Hamed Faghihi Kashani

Evaluating the Correlation Between the Geotechnical Index and the Electromagnetic Properties of Fouled Ballasted Track by a Full-Scale Laboratory Model

To determine the correlation between water content or fouling of a railroad track and ground-penetrating radar (GPR) signals, a full-scale railway track model was designed and constructed at the University of Massachusetts Amherst. A track section was simulated by creating a model consisting of rails and ties placed on a ballast layer on a subballast layer. The model was constructed three times with three fouling percentages. Each model was tested with water-content conditions of dry, field capacity, and two points in between these extremes. Frequency antennae of 450 MHz and 2 GHz were used to evaluate the conditions. The design and construction of the full-scale track in addition to the GPR data analysis and interpretation are presented in this paper. The results show that the dielectric permittivity and frequency spectrum can be used as an indicator of percentage of fouling and water content of a track. In addition, a linear correlation was observed between the percentage of fouling and the water content under field capacity conditions.

MODEL TRACK STUDIES BY GROUND PENETRATING RADAR (GPR) ON BALLAST WITH DIFFERENT FOULING AND GEOTECHNICAL PROPERTIES

In recent years there has been an increase in the knowledge of, and need for, non-invasive monitoring of ballast in order to identify the problematic sections of track and decrease the maintenance cost. Various technologies such as Ground Penetrating Radar (GPR) are becoming accepted for investigating the condition of ballast. However since these techniques were not originally developed for engineering applications, their applicability in ballast evaluations can be sometimes uncertain. Continued empirical studies and condition specific calibrations are needed to demonstrate repeatable and quantifiable results. In this study large-scale track models with trapezoidal section area were constructed at the University of Massachusetts to investigate the effects of breakdown fouling, and the effects of changing geotechnical properties on GPR traces. This paper presents the design and construction of large scale track models, and methods used for GPR data collection. GPR data are presented in this paper that demonstrate sensitivity to the track model properties and variables. In particular, the experiments are being used to evaluate changes in GPR data with changing geotechnical properties of the ballast such as density, water content, grain size distribution (GSD), and fouling percentage.

Ballast Life and Effective Parameters

Railway ballast under repeated traffic loading deforms and deteriorates. Increases in the rate of settlement in ballast decreases its useful life and contributes to geometry roughness and poor ride quality. Based on laboratory and field studies, as well as mechanic-based models, the fouling condition of the ballast has been shown to have a profound effect on settlement and overall ballast life. Quantifying ballast settlement and the effect of maintenance at different stages of ballast life can define the State of Good Repair (SGR) for ballast. This paper presents an approach for predicting ballast life based on geotechnical principles and maintenance management philosophy. Over 200 revenue-service locations have been studied for developing this model for different tracks including mixed passenger and freight as well as only freight traffic. The approach presented in this paper can be used for optimizing ballast’s life-cycle costs through a maintenance management approach.© 2018 ASME

Laboratory Evaluation of Fouled Ballast Under Heavy-Axle Load and High Traffic Conditions

Excessively fouled ballast can result a high amount of plastic settlement and reduction of vertical and lateral resistance of the track. A significant portion of railroad maintenance costs is associated with degraded fouled ballast. Therefore, it is important to understand the effects of ballast fouling at different moisture levels on the behavior of ballast under repeated loading conditions. Development of the testing equipment and procedure to better simulate and evaluate the performance of ballast under heavy loading and high traffic conditions can help the railroad industry to better understand the track risk factors.In this study a modified railroad ballast box test apparatus has been used to evaluate the effect of fouling on the plastic deformation of ballast in different moisture conditions up to 2,500,000 cycles, or the equivalent of 300MGT of heavy axle load traffic. The tests have been conducted under equivalent Heavy-Axle Load (HAL) loading conditions and for ballasts with <5%, 15% and 30% fouling. The tests simulate the gradual elastic and plastic deformation of fouled ballast by increase in repetitive cycles of load from dry condition to saturated condition. This paper presents the design and construction of the ballast box device with initial results of the tests. The results show a clear effect of water content and fouling percentage on the amount and rate of both plastic and elastic deformation in cyclic loading. Also, the factor of safety against track failure has been evaluated in highly fouled ballast at saturated conditions.Copyright

Modifying the One-Dimensional Response of Ballast Box System Using Resiliently Bound Ballast

The transition zones especially railroad bridge transitions are one the weakest track sections that need more maintenance in order to keep a good track performance. These locations are also commonly create noise and vibration pollution which is unpleasant specifically in urban parts of the city. A new product known as Resiliently Bound Ballast (RBB) is a new engineered material composed of Ballast, tire derived aggregate (TDA) and proprietary elastomeric epoxy binder which can be manufactured with different mixtures to meet various engineering properties. In order to study the workability of this material in railroad bridges, in this research a one dimensional (1D) two degree of freedom (2DOF) composite RBB-Ballast track on concrete deck bridge has been modeled with different RBB thicknesses from 0.01 in. (0.025 cm) to 23.99 in. (60.94 cm) and material damping of 2.5, 5 and 10 %. The range of properties for RBB are based upon values obtained from static and dynamic testing. The results show that the most peak amplitude reduction occurs between 2.5% to 5% damping, RBB has the ability to dissipate energy over a broader range of frequencies and as the damping increases, the RBB thickness becomes more effective in track dynamic performance.