Railway track is an integral engineering structure laid on the subgrade, serving as a guide for train operation. What are the structures and functions of each part of the track?
The track is a component of railway lines, including rails, sleepers, fasteners, ballast, anti-creep devices, and turnouts. As an integral engineering structure, it guides train operation and directly bears the huge pressure from locomotives, vehicles, and their loads. Under the dynamic action of train operation, all its components must have sufficient strength and stability to ensure trains run safely, smoothly, and continuously at specified speeds.
The function of rails is to directly bear the weight of trains and their loads transmitted by wheels and guide the train's direction. Take a train consisting of 60 60-ton open wagons as an example: its total payload and self-weight reach about 5,000 tons. For heavy-haul trains of 10,000 tons or even over 100,000 tons, the weight is even greater. Such huge pressure first acts on the rail shoulders. Thus, rails must have sufficient strength, stability, and wear resistance.
The cross-section of rails is I-shaped, consisting of three parts: rail head, rail web, and rail foot. This seemingly simple I-shape offers advantages like good force-bearing capacity, material efficiency, and optimal bending resistance.
Rail types and strength are expressed in kg/m. The heavier the rail per meter, the greater the load it can bear. The world's first railway used 18kg/m rails, while the heaviest rails, at 77kg/m, are in the United States.
| Classification | Height(mm) | Head (mm) | Bottom (mm) | Thick(mm) | Weight (kg/m) | |
| Light Rail | 8 KG/M | 65 | 25 | 54 | 7 | 8.42 |
| 9 KG/M | 63.5 | 32.1 | 63.5 | 5.9 | 8.94 | |
| 12 KG/M | 69.85 | 38.1 | 69.85 | 7.54 | 12.2 | |
| 15 KG/M | 79.37 | 42.86 | 79.37 | 8.33 | 15.2 | |
| 18 KG/M | 80 | 40 | 80 | 10 | 18.06 | |
| 22 KG/M | 93.66 | 50.8 | 93.66 | 10.72 | 22.3 | |
| 24 KG/M | 107 | 51 | 90 | 10.9 | 24.46 | |
| 30 KG/M | 107.95 | 60.33 | 107.95 | 12.3 | 30.1 | |
| Heavy Rail | 38 KG/M | 134 | 68 | 114 | 13 | 38.733 |
| 43 KG/M | 140 | 70 | 114 | 14.5 | 44.653 | |
| 45 KG/M | 145 | 67 | 126 | 14.5 | 45.546 | |
| 50 KG/M | 152 | 70 | 132 | 15.5 | 51.514 | |
| 60 KG/M | 176 | 73 | 150 | 16.5 | 60.64 | |
| Crance Rail | QU 70 | 120 | 70 | 120 | 28 | 52.8 |
| QU 80 | 130 | 80 | 130 | 32 | 63.69 | |
| QU 100 | 150 | 100 | 150 | 38 | 88.96 | |
| QU 120 | 170 | 120 | 170 | 44 | 118.1 | |
GB rail standards include 50kg/m, 60kg/m, and 75kg/m. Standard lengths are 12.5m and 25m. There are also shortened rails for inner curves: for the 12.5m standard rail series, shortened rails are 40mm, 80mm, and 120mm shorter; for 25m rails, they are 40mm, 80mm, and 160mm shorter.
Rails on the track are connected by fishplates and bolts, called rail joints. At joints, the wheel-rail dynamic action is strong, requiring heavy maintenance. Rail Joints are one of the weak links in track structure.
Joint connection forms are divided into suspended and supported types based on their position relative to sleepers. Based on the mutual position of joints on two rails, they are divided into butted and staggered types. China generally uses the butted suspended type, where joints of two rails are aligned left and right, located between two joint sleepers.
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