New developments in the construction of railway track bases without ballast

The conventional form of construction for permanent way, as first conceived about ISO years ago, adopted the ballast bed for supporting the railway track from what at that time was the most economical road building method, namely, macadam. By the same token, a p:esent-day innovative form of permanent way construt~ on should adopt the principle of the multi-layer pavement structures which have proved successful on motorways even under the heaviest traffic. The ballastless permanent way with elastic rail supports on a load-distributing slab actualizes this concept. The German Federal Railways have had experience with the ballastless concrete slab permanent way since 19~7. The fo:m of construction first employed at the ra~lway stat~on of Rheda in 1972, using prestressed concrete sleepers (rail ties) embedded in concrete has proved particularly satisfactory. The experien~e ga~ned with this system is reported. This substantially ma~ntenance-free permanent way is characterized by a reduction of the dynamic forces exerted by the wheels at speeds above 200 km/h. The drawback of the higher cost of construction is eliminated when this type of pe:manent way is installed in the vicinity of tunnels, br~dg~s and ~ther structures, because a supporting slab ~s prov~ded there anyway. For this reason the application of this construction method is par~icularl~ attractive on some new sections of railway line w~th a 39% proportion of civil engineering works. At present, this permanent way is being installed in two ~jor tunnels with lengths of 5501 m and 1127 m respect~ vely. Of particular importance are the design of points (switches), the structural transition from ballastless t~ ordinary ballast permanent way, the absorption of a~rborne sound and the devising of a suitable procedure for permanent way renewal after expiry of its service life. Structural possibilities and new developments are reported. Another field of application is in underground railways, more particularly in combination with elastically supported mass-spring systems whereby structureborne sound emission is reduced. The forms of construction used for the underground and the urban railway systems at Munich and Hamburg are described.