This paper presents the results from a laboratory study in which the influence of metal-free tire-derived aggregates (TDA) on the performance of ballast materials was evaluated. The use of waste TDA mixed with ballast of the same gradation is considered as an economic and environmentally friendly solution to reduce ballast degradation, which in turn increases the service life of the railway track. To evaluate the behavior of ballast–TDA mixture, a series of ballast physical tests incorporating different percentages of TDA was accomplished and then the durability of specimens was investigated. The results show considerable improvement of physical performance, especially in abrasive behavior. Moreover, the effects of TDA on ballast mechanical behavior including the shear strength and the deformation performance were determined, using the direct shear test and a ballast box test. Overall, an optimal value of 10% by weight is proposed for practical use at which the particle breakage and the long-term settlement of ballast will be reduced by 47 and 6%, respectively, while the ballast shear strength will be slightly reduced.

The influence of rail cant on the overall geometry conditions of railway tracks is assessed both theoretically and experimentally in this study. Extensive data obtained from a light railway line are used for experimental investigations. Modelling of rail—wheel contact using the ADAMS/Rail program is undertaken for theoretical investigations. The need to incorporate rail cant into the development of the track geometry indices is identified, and a method of performing this is proposed. Using this approach, a new track index is defined, for which the main geometry parameters, including alignment, profile, track twist, track gauge, and rail cant (rail twist), are considered. For the development of the new track index, these parameters are combined, assigning justified coefficients to each geometry parameter according to its contribution to the overall conditions of the track. The research methodology and the results are discussed. A practical use of the new index is presented to indicate its capability and applicability.

In this paper, the use of recycled tire-derived aggregates (TDA) mixed with ballast material is evaluated in order to reduce the train-induced ground-borne vibrations. For this purpose, a series of field vibration measurements has been carried out at an executed pilot track. The prepared ballast layer was mixed with different percentages of TDA in three sections. Moreover, another test section with pure ballast is considered as a reference. The vibrations generated by a motor-powered draisine at two different speeds are then recorded. Records of vibration data are provided using four seismometers placed once longitudinally and once transversely beside different sections. The outputs are then processed in both velocity–time and velocity–frequency domains. To verify the vibration mitigation performance of TDA in real operation conditions, field measurements under the passage of two planned passenger and freight trains are finally arranged. Results show that the best TDA mixture ratio, i.e., 10% by weight, can reduce the transmitted vibrations up to 12 dB for frequencies above 31.5 Hz. According to the obtained efficiency and the very low cost of the recycled materials, this solution can be considered as a competitive vibration countermeasure.

The movement of sand dunes in desert railways has various harmful effects on conventional ballasted tracks. Ballast layer solidification and line closure due to the retention of sands are major problems in such areas. In this study, a new superstructure called ‘humped slab track’ is introduced which can obviate the main problems for desert railway tracks to a significant extent. This system applies the main advantage of the ballastless track which is theballast layer's elimination for avoiding the filling of ballast voids via sand dunes. Moreover, the rail seats in this superstructure were elevated above the slab level by means of reinforced concrete protuberances called humps. Hence, the transmission of sand dunes occurred through the transverse channels between the humps and beneath the rails. To demonstrate the efficiency of the proposed system, several multi-phase fluid simulations (involving solid sand particles and air) were accomplished using the computational fluid dynamic method. The results obtained for the maximum sand flow conditions show that the ballasted track needs to be closed after a very short time whereas the humped slab track is capable of enduring considerable sand flow conditions without any need for line closure.