Pre-Cast Slab Track Approved For HS Lines - Germany: Track

International Railway Journal, Nov, 2001

Max Bogl Germany, has developed its own slab track system for high-speed railways, called FF Bogl. This uses pre-cast concrete panels which are connected. This means that the track can be opened to traffic more quickly than site-placed slab track and it is possible to replace the slabs relatively easily.

THE German civil engineering company, Max Bogl has adopted a pre-cast solution to slab track design compared with the Rheda and Zublin systems which require in-fill concrete to be poured on site once the track has been laid. Following trials with FF Bogl, Max Bogl now has general approval from German Rail (DB) to install the system on the DB network for operation up to 300km/h.

The first trial with Max Bogl's pre-cast slab track took place in 1977 on a 430m section of line near Karlsfeld designed for 160km/h operation. Pre-stressed pre-cast panels 4.76m long were joined together longitudinally. According to Max Bogl the section has not required maintenance or repair since it was laid despite carrying up to 100,000 tonnes of traffic a day.

More recently, a 735m-long test section (656m long excluding transition sections) was laid in 1999 at Rot-Malsch on the Karlsruhe--Heidelberg line to test the method of installation and behaviour of the track. Measuring devices were installed at varying depths at two cross-sections to record oscillation speeds, bearing pressures, and vertical elastic displacements.

According to Max Bogl, the measurement results generally indicated favourable behaviour regarding the dynamic loading. To check the amount and deformation behaviour of the slab track, the vertical deflection of the rail and panels were determined using a Benkelmann beam inspection tool moving along the track. "The results indicate a uniform behaviour of the deflections over the entire test section," says Max Bogl "This confirms a uniform load transfer of the permanent way."

Reduced Slab Width

A few months later, another test section was laid at Hattstedt on the Elmshorn--Westerland line in northern Germany. The 305m section had 33m of straight track, 145.2m transition curves, and a 36.8m curve with a radius of 920m. For this demonstration, the slab width was reduced from 2.8m to 2.55m and the slabs were made from steelfibre concrete. The slab track was laid on a 300mm thick asphalt base instead of a hydraulically-stabilised layer. According to Max Bogl, this test section demonstrated that pre-cast slabs can ensure exact alignment in curves and transition curves.

Work will start next year on the so-called Hipa (high-performance) track project in Ban, Italy, where a 500m test section will be laid. The objective is to develop pre-cast slab track into a continuously-supported permanent way. The area has a temperature range of 5 to 50[degrees]C. Max Bogl and the Fraunhofer Institute are leading the team which also includes Italian Rail Network (RFI), Milan Polytechnic, Thyssen, Germany, and Swietelsky, Austria.

FF Bogl consists of 200mm-deep prestressed panels 6.45m long. During manufacture, variations in specific track alignment are taken into account, and rail fastenings are fitted. Adjusting devices built into the slabs enable them to be aligned laterally and vertically.

On site, the slabs are lowered into position by crane. Rails are attached. The panels are aligned using a long-chord lining system and jacking screws fitted to the slabs. A bitumen-cement grout is poured through openings to flow beneath the slabs. When this has set, the joints between the panels are also grouted. Turn-buckles, connected to the threaded reinforcing bars protruding from the slab ends, are then tightened to connect the slabs together. FF Bogl has a construction height of 474mm.

Max Bogl estimates that it should be possible to lay up to 650m of slab track a day. Once the track has been aligned correctly, it should be operational within two hours.

FF Bogl can be corrected if problems occur such as settlement near bridges or on embankments. It is possible to cut under the slabs and inject new filler material to raise the level of the track.

Max Bogl is also developing a slab track system for light rail use.