ABSTRACT
This chapter describes the strength, deformation, and degradation behaviour of fresh and recycled ballast under monotonic, cyclic, and impact loadings. It discusses the effectiveness of various geosynthetics in stabilising recycled ballast through laboratory model test results. The chapter describes the benefits of shock mats in the effective mitigation of ballast degradation under impact loads. The deformation behaviour of fresh and recycled ballast under representative cyclic loading was investigated in the laboratory using the prismoidal triaxial apparatus. These model tests were conducted in both dry and wet states to study the effects of saturation. The difference between the settlement of ballast at the sleeper-ballast interface and the settlement of ballast-capping interface (measured by the settlement plates) was used to calculate the average vertical strain of the load-bearing ballast layer. The chapter explains energy-absorbing materials and particle breakage of ballast under impact loading.
