Laboratory Investigation of Cyclic Behavior of Clay-Fouled Geogrid-Reinforced Ballast Mixed with Tire Chips

This study presents the results of a laboratory large-scale track process simulation test (PST) and direct shear test conducted on clean and clay-fouled granite ballast (GB) mixed with varying proportions of tire chips (TC) under unreinforced (UR) and geogrid-reinforced (GR) conditions. The results of cyclic tests indicated that the deformation of GB-TC mix increases with increase in TC and fouling content for UR and GR conditions. The resilient modulus (Mr) decreases while the damping ratio (Dr) and energy dissipation (Ed) of GB-TC mix increase with an increase in TC content for UR and GR conditions. Further, the particle breakage also decreases with increase in TC and fouling content for UR and GR of the GB-TC mix. Further, GR of GB-TC mix at TC=6% indicated considerably improved cyclic behavior under different fouling levels as compared to the reference ballast (GB). Additionally, the results of direct shear tests confirmed that peak shear stress, friction angle, dilation angle, and performance index of GR of GB-TC (TC=6%) is higher than the reference ballast for all fouling levels. Thus, an optimum TC content of 6% is identified, providing improved mechanical performance under cyclic loading and different levels of fouling.