Train Tunnel Research Articles

Quasi-3D Geoelectrical Imaging as A New Application for Landslide Investigations: A Tunnel Case Induced by Blasting Activity

Landslides are a significant hazard in mountainous regions, especially when influenced by construction activities such as tunnel excavation. In this paper, we aim to conduct a slope stability analysis as a result of tunnel blasts using quasi-3D subsurface models based on resistivity values. The study site is a construction area for the Jakarta-Bandung High-Speed Train tunnel, located in a mountainous region undergoing drill-and-blast excavation. This excavation method makes the area susceptible to landslides, which pose a threat to settlements in the Padalarang subdistrict, West Bandung Regency, Indonesia. Data was collected along four lines in 2D, and the dipole-dipole array was used to enhance resolution. Data modeling was carried out using ResIPy v3.2.3 software to create 2D and quasi-3D subsurface models based on resistivity values. The study findings indicate that the study area exhibits three resistivity ranges: low resistivity (0-30 Ωm), medium resistivity (31-49 Ωm), and high resistivity (>50 Ωm). Utilizing quasi-3D imaging, we were able to identify the dimensions and presence of slip surfaces, which can be categorized as shallow (1.5-5 m) and deep (5-20 m) criteria. This study successfully applied the quasi-3D geoelectrical approach in a susceptible environment to detect potential landslide zones.

Investigation of Empirical and Analytical Methods Accuracy for Surface Settlement Prediction in Train Tunnel Excavation Projects

Investigation of Empirical and Analytical Methods Accuracy for Surface Settlement Prediction in Train Tunnel Excavation Projects

Airtightness Performance Test and Failure Models for Low-to-Vacuum Maglev Train Tunnel Joints

Abstract The airtightness at the joints of segment lining structures is one of the critical problems for low-to-vacuum maglev train tunnels that needs to be addressed. A new apparatus was designed to test the airtightness performance of the gasket-in-groove at longitudinal and circumferential joints. Based on the test results, four mechanical models based on the theory of elastic mechanics were developed to describe the short-term and long-term sealing failure behaviors of longitudinal and circumferential joints, which are subjected to vacuum pressure on one side of the gasket, and the corresponding air-leakage equations for contact interface were also deduced. The test results show (1) a higher initial contact pressure in the gasket-in-groove would result in faster stress relaxation; (2) a greater initial contact pressure would result in better joint sealing; and (3) for the same initial contact pressure, the sealing capacity of longitudinal joints is significantly better than that of circumferential joints. The test results are in good agreement with the models. The developed models can be used to interpret the sealing failure mechanism through the gasket contact pressure path. Moreover, the mechanical models show that the sealing capacity of the circumferential joint gasket is positively correlated with the airtightness coefficient and the gasket equivalent Poisson’s ratio, whereas the sealing capacity of the longitudinal joint gasket is positively correlated with the airtightness coefficient, the gasket equivalent Poisson’s ratio, as well as the tunnel outer diameter, and negatively correlated with the gasket width.

Rockfall source areas identification at local scale by integrating discontinuity-based threshold slope angle and rockfall trajectory analyses

Rockfall source areas identification of high steep fractured rock slope is a challenging task for hazard mitigation. Considering this difficulty, a new method integrating discontinuity-based threshold slope angle and rockfall trajectory analyses is introduced in this study and applied to a railway bridge in China. First, abundant discontinuity data are collected by means of the modern unmanned aerial vehicle (UAV) digital photogrammetry technique. Then, a threshold slope angle used to delineate rockfall-prone areas is comprehensively determined by probabilistic kinematic and block theory analyses. Next, physically based rockfall trajectory simulation with consideration of mean block size is used to distinguish the hazard level of each release point. Finally, rockfall sources causing moderate and high risks to the train tunnel entrance at the base of high steep fractured rock slope are determined using a semiquantitative risk matrix approach. The final rockfall source map can provide a quantitative reference for hazard mitigation. At the end of this paper, some issues associated with the proposed approach are discussed, such as parameter importance analysis of threshold slope angle, comparison between the two probabilistic approaches and uncertainties in rockfall source areas identification.

Effect of Normalising Process on the Corrosion Behaviour of U75V Rail Flash Butt Welded Joints in a Marine Environment

U75V rail steel is widely used in railways in China, including train tunnels in mountain and subsea projects, where it suffers from selective corrosion near welded joints. To ensure adequate railway service life, this study examines the effect of the normalisation process on the electrochemical behaviour of U75V rail-welded joints (URWJs) manufactured by flash butt welding (FBW) using potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS). Corrosion morphology and elemental distribution analyses were performed to investigate the corrosion behaviour. The results show that the grains within the joints became finer and more homogeneous after normalisation, with a lower corrosion rate and higher corrosion resistance. It is demonstrated that fewer corrosion products were formed on the surface of the normalised joints after electrochemical test, and the corrosion resistance of the URWJs improved, owing to the formation of denser passivation films caused by normalisation. These mechanisms of corrosion response help explain corrosion failure in railway lines, as well as also help optimise the welding process and normalising processes to obtain a corrosion-resistant microstructure and ensure the quality of welded joints.

Sons of Kemet, Gorilla, Manchester, United Kingdom—February 19, 2022

Sons of Kemet, Gorilla, Manchester, United Kingdom—February 19, 2022

Research on the movement law and traffic safety zoning of spalled blocks in the linings of high-speed railway tunnels

Recent years have brought to notice the spalling and falling off problem of the lining of high-speed rail tunnels, which is dangerous for traffic safety. In this study, a three-dimensional spalled block–train–tunnel–air gas–solid coupling calculation model was built using FLUENT numerical simulation software. This model was used to simulate the trajectory characteristics of the spalled blocks under the operating condition of a high-speed rail at a speed of 300 km/h. The spatial movement characteristics of the block falling from the lining under four influencing factors, namely, block's geometric size, density and positions and train's speeds were analyzed. During the operation of the train, the lateral displacement of the spalled block decreases with the increase of the density of the spalled block, increases with the increase of the vehicle speed, and first increases and then decreases with the increase of the geometric size of the spalled block. Considering the above influencing factors comprehensively, the safe area and dangerous area in the tunnel are divided depending on whether the traffic safety was threatened by the falling of the spalled blocks from tne tunnel lining. The results show that the area 4.5 m away from the ground is a dangerous area where the tunnel operation and maintenance need to be paid attention to. Meanwhile, it is recommended to install the auxiliary equipment in a safe area to avoid the peeling off of the surrounding lining and thereby threatening train-driving safety.

Comparison of aerodynamic performance of high-speed train driving on tunnel-bridge section under fluctuating winds based on three turbulence models

The coupled effect of canyon winds and rapid switching of operating scenes deteriorate the aerodynamic performance of the high-speed train (HST) running on the tunnel-bridge section (TBS). What's more, when investigating the aerodynamic performance of the HST by using CFD simulations, the calculation results obtained by various turbulence models show differences, which may have an uncertain effect on analysing the research results. This study aims to analyse the difference in calculation result of three turbulence models, when the HST running on the TBS. For this purpose, based on three mainstream turbulence models (LES, IDDES, and URANS) and the ‘mosaic’ meshing technology, a full-scale CFD dynamic model of 3D train–tunnel–bridge–air was established. Based on the on-site wind field sampling date, UDF program was compiled to load the aforementioned wind-speed time sequence on the velocity-inlet boundary, and the incoming wind field of the TBS was reconstructed. Finally, the aerodynamic load time history and flow field structure of the HST simulated by three turbulence models were revealed, when the HST was running on the TBS. The following conclusions were obtained. The time history of aerodynamic load changes and the fluctuation amplitude calculated by the two turbulence models of IDDES and LES are basically consistent (the difference is kept within 10%), when the HST running on the TBS. The influence of the turbulence model on the aerodynamic loads of the HST is mainly reflected in the head carriage, especially the side force. When the HST runs on the TBS, the side force, lift force, rolling moment, yawing moment and pitching moment of the head carriage calculated by the URANS model are 16%, 9%, 29%, 20%, and 13% higher than the corresponding values of the LES model. Based on the equivalent principle of the side force of the head carriage, a formula is proposed to quantitatively describe the relationship between the side force amplitude of the head carriage on the TBS calculated by the URANS model and the corresponding value of the LES model. The formula can be used to correct the boundary inflow wind speed conditions of the URANS model, so as to quickly obtain the calculation results equivalent to the LES model.

Numerical investigation on application of train body airflow diversion device to suppress pressure waves in railway high-speed train/tunnel system

ABSTRACT The development of the high-speed maglev train (HSMT) is important for the future of high-speed rail transit. A pressure wave (PW) is a common aerodynamic effect in high-speed railway tunnels. For HSMTs with a speed of 600 km/h, the amplitude of PW in the tunnel can be very big, which maybe far exceed the current design strength standard of the train body structure and seriously threatens the safety of the railway train/tunnel structure and passenger ear comfort. Therefore, aerodynamic PWs caused by a two-dimensional axisymmetric model with an ellipsoidal nose passing through a tunnel was investigate, and the numerical method adopted in this study was validated by two scaled moving model tests. The PWs caused by trains in four cases and the effects of train speed and tunnel length were analysed and compared. Some results show that diversion device significantly reduces the amplitude of the PWs (∆C p) on the train surface and tunnel wall. The diversion device on the train tail (C4) not only changes ∆C p, but also changes the waveform. The diversion device on the train tail (C3) and diversion device on both train head and tail which are connecting each other (C2) mainly reduced the ∆C p. When the decrease in both PWs on the train surface and tunnel wall is considered, C2 has the best effect. With an increase in the train speed, the effect of C2 on restraining the PW on the train surface and tunnel wall increases to a certain extent. However, the restraining effect on the micro-pressure wave (MPW) at the tunnel exit does not exceed 5%. The suppression effect of C2 on ∆C p on the train surface and tunnel wall decreases with an increase in the tunnel length. However, it does not change the distribution law of ∆C p along the train and tunnel. This study can provide a reference for the design of the body of HSMTs and the suppression of PW in tunnels.

Dynamic Response of a Heavy-Haul Railway Tunnel’s Bottom Structures in Hard Rock

A train–tunnel–surrounding rock numerical model was established by using ABAQUS to analyze the dynamic response of a heavy-haul railway tunnel in hard rock, quantify the influence of the train axle load on the tunnel dynamic response and determine its potential vulnerable position. The results suggested that: Under the 30 t train load and surrounding rock pressure coupling, the maximum principal stress caused by rock pressure was 1.27 MPa, located at the bottom of the structure below the side drain; the maximum dynamic response of the tunnel structure and base rock was located directly below the rail. The lower part of the side drain and rail was the vulnerable position in the tunnel bottom structure, and the probability of base disease under the rail may be higher than that in soft-rock tunnels, for it has a greater dynamic response and thinner structure compared to a soft-rock tunnel. The maximum principal stress amplitude of the tunnel structure and base rock were 129.3 kPa and 43.0 kPa, respectively. When the axle load increased by 1 t, the dynamic amplitude of the structure’s maximum principal stress increased by about 4.14 kPa, and the base rock’s maximum principal stress increased by about 1.33 kPa. The rock pressure was not negligible in the dynamic analysis of the railway tunnel, and the dynamic response of the tunnel bottom structure and base rock will decrease, obviously, when the rock pressure is ignored.

Aerodynamic Behavior and Impact on Driving Safety of Spalling Blocks Comprising High-Speed-Railway Tunnel Lining

The lining of operating high-speed-railway tunnels suffers from cracks, the peeling of material, and other deteriorations and defects, all of which seriously affect driving safety. However, the trajectory of a falling block from the tunnel lining in a tunnel train wind environment and its impact on driving safety are unknown. To study the movement of falling blocks under a coupling effect of tunnel train wind and the local flow field of the falling blocks, a three-dimensional gas–solid-coupling numerical calculation model of spalling blocks–train–tunnel–air was established using FLUENT software The aerodynamic evolution mechanism governing the spalling blocks of the lining was analyzed, and we found that the falling process of a spalling block is affected by the coupling of its own characteristics and transient train wind. Train wind directly induced the horizontal motion of falling blocks, generated curves and eddy currents, and changed the motion state of spalled blocks. Furthermore, by comprehensively considering the motion trajectories of flaky and blocky blocks at different positions, the impact of spalling blocks on driving safety was obtained. The dangerous area of spalling blocks was approximately 5.5 m above the ground, which must be paid attention to. Our results provide guidance for the operation and maintenance of high-speed-railway tunnels.

Analysis and Modeling of Propagation in Tunnel at 3.7 and 28 GHz

In present-day society, train tunnels are extensively used as a means of transportation. Therefore, to ensure safety, streamlined train operations, and uninterrupted internet access inside train tunnels, reliable wave propagation modeling is required. We have experimented and measured wave propagation models in a 1674 m long straight train tunnel in South Korea. The measured path loss and the received signal strength were modeled with the Close-In (CI), Floating intercept (FI), CI model with a frequency-weighted path loss exponent (CIF), and alpha-beta-gamma (ABG) models, where the model parameters were determined using minimum mean square error (MMSE) methods. The measured and the CI, FI, CIF, and ABG model-derived path loss was plotted in graphs, and the model closest to the measured path loss was identified through investigation. Based on the measured results, it was observed that every model had a comparatively lower (n

Linear problem of train tunnel entry with formation of variable width isobaric wake

Linear problem of train tunnel entry with formation of variable width isobaric wake

Analysis of the Train in Tunnel Paradox Based on Special Theory of Relativity

The train in tunnel paradox has always been a topic of debate in the scientific community, in order to allow readers to better understand its basic principles, and it needed to combine the basic knowledge of the theory of relativity to outline the train tunnel paradox. Taking Einstein’s special theory of relativity as the starting point of the argument, this paper elaborates on Einstein’s theory of relativity, focuses on the simultaneous relativity and the theory of physical motion shape change in the special theory of relativity, and clarifies the famous train in tunnel paradox. Based on the results of different reference systems, the author analyzes the paradox principle of trains and tunnels. Through the analysis, it can be seen that the special theory of relativity is meaningful in real life, and the learners should pay attention to the cultivation of their own logical reasoning ability when learning, and emphasize the understanding of the spirit of scientific criticism, so as to improve the learning effect of the special theory of relativity.

Aerodynamic response of high-speed trains under crosswind in a bridge-tunnel section with or without a wind barrier

High-speed trains experience a sharp transition to a strong crosswind environment when running in a bridge–tunnel section due to the perennial prevailing crosswind in the canyon, and this sudden transition seriously affects train safety. In this study, a 3D computational fluid dynamics numerical model of the train–tunnel–bridge–wind barrier is established based on the delayed detached eddy simulation turbulence model and porous media theory. A dynamic analysis model of wind–train–bridge coupling is adopted. The effects of wind barrier with a height of 3 ​m and porosity of 30% on the aerodynamic coefficient, flow field structure and running safety of high-speed trains under crosswind in the bridge–tunnel section are studied. Results indicate that the sharp change effect of the aerodynamic coefficient is significantly weakened by more than 50% by the wind barrier. The aerodynamic fluctuation amplitudes in the bridge–tunnel section are 1.25–5.5 times higher than those in the bridge section. The difference in pressure distribution in the longitudinal direction is significantly reduced because of the obstruction and diversion of the wind barrier and the space limitation on the windward side. Accordingly, the change in amplitude of the aerodynamic coefficients in the bridge–tunnel section is reduced, and so is the safety of train operation. The bridge–tunnel section is the weak link of safety control. Using a wind barrier with the same parameters for the bridge and bridge–tunnel sections is unreasonable, that is, the parameters should be separately designed.

Experimental Study on Stiffness Softening of Soil‐Rock Mixture Backfill under Metro Train Cyclic Load

Due to the thick soil layer, short backfill time, and low degree of consolidation of the soil‐rock mixture backfill in Chongqing city, metro train tunnels passing through this type of strata are prone to large settlements during operation, which greatly affects the stability of the tunnel and the safety of metro train operations. In response to this problem, the dynamic triaxial test of the soil‐rock mixture backfill under cyclic loading was carried out to study the dynamic characteristics of the soil‐rock mixture backfill under cyclic loading. The effect of initial consolidation degree, effective consolidation confining pressure, and rock content on the stiffness softening of soil‐rock mixture backfill was analyzed. The results show that the initial consolidation degree, effective consolidation confining pressure, and rock content are all important factors affecting the stiffness of soil‐rock mixture backfill under cyclic loading. As the number of cycles increases, the lower the initial consolidation degree and effective consolidation confining pressure, the faster the attenuation of the softening index, and the larger the amplitude. As the rock content increases, the softening index increases and the stiffness of the backfill changes from softening to hardening. Based on the test data, the softening‐hardening model of the soil‐rock mixture is established, which is in good agreement with the field test results. This study can provide a reference for predicting and controlling the postconstruction settlement of the metro tunnel in the soil‐rock mixture backfill.

Effect of train fire location on maximum smoke temperature beneath the subway tunnel ceiling

Smoke temperature beneath tunnel ceiling is one of the most important parameters to determine its fire safety. A double long-narrow space is formed when a subway train stops inside a tunnel, where the smoke movement is quite different from those inside traditional road or train tunnel. The related smoke distributions beneath the tunnel ceiling in this double long-narrow space have been rarely investigated previously. Therefore, through this study, the effect of train fire location on the maximum smoke temperature beneath the subway tunnel ceiling were investigated both numerically and theoretically. Results showed that the smoke temperature beneath the tunnel ceiling is closely related to the spill plume through the train door, which is significantly affected by the fire location. The maximum smoke temperature beneath the tunnel ceiling increases exponentially as the fire source moves away from the train center. A modified model was then developed to predict the maximum temperatures under the spill plume considering various heat release rates and fire locations.

Evaluation and Optimization of the Effective Parameters on the Shield TBM Performance: Torque and Thrust—Using Discrete Element Method (DEM)

Cutterhead torque and thrust are the two main designing parameters of the shield TBM, which have to be evaluated and optimized, based on the interaction between the TBM and excavated material. This study employs the discrete element method (DEM) to simulate the tunneling procedure of the line-7 of Tehran underground urban train tunnel utilizing the micro mechanical parameters calculated from back analysis on direct shear tests. The resultant torque and thrust are then compared against the actual parameters and then with those estimated from the numerical analyses. This result shows that DEM is able to estimate the TBM torque and thrust applying actual boundary conditions and material properties for the model. Furthermore, the impact of ground properties, overburden height, linear and radial velocity on cutterhead torque and thrust and its performance are evaluated and optimized.

Infrastructures of Feeling and the Right to the City

For over sixteen years, I have been tracing and retracing an idea through a set of projects involving the political economy and cultural politics of infrastructure—especially, the infrastructure of media. When I began those projects as a graduate student, my concern was a frustration with the image-centered studies of media and culture, which tended to get bogged down in representational politics and a focus on the micropolitics of interpretation and use. Infrastructure attracts similar debates, as anything from a train tunnel to a water use meter can be appropriated and used in unauthorized or subversive ways. The physicality of infrastructure and the relationships it has with the materiality of ideas, ideologies, and social processes is a growing dimension of cultural inquiry around inequality and power, especially in the study of electronic devices. In this article, I will report on a strand of my research that explores an urban history of interactive media that unfolds into our contemporary world of automated ecologies of surveillance, marketing, disinformation, and covert politics. In recent iterations, this strand intersects with the increasingly popular concept of the ‘right to the city.’

Large-scale urban underground hydro-thermal modelling – A case study of the Royal Borough of Kensington and Chelsea, London

The shallow subsurface of dense cities is increasingly exploited for various purposes due to the significant rise in urban populations. Past research has shown that underground activities have a significant impact on local subsurface temperatures. However, the resulting spatial variability of ground temperature elevations on a city-scale is not well understood due to the lack of sufficient information and modelling complexity at such large scales. Resilient and sustainable planning of underground developments and geothermal exploitation in the short and long-term necessitate more detailed, more reliable knowledge of subsurface thermal status. This paper investigates the impact of some common underground heat sources such as train tunnels and residential basements on subsurface temperature elevation on a large scale and highlights the influence of local geology, hydrogeology, density, and type and arrangement of the heat sources on ground thermal disturbance. To tackle the size issues and computational expenses of such a large-scale problem, a semi-3D hydro-thermal numerical approach is presented to capture the combined influence of underground built environment characteristics coupled with ground properties on ground temperature elevation within the Royals Borough of Kensington and Chelsea (RBKC), London. Numerical results show that the extent of ground thermal disturbance is mostly affected by geological and hydrogeological characteristics in permeable ground (River Terrace Deposits). Density and spatial distribution of heat sources, however, are critical parameters in ground temperature evaluation in highly impermeable ground such as London Clay Formation. The locality of temperature rise and potential ground energy within immediate impermeable ground surrounding heat sources versus significantly large extent of ground thermal disturbance in permeable ground, highlights the significant dependency of ground thermal state and geothermal potential at the studied site to the ground and underground built environment characteristics and necessitates a better understanding of shallow subsurface thermal state for a sustainable and resilient urban underground development.