We often see a lot of smaller stones on some railway tracks. Do these stones have any effect? These stones are called “ballasts” in the industry. Ballast, sleepers, steel rails, etc. together form a rail system. These ballasts played an important role in the rail system.
The gravel has irregular shapes, and there is a certain gap between them. When it rains, rainwater can directly penetrate into the ground from the cracks in the stones. When it is sunny, the flying dust will not accumulate on it. Therefore, the ballast ensures the drainage, strength and aesthetics of the railway track. In addition, water is easy to freeze and expand in winter in low-temperature climates, and gravel, as a loose body, offsets a part of the expansion by reducing the gap, avoiding damage to the railway track, and can play a role in resisting frost. Crushed stones are not only convenient for daily engineering maintenance, but also easy to replace, which can extend the life of railway tracks. When the train is running, the friction and redistribution of the gravel can offset a certain degree of vibration, and can also absorb noise and other forms of energy to ensure the stability of the train.
Ballast stones generally choose harder rocks, which have high hardness and high compressive strength. They can not be damaged under long-term friction and pressure, and can effectively bear the weight of the train. In addition, the ballast can spread the load applied by the train to the foundation, reducing the pressure on the train track. In addition, these high-strength gravel materials are cheap, have a wide range of sources, are easy to lay and replace, and the construction technology is not difficult.
With the upgrading of technology, the ballastless track structure has gradually become the mainstream design, and it has been widely developed and applied in tunnels, elevated structures and bridges. The ballastless track structure uses concrete track bed slab foundation to replace sleepers and track beds in traditional tracks. Under the track bed slab foundation is a special cushion layer poured with polymer or cement asphalt mixture. In this way, it is ensured that the foundation under the rail has sufficient strength and stability, but also has a certain degree of elasticity. The accumulation of residual deformation after repeated bearing of the load is small, and the track structure should not be damaged. In addition, compared with the traditional ballasted track, the ballastless track has a longer service life, can better maintain the geometry of the track, has a long maintenance period, and has low maintenance costs.
Paving the ballast under the rails is to:
1. Shock absorption, provide certain elasticity and damping, play the role of buffer and shock absorption;
2. Protect the subgrade, pass the train load through the rail → sleeper → track bed, spread the pressure on the subgrade, and improve the bearing capacity of the subgrade;
3. Improve the rigidity of the track frame, enhance the ability to resist the lateral bending and deformation of the rail row, and maintain the correct geometry of the track;
4. Maintain the smoothness and orientation of the track, so that the rail after the train is rolled can quickly restore the original correct position;
5. Prevent weeds from growing around the track, reduce cleaning time, and facilitate maintenance;
6. Drainage, rainwater directly seeps into the ground from the cracks in the stones; in winter rain and snow, it reduces the freezing damage to the track.