Теміржол төсегінің тасымалы (Temirjol tösegińin tasymaly)

Trackbed upon which railway ties are laid

Track ballast is the material which forms the trackbed upon which railroad ties (UK: sleepers) are laid. It is packed between, below, and around the ties. It is used to bear the compression load of the railroad ties, rails, and rolling stock; to facilitate drainage; and keep down vegetation that can compromise the integrity of the combined track structure. Ballast also physically holds the track in place as the trains roll over it. Not all types of railway tracks use ballast. A variety of materials have been used as track ballast, including crushed stone, washed gravel, bank run (unwashed) gravel, torpedo gravel (a mixture of coarse sand and small gravel), slag, chats, coal cinders, sand, and burnt clay. The term "ballast" comes from a nautical term for the stones used to stabilize a ship.

The appropriate thickness of a layer of track ballast depends on the size and spacing of the ties, the amount of traffic on the line, and various other factors. Track ballast should never be laid down less than thick, and high speed railway lines may require ballast up to thick. An insufficient depth of ballast causes overloading of the underlying soil, and in unfavourable conditions, overloading the soil causes the track to sink, usually unevenly. Ballast less than thick can lead to vibrations that damage nearby structures. However, increasing the depth beyond confers no extra benefit in reducing vibration. In turn, track ballast typically rests on a layer of sub ballast, small crushed stones which provide a solid support for the top ballast and reduces ingress of water from the underlying ground. Sometimes an elastic mat is placed between the sub ballast and ballast, significantly reducing vibration. Ballast can only be cleaned so often before it is damaged beyond re use. Ballast that is completely fouled can not be corrected by shoulder cleaning. One method of "replacing" ballast is to simply dump fresh ballast on the track, jack the whole track on top of it, and then tamp it down. Alternatively, the ballast underneath the track can be removed with an undercutter, which does not require removing or lifting the track. Chat Moss in the United Kingdom is similar. Regular inspection of the ballast shoulder is important. The shoulder acquires some amount of stability over time, being compacted by traffic, but maintenance tasks such as replacing ties, tamping, and ballast cleaning can upset that stability. After performing those tasks, it is necessary either for trains to run at reduced speed on the repaired sections, or to employ machinery to compact the shoulder again. If the trackbed becomes uneven, it is necessary to pack ballast underneath sunken ties to level the track again, which is usually done by a ballast tamping machine. A more recent, and probably better,

The quantity of ballast used tends to vary with gauge, with the wider gauges tending to have wider formations, although one report states that for a given load and speed, narrowing the gauge only slightly reduces the quantity of earthwork and ballast needed. The depth of ballast also tends to vary with the density of rail traffic, as faster and heavier traffic requires greater stability. The quantity of ballast also tends to increase over the years as more and more ballast is piled onto an existing roadbed. Some figures from an 1897 report listing requirements for light railways (usually narrower than standard gauge) are:

first class line – rail – second class line – rail – third class line – rail – .