metro rail system
Metro Rail System Fastening System and Rail Selection Criteria
Metro construction is a huge and complex project, which involves many fields such as urban planning, civil engineering, electromechanical installation and operation management. Metro as the core of urban transport, the safety and durability of the metro rail system requires very high. This paper mainly details the part of track laying in metro construction.
Overview of metro rail system
The track structure consists of the line part above the middle base surface or structural surface, which is composed of rails, fasteners, sleepers, roadbeds, etc.; the gauge is the shortest distance between the inside of the heads of two strands of rails at the specified distance below the rail surface; the international standard gauge is 1435㎜.
The metro rail system must be able to withstand the huge and repeated loads of the train, and effectively transfer the contact force between the wheels and the rail, vibration and shock to the foundation, so as to maintain the overall stability of the structure. The core role of metro rail is to carry the train load, guide the direction, conductive current (such as trams); pressure rail can reduce vibration and noise, prevent rail displacement, adapt to thermal expansion and contraction. So in the underground track rail product selection based on extremely high requirements.
Special requirements for rails in metro rail systems:
High axle weight, fatigue resistance, abrasion resistance, corrosion resistance (wet underground environment).
Comparison of international mainstream rail types:
Chinese standard: 60kg/m (e.g. CHN60), 50kg/m (CHN50) for heavy-duty high-frequency scenarios.
European standard: UIC60 (widely used in European metro), UIC54 (light rail or branch line).
North American Standard: AREMA 115RE/136RE (focusing on high strength and welding performance).
Japanese and Korean standards: JIS 50N, KR60, focusing on compact space adaptability.
Leader steel rail track suppliers from China, GloryRail steel rail products in strict compliance with international standards, to provide 60kg/m,kg/m and various over the standard (such as JISENDINGOST) steel rail products, to high-purity alloy steel as the core material, support rail customisation services.
Selection of rail clips in metro rail system
The function of rail clip in the metro rail system is mainly used to fix the rails and sleepers to prevent transverse or longitudinal displacement; provide elastic buffer to absorb the dynamic impact of the train.
The core requirements of metro rail clips:
Elastic fixation, dynamic stability, long life (free from frequent maintenance)
Main types and structure of rail presser
WJK Welding type rail presser: divided into three types: light rail, heavy rail and lifting rail, commonly used models include WJK-TG38, WJK-QU100, etc. Made of Q235 or Q345 material, it can withstand lateral force of 40-55kN, and is suitable for fixing steel crane beams and rails.
Spring type rail clip: easy to install, suitable for straight line section.
Hydraulic damping type: super vibration damping, suitable for sensitive areas (near hospitals)
Factors influencing the selection of rail presses in metro rail systems:
Type of track structure (ballasted/ballastless), ambient temperature and humidity (weather resistance of rubber parts), budget (whole life cycle cost)
The rail clip is the ‘anchor point’ of the track structure, which directly affects travelling safety. Their design needs to balance strength and adjustability. For example, on heavily loaded lines or curved sections, rail stabilisation needs to be ensured by high load capacity rail presses (e.g. QU series) to avoid the risk of derailment.
GloryRail offers a full range of rail presses: spring-loaded (V-Clip Pro), hydraulically damped (V-Shock) and intelligent monitoring presses (V-Sense) for ballasted and ballastless tracks. Customisation is supported.
Underground track system “skeleton”–rail sleeper
Rail sleeper is the metro rail system connecting rail and roadbed (or roadbed) of the core components, its role throughout the track structure of the mechanical support, geometric stability and system durability.
Common types of sleepers
Concrete sleeper: mainstream choice, long life (more than 50 years), suitable for ballast track.
Wooden sleeper: temporary line or shock absorption demand scene, but easy to moisture corrosion.
Steel sleeper: special environment (such as bridges, tunnels), but the cost is higher.
Nowadays, concrete sleepers are mostly used in metro system because of its good stability and durability.
Fastener system in metro rail system
It consists of fasteners, cleats, bolts, washers, etc. It is used to firmly fix the rails on the sleepers and at the same time to ensure the formation of an overall continuous structure between the various parts of the track.
Common types and structures of fastening systems
Elastic bar fastener system
The common types of snap fasteners include Ⅰ type, Ⅱ type, Ⅲ type and WJ-2 type.
WJ-2 type spring bar fastener
Adopting elastic separate design with iron pad, the buckling force is 4kN, and the spring range of front end is 11.5mm.
Equipped with composite rubber cushion to reduce friction, and insulating cushion board between the iron cushion board and the roadbed, it is suitable for ballastless track and high-speed railway.
It is suitable for ballastless track and high-speed railway. It has the ability to adjust the gauge ±10mm and height +30mm to meet the needs of different lines.
Fastener System
It consists of fastening plate, threaded studs, spring washers, etc. It was once widely used, but was gradually replaced by spring bar fasteners due to lack of elasticity.
Rail presses and fastening systems for rail stability
The rail press focuses on the lateral fixation and lateral force resistance of the rail, while the fastener system is responsible for the longitudinal restraint and elastic buffer of the rail. Together, they maintain the geometry of the rail when subjected to train loads, prolonging the life of the rail components and guaranteeing safety and comfort on the road.
The “foundation support” of the metro rail system – roadbed
Roadbed is the basic structural layer of the metro rail system located under the sleeper, usually composed of gravel, ballast or concrete and other materials. It plays multiple key roles in the track system, directly affecting the stability, durability and safety of train operation.
Ballast bed types and design points
Ballasted roadbed
Structure: It consists of gravel layer (thickness 250-300mm), ballast and roadbed.
Material requirements:
Crushed stone: basalt or granite, compressive strength ≥180MPa, particle size 20-50mm (to enhance the embedding force).
Containing dust rate <1% (to avoid slaking affecting drainage).
Advantages:
Flexible construction, easy to adjust the track geometry at a later stage.
Lower cost, suitable for ground section or low budget projects.
Disadvantages:
Frequent maintenance (regular consolidation and replenishment of gravel).
Not suitable for high-density routes (gravel is easily pulverised).
Ballastless track bed
Structure: consists of concrete track slab (C40-C60 strength), reinforcing mesh, vibration damping bedding and roadbed curing layer.
Type:
Prefabricated slab type: factory prefabricated track slabs, assembled on site, precision error ≤ 0.5mm.
Cast-in-place monolithic type: concrete is poured directly in the tunnel, reducing joints, but the construction period is long.
Advantages:
High stability, maintenance-free cycle can reach more than 30 years.
Suitable for elevated, tunnels and other space-constrained areas.
Disadvantages:
High initial investment (40-60% increase in cost compared to ballasted roadbed).
Difficult to repair (need to cut concrete).
The metro rail system is one of the core infrastructures of modern urban transport, and its design and operation directly affect the operational efficiency of the city and the quality of life of its residents. As the leader steel rail track suppliers from China, GloryRail supply the one-stop shop of railway system construction and guaranteed high quality rail products.
