Defining the process of including sustainable rubber particles under sleepers to improve track behaviour and performance

Abstract

The inclusion of rubber particles derived from end-of-life tyres (ELTs) under the sleepers has been demonstrated in previous studies to be a potential solution to improve the behaviour and durability of railway tracks, and then, minimizing the negative impacts associated with the need for maintenance. Nonetheless, more in-depth studies are still required to define the optimal procedure prior to its application in real tracks. The present paper therefore focused on assessing the main parameters for defining the procedure for adding rubber particles to create an elastic layer under sleepers through a two-step stoneblowing process. Such parameters included the size of the rubber particles; the position of the elastic layer (above or below the conventional small aggregates used in the stoneblowing process); the need to compact the first layer before injecting the subsequent one; the effect of rubber dosage; and the impact of service conditions (traffic levels and temperatures). For this purpose, a number of laboratory tests were carried out on testing boxes simulating the effects of train passages, assessing diverse properties such as particles percolation, section settlement, stiffness and dissipated energy. The results revealed that the inclusion of rubber particles (ranging between 14 and 20 mm) as an elastic layer over the compacted small stones through a two-step stoneblowing process, provides an effective solution to graduate and optimize global track behaviour by using different quantities of rubber, which could reduce the need for track maintenance and its environmental impacts.