INTRO: Inventor Peter Küsel wanted to ’fix the vertical stability of track’; his technique has been chosen for a 25 km section of main line being relaid in Namibia

BYLINE: Braam Le Roux*

BYLINE: * Braam Le Roux is President of Dynamic Rail Services in South Africa. He was previously Chief Executive of Spoornet

TUBULAR Track is a ballastless trackform consisting of twin reinforced concrete beams laid on a specially-designed formation, and held in place with galvanised steel gauge bars spaced to suit lateral forces. The design is optimised to meet specified axleloads, annual tonnages, speeds and the prevailing geotechnical conditions.

Rails are continuously supported and fixed using proprietary fastenings to shoulders which are welded to the gauge bars as well as to intermediate elements positioned between the gauge bars. These components encircle the beams, and are not cast into them, which results in all forces applied to the beams being in compression. The fact that components encircle the beams also means that they can be readily replaced should they be damaged. Another advantage is that they are not liable to work loose under the influence of dynamic forces, as would be the case if they were cast into the beams.

Resilience is provided by the use of continuous resilient pads placed between the rails and the beams. These are supplied by British manufacturer Tiflex.

Conventional track problems

While conventional ballasted track has undergone many improvements with different sleeper types and better quality, some inherent problems have never been completely solved, in particular the progressive degradation of the track structure under repeated dynamic loading. This is manifested in several ways: