Railway formation, substructure and superstructure

The railway track body is composed of different parts that have specific purposes and together make railway transportation safe, efficient, and robust.

The parts of the railway body consist of railway formation, substructure, and superstructure. An understanding of the standard regulations, design principles, and construction techniques of those parts is necessary to make a successful and working design and construct them fulfilling all essential requirements.

What is railway formation?

It is part of the railway infrastructure that provides support for the railway traffic and is either a natural ground or artificial ground that is made by excavating or constructing embankment fill. 

Railway formation is provided at the near ground level if the level of the ground is at the same level as the level of the track. If the level of the ground is lower then an embankment is constructed and if the level of the ground is higher the ground is excavated or cut.

Therefore, the terms embankment and cut refer to the construction parts that are involved in the related earthworks.

The railway formation is designed to provide the following functions:-

-Provide a stable, smooth, and uniform base for laying the tracks

-Withstand the loads from the traffic and transfer to the foundation safely

-Remove water from the railway tracks. 

Railway substructure

Railway substructure refers to the fundamental components that form the foundation and support system of a railway track. It plays a critical role in ensuring the stability, durability, and safety of the railway infrastructure. The substructure consists of various elements, including the formation,sub-ballast, and subgrade and drainage.

The formation refers to the natural or artificial level and compact prepared by cutting the ground or constructing an embankment with a suitable filling earth material. It provides the initial support and acts as a base for the entire substructure. The formation needs to be properly designed and prepared to ensure proper drainage and stability.

Below the ballast, there may be a layer of sub-ballast, which further enhances the stability and load-bearing capacity of the track system. Sub-ballast is typically made up of coarser materials like crushed rock or aggregate, providing additional support to the track and acting as a filter preventing movement of soil from subgrade to the ballast.

The subgrade is the layer of soil or natural ground beneath the formation. It forms the lowest part of the railway substructure and is responsible for distributing the loads from the track to the underlying soil and providing adequate support for the track with limited deflections. The subgrade needs to be adequately compacted and engineered to withstand the loads imposed by trains and maintain the track’s alignment and level.

Every deflection of the subgrade will be transmitted to the components in the track structure. Therefore, higher strength or stiffness or higher modulus of elasticity results in lower deflection. That is why adequate stiffness should be maintained in the subgrade material all year round.

The strength, stiffness, and total deflection of the subgrade can be improved by:

-Carefully selecting materials that are naturally strong (sand, gravel, boulders) with a high angle of internal friction.

-Limiting access to water to avoid the buildup of porewater pressure and subsequent reduction of strength.

-Improving the soil properties, using techniques such as compaction, in situ densification, grouting, and preloading.

-Maintain good drainage.

-Maintain stable subgrade geometry

Proper design, construction, and maintenance of the railway substructure are crucial to ensure a safe and efficient railway network. Factors such as soil type, drainage conditions, and climate play a significant role in determining the substructure requirements. Regular inspection, monitoring, and maintenance are essential to identify and address any issues promptly, such as track settlement, ballast degradation, or subgrade instability.

Railway superstructure

The railway superstructure refers to the essential components that make up the infrastructure of a railway track, ensuring its stability, safety, and functionality. It comprises various elements that work together to support the weight of trains, provide a smooth and durable running surface, and facilitate the safe movement of rolling stock.

The superstructure of the railway consists of the railway track, overhead contact power supply system, and the ballast that support directly the track components. Rails are long steel beams that form the running surface for the wheels of trains. They are carefully designed to withstand the forces exerted by rolling stock and provide a smooth and consistent ride. Sleepers, usually made of wood, concrete, or steel, are placed at regular intervals along the track to support and hold the rails in position. Fastenings, such as clips or spikes, secure the rails to the sleepers, maintaining their alignment and stability.

Ballast, a layer of crushed stone or gravel, is placed on top of the formation. It serves multiple purposes: distributing the loads from the train to the underlying layers, providing stable and uniform support, facilitating drainage, and reducing the effects of vibrations and impact forces. The ballast is carefully selected and compacted to meet specific engineering requirements.

To ensure safety and efficiency, the railway superstructure also incorporates a range of additional features. These include switches and crossings, which allow trains to change tracks, junctions, which enable trains to diverge or merge, and level crossings, where railways intersect with roads, requiring special safety measures.

The superstructure also includes bridges and tunnels, walls, and other engineering structures

Maintenance is crucial for the longevity and performance of the railway superstructure. Regular inspections, repairs, and replacements of worn-out components are necessary to prevent accidents and ensure a reliable and smooth railway network.

Types of railway formations design

Railway embankment design

Railway embankment design involves the engineering and construction of raised platforms or embankments to support railway tracks. It is an essential aspect of railway infrastructure, particularly in areas where the natural ground level is not suitable for track installation.

The design of a railway embankment takes into account several factors, including soil conditions, topography, drainage requirements, and load-bearing capacity. Engineers analyze the characteristics of the soil to determine its stability, strength, and settlement potential. This information helps in selecting appropriate embankment construction techniques and materials.

Topography plays a crucial role in embankment design, as it influences the alignment and slope of the embankment. Engineers assess the natural contours of the land and determine the most suitable route for the embankment. They consider factors such as gradients, curves, and obstacles to ensure a smooth and safe railway operation.

Proper drainage is a critical consideration in embankment design. Engineers incorporate effective drainage systems, such as ditches, culverts, and drainage pipes, to prevent water accumulation and subsequent erosion. Adequate drainage helps maintain the stability and integrity of the embankment, ensuring its long-term performance.

Load-bearing capacity is another crucial factor in embankment design. Engineers analyze the anticipated weight and dynamic forces exerted by trains and design the embankment to withstand these loads without significant settlement or deformation. They consider factors such as the type and frequency of trains, track configurations, and future growth projections.

Construction materials for embankments typically include compacted soil or engineered fill. The selection of materials depends on the specific site conditions and the desired embankment properties. Engineers ensure proper compaction and layering techniques during construction to achieve the required strength and stability.

Throughout the design process, engineers also consider environmental factors, such as the protection of habitats and mitigation of any potential ecological impacts. They work to minimize the disruption to natural ecosystems and, when necessary, implement appropriate measures for environmental conservation.

Railway cutting design

Railway cutting design refers to the planning and construction of excavated sections along a railway line, where the natural terrain is cut through to create a level pathway for the tracks. These cuttings are typically created in areas with elevated land or hilly terrain to maintain a consistent track alignment and gradient.

The design of railway cutting involves careful consideration of several factors. Firstly, the stability of the cut slope is paramount to ensure long-term safety and prevent landslides. Geotechnical engineers analyze the soil and rock properties to determine the appropriate slope angles and design measures such as retaining walls, terracing, or stabilization techniques to prevent slope failures.

Another important aspect of cutting design is the drainage system. Proper drainage is crucial to manage water runoff and prevent erosion within the cutting. Engineers incorporate features such as ditches, culverts, and channels to divert water away from the cutting and maintain its stability.

The design also takes into account the aesthetic integration of the cutting within the surrounding landscape. Where possible, efforts are made to blend the cutting into the natural contours of the land or use materials that complement the local environment. This helps to minimize the visual impact of the railway on the scenery and maintain the overall aesthetics of the area.

During the construction phase, heavy machinery and excavation techniques are employed to remove the excess soil and rock, creating the desired profile for the railway line. The excavated material is often used for embankments or other construction purposes, minimizing waste and reducing costs.

Railway cutting design plays a crucial role in ensuring the safe and efficient operation of trains. Proper planning and implementation of the cutting design result in a stable, well-drained, and visually pleasing railway corridor that seamlessly integrates with the natural landscape.

Railway embankment construction process

Railway formation involves the process of constructing the foundation and alignment for railway tracks. It involves the preparation of the ground, including the excavation, leveling, and compaction of the earth to create a stable and durable base on which the tracks will be laid. The railway formation plays a crucial role in ensuring the safety, stability, and longevity of the railway infrastructure.

The first step in railway formation is the surveying and design phase. Engineers assess the topography of the terrain and determine the optimal route for the railway tracks, taking into account factors such as gradients, curves, and obstacles. They also consider the soil conditions and drainage requirements to prevent waterlogging and erosion.

Once the alignment is finalized, the construction process begins. The first task is often earthwork, which involves the excavation of soil or rock to create a level surface. The excess material is typically used for embankments or cuttings along the route. This process requires heavy machinery such as excavators, bulldozers, and graders to shape the land according to the desired profile.

After the earthwork is completed, the formation undergoes a compaction process to ensure stability. Compaction involves using heavy rollers or compactors to compress the soil, eliminating air gaps and increasing its density. This helps prevent settlement and ensures that the formation can withstand the weight of the trains and the dynamic forces exerted during their operation.

Drainage is another critical aspect of railway formation. Proper drainage systems, including ditches, culverts, and drainage pipes, are installed to divert water away from the tracks and prevent waterlogging. Adequate drainage is essential to maintain the integrity of the formation and prevent erosion or softening of the soil.

In conclusion, railway formation construction encompasses the planning, excavation, leveling, compaction, and drainage of the ground to create a solid foundation for railway tracks. It is a critical process that ensures the safe and efficient operation of trains, while also accounting for factors such as topography, soil conditions, and drainage requirements.

What are the types of formations in railways?

In railway construction, there are generally three types of formations that are commonly used:

  1. Earth Formation: This type of formation involves excavating the natural ground to create a level surface for laying the railway tracks. Earth formation is suitable when the soil conditions are favorable, and the ground does not require extensive reinforcement. The excavated material may be used to create embankments or cuttings along the railway route, depending on the topography of the land.
  2. Embankment Formation: Embankment formation is used when the natural ground level is lower than the desired track level. It involves constructing raised platforms or embankments using fill materials such as compacted soil, rock, or engineered fill. Embankments are built to support the tracks and provide stability, especially in areas with low-lying or marshy terrain. Proper compaction and drainage systems are essential in embankment formation to ensure the embankment’s stability and prevent settlement.
  3. Cutting Formation: Cutting formation is the opposite of embankment formation. It is used when the natural ground level is higher than the desired track level. In this type of formation, the excess material is excavated to create a depression or cut along the railway route. The cut slopes are typically reinforced and stabilized to prevent landslides or erosion. Cutting formations are often necessary for hilly or mountainous areas where the tracks need to pass through ridges or elevated terrain.

These three types of formations can be combined and used in different sections of a railway line, depending on the local topography and engineering requirements. The choice of formation type is based on factors such as soil conditions, stability, drainage requirements, and the desired track alignment. Proper design and construction techniques are employed to ensure the safety, stability, and longevity of the railway infrastructure.

What are the 4 main parts of a railway?

The four main parts of a railway are as follows:

Tracks: Tracks form the foundation of the railway system. They consist of rails, sleepers (also known as ties or cross-ties), and ballast. Rails are long metal bars that provide a smooth surface for train wheels to run on. Sleepers are placed at regular intervals along the track to hold the rails in position and provide stability. Ballast, typically made of crushed stones, is spread over and around the sleepers to distribute the loads, provide drainage, and maintain track stability.

Rolling Stock: Rolling stock refers to the vehicles that operate on the railway tracks. This includes locomotives, which provide the power to move the train, and various types of cars or wagons that transport passengers or freight. Rolling stock can range from traditional steam or diesel locomotives to modern electric or high-speed trains. Each vehicle is designed to perform specific functions and has its own set of components, including engines, brakes, control systems, and passenger or cargo compartments.

Signaling and Control Systems: Signaling and control systems are crucial for ensuring the safe and efficient operation of trains on the railway network. They include various devices, such as signals, switches, and interlocking systems, that control the movement of trains and facilitate the coordination of traffic. Signals provide visual indications to train operators, indicating whether it is safe to proceed or stop. Interlocking systems prevent conflicting movements and ensure that trains can safely cross paths or change tracks without collisions.

Infrastructure and Stations: The railway infrastructure comprises the physical structures and facilities that support the railway system. This includes stations, platforms, bridges, tunnels, level crossings, and maintenance depots. Stations serve as the points of embarkation and disembarkation for passengers, providing ticketing services, waiting areas, and access to trains. Bridges and tunnels allow trains to traverse obstacles such as rivers, valleys, or urban areas. Level crossings are points where roads intersect with the railway, and appropriate safety measures are implemented to manage the interaction between trains and road traffic.

These four main components work together to create a functioning railway system, enabling the safe and efficient transport of passengers and goods over long distances. Each component plays a vital role in ensuring the smooth operation of the railway network.

Difference between embankment and cutting

The main difference between an embankment and a cutting in railway construction lies in their respective positions and the way they are formed:


An embankment is a raised platform constructed above the natural ground level.

It is created by adding layers of compacted fill material, such as soil, rock, or engineered fill, to raise the ground level.

Embankments are typically built when the natural ground level is lower than the desired track level. The purpose of an embankment is to provide a stable and level surface for the railway tracks to be laid upon.

Embankments are often used to traverse low-lying or marshy areas, allowing the tracks to pass above the water table. Adequate compaction and drainage systems are crucial in embankments to prevent settlement and ensure stability.


A cutting, also known as an excavation or a trench, is a depression or channel created by removing or excavating material from the natural ground.

Cuttings are made when the natural ground level is higher than the desired track level.

The excess material is removed to create a depression along the railway route, and the remaining slopes are typically reinforced and stabilized.

Cuttings are used to allow the tracks to pass through elevated terrain, hills, or mountains.

Cuttings help provide clearance for the tracks and maintain a consistent track level without requiring extensive embankments.Proper slope stabilization and drainage systems are essential in cuttings to prevent landslides, erosion, and water accumulation.

In summary, an embankment is a raised platform constructed above the ground level, while a cutting is an excavation or trench created by removing material from the ground. Embankments are used when the ground is lower than the desired track level, while cuttings are made when the ground is higher. Embankments provide a stable surface for track installation, while cuttings allow the tracks to pass through elevated terrain or hills.

Railway drainage

Railway drainage refers to the system of channels, pipes, and structures designed to manage and control the flow of water on railway tracks and surrounding areas. It is a crucial aspect of railway infrastructure as proper drainage ensures the safety, stability, and longevity of the tracks and associated structures.

The primary purpose of railway drainage is to prevent water accumulation and minimize the negative effects of water on the tracks. Effective drainage systems help in avoiding waterlogging, erosion, and softening of the soil, which can lead to track instability, settlement, and even derailments.

Railway drainage systems typically include the following components:

Trackside Ditches: Ditches are excavated alongside the tracks to collect and channel water away from the track area. They provide a path for surface water to flow, preventing it from pooling on the tracks.

Culverts: Culverts are structures installed underneath the tracks to allow the passage of water from one side to the other. They are typically made of concrete, steel, or other durable materials and are designed to handle the expected water flow without causing blockages.

Drainage Pipes: Drainage pipes are used to collect and divert water from the trackbed. These pipes are installed beneath the track formation and connect to the ditches or culverts. They are essential for managing subsurface water and preventing its accumulation in the track area.

Drainage Outlets: Drainage outlets or discharge points are designed to release the collected water safely away from the railway infrastructure. These outlets can be designed as open channels, discharge basins, or connections to natural drainage systems such as rivers or watercourses.

Proper maintenance and regular inspections of the railway drainage system are essential to ensure its effective functioning. It involves clearing debris, removing sediment, and checking for any blockages or damage to culverts, pipes, and ditches.

By efficiently managing water flow, railway drainage systems help in maintaining track stability, preventing erosion, and reducing the risk of flooding. They play a vital role in ensuring the safe and reliable operation of trains by minimizing the impact of water on the railway infrastructure.

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