Trackbed

Trackbed refers to the prepared foundation upon which railway tracks are laid. It is a critical component of the railway infrastructure, designed to support the weight of passing trains, distribute loads evenly, and maintain the stability and alignment of the track. The trackbed typically consists of several layers, beginning with the formation, which is the natural ground or excavated earth that has been graded and compacted.

Above the formation lies the sub-ballast layer, often composed of crushed stone or gravel, which acts as a drainage layer and helps to prevent the fine particles of the ballast from mixing with the formation. The ballast, the most visible layer of the trackbed, is usually made of angular, crushed stone. It serves to support the sleepers (ties), distribute the load from the sleepers to the sub-ballast and formation, provide drainage, and allow for adjustments to the track's level and alignment.

The design and construction of the trackbed are crucial for ensuring the safety, ride quality, and longevity of a railway line. Factors such as soil type, climate, and expected traffic loads influence the specific materials and construction methods employed. Proper maintenance of the trackbed, including ballast cleaning and tamping, is essential to preserve its structural integrity and operational efficiency.