Skip to main content
placeholder image

Performance evaluation of shock mats and synthetic grids in the improvement of rail ballast

Conference Paper


Abstract


  • In Australia, railways offer the most prominent transportation mode in terms of traffic

    tonnage serving the needs of bulk freight and passenger movement. Ballast is an essential constituent

    of conventional rail infrastructure governing track stability and performance. However, in recent

    time, high traffic induced stresses due to dramatically increased train speeds and heavier axle loads

    cause excessive plastic deformations and degradation of ballast. This seriously hampers safety and

    efficiency of express tracks, for instance, enforcing speed restrictions and effecting more frequent

    track maintenance. The problem becomes severe under impact loading because it accelerates ballast

    breakage. Therefore, understanding the complex mechanisms involved with the transfer of impact

    loads on the substructure and their effect on ballast breakage and degradation are essential for predicting

    the desirable track maintenance cycle as well as improving new track design. The measurement

    of track settlement is well established practice in conventional track monitoring systems, however, it

    is also important to monitor lateral deformations (parallel to sleepers) that affect track stability especially

    in the absence of sufficient confinement. Therefore, a field trial was conducted on a section of

    rail track in the town of Bulli (north of Wollongong City) to measure deformations and cyclic stresses.

    It was demonstrated that in the case of wheel flats, extremely high stresses would be transmitted to

    the ballast bed. Installing layers of synthetic materials such as rubber pads (shock mats) in rail tracks

    can lead to the attenuation of high impact forces and thereby mitigate ballast degradation. In order to

    evaluate the effectiveness of shock mats, a series of laboratory tests using a high capacity drop-weight

    impact testing equipment was carried out. The field trial further proved that the moderately-graded

    recycled ballast when used with a geo-composite layer was found to perform better in comparison to

    traditionally utilized highly uniform fresh ballast, with clear implications on reduced track maintenance

    costs and longevity. The results of large-scale direct shear tests also revealed that the appropriate

    application of geogrids significantly improved the performance of ballast. This keynote paper

    describes in detail, the results of large-scale laboratory testing of ballast and the observations from a

    full-scale instrumented field trial characterising the behaviour of rail ballast improved by shock mats

    and synthetic grids.

Publication Date


  • 2012

Citation


  • Indraratna, B., Nimbalkar, S. & Rujikiatkamjorn, C. (2012). Performance evaluation of shock mats and synthetic grids in the improvement of rail ballast. In S. Miura, T. Ishikawa, N. Yoshida, Y. Hisari & N. Abe (Eds.), Second International Conference on Transportation Geotechnics (pp. 47-62). London: CRC Press.

Scopus Eid


  • 2-s2.0-84867471485

Ro Metadata Url


  • http://ro.uow.edu.au/engpapers/5303

Has Global Citation Frequency


Start Page


  • 47

End Page


  • 62

Place Of Publication


  • London

Abstract


  • In Australia, railways offer the most prominent transportation mode in terms of traffic

    tonnage serving the needs of bulk freight and passenger movement. Ballast is an essential constituent

    of conventional rail infrastructure governing track stability and performance. However, in recent

    time, high traffic induced stresses due to dramatically increased train speeds and heavier axle loads

    cause excessive plastic deformations and degradation of ballast. This seriously hampers safety and

    efficiency of express tracks, for instance, enforcing speed restrictions and effecting more frequent

    track maintenance. The problem becomes severe under impact loading because it accelerates ballast

    breakage. Therefore, understanding the complex mechanisms involved with the transfer of impact

    loads on the substructure and their effect on ballast breakage and degradation are essential for predicting

    the desirable track maintenance cycle as well as improving new track design. The measurement

    of track settlement is well established practice in conventional track monitoring systems, however, it

    is also important to monitor lateral deformations (parallel to sleepers) that affect track stability especially

    in the absence of sufficient confinement. Therefore, a field trial was conducted on a section of

    rail track in the town of Bulli (north of Wollongong City) to measure deformations and cyclic stresses.

    It was demonstrated that in the case of wheel flats, extremely high stresses would be transmitted to

    the ballast bed. Installing layers of synthetic materials such as rubber pads (shock mats) in rail tracks

    can lead to the attenuation of high impact forces and thereby mitigate ballast degradation. In order to

    evaluate the effectiveness of shock mats, a series of laboratory tests using a high capacity drop-weight

    impact testing equipment was carried out. The field trial further proved that the moderately-graded

    recycled ballast when used with a geo-composite layer was found to perform better in comparison to

    traditionally utilized highly uniform fresh ballast, with clear implications on reduced track maintenance

    costs and longevity. The results of large-scale direct shear tests also revealed that the appropriate

    application of geogrids significantly improved the performance of ballast. This keynote paper

    describes in detail, the results of large-scale laboratory testing of ballast and the observations from a

    full-scale instrumented field trial characterising the behaviour of rail ballast improved by shock mats

    and synthetic grids.

Publication Date


  • 2012

Citation


  • Indraratna, B., Nimbalkar, S. & Rujikiatkamjorn, C. (2012). Performance evaluation of shock mats and synthetic grids in the improvement of rail ballast. In S. Miura, T. Ishikawa, N. Yoshida, Y. Hisari & N. Abe (Eds.), Second International Conference on Transportation Geotechnics (pp. 47-62). London: CRC Press.

Scopus Eid


  • 2-s2.0-84867471485

Ro Metadata Url


  • http://ro.uow.edu.au/engpapers/5303

Has Global Citation Frequency


Start Page


  • 47

End Page


  • 62

Place Of Publication


  • London