Application of in situ polyurethane geocomposite beams to improve the passive shoulder resistance of railway track

Abstract

Recent research has highlighted the effect of the individual contributions of the crib, shoulder, and base resistance to the lateral behaviour of a typical railway sleeper under loading. The contribution of the shoulder ballast has been seen to provide around 30 per cent of the lateral resistance for an unloaded sleeper. The addition of extra ballast in the shoulder area provides a very limited increase in lateral sleeper resistance. It is common in areas of high lateral loading, such as switch and crossings, to provide sleeper end plates to improve the passive resistance of the track. Sleeper end plates have, however, many disadvantages, not least is the need to disturb the ballast in order to facilitate their installation. The application of polyurethane reinforcement of the ballast shoulder to rapidly form an in situ GeoComposite shoulder beam (geobeam) has many advantages over end plates, including the ability of the lateral beam to be installed directly after the track geometry has been corrected; the lateral track geometry can then be ‘captured’ at installation. The beam can also be formed while the trains are still running. In this article the application of lateral GeoComposite side beams to improve the passive resistance of the shoulders is illustrated through analytical and numerical analysis. The application of the technique to actual problem sites is also presented and the performance of the technique at the Harford bridge transition site discussed.