Performance assessment of synthetic shock mats and grids in the improvement of ballasted tracks
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 times higher traffic induced stresses due to dramatically increased tgrain speeds and heavier axle loads have caused 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. Installing layers of synthetic materials such geogrids and rubber pads (shock mats) in rail tracks can significantly reduce ballast degradation. Field trials were conducted on rail track sections in the towns of Bulli (near Wollongong city) and Singleton (near Newcastle) to measure track deformations associated with cyclic stresses and impact loads. This paper describes the results of large-scale laboratory testing as well as the observations from full-scale instrumented field trials characterising the behaviour of rail ballast improved by shock mats and synthetic grids.