Field assessment of ballasted railroads using geosynthetics and shock mats

The ballasted railroads form an integral part of the modern transportation infrastructure in Australia. However, they are subjected to large stresses especially on mixed traffic lines, where heavy freight trains are operated. Under such adverse operational conditions, ballast progressively degrades contributing to overall track deformations and frequent maintenance. Maintaining geometry of ballast embankments is necessary to improve safety and efficiency of railway operations. The use of artificial inclusions (geosynthetics and shock mats) as well as recycled (discarded) ballast in track can be economically viable options. In order to gain more insight, the CGRE has conducted extensive field trials on two rail lines in Bulli and Singleton in New South Wales supported by Sydney Trains and Australian Rail Track Corporation, respectively. In these studies, different types of geosynthetics (geogrid, geotextile and geocomposite) and shock mats were installed beneath the ballast layer constructed on varying subgrade conditions. Relative advantages of different geogrids were studied. Traffic induced stresses, ballast breakage, transient and permanent deformations were routinely monitored using precise instrumentation schemes. This paper discusses the details of track construction, instrumentation, monitoring processes and results of these field studies.