Characteristics of Geogrid-Reinforced Rubber-Coated Ballast under Cyclic Loading Conditions

Abstract

Rubber-coated ballast (RCB) is a newly invented ballast made up of natural aggregates coated with recycled crumb rubber with the help of polyurethane binder. The deformation, degradation, resilience, damping, and acceleration time response for unreinforced (UR) and geogrid-reinforced (GR) RCB-natural ballast mix were explored under cyclic loading conditions. The results from the cyclic loading tests indicated that the deformation of RCB samples was higher than that of natural ballast owing to the softening properties of crumb rubber. It was also seen that the deformation of the RCB-natural ballast mix increased with the increase in RCB content. Furthermore, the resilient modulus ( Mr) of the RCB-natural ballast mix reduced while the damping ratio ( Dr) increased with the increase in RCB content. Moreover, the GR RCB-natural ballast mix exhibited lesser deformations, whereas the Mr and Dr improved compared with the UR RCB-natural ballast mix. Additionally, RCB significantly reduced the sleeper acceleration and ground-borne vibration compared with natural ballast. These accelerations were further reduced, to some extent, when the RCB-natural ballast mix was reinforced with geogrid. The particle breakage of the GR RCB-natural ballast mix was reduced considerably compared with the UR natural ballast. To minimize the volumetric strain and particle breakage of the RCB-natural ballast mix and maximize the Mr and Dr, it is recommended that around 50% of RCB content is mixed with GR natural ballast.