Subway Line Research Articles

Propagation of structure-borne noise in building adjacent to subway lines

Today, the need for development of metro lines in crowded urban environments is inevitable. Construction and operation of metro generally have adverse side effects (such as noise and vibration) on residents of buildings adjacent to the metros. Based on various published reports, train-induced Structural Borne Noise is mostly annoying, causing people discomfort. Addressing this issue, probabilistic assessment of train-induced annoyance level in buildings adjacent to subway lines was made in this study. For this purpose, a numerical model of typical buildings in vicinity of a subway line was developed. The model was validated by field tests performed in this study. Nine different sites along metro lines were selected to obtain vibration characteristics of train-induced accelerations received by the metro adjacent building foundations. Various possible vibration time histories were applied to the foundation of the model, using an Incremental Vibration Analysis. At each step of the analysis, the Sound Pressure Level in the building stories were obtained and compared with the limitations proposed by the Federal Railroad Administration. Using the results obtained, the probability of the Sound Pressure Level exceeding the allowable limits was derived. In this regard, a reliability index was obtained. Based on the reliability index, the propagation level of the impermissible Structure-Borne Noise in different stories of buildings was presented as a function of number of the building stories and the peak ground accelerations. Accuracy of the proposed function was illustrated by applying it to eight different sites, indicating the accuracy of more than 83%.

Exploring intra-urban human mobility and daily activity patterns from the lens of dockless bike-sharing: A case study of Beijing, China

In recent years, the emergence of dockless bike-sharing has brought new ways of transportation, while also providing support for observing urban dynamics at a finer granularity. This study uses dockless bike-sharing data, combined with point of interest (POI) data, to explore intra-urban human mobility and daily activity patterns, using Beijing as a case study. Here, we employ spatial statistics and graph network to quantify the characteristics of travel behavior. Firstly, spatiotemporal statistics analysis was conducted to investigate the travel patterns and spatiotemporal differences of bike-sharing in Beijing. It was found that bike trips have clear peak hours and highly overlap with the subway lines, indicating that the bike-sharing system effectively completes the ‘last mile’ of travel in Beijing. Secondly, graph networks were used to reveal the core patterns and community structures of human mobility in Beijing and their connections to daily activities. Our findings indicate that there are different core structures of human mobility in Beijing, some dominated by a single core node, while others are formed by the aggregation of multiple cores. Finally, POI data was used to analyze human daily activity patterns. We analyzed the temporal characteristics and the hotspot areas of each daily activity in Beijing and found that transferring to other transportation modes is the most popular activity for people riding bikes, followed by shopping, working, and eating out. These findings provide a reference for understanding urban human dynamics and urban structure from the perspective of dockless bike-sharing.

Dynamic and Static Analysis of Deep Excavation of Poligon Station in İzmir Metro Line

In this paper, the deep excavation stages of Poligon Station which is the located along the Üçyol–Fahrettin Altay subway line was modeled numerically. Although some parts of the metro line were constructed, some parts of metro line are currently under construction in İzmir. The Poligon Station is carried out with a surrounding diaphragm wall and top-down construction method. The foundation mat and four slabs of the station building are used as support elements. The excavation depth of the station is 18 meters. The soil properties of the numerical model were obtained engineering boreholes and laboratory tests. Lateral soil displacements were measured with inclinometers installed in the nearby soil layers. Displacements which were measured from inclinometers and obtained from numerical modeling were compared. Beside the static analysis, the Poligon station of the metro line was analyzed with a model earthquake. 16.12.1977 İzmir Earthquake (Ms=5.5, amax=0.21g) was used as a model earthquake for dynamic analyses. In addition, effects of changing the properties of the soil on computed results were numerically investigated using the software Plaxis.

Study on the Influence of an Under-Crossing Parallel Double-Line Shield Tunnel on the Existing Tunnel Structure

Extra care should be taken when new tunnels pass through an existing tunnel. If it is not handled properly, this will affect the operation safety of the existing line, and bring security risks to the train’s operation. In order to study the impact of an under-crossing parallel double-line shield tunnel on the existing shield tunnel structure, the influence of tunnel construction on the deformation of overlying strata was analyzed, and the formula for estimating the formation settlement at depth Z below the surface, caused by the excavation of a double-tunnel parallel tunnel, was deduced. Then, a series of three-dimensional finite element numerical simulations were carried out. We analyzed and systematically studied the adverse effects of the tunnel structure of Guangzhou subway Line 5, caused by the tunneling of subway Line 18, evaluated its structure and operational safety, and provided suggestions for site construction. This research demonstrates the following conclusions. (1) The tunnel structures of subway Line 5 and Line 18 are mainly in the strongly weathered argillaceous siltstone stratum, and lightly weathered argillaceous siltstone stratum, respectively, and the stratum where the Line 18 tunnel is located is relatively safe. (2) According to three-dimensional finite element numerical simulation analysis, during the shield-tunneling process of subway Line 18, the maximum X horizontal displacement, the maximum Y horizontal displacement, and the maximum Z vertical displacement of the tunnel structure in subway Line 5 are 1.09, 3.50, and 4.55 mm, respectively. It is considered that the impact of the shield-tunnel penetration of subway Line 18 on the tunnel structure of subway Line 5 is relatively controllable, and does not affect the structure and operational safety. (3) It is suggested that settlement monitoring should be strengthened within the range of 12 m (about 1.5 tunnel diameter D). before and after the excavation axis of the underpass tunnel, and it is necessary to carry out local reinforcement treatment, to prevent adverse effects on the operation of the existing tunnel.

Deep learning-based prediction of steady surface settlement due to shield tunnelling

Predicting ground movement produced by shield tunnelling in densely built urban areas is of practical significance. This study introduces an artificial intelligence method to predict the steady surface settlement caused by shield tunnelling. The proposed method comprises three models: a hybrid deep neural network model (HDNN), an error correction model (ECM), and an auxiliary model. Based on the settlement mechanism associated with tunnelling, the factors related to the ground movement were classified into five categories. The first four types of factors were used as the input parameters of the HDNN to predict steady surface settlement. The ECM considers unmeasurable factors. Five datasets from different subway lines were used to assess the performance and generalisation capacity of the proposed method. The results show that the proposed method outperforms classical deep neural networks as it considers the settlement mechanism and spatial and temporal characteristics of the input parameters.

Interaction of Segmental Tunnel Linings and Dip-Slip Faults—Tabriz Subway Tunnels

In some subsurface urban development projects, bedrock faults intersecting with the tunnel path are inevitable. Due to the high costs of urban tunnel projects, it is necessary to study the behavior of such concrete structures under fault movement risks. Using an advanced 3D numerical finite difference code and a plastic hardening constitutive model for the soil, this paper examined the performance of the straight and oblique segmented structures of Tabriz Subway Line 2 under large deformations. The Tabriz Line 2 tunnel passes through a reverse fault called the Baghmisheh Fault. The fault–tunnel simulations were validated by centrifuge tests on the segmental tunnel for normal faulting. In the centrifuge tests and validation models, there was a maximum difference of 15%. According to the results of the Tabriz Line 2 tunnel under reverse faulting, segmental structures outperform no-joint linings when it comes to fault movement. During reverse fault movement, line 2 segments did not collapse but showed slight deformations. However, continuous structures collapsed under faulting, i.e., the structural forces created exceeded the section strength capacity. Among the segmental structures, the lining with oblique joints showed better behavior against faulting than the lining with straight joints. For better tunnel performance under fault movement, oblique joints should be used in segmental structures in faulting areas.

Measuring modal accessibility gap using gridded population and network map platform data

Few studies have calculated the magnitude of the modal accessibility gap between public and private transportation (MAG) by taking into account both population characteristics and time-varying characteristics. To incorporate the aforementioned characteristics, this study computed MAG within each population grid using the anticipated travel time between two grids in real time. Moreover, a representative case study focuses on the MAG in the urban area of Xi'an during three time periods. Research results indicate that the average travel time for private transportation in the study area is significantly lower than that of public transportation. Further, the subway line has an obvious impact on improving MAG. In addition, the development of public transportation in the peripheral regions lags behind that of the city center, and the subway network is inadequately serviced. As a result of utilizing the MAG method presented in this paper, the problem related to urban transportation planning can be addressed by incorporating both the population and time-varying factors. At the end of the paper, the limitations and future works are discussed.

Optimization of energy-efficiency train schedule considering passenger demand and rolling stock circulation plan of subway line

Optimization of energy-efficiency train schedule considering passenger demand and rolling stock circulation plan of subway line

Shallow Tunneling Method and Control Measure for Ground Surface Settlement

In order to ensure that the tunnel deformation and surface settlement are controlled within the allowable range during the construction process, the design unit has compiled technical measures and monitoring schemes for ground settlement control of this project. Based on the example of a shallow tunneling project on Subway line 8, this paper analyzes and discusses the shallow tunneling method in detail and puts forward corresponding technical measures for ground settlement control.

Building vibration measurements induced by train operation on concrete floor

Buildings located near subway lines and railway lines are usually subject to train-induced vibrations. The rest and work of people in residential and office buildings, as well as the use of vibration-sensitive equipment in laboratories and precision manufacturing facilities are impacted by the vibrations. To explore the impact of train-induced vibration on over-track buildings, the measurements were conducted at Guangzhou Baiyun railway station, where the passenger and cargo trains operate on the concrete floor within the building. The vibration transmission law of the building height and the distance to the track was obtained. The vibrations induced by passenger and cargo trains were compared. It is found that the vertical vibration mainly attenuates with the increase of the distance from the source, while the horizontal vibration attenuates with different floors due to the propagation wave of vertical vibration in the floor slab and horizontal vibration in the column in terms of the bending wave. The vibrations caused by trains running on concrete floors decay more slowly than those caused by trains running on the soil. The results provide useful pre-construction vibration level estimation for designing similar buildings over the railway.

Superconducting DC power transmission for subway lines that can reduce electric resistance and save energy

Electric railway systems are widely used and DC systems have been employed in a number of metropolitan areas. However, they have some problems, such as cancelled regeneration and energy loss. Introducing superconducting feeder cables into railway feeding systems offers a lot of benefits: fewer substations, equalization of load among substations, reduction of cancelled regeneration, power transmission loss. Feeding systems adopted by railways throughout the world can be classified into feeding systems through overhead trolley wires and ground third rails. These problems are especially serious in third rail system because the voltage is low and the electric current is high. By using a newly developed superconducting feeder system on a third rail system, we conducted a power transmission test. Also, the feeding of the high current and regeneration current was proved to be successful in the course of the train running test on subway line. And, we specifically analyzed the energy generated when a cable was adopted into the third rail line. As a result of adoption of a superconducting feeder cable, the voltage drop specific to railways could be reduced even with a short cable. And, if the cable is adopted in subway line, we also observe large energy-saving effect.

Surface Subsidence of Nanchang, China 2015–2021 Retrieved via Multi-Temporal InSAR Based on Long- and Short-Time Baseline Net

Urban land subsidence threatens the safety of urban buildings and people’s lives. The time series interferometric synthetic aperture radar (InSAR) technology can provide us with large-area, high-resolution, and high-precision ground deformation monitoring. In this study, the time series InSAR technology and the strategy with long- and short-time baseline networking are used to obtain the surface deformation along the line of sight of Nanchang City based on the six-year (from December 2015 to December 2021) Sentinel-1 data. Longer datasets and better baseline strategies allow us to obtain more stable deformation results of Nanchang City than other researchers. The results of surface deformation show that the overall surface of Nanchang City is stable, but there are several obvious subsidence funnels. We carried out a field survey on four areas with significant surface subsidence. We considered that these subsidence areas may be related to soil compaction, building construction, and groundwater extraction. Based on the surface deformation results around the subway line, we analyzed the impact of subway construction on the surface along the line and identified the sections that need to be focused on by the managers to prevent the deformation area from affecting the surrounding buildings and subway line operation safety.

Long-Term Efficient Control of Structure-Borne Noise Inside Buildings Caused by Underground Railways by Using Novel Damping Fasteners

Damping fasteners provide vibration isolation to railway tracks because of their low vertical stiffness and improve the in-service performance of the tracks. In this paper, a new type of high lateral stiffness and vertical damping fastener is developed. First, the vibration suppression frequency band of the new fastener was determined from a field test, the design vertical stiffness was determined by calculating the P2 resonance frequency, and the vertical stiffness before and after a fatigue load test was found. Then, field experiments were carried out in buildings with known excessive subway train-induced vibration problems to assess the effectiveness of the proposed fastener, which showed that the damping fasteners reduced the vertical and transverse vibrations of the tunnel wall by 10 dB without increasing the transverse displacements of the rail. Furthermore, the structure-borne noise reduction in all measured buildings exceeded 3 dB. The study demonstrated that the replacement of novel damping fasteners is a feasible solution for controlling vibrations and noise in buildings adjacent to subway lines.

Clustering Analysis of Multilayer Complex Network of Nanjing Metro Based on Traffic Line and Passenger Flow Big Data

Complex networks in reality are not just single-layer networks. The connection of nodes in an urban metro network includes two kinds of connections: line and passenger flow. In fact, it is a multilayer network. The line network constructed by the Space L model based on a complex network reflects the geographical proximity of stations, which is an undirected and weightless network. The passenger flow network constructed with smart card big data reflects the passenger flow relationship between stations, which is a directed weighted network. The construction of a line-flow multilayer network can reflect the actual situation of metro traffic passenger flow, and the node clustering coefficient can measure the passenger flow clustering effect of the station on adjacent stations. Combined with the situation of subway lines in Nanjing and card-swiping big data, this research constructs the line network with the Space L model and the passenger flow network with smart card big data, and uses these two networks to construct the multilayer network of line flow. This research improves the calculation method of the clustering coefficient of weighted networks, proposes the concept of node group, distinguishes the inflow and outflow, and successively calculates the clustering coefficient of nodes and the whole network in the multilayer network. The degree of passenger flow activity in the network thermal diagram is used to represent the passenger flow activity of the line-flow network. This method can be used to evaluate the clustering effect of metro stations and identify the business districts in the metro network, so as to improve the level of intelligent transportation management and provide a theoretical basis for transportation construction and business planning.

The complementary effect of ride-sharing on public transit: evidence from a natural experiment

PurposeIdentifying the complementary effects of ride-sharing on public transit is critical to understanding the potential value of growing partnerships between public transit agencies and ride-sharing platforms. The purpose of this paper is to investigate whether and how ride-sharing services complement public transit.Design/methodology/approachTaking advantage of a natural experiment whereby subway Line 2 opened after the entry of ride-sharing services in Xiamen, this study uses a difference-in-differences approach to identify the complementary effects of ride-sharing on public transit based on a proprietary fine-grained trip-level data set from a large ride-sharing platform.FindingsThis study obtained the encouraging finding that ride-sharing has a significant complementary effect on the subway, as the number of ride-sharing pickups and drop-offs at subway stations increased by 130% and 117.9%, respectively, after the subway opening. Moreover, mechanism analysis shows that the complementary effect of ride-sharing services is stronger when connection distance is short (i.e. under 6 km) and when the transportation availability is limited (i.e. at night or in the areas with low transit supply and low population density).Practical implicationsThe findings provide guidelines for promoting cooperation between public transit agencies and ride-sharing platforms to build an efficient and sustainable urban transport system.Originality/valueThis study is the first to examine the complementary effect of ride-sharing services on public transit via unique fine-grained ride-sharing trips data, and further reveal the underlying mechanism behind this effect.

Multiobjective Optimization of Traction Substation Converter Characteristic and Train Timetable in Subway Systems

Currently, power supply accidents and excessive energy consumption occur frequently in DC traction power systems of multitrain subway lines. Rail potential (RP) exceeds the standard limit frequently, energy consumption and fluctuation of the traction current are high, which are directly affected by the traction substation converter characteristic and train timetable. In this paper, multi-objective optimization of traction substation converter characteristic and train timetable is conducted to realize the safe and economic operation of subway systems. Firstly, a power flow calculation platform with multitrain running dynamically is established to work out the operating parameters of the system. Then, a multi-objective optimization model consisting of maximum RP, energy consumption and maximum traction current is designed. For the coordination of multiple goals to be optimized, an enhanced Non-Dominated Sorting Genetic Algorithm-III (NSGA-III) is proposed to obtain an optimal traction substation converter characteristic and train timetable. Finally, the multi-objective optimization is conducted with the data of Guangzhou Metro Line 2. Results indicate that three optimized objectives are dropped by 43.8%, 33.4% and 40.3% respectively based on the proposed optimization method, which will greatly enhance the energy conservation and power supply safety of subway systems.

Computer Vision-based Monitoring Method for Differential Settlement of Shield Tunnels

Shield tunnels in soft soils are inevitably subject to large differential settlement during construction and long-term operation, which can lead to various diseases and then impair structural safety and durability. Due to the inefficiency of traditional inspection methods, timely and accurate monitoring methods are necessary to ensure the safe operation and long-term maintenance of tunnels. In this study, a computer vision-based monitoring method for differential settlement of shield tunnels was developed and implemented. The monitoring area is located in an interval tunnel of a subway line in Shanghai during the freezing construction of its side channel. The influence of camera position’s micro-change was considered. The field equipment mainly consists of high-resolution industrial CMOS (complementary metal oxide semiconductor) digital camera sets, LED (light emitting diode) lights and power modules. The differential settlement relative to datum points are obtained and vertical displacement of one ring acquired by total station is compared with the proposed method to verify the feasibility of the monitoring system. The results indicate that the monitoring system is reliable and can be further applied.

The Influence of Geological Characteristics on the Surface Potential Distribution of Metro Stray Current

In recent years, the transformer DC bias phenomenon has often occurred in transformer transformers near subways in China. Due to the serious exceeding of the operating voltage and current, the safe operating state of the transformer and the quality of the power system supply and transmission are threatened. Analyzing the influence of DC bias on the surrounding transformer, the magnitude of the inflow current in the surrounding area can be studied, but the most direct is to study the distribution law of the surface potential in the surrounding area. In this paper, a simulation model is established based on the field geological characteristics of a certain area in Guangzhou, and the surface potential is calculated through the model, and then the correctness of the simulation model is verified by the surface potential data measured on the spot. The simulation model analyzes the influence of different soil structures on the surface potential of subway lines and groundwater systems. The results show that compared with the factor of rail burial depth and the resistivity factor of the river, the soil resistivity has a greater influence on the surface potential, and the surface potential is greater when the soil resistivity is greater.

Personal measurements and sampling of particulate matter in a subway – Identification of hot-spots, spatio-temporal variability and sources of pollutants

A mobile measurement system for complex characterization of particulate matter (PM) was developed together with the proposed methodology and applied in the subway system of Munich, Germany. The main objectives were to observe the spatio-temporal variability of PM, personal exposure, identify hot-spots and pollution sources. Particle mass (PMx) and number (PNC) concentrations, and equivalent black carbon (eBC) were measured at 0.1–1 Hz. On the U5 subway line, PM10, PM2.5 and PM1 concentrations at platforms ranged from 59 to 220, 27–80, and 9–21 μg m−3, respectively. During rides towards downtown, average PM10, PM2.5 and PM1 levels gradually increased from 8 to 220, 2 to 71 and 2–20 μg m−3, respectively, with a similar dynamic of decrease on the return journey. Spatial variability of PM was generally more important than temporal, and significant differences were observed between platforms. During the rides, air exchange between train and tunnel was high in both air-conditioned and old passively ventilated trains. Peak PM concentrations on platforms were associated with arriving/departing trains. Subway PNC were not significantly elevated, but a few cases of intake of traffic-related particles from outside were observed, otherwise air exchange was considered low. Generally, most of the aerosol mass was composed of iron corrosion products from rails and wheels (Fe up to 66 μg m−3 in PM2.5). The effective density of PM2.5 was 2.1 g cm−3. Particles were classified as 75.4% iron oxides, 5.35% metallic Fe, 1.23% aluminosilicates and 17% carbon and oxygen rich particles. The iron oxide particles consisted predominantly of Fe (63.4 ± 8.7 wt%) and O (36.2 ± 8.2 wt%). To effectively monitor subway PM and reduce overall PM exposure, we propose to identify hot-spots using our methodology and focus on improving their ventilation, as well as installing filters in air-conditioned wagons.

궤도회로 경계 구간에서 S-bond 공진회로 특성에 관한 연구

The FTG-S 917 track circuit device installs an S-bond composed of cables instead of an impedance bond, which is a heavy object, at the boundary point of the existing track circuit, thereby simplifying the facility, improving the comfort of the train, and improving maintenance efficiency and stability. can improve However, as a disadvantage, precise frequency tuning is required during installation, and it is not easy to identify the location and cause of failure when a failure occurs.[1] Because of these problems, it is very important to theoretically analyze and confirm the frequency resonance characteristics of the S-bond boundary section and mutual induction and cancellation with the rail when current flows. In this paper, the electrical characteristic components of the electrical insulation part between the S-bond and the rail of Seoul Subway Line 2 were defined, and the flow of current was modeled through mathematical analysis. The modeled circuit was simulated with Matlab and the results obtained were verified by comparing them with field measurement results.