Revision of the French reference document of frost design method for High Speed Railway Lines.

Résumé

The revision of the project of typical railway structure s catalog has lead Société Nationale des Chemins de Fer français (SNCF) to consider a modernization of its “frost design method”. In particular, high speed railways required very severe levelling margins. Very high speeds need perfect evenness to prevent any defect of lengthwise level, which would generate unballasting risk and vertical movement injurious for the lifetime of structures. A collaboration has been engaged with the Laboratoire Régional des Ponts et Chaussées (LRPC) de Nancy. The aim was to build a new technical SNCF reference document using the design pavement method developed by the network of Laboratoires des Ponts et Chaussées. during the past three decades. This approach is based on thermal modelling of structures and winter characterization through the freezing index concept.
The process followed for the realization of this document consisted in reproducing the scheme employed for the road frost design method, adjusting it to the railway problematic. Indeed, besides use’ specifities, rain penetrates railway structures. Energy exchanges are enhanced with atmosphere, the water continuously modifying physical properties of railway components. Moreover, use of atypical materials for roads builders, such as ballast, obliged additional laboratory tests in order to know their physical properties and thermal behavior.