Performance assessment of geogrid-reinforced railroad ballast during cyclic loading

Abstract

Recently, rail practitioners have resorted to the use of geogrids as a low-cost solution to stabilise ballast. In view of this, large-scale cyclic tests have been conducted on reinforced ballast using a modified process simulation test (MPST) apparatus at a loading frequency of 20Hz, with geogrid placed at the subballast–ballast interface and within the ballast. Fresh latite basalt having a mean particle size of 35mm and geogrids with different aperture sizes was used. The experimental results indicate that the geogrid arrests the lateral spreading of ballast, reduces the extent of permanent vertical settlement and minimises the particle breakage. However, the in track performance is shown to be influenced by the shear behaviour at the ballast–geogrid interface, wherein the extent of both lateral and vertical deformation reduce with the increase in shear strength at the ballast–geogrid interface. Moreover, the geogrid also helps in minimising the extent of differential track settlement that arises due to the difference in sleeper–ballast contact stress along the track length. The efficiency of geogrid is found to be identical at vertical stresses of 230 and 460kPa. These test results highlight the role of geogrid in stabilising ballast, thus encouraging its use in railway applications.