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Ballast Layer

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Eduardo Fortunato – One of the best experts on this subject based on the ideXlab platform.

  • Non-Linear Behaviour of Geomaterials in Railway Tracks under Different Loading Conditions
    Procedia Engineering, 2020
    Co-Authors: Andre Paixao, Eduardo Fortunato, J. N. Varandas, Rui Calçada

    Abstract:

    Abstract The resilient behaviour of the geomaterials used in railway tracks, particularly the Ballast Layer, is mostly non-linear and depends mainly on the loading stress path. However geomaterials are frequently considered as linear elastic in structural analyses, assuming that it somewhat reproduces the results of non-linear models for a given load amplitude. This study focuses on whether this consideration is adequate to simulate not only the overall track behaviour, but also the response of the Ballast Layer, considering different loading conditions. The authors used three-dimensional train-track-soil system models, validated with experimental data, and the results of linear-elastic models are compared against non-linear models. Although the linear elastic models required significantly lower computational effort and can provide accurate estimates of the overall track response, they strongly underestimate the stress levels inside the Ballast Layer. This aspect can be an important hindrance to studies using linear-elastic models to analyse resilient and plastic deformations of the Ballast Layer in railway tracks.

  • Short soil–binder columns in railway track reinforcement: three–dimensional numerical studies considering the train–track interaction
    Computers and Geotechnics, 2018
    Co-Authors: André Francisco, J. N. Varandas, Andre Paixao, Eduardo Fortunato

    Abstract:

    Abstract The authors present a numerical study on railway track subgrade reinforcement using short soil-binder columns through injection, below the Ballast Layer. A 3D FEM program developed in MATLAB that considers the dynamic train–track interaction and the non-linear elastic behaviour of the Ballast is used to study the response of the train–track–substructure system and assess stresses in the subgrade. Results suggest that reinforcements have limited impact on the train–track interaction and reduce deviatoric stresses between columns, at the top of the foundation. This method may be particularly relevant in the rehabilitation of old single railway tracks.

  • improving the use of unbound granular materials in railway sub Ballast Layer
    2nd International Conference on Transportation Geotechnics (ICTG)International Society of Soil Mechanics and Geotechnical Engineering (ISSMGE), 2012
    Co-Authors: Eduardo Fortunato, Andre Paixao, S Fontul

    Abstract:

    The rational use of materials to be applied in the supporting Layers of railway tracks is an important aspect that can contribute to reduce the life cycle cost of such infrastructure. In recent construction and renewal rail track projects carried out in Portugal, the sub-Ballast Layer has been typically implemented in the track structure, using Unbound Granular Materials (UGM). This Layer and the characteristics of the materials play a fundamental role in the track behavior. Nevertheless, there is a lack of consensus worldwide on the requirements established for such materials. In Portugal and in other European countries, very stringent requirements based on empirical tests have been adopted, making it difficult to find materials that fulfill such requirements. There is also evidence that some of these materials, which do not comply with all the requirements, can still be considered as appropriate for sub-Ballast. Within the scope of this study, the construction of a new railway section was supervised. During construction, it was difficult to obtain the desired quantity of granite material for the 30 cm thick sub-Ballast Layer that would fulfill the requirements and still comply with the contract deadline. As an alternative, another structural solution was used that considered the replacement of the bottom 15 cm of granite material sub-Ballast Layer by limestone material which did not comply with some requirements. In order to study the feasibility of this change, to evaluate its consequences and establish new quality assurance indicators to be adopted afterwards, several studies were developed, such as in situ characterization and cyclic triaxial load tests on different UGM. The studies performed and the results presented in this paper show that, taking into account a mechanistic approach, some materials that do not comply with all requirements based on empirical tests might present adequate performance to be applied in the sub-Ballast.

Zeena W Abbawi – One of the best experts on this subject based on the ideXlab platform.

  • soft soil improved by stone columns and or Ballast Layer
    Proceedings of the Institution of Civil Engineers – Ground Improvement, 2015
    Co-Authors: Namir Khoursheed Said Al Saoudi, Falah Rahil, Zeena W Abbawi

    Abstract:

    Iraq has the oldest railway network in the region. Currently the Iraqi railway company is rehabilitating the existing network in different regions and planning to expand it for the future. About 30…

  • Soft soil improved by stone columns and/or Ballast Layer
    Proceedings of the Institution of Civil Engineers – Ground Improvement, 2015
    Co-Authors: Namir Khoursheed Said Al Saoudi, Falah Rahil, Zeena W Abbawi

    Abstract:

    Iraq has the oldest railway network in the region. Currently the Iraqi railway company is rehabilitating the existing network in different regions and planning to expand it for the future. About 30…

Manuel Matos Fernandes – One of the best experts on this subject based on the ideXlab platform.

  • characterization of the fouled Ballast Layer in the substructure of a 19th century railway track under renewal
    Soils and Foundations, 2010
    Co-Authors: Eduardo Fortunato, Antonio Pinelo, Manuel Matos Fernandes

    Abstract:

    The purpose of these field and lab studies undertaken during rehabilitation work being done on an ancient railway line was to characterize a Layer of Ballast fouled with soil found in the track substructure. The field studies included the characterization of the thickness, grain size distribution and void ratio of the fouled Ballast Layer, as well as a large number of plate load tests, both on the fouled Ballast Layer and on the subgrade. The resilient behaviour of the fouled Ballast was evaluated in the lab by cyclic triaxial tests on large size reconstituted specimens with distinct fouling indexes (different grain size distribution) and distinct humidity states (dry or wet). The results obtained were used as support for the decision to maintain the fouled Ballast Layer under the new sub-Ballast in a number of stretches of the renewed line.