Papers

@article{alves_steel_2024,

title = {Steel Slag Sub-Ballast for Sustainable Railway Track Infrastructure},

author = {Rubens Alves and Ana Ramos and Alexandre Castanheira-Pinto and Sara Rios and Jesús Fernández-Ruíz},

url = {https://www.mdpi.com/2412-3811/9/7/106},

doi = {10.3390/infrastructures9070106},

issn = {2412-3811},

year  = {2024},

date = {2024-07-01},

urldate = {2026-04-28},

journal = {Infrastructures},

volume = {9},

number = {7},

pages = {106},

publisher = {Multidisciplinary Digital Publishing Institute},

abstract = {Railway lines require a significant amount of natural raw materials. Industrial by-products can be used instead, reducing the costs of natural aggregate exploration. This work analyzes a ballasted track’s short- and long-term performances when replacing conventional sub-ballast aggregate with steel slag. After an extensive laboratory characterization of the steel slag, the material performance was analyzed in a 3D numerical model of a ballasted track when included in a railway track. An empirical model was implemented and calibrated to predict the long-term permanent deformation induced in the track after many train passages. The results are compared with the allowable deformation limits required for conventional high-speed ballasted track railway lines. An additional analysis was conducted to assess the influence of steel slags on the critical speed of conventional railway tracks when used. The results show a residual impact on the critical speed value compared to the conventional sub-ballast made with natural aggregates.},

keywords = {3D numerical model, critical speed, cyclic triaxial tests, EAF, short- and long-term performances},

pubstate = {published},

tppubtype = {article}

}

@article{ramos_predicting_2023,

title = {Predicting Critical Speed of Railway Tracks Using Artificial Intelligence Algorithms},

author = {Ana Ramos and Alexandre Castanheira-Pinto and Aires Colaço and Jesús Fernández-Ruíz and Pedro Alves Costa},

url = {https://www.mdpi.com/2571-631X/6/4/53},

doi = {10.3390/vibration6040053},

issn = {2571-631X},

year  = {2023},

date = {2023-12-01},

urldate = {2026-08-13},

journal = {Vibration},

volume = {6},

number = {4},

pages = {895–916},

publisher = {Multidisciplinary Digital Publishing Institute},

abstract = {Motivated by concerns regarding safety and maintenance, the operational speed of a railway line must remain significantly below the critical speed associated with the track–ground system. Given the large number of track sections within a railway corridor that potentially need to be analyzed, the development of efficient predictive tools is of the utmost importance. Based on that, the problem can be analyzed in a few seconds instead of taking several hours of computational effort, as required by a numerical analysis. In this context, and for the first time, machine learning algorithms, namely artificial neural networks and support vector machine techniques, are applied to this particular issue. For its derivation, a reliable and robust dataset was developed by means of advanced numerical methodologies that were previously experimentally validated. The database is available as supplemental data and may be used by other researchers. Regarding the prediction process, the performance of both models was very satisfactory. From the results achieved, it is possible to conclude that the prediction tool is a novel and reliable approach for an almost instantaneous prediction of critical speed in a high number of track sections.},

keywords = {Artificial intelligence, critical speed, numerical modeling, Railway dynamics, scoping tool},

pubstate = {published},

tppubtype = {article}

}

@article{castanheira-pinto_simplified_2022,

title = {Simplified approach for ground reinforcement design to enhance critical speed},

author = {Alexandre Castanheira-Pinto and Aires Colaço and Jesús Fernández-Ruíz and Pedro Alves Costa and Luís Godinho},

url = {https://www.sciencedirect.com/science/article/pii/S0267726121005005},

doi = {10.1016/j.soildyn.2021.107078},

issn = {0267-7261},

year  = {2022},

date = {2022-02-01},

urldate = {2022-02-01},

journal = {Soil Dynamics and Earthquake Engineering},

volume = {153},

pages = {107078},

abstract = {In recent years, there have been significant advances in the railway sector, with a substantial increase in train speed, resulting in new challenges for the technical community in terms of infrastructure performance. When the supporting soil of the railway track is soft, the train speed can approach the speed of wave propagation in the track-ground system, giving rise to the so-called critical speed effect. This effect is characterized by the great amplification of the track response with dramatic consequences in terms of safety, ground-borne vibrations and maintenance costs. This well-known issue can be mitigated in several ways, one of them based on the reinforcement of the soil with columns. Bearing that in mind, the present paper aims to study the enhancement in the critical speed of the railway system achieved by a soil reinforcement with jet grouting columns, for a homogeneous and layered ground. Despite the inefficiency verified for the homogeneous scenario, the reinforcement of layered grounds produces a considerable improvement in the critical speed of the system. It has been proved that deepening the reinforced columns in the stiffer layer does not lead to a continuous improvement in the critical speed of the system. Furthermore, a simplified methodology capable of accurately predicting the critical speed for reinforced grounds is proposed. A validation study showed the high accuracy of the simplified methodology in predicting critical speed, proving to be an interesting tool for engineering purposes.},

keywords = {3D FEM-PML Periodic modelling, critical speed, Discrete soil reinforcement, Dispersion analysis},

pubstate = {published},

tppubtype = {article}

}

@article{fernandez-ruiz_improvement_2021,

title = {Improvement of the critical speed in high-speed ballasted railway tracks with stone columns: A numerical study on critical length},

author = {Jesús Fernández-Ruíz and Marina Miranda and Jorge Castro and Luis Medina-Rodríguez},

url = {https://www.sciencedirect.com/science/article/pii/S2214391221001185},

doi = {10.1016/j.trgeo.2021.100628},

issn = {2214-3912},

year  = {2021},

date = {2021-09-01},

urldate = {2021-09-01},

journal = {Transportation Geotechnics},

volume = {30},

pages = {100628},

abstract = {The pressure to achieve a higher speed of train operation has increased in the last few years due to the development of high-speed railway lines. In the presence of soft soils, this speed increase is not possible without undertaking soil improvement measures, since the critical speed is lower than the desired speed of train operation. One of the most widely used soil improvement techniques is that of stone columns. In relation to these is the concept of critical length which, up to now, has only been studied for static cases. This research focuses, for the first time, on the enhancement of the critical speed in high-speed railways with stone columns and with special reference to critical length. Moreover, others parameters such as: maximum rail displacement and Dynamic Amplification Factor (DAF) are also studied. Analysing three profiles of ground representative of soft soils, it can be observed how the effect of the stone columns on critical speed is relevant, showing that critical length is different with respect to the three parameters above, the most restrictive one being that which corresponds to the critical speed. The influence of other parameters on the critical length and on the effectiveness of stone columns, such as the area replacement ratio, the dynamic pressure bulb and the existing soil stiffness is analysed and discussed.},

keywords = {3D dynamic numerical model, Critical length, critical speed, High-speed railway lines, Stone columns},

pubstate = {published},

tppubtype = {article}

}