tested, on which students can simulate the path ejection in practice, which is very important for the study of this destructive phenomenon. The university training ground includes a 70 m long railway track with a 400 m radius curve. With the help of hydraulic cylinders, it is possible to create a load of up to 300 tons, set various deviations in the maintenance of the railway track, and fix under what loads and conditions the release will occur. In this case, the process takes place on a real structure.
