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In transport engineering, subgrade is the native material underneath a constructed road, [1] pavement or railway track (US: railroad track). It is also called formation level . The subgrade provides support to the subbase level and acts as an integral load-bearing layer.
A railway track (CwthE and UIC terminology) or railroad track (NAmE), also known as permanent way (CwthE) [1] or "P Way" (BrE [2] and Indian English), is the structure on a railway or railroad consisting of the rails, fasteners, sleepers (railroad ties in American English) and ballast (or slab track), plus the underlying subgrade.
Section through railway track and foundation showing the sub-grade. Grading in civil engineering and landscape architectural construction is the work of ensuring a level base, or one with a specified slope, [1] for a construction work such as a foundation, the base course for a road or a railway, or landscape and garden improvements, or surface drainage.
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It is designed primarily to reduce the stress on the subgrade. Other definitions include the surface of the ballast on which the track is laid, [ 1 ] the area left after a track has been dismantled and the ballast removed [ 1 ] or the track formation beneath the ballast and above the natural ground.
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This article provides a list of operational and under construction (or approved) high-speed rail networks, listed by country or region. While the International Union of Railways defines high-speed rail as public transport by rail at speeds of at least 200 km/h (124 mph) for upgraded tracks and 250 km/h (155 mph) or faster for new tracks, this article lists all the systems and lines that ...
The railway track or permanent way is the elements of railway lines: generally the pairs of rails typically laid on the sleepers or ties embedded in ballast, intended to carry the ordinary trains of a railway. It is described as a permanent way because, in the earlier days of railway construction, contractors often laid a temporary track to ...