Permanent Way: Components & Types | Civil Engineering Optional Notes for UPSC PDF Download

Evolution of Rails, Sleepers, and Attachment Methods in Railways

The development of manufacturing technology has significantly impacted the design, production, and installation of rails, sleepers, and attachment methods in railways.

• Early Rail Technology: In the 1790s, railways used cast iron rails measuring 4 feet (1.22 m) long. By 1820, wrought iron rails, 15 feet (4.57 m) in length, had replaced them.
• Introduction of Steel Rails: In 1857, the first steel rails were manufactured, marking a significant advancement. Subsequently, standard rail lengths increased from 30 to 60 feet (9.14 to 18.29 m).
• Sleepers and Materials: Railway sleepers, traditionally made of Creosote-treated hardwoods, have been a constant feature, providing support for the rails.
• Modern Innovations: In the mid-1960s, the United Kingdom introduced continuous welded rail, followed by the adoption of concrete rail.
• Rail Joining and Fastenings: Rails are permanently joined through welding or fish plates and are secured onto sleepers using various types of fastenings.
• The Permanent Way: The combination of rails, sleepers, ballast, and subgrade forms the permanent way. This also includes track and bridge infrastructure such as retaining walls, drainage systems, access roads, cuttings, embankments, and tunnels.

The Permanent Way in Railways

The permanent way is a critical component of railway lines, comprising pairs of rails laid on sleepers or ties embedded in ballast. This infrastructure is designed to support and guide trains efficiently. The term "permanent way" originates from the early days of railway construction when temporary tracks were laid to transport materials during construction. Once construction was nearly complete, these temporary tracks were replaced with the permanent way.

Components of the Permanent Way

1. Rails: Rails are the primary load-bearing elements of the track. They are typically made of steel and are laid parallel to each other, forming the track's running surface.

2. Sleepers: Sleepers, also known as ties, are rectangular supports that hold the rails in place and distribute the loads from the rails to the underlying ballast and subgrade. Traditionally made of wood, concrete and steel sleepers are also used in modern railways.

3. Ballast: Ballast is a layer of coarse stone or gravel that is placed beneath the sleepers to distribute the load from the rails and provide stability to the track. It also helps with drainage and reduces the growth of weeds.

4. Fastenings: Rails are joined together using welding or fish plates, and they are fastened to the sleepers using various types of fasteners such as clips, bolts, and screws. These fastenings ensure that the rails remain in place and maintain proper alignment.

5. Formation: The subgrade or formation is the prepared ground on which the track is built. It provides a stable foundation for the track and helps with drainage.

6. Track Infrastructure: The permanent way also includes other infrastructure such as turnouts, crossings, bridges, and tunnels, which are essential for the safe and efficient operation of the railway line.

The proper construction and maintenance of the permanent way are essential for the safe and efficient operation of railway lines. Regular inspections and maintenance are carried out to ensure that the track is in good condition and meets the required standards for safe train operation.

Requirements of an Ideal Permanent Way 

An ideal permanent way is essential for the safe and efficient movement of passengers and freight. The following are the requirements of an ideal permanent way : 

• A uniform and correct gauge are necessary.
• The level of both the rails should be the same on a horizontal track.
• At the curved locations, superelevation in a permanent way must be provided properly by raising the outer rail of the track.
• The design of the permanent way should be done in such a way that the load is uniformly distributed between two rails. 
• The track should possess the required elasticity and lateral strength.
• All joints, points and crossings should be properly designed in a permanent way.
• The drainage system must be properly installed.
• Scope for maintenance and renewables must be provided.

Rails in the Permanent Way

Rails are the foundational element of railway tracks, providing a smooth surface for trains to travel on and serving as lateral guides during turning operations. They bear the vertical loads of trains, transmitting these loads to the ballast and, ultimately, to the subgrade and formation. Rails are typically made of steel girders, ensuring strength and durability.

Types of Rails

1. Double-Headed Rails (D.H. rails): Initially widely used, these rails had the same dimensions at the foot and head. However, their design proved flawed as their foot became corrugated under wheel loads, rendering them unsuitable for reuse. They are no longer used by Indian Railways.

2. Bull Headed Rails (B.H. rails): These rails have larger head dimensions than foot dimensions, providing better strength and alignment. They require chairs to keep them in place and are particularly useful for points and crossings, although they require heavy maintenance.

3. Flat Headed Rails (F.H. rails): Invented by Charles Vignole in 1836, these rails have flat feet rolled flat. Initially thought to be fixable directly to wooden sleepers, they required steel bearing plates to prevent sinking into the sleepers under heavy loads. They are commonly used in India.

Sleepers in the Permanent Way

Sleepers are transverse members placed beneath the tracks to support them and maintain their position. They transmit the loads from the rolling stock to the ballast and formation subgrade. Sleepers also provide an elastic medium between the rails and ballast, helping to distribute loads evenly.Types of Sleepers

1. Wooden Sleepers: These are the only acceptable sleepers for track circuiting due to their insulation properties and meeting all criteria for good sleepers. They are made from woods like Sal, Teak, Deodar, and chair wood.

2. Steel Sleepers: Composed of steel throughs, these sleepers have ends bowed down to prevent ballast from escaping. They come in key type and clip and bolt type varieties.

3. Cast Iron Sleepers: Made from cast iron, these sleepers are widely used globally. The CST-9 type is the most common.

4. RCC Sleepers: Reinforced concrete sleepers are stable and low-maintenance, suitable for high-speed rails. They are often prestressed to withstand high pressure.

5. Composite Sleepers: Made from waste plastic and rubber, these sleepers are eco-friendly, recyclable, and have a service span of over 50 years.

Ballast in the Permanent Way

Ballast is a granular material, often broken stone, placed on top of the railway formation and around the sleepers. It provides elasticity to the track, drains water, prevents weed growth, and helps distribute axle loads evenly to the subgrade.Types of Ballast

• Materials used for ballast in India include broken stone, gravels, sand, blast furnace slag, murrum, cinder, and broken bricks. Good ballast should resist crushing, be durable, provide adequate drainage, and be chemically inert.

Fixtures and Fastenings

• These components join rail to rail and rail to sleepers, maintaining track alignment and providing expansion gaps. 
• Types include fish plates, bearing plates, spikes, chairs, bolts, keys, and anti-creepers, each serving a specific function in ensuring the stability and safety of the track.