Gravel

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Track position on the platform before and after the ballast

As high gravels or Aufschottern is called the lifting of a track, and thus the top of the rails by filling the track bed with gravel.

In tram construction , subway sections that are initially to be traveled on in advance of the light rail operation are graveled to avoid reconstruction of the platforms when switching to subway operation. From the beginning, platforms for high-floor underground vehicles are built, but then the ballast bed of the track is raised by gravel so that conventional trams with low entry and light rail trains with folding steps can serve the platforms and the entire length of the platform can be used remains.

The ballasting up and later removal of the ballast is much less time-consuming and therefore cheaper than converting the platform, since the installation and removal of the track and the filling and removal of the ballast can be carried out efficiently and largely automatically using special track construction machines . The disadvantage is that tunnels have to be built higher in order to provide a sufficient clearance profile even after being graveled .

An alternative to high-ballasting is the installation of divided platforms with high and low sections, which, compared to high-ballasting, shortens the usable platform length for individual trains, but allows more flexible vehicle use. Split platforms were installed in some stations of the Stuttgart Stadtbahn , for example .

Like many provisional arrangements, heavily graveled tunnel sections often exist for a long time or permanently if the final extension to the subway is not completed or has been postponed for political and financial reasons.

Examples

High gravel platforms are, for example, in the Bochum Hauptbahnhof subway station , level -3. On two parallel central platforms, the two outer tracks are graveled, while the inner tracks are used as normal elevated platforms.

A particular example of the achievable by high flexibility gravels is the station Köln-Chorweiler the rail Cologne , which was hochgeschottert of its opening 1973 to 1995 and was operated with tram line 9 with a low entry. For a line changeover in 1995, the track was lowered by 55 cm in order to be able to serve the station with high-floor trams on line 18. In the course of a further line reform in 2001, Chorweiler was again added to the low-floor network, then again graveled in the summer of 2007 and since then approached by low-floor trams with an entrance height of 35 cm.