Behaviour of subballast reinforced with used tyre and potential application in rail tracks

Abstract

Rubber tyres have a three dimensional cylindrical structure, and as such could be used to stabilise foundations by increasing the bearing capacity and reducing settlement for transport infrastructure. It is therefore expected that in railroad engineering, a capping layer reinforced with rubber tyres could help to reduce the thickness of the granular layer (i.e. ballast), improve the track bearing capacity, and reduce the frequency of maintenance. However, there is a notable gap between the conceptual theories and real-life applications pertaining to the mechanisms of rubber tyre-reinforced foundations. In pavement engineering, the bearing capacity is closely linked to plate load tests. In this study, plate load tests were carried out on a single tyre filled with subballast material and subjected to a vertical load. This testing process was then modelled using the Finite Element software ABAQUS to study and quantify the interaction between the tyre and the granular medium. The experimental and numerical results reveal that the rubber tyre can significantly increase the modulus and ultimate bearing capacity of the granular layer. The numerical process was further extended to a finite element track model to demonstrate the expected response of a ballasted railway track with and without tyre reinforcement.

Current research into ballasted rail tracks: model tests and their practical implications

“…The FEM results of the load-deformation relationships for tyre confined and unconfined plate load tests agreed reasonably well with the experimental results as shown in Figure 12 (Indraratna, Sun and Grant 2017). Having calibrated the FEM model with a single tyre unit, a plane strain section of half a ballasted substructure was simulated to examine how the foundation would react under load, with or without being confined by tyres.…”

Evaluation of additional confinement for three-dimensional geoinclusions under general stress state

“…Fig. 4a shows the load vs. strain curves of the 231 five materials obtained from tension tests (Henkel and Gilbert 1952;Koerner 2012;Biabani 232 2015; Indraratna et al 2017;Lal et al 2017 Similar behavior is observed in the direction of σ'2. The magnitude of kσ,2 is the highest 252 for rubber tire followed by HDPE, coir geotextile, polypropylene geotextile and rubber 253 membranes.…”

“…The investigations in the past have demonstrated the beneficial 52 role of geocells (e.g., Raymond 2001;Satyal et al 2018) and scrap tires (e.g. Forsyth and Egan 53 1976; Garga and O'shaughnessy 2000;Indraratna et al 2017) in improving the stability of 54 railway tracks and embankments. However, the lack of a well-established method to evaluate 55 the magnitude of additional confinement provided by these geoinclusions has limited their 56 application in the railway tracks.…”

Numerical Simulation of the Dynamic Response of Ballasted Track Overlying a Tire-Reinforced Capping Layer

“…Indraratna et al (2017) proposed a rubber tire based capping layer for railway track where one sidewall is removed and the tire is then filled with gravel; a geotextile can be placed between the rubber tire and the ground as a separator. Plate load tests (Indraratna et al, 2017) and prototype process simulation carried out by Indraratna et al (2018) revealed that a tire cell has three primary engineering benefits: (i) the confinement provided by the cellular assembly can increase the stiffness of the contained aggregate, which then reduces lateral spreading and vertical deformation within the capping and ballast layers; (ii) the tires and gravel composites allow a reduced and more uniform stress distribution to the subgrade; and (iii) tire cells can enhance the damping properties of the system, and thus its ability to attenuate dynamic forces imposed by rail traffic. However, since the dimensions are limited by the size of the experimental facility (i.e., 800 × 600 × 600 mm), a light vehicle tire having a diameter of 560 mm was tested.…”

“…These models were based on the assumption that substructure materials are purely elastic and this will lead to inaccurate prediction. Recently, a finite element 3D model has been developed to investigate the load transfer mechanism between tires and infill gravels under static loading (Indraratna et al, 2017). It was reported that the confining effect causes the tire and gravel infill composite to act as a stiff but flexible "mattress" that can effectively reduce the amplitude of stresses transmitted to the subgrade.…”