Railway Track And Structures | AGICO Rail

26 May.,2025

 

Railway Track And Structures | AGICO Rail

Superstructure

The superstructure is the part above subgrade that you can see it with your eyes. Its components include rails, sleepers, fasteners, and ballast. Typical classification for the superstructure is ballasted track and ballastless track, or jointed track (tracks with gaps) and welded track (seamless track).

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Ballasted track

A ballasted track refers to a track with ballast (usually made of crushed stones) under the track. It is one of the main forms of track structure. It has the advantages of good flexibility, low price, convenient replacement and maintenance, and good noise absorption. However, compared with the ballastless track, it also has the disadvantages that the line plane geometry is not easy to maintain, most of them are short, and the maintenance workload is large.

The bottom of the track is ballast, which provides flexibility and drainage for the track. Railway sleepers are embedded in ballast and are generally laid laterally. They are made of wood, reinforced concrete or steel. The original rails were cast-iron rails and then developed into I-shaped steel rails. They are laid on sleepers and fixed with other track material.

Ballastless track

A ballastless track is a track structure that uses concrete, asphalt mixture and other integral foundations to replace the loose gravel trackbed. The sleepers of the ballastless track are made of concrete, and the roadbed does not need gravel. The steel rails and sleepers are directly laid on the concrete road.

Ballastless track is an advanced track technology in the world today. The advantages of ballastless track over the ballasted track are in several aspects.

  1. Low maintenance costs.
  2. Slow track deformation and good durability bring long service life, good line condition.
  3. There will be no stone ballast splashing when driving at high speed.
  4. It is more comfortable and the train speed can reach more than 500 kilometers per hour.

Jointed track

The jointed track is a type of track structure using bolted rail joints (joint bars) to connect rails end to end. The jointed track was originally used because modern technology cannot provide any alternatives. The defects at the joints always happen because the discontinuous and uneven rail surface which lead to the additional load. As a result, it greatly affects the smooth driving and even causes geometry deformation and rail broken. Extensive maintenance work needs to be done to avoid the damages.

Welded track

Welded track or seamless railway track is not completely free of gaps, but the number of gaps in the entire railway section is so small that it is almost negligible. It is a concept comparing to jointed track. Generally, it is formed by welding multiple short rails in sequence. When a rolling stock runs over, the adjacent steel rails are stressed at the same time, so that the wheels can pass through the joints of the two steel rails smoothly without vibration. The welded track has the following advantages.

Noise reduction

Reduce noise pollution. The ultra-long seamless track is composed of many standard steel rails connected to long rails, and the length is generally two to three kilometers.

Cost-saving

Abrasion is greatly reduced. Compared with ordinary rails, seamless rails eliminate a large number of rail joints. The direct effects are eliminating the impact of joints, reducing line damage, saving a lot of raw materials. The line maintenance is estimated can save 30%-75% of costs.

Speed up

Improve the reliability of the track, and the speed of the train will increase accordingly.

Improve smoothness

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Increase the stability and comfort of passengers.

Subgrade

The subgrade is the fundamental structure for railway tracks. Under the ballast is the part called subgrade. The railway subgrade is a structure that bears and transmits the gravity of the track and the dynamic action of the train. It is the foundation of the track and an important building to ensure the operation of the train.

The composition of subgrade

  • Main body

The main body includes embankments filled with natural soil and stone, and road cuts dug in the natural stratum.

  • Drainage facility

Ground drainage: Side ditch, drain, gutter

The surface water that may be stagnated within the range of the subgrade is quickly drained out, and the outside surface water is prevented from flowing into the subgrade range, so as not to seep and wet the basic body of the subgrade or form overflow to wash the subgrade slope.

Underground drainage: drainage channel, seepage ditch, seepage well.

According to hydrological or geological conditions, it is built to a certain depth below the ground to intercept, drain, draw out groundwater or lower the groundwater level, to keep the roadbed and slopes dry and improve the stability of the soil.

  • Protection and reinforcement facility
  1. Slop protection equipement.

Paving turf, spraying, plastering, pounding, retaining walls, slope protection is used to protect soil slopes that are susceptible to damage by natural action and slope deformation. Intercepting and shielding structures built to protect against falling rocks, such as shed holes.

  1. Scour protection equipment.

It is used to protect the subgrade from scouring by water or waves, such as turf, riprap, masonry slope protection, retaining walls, dams, dams, etc.

  1. Support reinforcement equipment.

Retaining wall or pillar used to support and stabilize the subgrade.

  1. Anti-sand, Anti snow equipment.

Fences and protection forests are used to prevent sand, wind and snow from burying the subgrade.

The feature of subgrade

It's All About Types of Rail Joint | AGICO Rail - Railway fasteners

It's All About Types of Rail Joint

Jun 15,

This is an informational post, please check the rail joint page if you are searching for the product.

Rail joint, also called rail fish plate or joint bar, is one of several railway components. It takes on the task of connecting two rails and usually installed with fish bolt and nuts. Rail joint is one of the weak links in the whole railway track structure. So how to install rail joints and how to perform routine maintenance are particularly important. Before that, we need to figure outwhat is rail joint and how many different types of rail joint. Today, we will discuss the second one-- How many different types of rail joints.

Three Factors Affecting Classification

In various kinds of rail joints, we divide them roughly into three categories according to the position of railway sleepers, the position of rail joints and the performance of rail joints. Next, I will share you more details about the three categories.
 

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♦ Based on the Position of Sleepers

Under this category, we can still subdivide it into suspended rail joint and supported rail joint.


Suspended rail joint

In this type, rail joints are suspended between two sleepers. It has good stress condition, simple structure and it is easy to maintain. While the shortcoming of this joint is the fish plates are easily broken, as the fish plate is under greater pressure due to the rail deflection after wheel rolling. Therefore, in order to solve this problem, we need to reduce the space between sleepers to increase the flexural resistance of the joints. Although this type of joint is not perfect it is the most widely used one in railway construction worldwide.


Supported rail joint

This kind of rail joints is placed directly on the sleepers. According to the number of sleepers, we can still divide it into:
  • Single-sleeper supported rail joint
  • Double-sleeper supported rail joint.
The former has only one sleeper under the rail joint. When the train passed through, the pressure transferred to the sleeper is uneven and the sleeper is shaken before and after. So the single-sleeper supported rail joint has poor stability.
The latter has two sleepers under the rail joint. They help to disperse more impact force for joint. At the same time, the sleeper is a flexible support. There is a small seam between it and the rail joint. So it also has rail deflection but very small. The pressure on the joint is relatively small, too. But unfortunately, this kind of joint has high rigidity and difficult to tamp.

Based on the Position of Joints

There are also two types included in this category. The first one is the square joint and the second one is staggered joint.

Square joint

Rail joints on one track are exactly opposite to the joints on the other side are called square joints. This kind of joint is suitable for the straight rail line,and the rail line can be laid mechanically section by section. When trains passed through, the opposite two joints bear the impact force at the same time. It reduces the number of hits to the rail track. The running of the train will be more smoothly. At present, such joints are commonly used on railway lines.

Staggered joint

In this case, the distance between two opposite joints staggered half a rail. It mainly applies to the curved rail line and will disperse the impact force from wheel rolling, but it is not good for stability.

Based on the Performance of Rail Joints

The third category is based on the performance of rail joints. Under this category, we subdivided it into standard rail joint,compromise rail joint,conducting rail joint,insulated rail joint and welded rail joint.

Standard rail joint

It is the most basic rail joint. The rails it connected are having same weight and length. There will be an 8-10mm seam left between two rails for expansion and contraction, but the seam will cause the damage to rail and track bed in the joint area. Therefore, we usually replace it with welded rail joint.



Compromise rail joint

It is mainly used to connect two different types of rails to make sure the continuity of railway. Under normal conditions, in order to make the top surface and the inner side head of rails are matched up, it will use the corresponding special-shaped rail joint andrail pad with it.

Conducting rail joint

This joint is regarded as a connector used for conducting track current or as a traction current circuit, usually applied to automatic block and electric traction area.

Insulated rail joint

This kind of joint adopts insulating material to prevent current conduction between two adjacent automatic block sections. For insulation purpose, we will use nylonrail track bolt sleeve and nylon rail joint to separate rail, joint and bolt.

Welded rail joint

In this type, the end of rails is welded together to form a continuous long rail by resistance welding, small pressure welding or aluminum hot welding. The end of rails does not need to drill bolt hole and this rail joint is mostly used for seamless lines.

 
Above is the classification of rail joints. Each one has its own advantages and disadvantages. Hope this article will help you to find the most suitable rail joint.