Causes, effects and control of seasonal frost action in railways

Seasonally cold climate and resulting frost action set great demands to railway track substructure in order to maintain track geometry. Challengesculminate on high-speed lines, where the tolerances for roughness are the tightest. Problems may result in highly increased trackmaintenance and need for temporary speed restrictions. The causes of frost action can be associated with subsoil, subballast or ballast. Themajor concern in frost protection is to avoid the freezing of frost susceptible subsoil by using sufficient thickness of subballast and relying onnon-frost-susceptible subballast material. This paper provides an overview of the main research findings on the role of ballast, subballast andsubsoil in frost action. In new construction the material specifications, design procedures and construction methods have been developed toensure adequate performance of track substructures, but special challenges exist in managing existing tracks that were not designed formodern requirements. In order to perform cost-effective and sustainable track maintenance, it is necessary to recognize the problem areas anddefine the root-causes of problems. For locating the problem sections and defining the causes of defects, a sophisticated analysis based onintegration of track geometry and ground penetrating radar (GPR) data has been developed and is summarized in this paper.