Any railway track is a complex complex of various kinds of engineering structures that form a road with a guide rail track. It consists of two main parts - the lower support and the upper. The latter is actually the road along which the rolling stock walks.
Main purpose
When the train moves, the upper structure of the track perceives both vertical and horizontal loads from its wheels and transfers them to an earthen or artificial foundation. The track itself determines the direction of movement of the train. VSP is designed primarily taking into account the fact that in the future it should provide a safe passage of trains with given maximum speeds.
Design features
The upper structure of the railway track consists of two main parts:
sleeper rail;
ballast prism.
The lattice design, in turn, includes the rails themselves, as well as sleepers made of different materials. The prism of the upper path can be single or double layer. Most often, the last option is used in the construction of the railway line. A two-layer ballast prism usually consists of:
For filling a single-layer prism, materials such as sand and gravel, crushed stone, asbestos waste, slag, and shell rock can be used.
In addition to the grating and prism, the following elements of the upper structure of the path are distinguished:
fastenings;
anti-theft;
intersections are deaf;
turnouts.
VSP Design
Drawing up drawings of such an important structure as the track’s upper structure , engineers must solve the following problems:
Define class, category, and path group
determine the design of the VSP;
determine the conditions for its installation;
calculate the increased and lowered temperature of the lashes, taking into account their strength and stability;
calculate lashing intervals;
determine elevation of rails and track gauge in a curve.
The upper structure of the railway track: rails
This design element VSP is designed specifically for the direction of movement of the composition. In some cases, the rails can also serve as a conductor of electric current (in areas with electric traction or self-locking). This VSP element can be labeled as P50, P65, P75 and P43. Currently, in the construction of railways, the P65 variant is mainly used. Actually the rail itself consists of:
The standard length of rails in the Russian Federation is 25 m. In some sections of the lines, shortened guide elements can also be laid - by 24.84 m and 24.92 m. In order to reduce the number of joints between the rails, they are often welded in a whip of 800 m length and more.
Top Track Materials: Rail Manufacturing
This VSP element is usually made at the enterprises of the metallurgical industry from open-hearth carbon steel. In this case, the rails are subjected to thorough heat treatment along the entire length by quenching in oil and tempering in the furnace. This procedure is carried out primarily in order to increase the wear resistance of the alloy. Hardened rails serve one and a half times longer than untreated. Currently, when assembling railway tracks, steel elements can be used:
The latter kind of rails is usually used for laying tracks in areas with severe climatic conditions - in the Far East, Siberia, etc.
VSP sleepers
The main purpose of the rail supports in the track is to absorb the load from the rails and transfer them to the ballast. Also, sleepers provide stability of the track width in plan and profile. Sleepers can be made in our time either from reinforced concrete or from wood. Due to its susceptibility to corrosion, metal is not used. 80% of the sleepers laid in the country are made of wood. In the production of this VSP element, species such as fir, birch, larch, pine, etc. can be used.
Reinforced concrete sleepers are usually laid only on artificial structures - in tunnels and on bridges. Such supports can be small-sized frames or plates.
The length of the sleepers depends on the characteristics of the section of the path on which they are laid. So, wooden poles have a standard length of 2.75 cm. The tolerance for deviation from the norm is 2 cm. The length of turnout reinforced concrete beams is 3-5.5 m, and of bridge - 3.25 m.
In cross section, wooden sleepers can be:
trimmed;
half-edged;
unedged.
Reinforced concrete sleepers are made with a variable cross-sectional length. For their production, heavy concrete of the M500 or F200 brand is used. The fittings are used with 3 mm wire. Sleepers are laid on the track in the amount of 2000 pcs / km on difficult sections. On the lines they are distributed at 1440-1600 pieces per kilometer.
Classification of sleepers
Reinforced concrete track supports depending on the degree of crack resistance and accuracy of geometric parameters are divided into products of the first and second grade. The device of the upper track structure in different cases involves the use of wooden sleepers of the following classes:
The first (I) is for the main paths.
The second (II) - for stationary and access.
The third (III) - for industrial routes that are not exposed to frequent loads.
Wooden sleepers serve without the need for replacement 12-15 years, reinforced concrete - up to 50 years. The disadvantages of the latter, however, are considered their large weight and a high degree of conductivity.
VSP ballast layer
The purpose of this VSP element is to transfer the load from the rails and sleepers directly to the layers of such a base as a subgrade (upper) . The structure of the upper path on mine is a little different. The ballast prism in this case is not equipped. On earthen plots e e are most often made from crushed stone of hard rocks. Sand and gravel ballasts, since they poorly remove water, are equipped only on low-value lines. In heavily clogged areas, in most cases, an asbestos substrate is poured and rammed . During rain, a not too thick crust forms on it. The latter serves as a good obstacle to the penetration into the ballast of various kinds of weeds.
VSP turnouts
The structural elements of the upper structure of this type of track can serve to ensure the movement of trains from one track to another or to turn the crew 180 degrees. They are also used when crossing paths at the same level. The main elements of the turnout are:
The main types of VSP
Currently, the following types of track superstructure are used on the main roads of the Russian Federation:
The class of VSP is determined depending on its gross payload. This is primarily due to the fact that, unlike most other engineering structures, all its components work with accumulating residual deformations.
The heavy upper structure of the track involves the use in most cases of rails of class P75. In this case, a prism from crushed stone or asbestos waste is used. Such structures are intended for highways with a cargo intensity of 80 million tkm / km per year.
The middle type involves laying P65 rails. It is intended for lines with a cargo intensity of 25-80 million tkm / km per year. Also, such tracks are laid for high-speed passenger trains and in areas with especially heavy traffic.
The light type of VSP, in turn, is divided into two main varieties:
In the first case, when laying, P50 rails are used. Also in such areas old steel rails P75 or P65 can be used. For laying tracks with an intensity of 5 million tkm / km per year, used P50 rails are usually used. A prism of a light type of VSP is usually equipped with a gravel-sand mixture.
Jointless Railways
In areas with reliable soil, it is recommended to equip this particular type of VSP. In Russia, the length of the lash of jointless paths is on average 500-600 m. Their undoubted advantages include:
facilitation of such a procedure as repair of the upper track structure;
increase in the service life of VSP;
increased smoothness of train traffic.
The jointless path is, in fact, a more advanced design compared to the usual one. However, designing it is a bit more complicated procedure. Indeed, in this case, additional temperature stresses arise in the rails.