An evaluation of the interface behaviour of rail subballast stabilised with geogrids and geomembranes

In a rail track, the compacted granular medium (subballast) placed underneath the ballast influences track resiliency, and controls the load propagation to the softer subgrade (e.g. clay). A series of large-scale direct shear tests were carried out to investigate the interface shear strength of subballast stabilised with geogrids and geomembranes, respectively. In this study, the beneficial effects of these two different types of geosynthetics on the stress-strain behaviour of unreinforced and reinforced subballast were examined. The influences of normal stress (σn), relative density (DR), and the shearing displacement rate (SR) were studied. The results showed that the shear strength of the subballast–geogrid interface was significantly higher than that of the subballast–geomembrane interface. These results also showed that the reinforced subballast with a higher density provided enhanced performance over a wide range of relative densities. The results also indicated that the shear strength was significantly affected by the shearing rate.