Many of the European railways have been designed for completely different traffic conditions than thoserequired today. Upgrading of existing railway lines for higher axle loads and speeds requires new modernmethods for in situ investigation of the railway ballast and substructure. Combination of continuousmeasurements of track geometry quality and non-destructive methods like dynamic track stiffness and Ground Penetrating Radar (GPR) can be a good example of obtaining the important information about theconditions of existing railways. A new methodology for evaluation of all available measurementscompleted with results from geotechnical investigations is proposed to study problems dealing with railway structure and subgrade in case upgrading or maintenance work is required.
Railway investigations using Banverket´s Rolling Stiffness Measurement Vehicle (RSMV) equipped withGPR, and a methodology of comprehensive evaluation of all relevant available information have beentested on a few railway lines in Sweden since 2002. Results from these investigations are used forassessment of the root cause of existing or possible future problems with repeated track maintenance,settlement and stability when upgrading a track for higher axle load and/or speed.
The paper presents practical results of investigations and a new methodology to evaluate several types ofmeasurements in comparison with real track – substructure conditions. Suggestions on upgradingactivities are given for a case study of 25 km of track with a planned increase of axle load from 22.5 to 25metric tons. The goal is to minimize the upgrading and maintenance cost in a Life Cycle Cost (LCC)perspective.