Railroad steel rails are used on railroads and in cooperation with switches so that trains can move without turning.The track is usually composed of two parallel rails, the rail is fixed on the rail pillow, under the sleeper is the ballast, including the roadbed, the connecting parts of the rail and so on.
Railway bed is the foundation of railway track or road surface, it is the structure that bears and transmits the gravity of rail and the dynamic action of train, and it is the important structure to ensure the train running.The railway bed should have enough strength and stability, that is, the foundation should not be too large subsidence under its own static action.Excessive elastic and plastic deformation should not occur under vehicle dynamic action.The roadbed slope should be stable for a long time without slumping.Therefore, it is necessary to build some drainage ditches, slope protection, retaining structures and other railway bed ancillary structures beside it.The railway bed is a kind of linear structure, which has the characteristics of long route and wide contact with nature.
Structure of railway tracks:
From bottom to top, the track structure is respectively arranged on the top surface of the roadbed, buried in the track bed sleeper, and by connecting parts and sleeper connected rail.The function of the track bed is to transmit the dynamic load and static load itself and above to the roadbed, and prevent the sleeper displacement.The sleeper is used to bear the load from the rail and transmit it to the track bed together with its own weight.The rail is the uppermost structure of the track, which directly bears the wheel load and guides the locomotives and vehicles.
Composition of railway subgrade:
The roadbed is composed of two parts, the road base and the ancillary facilities.Subgrade surface, subgrade and subgrade slope constitute the road matrix.Subgrade auxiliary facilities are to ensure the strength and stability of the subgrade, including drainage facilities, protection facilities and reinforcement facilities.Drainage facilities have drainage ditches, protection facilities such as planting grass and trees, reinforcement facilities have retaining walls, buttresses retaining structures.
Rail and sleeper:
Steel rail is the basic load-bearing structure of railway tracks, which is used to guide the rolling of locomotives and vehicles and provide the contact surface with the least resistance for the rolling of wheels.Steel rail should have sufficient bearing capacity, bending strength, fracture toughness, stability and corrosion resistance.The track bed under the rail is generally laid horizontally with sleepers, which bear the pressure from the rail and pass to the track bed, while using fasteners to effectively maintain the track gauge and position.
Connecting parts of the rail:
A rail coupling part includes a joint coupling part and an intermediate coupling part.The rail joint connecting part is composed of splint, bolt, spring washer, etc. Its function is to connect the rail at the joint, so that the rail joint part has the same integrity as the rail, so as to resist bending and displacement.Joints should also meet the requirements of rail expansion.The connection between the rail and the sleeper is realized through the intermediate connecting parts.Intermediate connection parts, also known as fastenings, require sufficient strength, durability and certain elasticity, in order to effectively maintain the reliable connection between rail and sleeper for a long time, prevent the movement of rail relative to sleeper, and can give full play to its buffering performance under the dynamic action, delay the accumulation of residual deformation of track.