Preparing The Trackbed
The work on a high-speed line (ligne à grande vitesse, or LGV) begins with earthmoving. The trackbed is carved into the landscape, using scrapers, graders, bulldozers and other heavy machinery. All fixed structures are built; these include bridges, flyovers, culverts, game tunnels, and the like. Drainage facilities, most notably the large ditches on either side of the trackbed, are constructed. Supply bases are established near the end of the high-speed tracks, where crews will form work trains to carry rail, sleepers and other supplies to the work site.
Next, a layer of compact gravel is spread on the trackbed. This, after being compacted by rollers, provides an adequate surface for vehicles with tyres. TGV tracklaying then proceeds. The tracklaying process is not particularly specialized to high-speed lines; the same general technique is applicable to any track that uses continuous welded rail. The steps outlined below are used around the world in modern tracklaying. TGV track, however, conforms to stringent requirements on materials, dimensions and tolerances.
Read more about this topic: TGV Track Construction
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