Railway Section Research Articles

Study on the Interaction between Wheel Polygon and Rail Corrugation in High-Speed Railways.

The wheel polygonization and rail corrugation are typical wheel-rail periodic wear problems, which seriously affect the safe operation of high-speed railways. In the present paper, the interaction between the wheel polygon and the rail corrugation in the long-slope section of high-speed railways is mainly studied based on theory of friction coupling vibration. Firstly, the simulation model of the wheel-rail contact model is established, as well as the polygonal wear of the wheel and the corrugated wear of the rail. Then, the stability analyses of the wheel-rail system with periodic wear are studied, in which the four working conditions of smooth rail-smooth wheel, polygonal wheel-smooth rail, smooth wheel-corrugated rail and polygonal wheel-corrugated rail are compared. Finally, the competition mechanisms between the wheel polygon and rail corrugation under different parameters are discussed, including the wheel-rail friction coefficient and the depth of periodic wear of the wheel-rail system. The numerical results show that both the periodic wear of the wheel and rail with certain relevance will increase the friction coupling vibration of the wheel-rail system, which may aggravate the subsequent relevant wheel polygonal and rail corrugation wear. With the increase of the friction coefficient between wheel and rail, as well as the depth of the wheel polygon and rail corrugation, the vibration trend of the friction coupling vibration of the wheel-rail system increases gradually. Moreover, the proportion of the wheel polygon's influence on the friction coupling vibration of the wheel-rail system is greater than that of rail corrugation.

Calculation method and model tests of pile frost jacking for railway overhead contact systems in permafrost regions

One of the major challenges encountered in electrification reconstruction project of Golmud-Lhasa section of Qinghai-Tibet railway of China is ensuring the frost jacking stability of the pile foundation of overhead contact system mast (OCSM). To evaluate the resisting frost jacking performance of OCSM pile in permafrost regions, a theoretical model of OCSM pile in permafrost soils under the effect of frost heave was constructed based on superposition principle and deformation coordination relationship between the pile and soil. The model was solved by using the finite difference method combined with MATLAB. Then, large scale model tests were performed to investigate the thermodynamic behaviors of OCSM piles with different sections (equal section circular pile, straight cone cylindrical pile and curved cone cylindrical pile) in the permafrost soils under freeze-thaw actions, after which the theoretical model were validated. It was found that distribution curves of pile axial force obtained by the calculation method is basically consistent with model test results in the overall trend, implying that the calculation model is reasonable and feasible. During soil freezing, the pile is under tension as a whole, and the axial force is greatest near the depth of frost penetration. The maximum value of tangential frost-heave stress occurs near the ground surface. The total tangential frost heaving force of the curved cone cylindrical pile is the smallest, and the effect of resisting frost jacking is the best. These research results can provide a reference for resisting frost jacking design of OCSM pile in permafrost regions.

Laboratory and field studies to ensure the regulatory framework development and the transport facilities’ safety in the wave effect conditions

This article is part of the author’s dissertation research in the field of scientific substantiation of the development and improvement of the regulatory framework for ensuring the safety of transport facilities in conditions of wave effect. The article deals with such transport structure elements as bridge piers and railway roadbeds, which are located on the shores of the seas and are exposed to wave effects, and, as a result, need to be protected. The relevance of the issue is due to the fact that an insufficient justification degree of design solutions for engineering protection structures can lead to environmental disasters and large financial losses. Usually, competent and strict regulation of the design process and survey work allows for avoiding large financial losses. Regulatory framework development will improve the reliability of transport facilities located in the wave effect zone. At the same time, technical regulations requirements must be substantiated by scientific research. The article presents some results of scientific research carried out by the author to ensure the regulatory framework development and the safety of transport facilities in wave effect conditions. The following methods of scientific research were used in the work: field observations and surveys of the coastal zone and engineering protection structures of transport facilities from wave effect and physical (hydraulic) modeling. The results of long-term field observations and surveys of the coastal zone and engineering protection structures of the railway roadbed are used: sea wall, protective wave-damping strips, groins, breakwaters, etc. at the Tuapse-Adler sections of the North Caucasian Railway and Korsakov-Nogliki of the Far Eastern Railway. The author presents laboratory studies results of the wave protection structures operation (protective slopes, wave-damping strips with retaining structures, etc.), which were carried out by the physical (hydraulic) modeling method in wave pools and flumes. Provides information about the regulations developed with the author’s participation based on the research. The expected efficiency from the practical application of the developed normative documents is described.

A Study on the Train-Induced Vibration Responses of Heavy Haul Railway Subgrade in Seasonally Frozen Regions Using Field Experiments

The dynamic response resulting from heavy haul train leads to the deterioration of the railway subgrade, especially those built in seasonally frozen regions. In this work, a typical heavy haul railway section in a seasonally frozen region is monitored on-site. The time domain and the frequency domain analysis of the subgrade vertical vibration acceleration, dynamic speed, and displacement during the non-frozen period and the frozen period are investigated. The results show that the vibration response of the subgrade is affected by various factors, including the train type, locomotive, traveling speed, train formation, heavy load, and the prevalent season. Further, it is observed that the maximum and average vertical acceleration of the subgrade, the vibration speed, and the dynamic displacement increase during the frozen period. However, the main frequency of the natural vibration remains significantly higher than that before freezing. Moreover, the frozen soil has a significant amplification effect both on the acceleration and the attenuation rate. Similarly, the subgrade’s vibration mode has a low frequency and high amplitude during the freezing period, and the dynamic response characteristics become increasingly apparent as the axle load increases.

Investigation into the Abnormal Phenomenon of Rail Corrugation Superposition in Small-Radius Curve Section of Intercity Railway

Focusing on the mechanism of the abnormal phenomenon of rail corrugation on the low rail of small-radius curve section of Guangzhou–Zhuhai intercity railway, the distribution regularities and the track irregularities are studied through the overall and local field surveys. Then, the dynamic model of vehicle-track system on the section is established to explore the wheel-rail dynamic characteristics. Next, the relevant finite element model of the wheel-rail system and the wear model of rail corrugation are established. The friction self-excited vibration analysis and feedback vibration analysis are carried out to investigate the dynamic causes of such abnormal rail corrugation. Field survey proposes that the dominant wavelength of the abnormal rail corrugation is 200–300 mm and the sub-wavelength is 70–100 mm. Analyses show that the friction self-excited vibration of the multi-wheelset-track system caused by the saturated creep force on the guide wheelset in the small-radius section may induce the rail corrugations with these two wavelengths. The possibility of inducing the rail corrugation with 200–300 mm wavelength is greater. On the other hand, the feedback vibration of corrugated wear will aggravate the development of the two corrugated wears. Overall, the generation and development of the abnormal rail corrugations are affected by the self-excited vibration of the wheel-rail system and the feedback vibration of track irregularity.

Debris Flow Susceptibility Assessment of Sichuan-Tibet Railway Based on GIS and CF-LR Coupling Model

Sichuan-Tibet Railway is an important transportation system in China, which is of great significance to promote the communication between Tibet and the mainland. This paper takes the lin-chang section of the Sichuan-Tibet railway with a width of 2km on both sides as the research area. The occurrence of debris flow must have appropriate solid source, water source and topographic conditions. In this paper, ten disaster-causing factors are selected, including relief degree of land surface, profile curvature, silty soil, distance to the rive, distance to the fault, elevation, slope aspect, NDVI, average annual rainfall and land utilization rate. The information of disaster-causing factors was extracted from Arcgis and evaluated by the certainty factor model. The probability of debris flow in the study area was calculated by the coupling model of binary Logistic regression model combined with certainty factor model. ROC curve analysis of the CF-LR model shows that AUC is 0.89, indicating that the model has a good effect. The distribution map of debris flow susceptibility in the study area was obtained by using grid calculator in GIS. The results show that under the CF-LR model, extremely low, low, medium and high prone areas cover 2547km₂, 235km₂, 246km₂ and 1099km₂ respectively, accounting for 61.72%, 5.69%, 5.96% and 26.63% of the total area of the study area, respectively. The high risk areas are mainly in Milin, Nyingchi and Bomi counties. This study provides an important reference for assessing the risk of debris flow geological disaster on Sichuan-Tibet Railway.

Numerical analysis of engineered metabarrier effect on ground vibration induced by underground high-speed train

The construction of the underground section of the Chengdu-Zigong High-speed Railway, the fastest underground railway worldwide with a design speed of 350 km/h, has attracted extensive attention in the transportation and environment communities because it passes through many areas with vibration-sensitive equipment. In this context, an in-situ wheelset-dropping experiment is conducted in the high-speed railway tunnel to probe the vibration transfer characteristics of the tunnel-soil system. Further, an elaborate spatial dynamics model is built based on a hybrid time-frequency domain method to explore the feasibility of an engineered metabarrier for mitigating the ground vibration induced by underground high-speed trains from the perspective of numerical analysis. The bandgap characteristics of the metabarrier and the sensitivity of ground vibration attenuation rate to metabarrier depth are revealed. The results show that the horizontal vibrations cannot be ignored, the metabarrier can effectively suppress the ground vibration at 29.11–80.74 Hz, and the ground vibration attenuation rate first increases and then tends to be stable with the increasing metabarrier depth. The in-situ excitation test fills the experimental gap in the field of environmental vibration caused by underground high-speed trains and the research on the application of metabarrier provides fresh insights for preventing railway induced vibration, specifically in studies where metabarriers are considered as mitigation measures.

Cooperative Optimal Control of the Following Operation of High-Speed Trains

The following operation of multiple high-speed trains (HSTs) with high speed and great density based on the moving block and virtual coupling control system can significantly improve the performance of railway systems concerning operation safety and line capacity. However, it is difficult for HST’s conventional control approach to satisfy the service demand, including safety, energy-saving, and ride comfort, due to the significantly increasing longitudinal interaction between adjacent trains in the following operating conditions. In this paper, the characteristic model of multiple HSTs’ following operation was formulated to effectively and accurately describe train control constraints derived from the coupling relationship among adjacent trains’ operation states. Then, the cooperative model predictive control (CMPC) strategy with a multiobjective rolling optimization scheme is developed. The overall line capacity, energy consumption, and ride comfort of train platoons in the railway section are defined as optimization indexes. Furthermore, some sufficient conditions for the consensus stability of the CMPC of HST are given, based on the proposed multiple HSTs following characteristic model and cooperative optimal control strategy. Simulation experiments are carried out by using HST’s operation data collected from real-world runs. Results demonstrate the effectiveness and feasibility of the proposed modeling and control method.

The role of environmental, structural and anthropogenic variables on underpass use by African savanna elephants (Loxodonta africana) in the Tsavo Conservation Area

Wildlife crossing structures are effective interventions for mitigating fragmentation of habitats by linear infrastructure. The 2017 construction of a new railway cutting through the Tsavo Conservation Area (TCA), home to the largest elephant population in Kenya, affected wildlife movement and habitat connectivity. Although numerous studies have investigated the use of wildlife crossing structures by a wide range of species, few have focused on their use by megaherbivores. In this study, we examined use of 41 wildlife crossing structures by African savanna elephants (Loxodonta africana) along a 133 km section of new railway in Tsavo, Kenya. We used a generalized linear mixed modeling approach to assess the relationship between elephant crossing rate over 28 months between July 2017 to April 2021 and explanatory factors including crossing structure attributes, livestock presence and proximity to highways, water points and human settlement. We found that structural attributes of crossing structures were most strongly associated with the elephant crossing rate, particularly height and its interaction with type of crossing structure (bridges, wildlife underpasses and culverts). Higher crossing structures were associated with higher crossing rate, with the largest influence of height at culverts and wildlife underpasses. Although bridges comprised only 19.5 % of the 41 available crossing structures, they accounted for a disproportionately high number of elephants crossing events (56 %). The results demonstrated the importance of bridges over designated crossing structures for elephants, with predicted seasonal counts of elephant crossings being 0.31 for average sized culverts, 2.88 for wildlife underpasses and 5.86 for bridges. The environmental and anthropogenic variables were not strongly associated with elephant crossing rate. Our findings have direct application for future siting and design of crossing structures across elephant ranges.

ОСНОВНЫЕ ЭТАПЫ РАЗВИТИЯ ЖЕЛЕЗНОДОРОЖНОГО СООБЩЕНИЯ В ЕНИСЕЙСКОМ РЕГИОНЕ В XIX—XXI ВВ.

The influence of the Trans-Siberian Railway on the economic, social and cultural development of Siberia can hardly be overestimated. Contemporaries noted that from the very beginning of the operation of the Siberian railway, the economic and cultural development of Siberia accelerated: the railway opened the way for Siberian manufacturers to Western markets; also, the industrial development of Siberia required an influx of labor, and streams of migrants, peasants, employees, and merchants poured into Siberia. The section of the Trans-Siberian Railway, passing through the territory of the modern Krasnoyarsk Territory, at different periods of its existence was part of the Great Siberian Railway, the West Siberian, Tomsk, East Siberian Railways. The change of ownership of the Krasnoyarsk Railway from one section of the Trans-Siberian Railway to another was due to the tasks of industrial development facing society. Each time the reformation of the structure of the Trans-Siberian Railway was accompanied by corresponding personnel and organizational changes in the management structure of the Krasnoyarsk Railway itself. The article considers the key events in the history of the development of the railway transport of the Yenisei region. The authors analyzed the prerequisites and historical conditions that determined the pace of development of the railway network at each historical stage, showed the importance of individuals who had a significant impact on the development of the railway in the Yenisei region, considered the historical conditions that determined the pace of development of passenger traffic. The authors provide statistical information indicating a high level of demand for railway communication among the local population. It should be noted that the invariable direction in the activity of the Krasnoyarsk Railway was the development of infrastructure, which made it possible to ensure the economic development of the region in different historical periods.

STUDY OF THE INFLUENCE OF THE PASSAGE OF HEAVY TRAINS ON THE THROUGHPUT AND CARRYING CAPACITY OF RAILWAY SECTIONS WITH ELECTRIC TRAIN TRACTION

The criterion for the effectiveness of the organization of heavy traffic on the sections of the Russian railway network is the presence of large correspondences of bulk goods presented by the consignor for transportation. An obstacle to the development of a promising cargo traffic are areas with limited throughput and carrying capacity, the overcoming of which is the organization of heavy traffic. All countries that have railways, at a certain stage of development, face capacity constraints. Summarizing the world experience, we can conclude that the priority in the development of increasing volumes of “heavy cargo” is increasing the weight norms of freight trains. The problem of passing heavy trains for Russian Railways is urgent, because the capacity of some sections has exhausted itself completely. The very timely appearance of heavy traffic becomes one of the options for solving the problem of increasing the carrying capacity of sections and directions and, as a result, creating a reserve of carrying capacity. In this article, a study of the influence of their movement on the carrying capacity and carrying capacity has been carried out.
 Aim. To consider the effectiveness of the formation and passage of heavy trains. The influence of the organization of the movement of such trains on the throughput and carrying capacity of railway sections.
 Methods. To solve the problem, graphic and analytical methods of mathematical modeling, scientific methods of collecting and processing statistical data, modern achievements in terms of general principles and methods of risk management was used.
 Results. The authors have developed a formula for determining the rate of removal of freight trains. The analysis of the influence of the values of the inter-train intervals of freight trains and heavy trains on the removal rate is given.
 Practical relevance. As the main alternative to increasing the size of traffic on the main cargo-intensive directions, with a shortage of traffic capacity, it is proposed to use the technology of heavy traffic. In modern market conditions, an increase in the weight and length of a freight train is one of the main reserves for increasing throughput and carrying capacity. By passing heavy trains, we get an increase in carrying capacity. In the article, we prove the consistency of these measures. The increase in carrying and carrying capacity is considered in the context of increasing unified weight standards.

Influence of Biaxial Geogrid at the Ballast Interface for Granular Earth Railway Embankment

The development of reinforcements for soil has made an impact in most of the civil engineering sectors especially transportation. The use of geogrids is frequent in roadways but they are also finding use in railways. The major impact that geogrids could have is providing desired stiffness to a section by reducing material and serving as a proper reinforcement material. In the current study, an attempt has been made to redesign the railway embankment economically with the help of geogrids. Biaxial geogrid is used to substitute the blanket layer (thickness up to 100 cm) in the railway embankment by fulfilling the strain modulus requirement of the embankment, calculated using a plate bearing test as per DIN 18134. The experiment is performed on the embankment replicated in a metallic test chamber with granular soil as subgrade and geogrid is placed beneath the ballast. The experimental study is validated by a 3-D numerical model using Midas GTS NX software. The experimental analysis shows an improvement of 31.47% in the second modulus of the earth embankment. For the implementation of this study, a design section of Indian railways is adopted. With the help of geogrid, a reduction of 50% is observed in the embankment height, thereby reducing the overall costs.

Статистический анализ поездопотока на участке Палласовка — Верхний Баскунчак с целью выявления ветровых нагрузок

Purpose: The given article is devoted to energy consumption problematics. The article relevance is especially high for our country steppe regions where high speed winds prevail most of the year that have a significant impact on fuel and energy resource (FER) consumption increase in train traction. This question is open and no analysis methods have been developed. Also, in locomotive depots, there is no clear energy expenditure normalization for train traction under exposure to additional drag to movement. Wind burden impacting train cars is one of the essential factors affecting energy consumption in a traction. Methods: The article shows high significance of this problem for Russian Railways (“Russian Railways” JSC). The article analyzes main factors, affecting fuel and power consumption, and major methods of normalization for FER. For the consideration, Pallasovka — Verkhniy Baskunchak section of Privolzhskaya railway in the traction with 2TE25KM series diesel locomotive was chosen. Histograms of specific fuel consumption for trains with fixed minimal and maximal axle loads were built and analyzed on the basis of samples from the given foot-plateman routes. Results: Conclusions on the effect of wind loads on specific fuel consumption were made basing on the numerical characteristics of the obtained samples. Contributions of wind loads to a significant increase in a specific fuel consumption have been proved in the article. Moreover, wind burden impact is higher for empty trains. Practical significance: The need to clarify fuel consumption norm is shown. The norm adjustment will allow to improve definition and record accuracy for energy resource expenditures at their normalizing in locomotive depots. The proposed adjustments can be recommended for a practical use on the considered section.

Оценка экономической эффективности проекта модернизации технологий электрификации железнодорожного участка

Purpose: To evaluate the economic efficiency of contact network modernization project for the railway section of the St. Petersburg - Baltiyskaya power supply distance of the Oktyabrskaya Railway (OR). The study subject is the operation protocol for contact network modernization. Methods: Analysis basic methods are applied — target indicator statistical analysis of electrified section specific weight in the total operational length of public railway tracks; target indicator statistical analysis of railway line electrification. Results: The modernization of electrification technologies on the railway section of “St. Petersburg-Baltiyskiy” OR railway distance is justified. Implementation main stages for contact network modernization project are systematized. Economic effect being obtained from electrification technologies modernization is determined. Practical importance: The obtained results represent an applied character since they propose and justify measure series aimed at servicing effectiveness raise for the railway section servicing of the St. Petersburg-Baltiyskiy OR railway power supply distance.

Increasing the performance of the Far Eastern Railway traction power supply system

Introduction. The purpose of the study is to develop measures determined by the strategic programmes for the development of Russian railway transport based on the analysis of power supply schemes for the traction network of the Far Eastern Railway, a branch of Russian Railways.Materials and methods. Evaluation of the performance of the traction power supply system was made based on the analysis of the actual performance of the Far Eastern Railway section, as well as the theories of electrical engineering and power supply of the 25 kV AC electrified railway system.Results. Based on the analysis of the joint operation of the external and traction power supply systems of the Far Eastern Railway, four traction substations with low technical and economic indicators were identified. Network sections that feed the substations are a bottleneck in the traction power supply system. It is proposed to increase the efficiency by switching the connection of the windings of transformers of traction substations to the systems of external and traction power supply according to the typical star – delta scheme. Such a connection will ensure an increase in the speed of trains, a reduction in train succession time and losses of electricity, an increase in the quality of electric energy in the external power supply system and electric networks of the Far Eastern Directorate for Energy Supply (a structural subdivision of Transenergo, a branch of Russian Railways).Discussion and conclusion. Normalisation of the connection of four traction substations according to the feeding scheme is ensured by changing the phasing in such a way that the power supply of the two legs of one winding of the power transformer is transferred to two windings. Alignment of the current modules in the windings of transformers of traction substations makes it possible to reduce the voltage drop in the most loaded phase and, accordingly, increase the voltage in the traction network, which ensures an increase in the speed of trains and a reduction in passing intervals. Switching the power supply of the arms from one winding of the transformer to two reduces the loss of electrical energy in power transformers and the external power supply system. Reducing the current unbalance in the windings of the power transformer improves the quality of electrical energy in the system of external and district power supply. An increase in the service life of the power transformer is ensured by a decrease in the intensity of thermal wear of the insulation of the most loaded winding.

Influence of different railway lines on wheel damage of high-speed trains: Data-driven modelling and prediction

Wheel damage of high-speed trains has received great attention since it is detrimental to safety and reliability and consumes huge maintenance costs. However, the mixed operation mode of electric multiple units (EMUs) in China induces great challenges in distinguishing the influence of different railway lines on wheel damage. This paper develops a data-driven approach to quantify the influence of different railway lines on wheel damage and further applies it to damage risk prediction. First, under several fundamental assumptions, linear discriminant analysis and the proposed data padding strategy are used to quantify the influence on wheel damage due to per unit mileage of running on each railway section. The result shows that the influence on wheel damage varies significantly for different railway sections. Then, a route-based predictor is defined to represent the cumulative influence of an EMU’s routes on its wheel damage. Further, a wheel damage prediction model is developed based on a support vector machine using the route-based predictor and three other predictors from the operational data. Validation and test results demonstrate that the actual damage rate is higher for wheelsets predicted with higher damage probabilities. The proposed methodology has the potential to be applied to the risk-based operation and maintenance of high-speed trains.

Оценивание электромагнитной обстановки для аппаратуры автоматики и телемеханики на электрифицированных участках железных дорог

Unstable operation of rail chain equipment and locomotive equipment of automatic locomotive signaling causes false switching of traffic lights that negatively affects the capacity of railway sections and train traffic safety. Such failures in automatic locomotive signaling operation impacts negatively on locomotive crew mentality. At increased intensity of the failures, it is allowed to turn off automatic locomotive signaling equipment as faulty one that significantly worsens train traffic safety. On electrified railways, the main cause of failures in this equipment operation is the interfering effect of traction currents.
 Traction current most strongly interferes with the operation of these devices at this current inequality in rail lines at those places where rail chain equipment is connected or under receiving locomotive coils of automatic locomotive signaling. The interfering activity occurs while an asymmetry (difference in values) of longitudinal and/or transverse resistances of a rail line due to the deterioration of the state of rail butt connectors, throttle jumpers and/or the breakdown of spark arresters in the circuits of connection to rails of grounding circuits of various structures. It is difficult to control the state of electrically conductive elements in rail lines because of their multiplicity and also as their electrical resistance in a tolerance area has milliohm order. It causes the necessity to work out better ways on electro-magnetic situation check and approaches to define the condition of indicated elements such as numerous grounding circuits. It’s time-consuming task but must be carried out with the fulfillment of all requirements for operation in high-voltage lines. This article presents some results on the development of methods for controlling electrically conductive and insulating elements in rail chains and that are more suitable for performing maintenance work of equipment of rail chain and locomotive automatic signaling.

Analysis of wheel pairs slip control of electric freight locomotive with asynchronous traction motors

Introduction. Every year, the amount of electric rolling stock with asynchronous traction motors is continuously increasing on the Russian railway network, since such traction drives have a number of advantages over drives with DC motors. One of the problems associated with the introduction of asynchronous motors and an increase in the mass of trains is the implementation of the maximum traction force by an electric locomotive at the threshold in terms of wheel – rail adhesion. Timely recognition of excessive slip of wheel pairs is the most important indicator of the efficiency of the traction drive in realising the maximum traction properties of the electric locomotive at all axles.Materials and methods. The article reflects the results of the study of slip of electric locomotive wheel pairs with asynchronous traction motors and axial control of the traction force, obtained during experimental runs on a railway section under various adhesion conditions. The article presents a technique for studying the wheel pair adhesion failure of electric locomotives with asynchronous traction motors.Results. During the comparison of the obtained experimental results with the calculated parameters by the O. Polach mathematical model, an updated range of the relative slip of wheel pairs is given, in which the electric locomotive control system could realise the maximum tractive effort. Exceeding this range will lead to increased wear of wheel pairs without increasing traction properties.Discussion and conclusion. It is advisable to use the results of the study in the future when developing systems for controlling the tractive effort at the limit of adhesion and systems for controlling the slip of wheel pairs of electric freight locomotives with asynchronous traction motors.

The modelling of railway subgrade strengthening foundation on weak soils

Abstract As a consequence of increased axle loads and speeds of trains on modernised railway lines, there may occur problems with bearing capacity and stability of the subgrade in some sections of the railway network. This is the situation we are dealing with right now on the Polish State Railways network. Therefore, as a case study, a fragment of an existing railway embankment based on a weak foundation was chosen for the analysis of train–track–subgrade interaction. A two-stage train–track–subgrade model has been developed. The model consists of the upper part (train–track) and the lower part (subgrade-foundation). The first part is modelled as a self-contained system of differential equations which are solved by means of finite difference method and yield the stress levels on the subgrade. These stresses are treated as a load for the lower system modelled using FEM. The model has been validated using experimental data from literature, authors’ measurements, and railway staff measurements of the track geometry. Several cases of strengthening methods were calculated and compared with measurements on the railway section under consideration. Good agreement between the prediction and the measurement was found. The novelty of the model is including the heterogeneity of the subgrade, the strengthening methods, and very deep layers of its foundation as well as adding the influence of vibration on the weakening of soils. It was found that this influence is noticeable and should be included in the prediction of railway subgrade behaviour

Life cycle assessment of tunnel structures: Assessment of the New Austrian Tunnelling Method using a case study

One important measure to combat progressing climate change is compliance with and under no circumstances to exceed the decreasing greenhouse gas budget. Every economic sector must strive to make its ecological contribution to achieve this objective. The construction sector is largely responsible for these negative environmental burdens. Although tunnels are considered to have extensive energy and material consumptions the literature has failed to present their environmental impacts. Aimed at this knowledge gap, the objective of this study is to present the life cycle assessment (LCA) of a tunnel construction project situated in Bulgaria. The study analyzes the impacts of the New Austrian Tunnelling Method (NATM) using the case study “Modernization of Railway Section Elin Pelin-Kostenets – Lot 3”. Moreover, by applying dominance and sensitivity analyses, the environmental drivers and optimization potential for reducing greenhouse gas emissions are identified. The results show that steel, shotcrete, and concrete, contribute the most to the global warming potential indicator and are responsible for 85% of this. Furthermore, the life cycle stages for the production of materials and components have a share close to 85 % of the total global warming potential. These findings may help future tunnelling construction projects to improve the environmental performance and thus to combat the alarming development of climate change.