Introduction
Track is the ba upon which the railway runs. To give a train a good ride, the track alignment must be t to within a millimeter of the design. Track design and construction is part of a complex and multi-disciplinary engineering science involving earthworks, steelwork, timber and suspension systems - the infrastructure of the railway. Many different systems exist throughout the world and there are many variations in their performance and maintenance. This page looks at the basics of infrastructure and track design and construction with drawings, photos and examples from around the world. Some information was contributed by Dan McNaughton, Simon Lowe and Mike Brotzman.
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Background - Basic Construction - The Sub-Structure - Ballast - Track - Sleepers (Ties) - Rails - Rail Welding - Gauge - Modern Track Forms - Ballasted vs Non-Ballasted Track - Structures - Gauging - Monuments and Datum Plates - Curves - Cant - Turnouts - Crossings - Types of Turnouts - Examples of Turnouts. 哺乳期可以烫发吗
Background
The track is a fundamental part of the railway infrastructure and reprents the primary distinction between this form of land transportation and all others in that it provides a fixed guidance system. The track is the steering ba for the train and has evolved from an ancient design of vehicle guidance with origins dating, some historians have suggested, from the Sumerian culture of 2000 BC. The modern railway version is bad on the steel wheel running on a steel rail. Other forms of guided vehicle technology exist; rubber-tyred trains, magnetic levitation and guided busways, for example, but the are not dealt with here. There is a good description of the French-bad rubber tyred train technology available at The Rubber Tyred Metro.
Basic Construction（this fucking pic！）
Track is the most obvious part of a railway route but there is a sub-structure supporting the track which is equally as important in ensuring a safe and comfortable ride for the train and its pasngers or freight. The infrastructure diagram here shows the principal parts of an electrified, double-track line.
The total width across the two-track alignment will be about 15 m (50 ft) for a modern formation. The "cess" shown each side of the alignment is the area available for a walkway or refuge for staff working on the track.
九江煎堆The Sub-Structure
This part of the road consists of three main elements; the formation, the sub-ballast and the ballast. The formation is the ground upon which the track will be laid. It can be the natural ground level or "grade" or it can be an embankment or cutting. It is important that the formation is made of the right materials and is properly compacted to carry the loads
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The formation under the track has a "camber" rather like that en on a roadway. This is to ensure ea of water run-off to the drains provided on each side of the line. The track itlf is supported on "ballast", made up of stones - usually granite or, in the US, basalt - below which is a layer of sand, which parates it from the formation. For new or renewed formations, the sand is normally laid over some sort of geotechnical screen or mesh to parate it from the foundation material below. In the past, asphalt or plastic sheeting has been ud to prevent water epage.
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Catenary masts (if the line is electrified on the overhead system) are located outside the drains and, beyond them, there is a walkway area. This may just be a cleared path for staff to walk safely, avoiding passing trains or, on modernid routes, a properly constructed path. Next to this path will be a cable trough. The were originally concrete but are nowadays often made of plastic. Cables crossing the track are protected by a plastic tube, usually bright orange in the UK. Proper cable protection is esntial to prevent damage by animals, track maintenance tools, weather and fire.
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Usually, the edge of the railway property is outside the pathway or cable runs. If the line is built through an area requiring an embankment or cutting, the slopes will be carefully designed to ensure that the angle of slope will not take an excessive width of land and allow proper drainage but without risking an earth slip. The slope angle depends on the type of soil available, the exposure, the climate and the vegetation in the area. Drainage ditches are often added along the edges of cuttings and embankments. In the UK, fences are always provided along the boundary line of the railway to protect the public from wandering onto the track. Even so, there are a few accidents every year when trespasrs are killed or injured by trains or electric conductor rails. Many countries around the world don't fence their railways, assuming people will treat them like roads and look both ways before crossing. They don't.
Ballast
Ballast is provided to give support, load transfer and drainage to the track and thereby keep water away from the rails and sleepers. Ballast mustsupport the weight of the track
帅气男生壁纸and the considerable cyclic loading of passing trains. Individual loads on rails can be as high as 50 tonnes (55 US or short tons) and around 80 short tons on a heavy haul freight line. Ballast is made up of stones of granite or a similar material and should be rough in shape to improve the locking of stones. In this way they will better resist movement. Ballast stones with smooth edges do not work so well. Ballast will be laid to a depth of 9 to 12 inches (up to 300 mm on a high speed track). Ballast weighs about 1,600 to 1,800 kg/cu/m. See also Ballasted vs Non-Ballasted Track below.更好的拼音
Track
The usual track form consists of the two steel rails, cured on sleepers (or crossties, shortened to ties, in the US) so as to keep the rails at the correct distance apart (the gauge) and capable of supporting the weight of trains. There are various types of sleepers and methods of curing the rails to them. Sleepers are normally spaced at 650 mm (25 ins) to 760 mm (30 ins) intervals, depending on the particular railway's standard requirements.
