Performance improvement of railway ballast using shock mats and synthetic grids
Railways in Australia still play a significant role in the intrastate transport of passenger and freight. In recent years, the increased demand for heavier and faster trains has posed greater challenges to railway industry to improve efficiency and stability of track while decreasing track maintenance costs. The ballast layer plays a key role in governing the stability and performance of rail tracks. However, high traffic induced stresses always result in large plastic deformations and degradation of ballast, which in turn leads to significant loss of track stability. This problem becomes severe under impact loading because it accelerates the breakage of ballast particles. Therefore, understanding the complex mechanisms involved with the transfer of impact loads on the substructure and their effect on ballast breakage and degradation is essential when designing new tracks and rehabilitating existing ones. The field trial in Bulli (near Wollongong) demonstrated that in case of train with wheel flats, extremely high pressure can be transmitted to the ballast bed. Installing resilient mats such as rubber pads (shock mats) in rail tracks can lead to attenuation of impact forces and subsequent mitigation of ballast degradation. In view of this, a series of laboratory tests using a high capacity drop-weight impact testing equipment has been carried out to evaluate the effectiveness of shock mats. This paper describes large-scale laboratory testing and full-scale instrumented field trial carried out to quantify the geotechnical behavior of ballast improved by using shock mats and synthetic grids respectively.