Search Results (20)

The rapid development of urban transportation renovation and transportation networks in China has driven the construction of an increasing number of large-span, large cross-section tunnels under sensitive environments, such as airport runways, critical infrastructure, and high-speed railways. These projects often require strict settlement control within a millimeter-level tolerance range, thus theoretical methods and key technologies for micro-settlement control have been developed. This study first derives a calculation formula for surface settlement associated with large cross-section tunnels and elucidates its correlations with factors such as pipe-roof stiffness, support system stiffness, pipe-roof construction procedures, and groundwater level changes. Theoretical approaches for controlling micro-settlement are introduced, including increasing pipe-roof stiffness, reinforcing the support system, mitigating group pipe effects, maintaining pressure and reducing resistance around the pipe, and controlling groundwater levels. A method is proposed for determining the appropriate stiffness of the pipe roof and support system. The stiffness should be selected from the transition segment between the steep decline and the gentle slope on the stiffness-settlement curves of the pipe roof and the support system. If the stiffness of the pipe roof and primary support combined with temporary support fails to meet the micro-settlement control requirements, an integrated support system with greater stiffness can be adopted. A reasonable pressure-regulating grouting technique for maintaining pressure and reducing resistance around the pipe is proposed. It is recommended that the spacing for simultaneous jacking of pipes be greater than half the width of the settlement trough. For over-consolidation-sensitive strata such as medium or coarse sands, water-blocking measures, including freezing, grouting, or a combination of both, are recommended. For over-consolidation-insensitive strata like gravels and cobbles with strong permeability, water-blocking treatments are generally unnecessary. The proposed theoretical approaches have been successfully implemented in projects such as the tunnel beneath Beijing Capital Airport runways and Taiyuan Railway Station, demonstrating their reliability. The research findings provide valuable insights into surface micro-settlement control for similar projects. Full article

Most European Union governments and numerous railway operators have announced plans to replace most of their diesel units by 2030–2040. However, a significant portion of the rail network remains non-electrified. In some cases, the proposed solution has been to close certain tracks, but this approach entails considerable societal costs for small cities and represents a loss of prior railway investments. Consequently, hybrid locomotives and multiple units (either new or refurbished) emerge as a viable solution during this transitional period to enhance energy efficiency and preserve services on these lines, particularly for freight operations. These hybrid units can operate on both electrified and non-electrified tracks and can also serve as “railway prosumers”, contributing to both storage and generation in fully or partially electrified areas. However, implementing these “prosumer tasks” faces challenges, such as the rapid power demand fluctuations during acceleration and the loss of energy recovery potential during braking in hybrid or fully electric units. These losses may also impact the overall power system. This paper presents an alternative approach to modeling double-layer capacitors (supercapacitors) combined with electrical equivalent models for lithium-ion batteries. The Differential Transformation Method (DTM) is used to solve the non-linear ordinary differential equations governing the supercapacitor model, while parameter optimization is achieved through a grid search approach, demonstrating high accuracy compared with laboratory trials. This framework highlights the potential of hybrid units, as illustrated through simulations that analyze storage sizing, energy management, increased energy recovery, and changes in unit performance. These models facilitate a pre-feasibility evaluation of energy storage systems for hybrid railway applications. Full article

The rapid growth of cities and their populations in recent years has resulted in significant tidal passenger flow characteristics, primarily manifested in the imbalance of passenger numbers in both directions. This imbalance often leads to a shortage of train capacity in one direction and an inefficient use of capacity in the other. To accommodate the tidal passenger flow demand of urban rail transit, this paper proposes a timetable optimization method that combines multiple strategies, aimed at reducing operating costs and enhancing the quality of passenger service. The multi-strategy optimization method primarily involves two key strategies: the unpaired operation strategy and the express/local train operation strategy, both of which can flexibly adapt to time-varying passenger demand. Based on the decision variables of headway, running time between stations, and dwell time, a mixed integer linear programming model (MILP) is established. Taking the Shanghai Suburban Railway airport link line as an example, simulations under different passenger demands are realized to illustrate the effectiveness and correctness of the proposed multi-strategy method and model. The results demonstrate that the multi-strategy optimization method achieves a 38.59% reduction in total costs for both the operator and the passengers, and effectively alleviates train congestion. Full article

The prevention of ecological risks is a critical determinant influencing sustainable development. Driven by rapid socio-economic development, the ecosystems of mountainous cities within agro-pastoral transition zones are increasingly vulnerable to complex disturbances, constituting a significant threat to sustainable development and human well-being. To help achieve sustainable development, it is essential to conduct research on addressing and mitigating ecological risks from the perspective of collaborative management networks in mountainous cities. Taking Zhangjiakou as the study area, this paper employed the land use transfer matrix and standard deviation ellipse methods to analyze the dynamic land use changes. Additionally, using Fragstats 4,2 to calculate the landscape indices with land use data, this paper evaluated the landscape ecological risk (LER) from 2000 to 2020. Furthermore, the social network analysis (SNA) method was utilized to explore the spatial correlation characteristics of the LER. The findings indicate that: (1) Cultivated land and grassland were the predominant land use types in Zhangjiakou. During 2000–2020, Zhangjiakou experienced significant changes in land use, dominated by the transfer among cultivated land, forestland, and grassland. It indicated that the issue of unstable ecological land use continued to exist. Affected by human activities, construction land showed a consistent upward trend, primarily concentrated in the urban built-up areas and areas along the Jing-Zhang Railway. (2) The LER of Zhangjiakou was predominantly characterized by low risk, medium risk, and high risk levels. In the transitional areas and foothills, the LER was relatively higher. During 2000–2020, Zhangjiakou showed a declining trend of LER. This suggested that the ecological protection policies in Zhangjiakou were effective, leading to an improvement in the local ecological environment. (3) The LER in Zhangjiakou demonstrated a spatial clustering pattern that exhibited an upward trend, which was supported by both spatial autocorrelation and the SNA analysis. In the LER collaborative management network, Xuanhua, Qiaodong, Qiaoxi, Wanquan and Zhangbei consistently upheld pivotal roles. Based on the number of inward and outward connections, 16 counties in Zhangjiakou were classified into four categories and three zones accompanied by corresponding recommendations. The findings of this study can serve as a valuable reference for subsequent landscape pattern optimization and ecological restoration in Zhangjiakou. Full article

With the rapid development of urban rail transit networks, constructing shield tunnels often requires passing underneath existing buildings, which can potentially impact their safety. This study examined the impact of constructing a double-line shield tunnel underneath a railway bridge on the adjacent pile foundation via numerical simulation. Protective measures, including construction parameter control, grouting methods, monitoring, and early warning systems, were implemented to mitigate impacts. The results indicated that the bridge deformation fell within acceptable limits, with maximum horizontal and longitudinal displacements of 0.06 mm and a maximum vertical displacement of −0.31 mm. The railway bridge pile foundation experienced maximum horizontal and longitudinal displacements of 0.47 mm and vertical displacements of −0.23 mm during construction. Enhanced construction quality control and monitoring effectively controlled deformation to ensure the railway safety. This study provides valuable guidance for similar projects and future urban rail transit developments. Full article

The precise identification of railway subgrade defects remains a significant challenge for the railway industry globally. Due to the limitations of individual monitoring techniques, comprehensive information on subgrade defects cannot be obtained. In fact, the presence of subgrade defects can significantly increase the risk of traffic accidents during high-speed train operations, which may affect the safety of train operations and economic development. The monitoring of subgrade health status is used as a pre-disaster planning method that is urgently required to avoid accidents and guide the maintenance strategy. Therefore, a novel “integrated” holistic monitoring approach for subgrade structures is presented based on satellite remote sensing, a comprehensive inspection vehicle, and a ground-based testing technique. Additionally, the monitoring content is more clearly defined during the service life of the subgrade. The method is used to investigate the location, development trend, and the cause of subgrade defects on the Shanghai–Nanjing high-speed railway. Some new viewpoints are put forward: First, the monitoring content for assessing the health status of the subgrade should encompass the foundation settlement, the track geometry status, and the monitoring of deformation and defects within the subgrade. Second, the mileage points K235 and K299 of the subgrade, as well as K236 and K237 of the bridge–subgrade transition sections, are estimated to be locations with potential defects based on the differential InSAR and track quality index. Third, the result of settlement monitoring and ground-penetrating radar analysis illustrates that sections K235 +540 to +680 and K299 +680 to +750 are diagnosed as defect positions triggered by the rapid drop of water level and engineering activity, respectively. Fourth, the “integrated” holistic monitoring technique for subgrade service status might be expected to be a promising method that can be useful in developing maintenance plans and implementing fault recovery for railway infrastructure. Full article

Transportation significantly influences economically underdeveloped arid regions, impacting economic growth and social progress. Analyzing Transport Superiority Degree (TSD) and its implications in such regions is crucial. A new arid region-specific evaluation framework addresses traditional limitations by considering indicators like route connectivity and desert interference. This article conducts an empirical study using Southern Xinjiang as a research case. It combines comprehensive evaluation methods, spatial autocorrelation methods, spatial Durbin models, and coupling coordination models to depict Transport Support Capability (TSC), Transport Access Capacity (TAC), and Transport Guarantee Capacity (TGC) at different scales in Southern Xinjiang from 2000 to 2020. The study reveals spatial patterns, evolutionary characteristics, economic impacts, and social effects of TSD at various scales. Key findings include: (1) Rapid expansion of transportation infrastructure in Southern Xinjiang. The levels of TSD at different scales have gradually increased, and spatial and temporal pattern differences are evident. At the county level, TSD forms a “core-periphery” spatial pattern centered around the Southern Xinjiang Railway, with “high-high” agglomeration areas centered around Kashgar city and “low-low” agglomeration areas centered around Qiemo County. (2) Prefectural-level TSD improvements have limited impacts on regional development, while county-level TSC, TAC, TGC, and TSD positively affect economic and social growth but also exhibit competitive effects. (3) TSD is transitioning from non-coordinated to coordinated development with economic and social progress at different scales. This research informs transportation facility evaluation in arid regions. Full article

Urban rail transport has advantages that determine its particular usefulness. However, despite decades of technical development, it is still difficult to speak about satisfactory solutions. Safe, independent access to this transport and public infrastructure for passengers with reduced mobility (PRM) is an essential element of civil rights and an interesting subject of scientific research. In relation to that, the interface between rail vehicle and platform, despite multiple efforts aiming at improving this situation, is one of the hardest problems to overcome. This paper presents a summary and analyses of distinctive features of selected transit systems that are interesting from the viewpoint of finding various solutions to improve the safety of passengers on platforms. This analysis led to preparation of a new, improved standard of the vehicle–platform interface, illustrated with an example of the city of Wrocław, as discussed further in this paper. Some of the main conclusions of this paper are that insufficient progress has been made with developing the vehicle–platform interface, there are a multitude of systems and ways of (more or less effectively) ensuring independent access for PRM, and further research and development work is needed to optimize engineering solutions in this domain so they are both sustainable and economical. Full article

With rapid high-speed railway (HSR) developments in China, HSR-based transit-oriented development (TOD) has proliferated across the country. Although local governments claim that HSR station areas are planned according to TOD principles, some scholars argue that these station areas actually contribute to unsustainable development. This study investigates two main questions: (1) what success factors should be included in a TOD plan for HSR station areas? (2) to what extent are these factors considered in the plans of Chinese HSR station areas? To answer these questions, we use content analysis to compare spatial plans for 15 HSR station areas across China, triangulating the findings via in-depth interviews and field investigations. This study reveals that most of the factors in the plans for HSR station areas deviate from TOD principles, especially in small- and medium-sized cities. We find that Chinese local governments mainly use TODs as a tool to promote suburban expansion around HSR stations. Full article

Traffic is a major source of particulate pollution in large cities, and particulate matter (PM) level in Bangkok often exceeds the World Health Organisation limits. While PM_2.5 and PM₁₀ are both measured in Bangkok regularly, the sub-micron range of PM, of specific interest in regard to possible adverse health effects, is very limited. In the study, particle number concentration (PNC) was measured on public transport in Bangkok. A travel route through Bangkok using the state railway, the mass rapid transport underground system, the Bangkok Mass Transit System (BTS) Skytrain and public buses on the road network, with walking routes between, was taken whilst measuring particle levels with a hand-held concentration particle counter. The route was repeated 19 times covering different seasons during either morning or evening rush hours. The highest particle concentrations were found on the state railway, followed by the bus, the BTS Skytrain and the MRT underground with measured peaks of 350,000, 330,000, 33,000 and 9000 cm⁻³, respectively, though particle numbers over 100,000 cm⁻³ may be an underestimation due to undercounting in the instrument. Inside each form of public transport, particle numbers would peak when stopping to collect passengers (doors opening) and decay with a half-life between 2 and 3 min. There was a weak correlation between particle concentration on bus, train and BTS and Skytrain with carbon monoxide concentration, as measured at a fixed location in the city. Full article

Rapid transit systems play a significant role in supporting rapid social and economic development in large cities all over the world. However, the systems consume a large amount of energy, which brings increasing environmental concerns. A number of energy-saving technologies have been studied on railways. However, few of the outcomes have been tested and evaluated in practice. This paper presents the development of a timetable optimization and trial test on a metro line to reach the full potential of the train regenerative braking system. To achieve this purpose, a timetable optimization algorithm has been developed, and a trial test of the optimal timetable has been arranged on a metro line for a whole day. In the test, all the trains running in the network were organized to operate in accordance with the optimal timetable. The trial test results indicate that by applying the optimal timetable, the regenerative braking energy utilization can be improved, thereby reducing the overall network energy usage. Full article

With the rapid development of urban modernization, traffic congestion, travel delays, and other related inconveniences have become central features in people’s daily lives. The development of subway transit systems has alleviated some of these problems. However, numerous underground subway stations lack adequate fire safety protections, and this can cause rescue difficulties in the event of fire. Once the fire occurs, there will be huge property losses and casualties. In addition, this can have a vicious impact on sustainable development. Therefore, in order to make prevention in advance and implement targeted measures, we should quantify the risk and calculate the fire risk value. In this study, through consulting experts and analysis of data obtained from Changzhou Railway Company and the Emergency Management Bureau, the fire risk index system of subway stations was determined. We calculated the index weight by selecting the combination weighting method of game theory to eliminate the limitations and dependence of subjective and objective evaluation methods. The idea of relative closeness degree in TOPSIS method iwas introduced to calculate the risk value of each subway station. Finally, the subway station risk value model was established, and the risk values for each subway station were calculated and sorted. According to expert advice and the literature review, we divided the risk level into five levels, very high; high; moderate; low and very low. The results shown that 2 subway stations on Line 1 have very high fire risk, 2 subway stations on Line 1 have high fire risk, 2 subway stations on Line 1 have moderate fire risk, 8 subway stations on Line 1 have low fire risk, and 13 subway stations on Line 1 have very low fire risk. We hope that through this evaluation model method and the results to bring some references for local rail companies. Meanwhile, this evaluation model method also promotes resilience and sustainability in social development. Full article

Background: This study addresses the mobility practices of the inhabitants of the peripheries of Dakar and the transport services they use to meet their mobility needs, in particular the unlicensed shared taxis (“Clandos”). In the peripheries, which suffer from a lack of jobs and amenities, mobility is essential to meet household needs and for social integration. Current transport policies focus on formalizing supply and organizing the system around high-capacity transport facilities, such as the Regional Express Railway (TER) or Bus Rapid Transit (BRT), but they have difficulty in dealing with the mobility problems facing the outskirts of the city. Methods: The study is based on secondary analysis of the 2015 Household Travel Survey and on a survey on the activity of Clandos conducted in 2021 in Dakar. Results: The analysis highlights the daily mobility practices of the inhabitants of the peripheral areas. These residents, who are on average poorer than the others, travel mainly on foot. Their access to public transport remains limited and, when they use it, a significant proportion of their trips are made by Clando. Clandos have a dual function. On one hand, they are used for long trips to the center, in competition with buses, but more often they operate as a complement to buses. On the other hand, they are mostly used for local mobility within the peripheries. Conclusions: Although relatively expensive, Clando services are valuable for the inhabitants of the peripheries and their daily mobility. They should be better integrated into transport and planning strategies for the peripheral areas. Full article

A transport business that has reached financial sustainability is one that is providing a service at a price that not only covers its costs but also creates a profit for upcoming contingencies. A focus on rail infrastructure financial sustainability is of paramount importance to guarantee the availability of punctual rail transport to remote potential users. To evaluate the sustainability of mass rapid transit on the relation among hypothetical key aspects of sustainability—perception of property; willingness to pay for maintenance, repair, and operations; confidence in the Roads and Transport Authority; and citizen participation in the rail project—and railway service punctuality, the most important result variable, was studied according to the specialized literature on rail transport sustainability. Leading information was collected by means of personal questionnaires of more than 1000 railway users according to the Krejcie Morgan formula for the calculation of the sample size knowing the population size. Qualitative plus quantitative information was gathered from different ways (technical test of the rail system, discussions with users, focus-group discussions, and interviews with key informers).The outputs by means of the statistical analysis allowed understanding two key perceptions. Firstly, beyond a half decade after construction, during a system intervention, a smaller perception of public property for the railway system was related to better service punctuality. This idea contrasts with the vast majority of the publications, which highlight a regular, direct relationship between perception of property and sustainability of railway systems. Secondly, in spite of three-quarters of users accepting that they would contribute monetarily for maintenance, repair, and operations service, such payments were not imminent because of the lack of confidence in the Roads and Transport Authority. In this situation, more than one-third of the metro stations were identified as non-punctual, beyond a half decade after construction. Full article

With the rapid development of the world’s railways, rail is vital to ensure the safety of rail transit. This article focuses on the magnetic flux leakage (MFL) non-destructive detection technology of the surface defects in railhead. A Multi-sensors method is proposed. The main sensor and four auxiliary sensors are arranged in the detection direction. Firstly, the root mean square (RMS) of the x-component of the main sensor signal is calculated. In the data more significant than the threshold, the defects are determined by the relative values of the sensors signal. The optimal distances among these sensors are calculated to the size of a defect and the lift-off. From the finite element simulation and physical experiments, it is shown that this method can effectively suppress vibration interference and improve the detection accuracy of defects. Full article