Study of Ballast Track Dynamic Behavior Evaluation Comparative Analysis According to the On-Site Laying of Rectangular-Parallelepiped Fiber Reinforcement Sack

The roadbed reinforcement method using cuboidal fiber reinforcement is an eco-friendly method that compensates for the shortcomings of various existing roadbed reinforcement technologies. A rectangular parallelepiped fiber reinforcement was installed in section oo of the existing line where fine-grained gravel, floating sleepers, and sleeper cracks occurred. The basic physical property test of the upper subgrade was conducted, and the vertical displacement and acceleration of rails and sleepers were compared and analyzed according to the train operation of the reinforced and non-reinforced sections. A comparative analysis of the vertical displacement and acceleration according to train operation after laying the rectangular parallelepiped fiber reinforcement demonstrated that the vertical displacement and acceleration were reduced by up to 84% and 80%, respectively. The dynamic movement of the rail was reduced owing to the reinforcing effect of the rectangular parallelepiped reinforcement, thereby improving the roadbed bearing capacity and stability.

Monitoring Track Transition Zones in Railways

This manuscript presents the first measurement program and data collection on the Dinatrans track transition solution after it was installed in a track section in the north of Spain (Galicia). The Dinatrans solution was created to address the limitations of several track transition solutions. This novel solution consists of two inner and outer rails from slab track to ballast track, pads with different stiffness over sleepers of variable lengths installed from ballast track to slab track, and a simple substructure formed by non-structural concrete poured over the natural ground. The main objective of this research was to assess the suitability and the initial performance of the Dinatrans track transition solution. The measured variables for these initial real-world tests were vertical accelerations on sleepers, shear stress on rails, vertical displacements on rails and vertical displacements on sleepers. All measurements of these variables were obtained in an in-situ program by installing vertical accelerometers and LVDTs on the track structure and extensometer gauges on the rails and sleepers. The methodology and the procedures followed are described. The Dinatrans initial solution was compared with the Standard solution used in Spain using these initial measurements. This field analysis provides an initial understanding of the performance of the new track transition. Further measurements will be required to check the track transition performance over the long term; however, no maintenance works have been necessary since construction (2016).

Development of Condition Assessment Index of Ballast Track Using Ground-Penetrating Radar (GPR)

The condition of the ballast is a critical factor affecting the riding quality and the performance of a track. Fouled ballast can accelerate track irregularities, which results in frequent ballast maintenance requirements. Severe fouling of the ballast can lead to track instability, an uncomfortable ride and, in the worst case, a derailment. In this regard, maintenance engineers perform routine track inspections to assess current and future ballast conditions. GPR has been used to assess the thickness and fouling levels of ballast. However, there are no potent procedures or specifications with which to determine the level of fouling. This research aims to develop a GPR analysis method capable of evaluating ballast fouling levels. Four ballast boxes were constructed with various levels of fouling. GPR testing was conducted using a GSSI (Geophysical Survey Systems, Inc.) device (400, 900, 1600 MHz), and a KRRI (Korea Railroad Research Institute) GPR device (500 MHz), which was developed for ballast tracks. The dielectric permittivity, scattering of the depth (thickness) values, signal strength at the ballast boundary, and area of the frequency spectrum were compared against the fouling level. The results show that as the fouling level increases, the former two variables increase while the latter two decrease. On the basis of these observations, a new integrated parameter, called a ballast condition scoring index (BCSI), is suggested. The BCSI was verified using field data. The results show that the BCSI has a strong correlation with the fouling level of the ballast and can be used as a fouling-level-indicating parameter.

Preparation and Mechanical Properties of Polyurethane Material for Railway Ballast

ABSTRACTThe elastic solidification of track bed is a new track structure improvement technology between the traditional gravel track bed and the ballast less track monolithic track bed. It can effectively solve the main technical problems of heavy haul railway transportation, such as large impact force of wheel rail, serious deformation of track bed and frequent maintenance etc. In this paper, combined with the characteristics of polyurethane properties affected by its chemical composition, a solidified ballast polyurethane material suitable for heavy haul railway was developed by adding diluents and other materials. Physical property test and mechanical triaxial test were carried out to assess the influence of diluent content on the hardening effect of ballast; the physical process and mechanical properties of different proportion materials were analyzed. The experimental results show that adding appropriate amount of diluent into polyurethane material can effectively improve the integrity of ballast bed, increase the strength, reduce the deformation, and prolong the service life of ballast track bed.