Outbursts are a serious threat to rail. Passengers may be injured. And in the event of such an accident, the movement on the web site is closed. So what is it and what is it connected with?
Official statistics
According to official data from the Department of Railways and Structures of the Ministry of Railways of the Russian Federation, from 1998 to 2001 nine train crashes on the Volga, East Siberian, North Caucasian, Moscow and South-East roads occurred due to the ejection of a section of the canvas under the trains. All crashes occurred from noon to 4 p.m. from April to September.
Deformations occurred with typical constructions of a continuous joint path, P65 rails . Reinforced concrete sleepers, crushed stone ballast lay under the canvas. 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 units of the rolling stock that went off the rails. The materials of the Ministry of Railways of the Russian Federation do not have these data. However, it is important that the track was ejected at the end of the train, and not in front of it, and all the gatherings of the cars took place precisely for this reason.
The above examples indicate that train crashes due to this can happen in the future. Measures must be taken to prevent emissions under the trains.
Outlier - what is it?
There are several types of railway track malfunctions: ejection, skew, splash, theft.
The ejection of the track is the result of an increase in the voltage in the rails and its spontaneous discharge. Temperature stress is one of the types of mechanical stress that occurs with an uneven temperature distribution. In a solid, such stress arises due to the limitation of the possibility of expansion or contraction from other bodies. In particular, the lining of the joint and the resistance in the supports prevent the elongation or shortening of the rail.
When heated, the length would increase by a certain amount in accordance with the coefficient of thermal expansion of the steel. Accordingly, it would decrease with a decrease. For such changes, structural clearances between the rails are provided. If the deformations are greater, the latter stretch or close. Thus, in the winter, a cut of the butt bolts is possible, in the summer - a violation of the stability of the rail-sleeper.
The temperature ejection of the track is a sharp, in a time of the order of 0.2 second, curvature of rails with several waves from 30 to 50 cm, which occurs in a horizontal plane at a distance of up to 40 m. Crushed stone is scattered at the same time, some of the sleepers are cracked. The rails become unsuitable for further operation, as they acquire permanent deformation.
How to avoid?
To prevent the emission of a jointless track, it is necessary to observe the temperature regime when laying railway tracks. So, the size of the butt gap should be set in strict dependence on the heating of the canvas. In the jointless path, the middle part of the rail lash is motionless. Only the ends can be shortened or lengthened. The voltage 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. Permissible compressive and tensile stresses correspond to temperature differences. There are special formulas by which you can determine the minimum and maximum temperature. Work must be done at rail temperature, which corresponds to the upper third of the calculated interval. If the conditions differ from the optimum, the length of the rail lash is forcedly changed by a hydraulic tensioner. Thus, the rail is introduced into the desired temperature regime.
Unfavourable conditions
If the calculated temperature range is less than 10 ° C or negative, the subsequent use of the railway bed is only possible with periodic voltage discharges.
To do this, it is necessary to fix the leveling lashes. In such designs, the rails can be periodically replaced with longer or shorter ones. Equalizers can also be used.
Research
In the world, emissions have been seen by units. People are already faced with its consequences. In Russia, a stand was built and tested at one of the departments of the Samara State University of Transport and Transport, on which students can in practice simulate a path ejection, which is very important for studying this destructive phenomenon. The university training ground includes a railway track with a length of 70 m with a curve radius of 400 m. Using hydraulic cylinders, you can create a load of up to 300 tons, set various deviations in the content of the railway track and record under what loads and conditions there will be an ejection. In this process occurs on a real design.