Stiffness and damping properties of railway ballast aggregate considering influence of degradation of aggregate and incorporation of crumb rubber

Abstract

Impact loads over ballasted railway tracks can accelerate ballast aggregate degradation and deformation. The incorporation of energy-absorbing materials is a practical method to improve the stiffness and damping characteristics of granular layer and diminish aggregate degradation. This study investigated the dynamic responses of ballast aggregates subjected to the drop-weight impact loading test to further illuminate the effect of loading conditions and crumb rubber (CR) incorporation on the stiffness and damping coefficients of ballast material. Experimental measurements were combined with the analytical approach to link the aggregate degradation level to energy evolution and characterize the relationship between the induced impact load and the dynamic properties of granular material. The results demonstrated that the damping properties of ballast material decreased as the number of loading steps increased, which is mainly attributed to further aggregate degradation. The experimental-analytical analysis corroborated lower stiffness and higher damping coefficient for CR-reinforced mixtures. Smaller CR particles led to greater energy dissipation. A linear relationship was also found between the breakage level of aggregates and the energy induced due to friction development between particles and individual aggregate breakage.