Monitoring the Vertical Deformation Behaviour of Road and Railway Structures

Research output: Book/ReportDoctoral thesisMonograph


Vertical deformation in road and railway structures acts in many ways as an indicator of structural integrity. Traffic loading causes a vertical displacement (i.e. deflection), the magnitude of which indicates the structure’s ability to withstand the effects of external loads. Deflection varies lengthwise across a road or railway structure, and the variation in deflection indicates the ability of different cross-sections to withstand traffic loading. Temporal deflection variation, in contrast, indicates a change in the structure’s integrity or in the surrounding conditions. Furthermore, the structure itself can be affected by freezing, compaction or settlement and these phenomena, together with traffic loading, will result in unevenness over time.
Deformations caused by traffic loading are mainly recoverable, but a small percentage will always be permanent. These permanent deformations accumulate in proportion to the traffic volume and cause a gradual development of unevenness in the surface of the structure. The need for road and railway maintenance, and partially also the length of road and railway service life, is often determined based on the permanent deformations. Unevenness that requires maintenance first develops in those areas of structural change where the accumulation rate of permanent deformations is changing.
As part of this study, methods have been developed to measure and monitor the vertical displacements and deformations in earth structures. Sensors installed in a structure enable long-term observations (i.e. monitoring). This monitoring produces detailed data about the measured parameter from a specific location of the structure. The main benefit of monitoring comes from the assessment of a structure’s load-bearing capacity. Through monitoring, the amount of permanent deformation in relation to time can be identified, and the effects of the environmental conditions and maintenance efforts can be verified. In addition, monitoring can be used to estimate future maintenance needs regarding individual cross-sections. Expanding the analyses to cover the entire road or railway network requires, however, the use of network-level measurement methods.
Therefore, a measurement device operating continuously on railways, the Stiffmaster, was developed to measure track stiffness. The device measures track deflection caused by a moving train. The measuring method helps in detecting those areas of a railway track with an abrupt deflection variation or significant changes in the deflection level. The measurement results will help in identifying the factors causing unevenness.
The measuring methods developed as part of this study will increase the understanding of how road and railway structures function and thus contribute to lengthening the service life of roads and railways. Measurement data on the structures’ true behaviour will significantly ease the planning of appropriate maintenance measures.
Original languageEnglish
PublisherTampere University
Number of pages141
ISBN (Electronic)978-952-03-1134-6
ISBN (Print)978-952-03-1133-9
Publication statusPublished - 25 Jun 2019
Publication typeG4 Doctoral dissertation (monograph)

Publication series

NameTampere University Dissertations
ISSN (Print)2489-9860
ISSN (Electronic)2490-0028


  • monitoring
  • road
  • railway track
  • track stiffness


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