Underground Station Research Articles

Метод математического моделирования пассажиропотоков для обоснования объемно-планировочных решений станций метрополитена и расчета безопасной эвакуации пассажиров

Introduc tion. Space-planning solutions for underground stations have an effect on the comfort and safety of passengers. Mathematical modelling is a perspective method for solving problems dealing with the determination of adequacy of adopted space-planning solutions for stations depending on passenger traffic. Aims and purpo ses. The purpose of the study is to justify the method of mathematical modelling of passenger flows to develop optimal space-planning solutions of interchange stations of underground. To achieve this goal, the following tasks were solved: the development of a model interchange station concept; modelling passenger flows with initial and optimized volume planning solutions; modelling of passenger evacuation from the station in case of fire in the basement of the arriving train’s central carriage. Methods. The paper presents a method of mathematical modelling to justify the space-planning solutions of underground stations. The software package Pathfinder developed an individual flow model of the interchange station, which simulated the passenger flows with initial and optimized volume-planning solutions. The software package PyroSim was used to simulate the spread of fire hazards. Result s and discussion. Based on the results of mathematical modelling, the optimal space-planning solutions for underground stations were determined, on the basis of which the passenger evacuation scenario was performed. It is obtained that there are 3,684 passengers and 296 workers at the station when the evacuation begins. The simulation results showed that the total estimated evacuation time from a typical transfer station is 814 seconds . It is obtained that the values of dangerous fire factors in the calculated points do not reach critical values until the evacuation is completed. Co nclusions. A mathematical model of a typical interchange station has been developed and implemented to determine the optimal space-planning solutions and calculate the safe evacuation of people. On the basis of this study in the new edition of the Code of Practice 120.13330.2022 “Underground” made amendments that determine that the estimated number of passengers evacuating from the station in case of fire, is based on mathematical modelling of passenger traffic during the rush hour.

Transverse - longitudinal flexural performance of steel tube slab composite slabs: A novel pipe roofing system for metro station

The steel tube slab (STS) structure is a novel pipe-roofing structure, which is used as the support system for underground stations. The pipe-roofing structure is generally assumed as a beam structure in previous research, which is questionable, because the transverse and longitudinal coupling force mechanism is ignored. Hence, this work aims to investigate the flexural performance of STS composite slab through experimental test and establish a design approach for STS structure. Firstly, based on six tests on flexural performance of the STS composite slabs, the crack development, failure mode and deformation mechanism were analysed. Each of the specimens demonstrated a high bearing capacity that exceeded 3000 kN. Furthermore, the specimens exhibited ductility during testing with the failure occurring at either the flange or concrete between the steel tubes. Subsequently, the effect of the length–width ratio and spacing between the tubes on the flexural performance of the tested specimens were examined. The result indicated that the length–width ratio and the spacing between the tubes significantly affected the flexural stiffness, but had limited effects on the flexural capacity. Finally, a design approach was proposed to estimate the elastic capacity of STS composite slabs, and finite element (FE) models validated by the test results were established to increase the general applicability of the theoretical model. The predicted outcomes demonstrated a satisfactory correlation with both the test and FE results, with an average relative error of 9.8%. The study's findings are anticipated to serve as a dependable resource for the design and application of STS structures.

Modified stochastic medium prediction model for the deformation response of concealed underground stations under existing pipelines

The underground pipeline network in the city is so intertwined that the concealed excavation of a metro station inevitably leads to a series of underground pipelines, causing settlement deformation and further risk of leakage. The existing theoretical methods for analysing settlement deformation are mostly for circular chambers, whereas metro stations have a nearly square cross-sectional form and different construction methods are very different, which have a greater impact on the deformation of the overlying pipelines. In this paper, based on the random medium theory and Peck's formula, the improved random medium model for predicting ground deformation is modified, the correction coefficients λ and η for the influence of different construction methods are proposed, the prediction model of underground pipeline deformation under different construction methods is obtained, and the numerical models of four work methods commonly used in urban tunnel construction: pillar hole method, side hole method, middle hole method and Pile-Beam-Arch (PBA) method are constructed through simulation, and the mathematical analysis software was used to fit the results to the model and obtain the range of correction coefficients λ and η for each of the four methods, and the accuracy and applicability of the theoretical model was verified by combining with actual engineering cases. The influence on the overlying pipes is in descending order: side hole method, pillar hole method, middle hole method and PBA method. The theoretical model provided in this paper for predicting the deformation of pipes in any overlying strata of the tunnel is well suited to the actual project and has a high degree of correlation with the measured results.

Research on the Seismic Isolation Effect of the Ring Spring–Friction Pendulum Bearing in the Dakai Underground Subway Station

During strong earthquakes, the vertical seismic force becomes an essential factor affecting shallow underground structures that cannot be ignored. In this situation, it is proposed that ring spring–friction pendulum two-way seismic isolation bearings be set up at the bottom of such structures. Targeting the Dakai underground station and the Kobe earthquake, a soil-structure force model was established based on the damage to the underground structure and dynamic simulation was carried out using Abaqus software. The advantages of the ring spring–friction pendulum bearing over the ring spring bearing alone and the friction pendulum bearing alone were compared. The simulation results showed that the structure displayed a good seismic isolation effect in both horizontal and vertical directions after setting the ring spring–friction pendulum bearing. The deflection in the midspan of the roof reduced to less than 5 cm, the horizontal relative displacement of the structure reduced to less than 3 cm, there was no obvious damage to the structure, the axial pressure ratio of the mid-pillar reduced to less than 0.5, the axial force on the mid-pillar reduced by more than 50%, and the shear force reduced by more than 30%. In addition, by comparing the damage to the structure after setting the annular spring bearing and the friction pendulum bearing, we found that a vertical seismic isolation device is more crucial than a horizontal seismic isolation device for shallow underground structures. Setting a vertical damping device can make the structure retain part of the ductility and reduce the damage to the structure, so the ground vertical seismic mitigation design should be strengthened when a shallow underground structure is designed.

Geotechnical challenges and innovations in urban underground construction – The Klang Valley Mass Rapid Transit project

AbstractThe Klang Valley Mass Rapid Transit (KVMRT) project involves the construction of an urban passenger transport system, i.e., Mass Rapid Transit (MRT) system, together with the existing urban rail network, will form the backbone of the public transport system in the Greater Kuala Lumpur/Klang Valley region in Malaysia. The first MRT line implemented is the 47 km Kajang Line, of which 9.5 km is underground tunnels with seven underground stations. Construction of the line began on 8 July 2011 and achieved the full line opening on 17 July 2017. The second MRT line―Putrajaya Line―began fully operations on 16 March 2023, stretches from Sungai Buloh to Serdang and ends at Putrajaya for a length of 57.7 km, of which 13.5 km is underground tunnels with 10 new underground stations. Like all other metro underground stations/tunnels designed as part of the urban city, the KVMRT underground construction faces challenges from a technical (engineering design and construction) as well as social (environmental and land related) point of view. Needless to say, underground construction in Klang Valley is intensified with the inherent geotechnical challenges presented by complex ground conditions ranging from hard granite, heterogeneous Kenny Hill formation and extreme karstic limestone with fully developed weathered profiles to soft recent deposits including alluvium and mine tailing that is under‐consolidated in places due to past mining activities. The development of this large‐scale infrastructure project has not only opened up tremendous works and new frontier for tunnelling and geotechnical engineering in Malaysia, but it also provided a wealth of information of unique geotechnical challenges/accomplishments as well as technology breakthrough and design innovation in underground engineering. This article discusses some aspects of geotechnical challenges and interesting lessons learnt as well as numerous innovations embedded into this highly complex urban underground construction project.

Justification of vaulted structures of the Kyiv underground station as design in terms of shallow foundation

Purpose. Analysis of the effectiveness and competitiveness of single-span vaulted structures for shallow-depth underground stations. The following objectives were set to achieve the aim: 1. Technical and economic comparison of the proposed designs for shallow-depth underground stations. 2. Calculation of the load-bearing capacity of the structure. The methods. The following methods were employed to address the stated objectives: Calculation of volumes and costs of major construction works for station construction using different designs (at a depth of 0.75 meters). Determination of normal forces and bending moments at the joints of the structure. Findings. During the research, the stress state of the vault blocks was determined by solving a system of 11 linear equations, taking into account vertical and horizontal loads, as well as stress at the rock interface at the joint level. A technical and economic analysis was also conducted using aggregated indicators, indicating the competitive advantages of the proposed designs among single-span structures for shallow-depth underground stations. The originality. Correlations found lies in substantiating the effectiveness of the designs and implementing various configurations of single-span vaulted stations for shallow-depth metro construction. Practical implementation. Based on the technical and economic analysis of the options presented in Tables 2 and 3, it can be observed that compared to the first variant, the third variant incurs reduced costs of monolithic concrete. Additionally, there is no need to deviate from the planned track route during the construction of support tunnels and, consequently, manipulate the rings of the structure. Furthermore, the structural features of the third variant allow for the passage of a larger-sized mechanized tunneling complex compared to the first and second variants. The obtained results from the calculations, in combination with the conducted technical and economic comparison and justification of the proposed designs, indicate that the proposed single-span vaulted station designs with an island platform type fully satisfy the engineering and geological conditions, possess sufficient load-bearing capacity, and are competitive among single-span structures for shallow-depth underground stations.

The diverse landscape of memory T-cell heterogeneity.

The diverse landscape of memory T-cell heterogeneity.

Occupational exposure and personal exposure to hazardous air pollutants in underground metro stations and factors causing poor indoor air quality

Occupational exposure and personal exposure to hazardous air pollutants in underground metro stations and factors causing poor indoor air quality

A theoretical and applied convective heat transfer model for deep-buried underground tunnels with non-constant wall temperature

Underground tunnel ventilating has been used in many hydropower stations to reduce the building energy consumption of the underground space by precooling or preheating air. The tunnel wall temperature has an important influence on the cooling or preheating performance of the deeply buried underground tunnels. To solve the problem that the heat balance equation is difficult to solve due to the wall temperature variation along the tunnel, a simple heat transfer model under the non-constant wall temperature condition was developed. The developed model is validated against field tests which showed good agreement between the model results and test data. Field tests of underground traffic tunnels in 5 hydropower stations show that the maximum and minimum attenuations reach 13.0 °C and 2.2 °C, respectively. The comparison results show that the relative deviation of the prediction value of the developed model is 3.72% lower than that of the existing constant wall temperature model. Furthermore, the developed model is used for performance simulation of tunnel ventilation for real great hydropower stations, and the conclusions show that the maximum deviations between the calculated model and tested values range from 0.34 °C to 2.76 °C, and the maximum relative deviations range from 1.89% to 9.69%. In addition, the average relative deviations range from 1.13% to 2.40%. Data comparison verifies that the developed model established in this paper has accurate prediction performance, which is conducive to the design optimization of air conditioning and utilization of natural thermal for underground hydropower stations.

Improving Speech Intelligibility from PA Systems in Transportation Terminals

ACRP 175 was published in 2018 and provides basic guidelines for design, installation, and operation of public address systems in airport terminals. There are approximately 400 airports in the US, and with over 550 underground stations and 2,600 above ground stations in the US , many of these guidelines developed for airports can also be easily adapted for these transit stations. This paper provides an overview of ACRP 175 guidance with a focus on key factors for successful design and commissioning. As part of the research acoustic field studies were performed at six airports and a total of 45 different spaces including ticketing, concourse, gate lounges, food courts, arrival/departure halls, baggage claim, and curbside locations. We describe experience using ACRP 175 on current design-build projects and discuss other relevant industry standards.

Dynamic analysis on the structure of metro station under high-speed railway load

High-speed railways often run over underground metro stations. Dynamic load induced by high-speed train can influence the internal force of underground structure and hence can pose danger to the underground structure. Hence, it is necessary to estimate the safety of underground structure due to high-speed train load. In this paper, the effects of dynamic load induced by high-speed train on metro station are investigated by carrying out three-dimensional numerical analysis. Guinan high-speed railway, which is designed to run over Jinqiao metro station in Nanning, Guangxi province of China are adopted as the background of this case study. The hardening soil model with small-strain stiffness was adopted to model the behaviour of soil. Two typical speed of railway train (i.e., 160 km/h and 350 km/h) are considered in this study. Based on the numerical analysis, vertical vibration acceleration and bending moment of the structure of the metro station are presented and analysed.

Numerical Simulation and Analysis of the Influencing Factors of Foundation Pit Dewatering under a Coupled Radial Well and Curtain

It is crucial to use a suitable dewatering technique to prevent land subsidence and substantial decreases in groundwater levels caused by the dewatering of groundwater during the construction of underground projects. Therefore, in this study, a generalized three-dimensional numerical model of groundwater flow was implemented for an underground station pit project. The dewatering efficiency of the coupled radial well-curtain method was investigated and compared with that of a traditional method. In addition, the influence of different structures and parameters (radial pipe diameter, conductance, number of radial pipes, and shaft drawdown) on the dewatering efficiency was assessed. The results showed the following: (1) radial wells caused less disturbance to the groundwater seepage field and extracted less groundwater during the dewatering process compared with pumping wells; (2) the structure and parameters of the radial wells positively correlated with the dewatering efficiency; (3) the curtain improved the dewatering efficiency, resulting in lower amounts of groundwater discharged and less disturbance to the groundwater flow field; and (4) the coupled radial well-curtain method is an efficient dewatering method that could effectively prevent the lowering of groundwater level outside the foundation pit, thus reducing the risk of land subsidence in the surrounding area.

21 Moorfields: designing against disproportionate collapse using a performance-based framework

21 Moorfields is an over-station commercial office development, located above Moorgate underground station in the heart of the City of London. The multistorey office building spans 55m between supports using an innovative combination of arches coupled with launching trusses and mega-trusses along the east and west facades. Due to the nature and location of the development, the project brief imposed tight robustness requirements, including designing for dynamic forces derived both from multiple permutations of member-removal and event-specific scenarios. This article discusses a performance-based approach to robustness assessment which was implemented on the project, in which the intent of the relevant building regulations was explicitly checked through realistic physics-based simulations.

Performance of Flowable Concrete for Application in Underground Structures -NATM Tunnel and Station Box of Mumbai Metro Project

Abstract: High-performance flowable concrete offers special combinations of performance, uniformity, and consistency requirements that cannot be possible by traditional normal slump concrete. It is an advanced concrete than traditional concrete with high workability without segregation, bleeding and it is suitable for placing in structures with congested reinforcement of structure, long distance pumping concrete-like inside NATM tunnel, cross passages, and underground station box concrete structures. Flowable concrete can be flow itself but does not have the self-compacting capability. Flowable concrete required vibration to ease flow to reach each corner of formwork and compaction for achieving a smooth surface finish after deshuttering. Mix proportion of flowable concrete must ensure a good balance between deformability and stability. The behavior of concrete can be affected by the characteristics of selected ingredients in concrete and the mix proportions. It becomes necessary to evolve a procedure for mix design of flowable concrete. The paper presents an experimental procedure for the mix design of flowable concrete for grade M40 and implementation of the same mix at the cast in situ Base slab, Roof slab Rcc walls for underground metro stations, NATM tunnel & cross passages in Mumbai Metro Project, package -UGC-07. The test results for acceptance characteristics of M40 grade flowable concrete such as flow table test, compressive strength at the ages of 7, 28, and 56 days determined, and results are included here. Successful production of temperature control flowable concrete from batching plant, transportation, placement procedures, and proper planning of handling and execution of flowable concrete at the site are presented in this article.

Effects of control zone, exhaust rate and station extent on smoke dispersal during emergency concourse fires in underground stations

Effective mass rapid transit plays an essential role in public transportation for sustainable urban development. This study investigates the temporary spreading behavior of smoke in the concourses of underground stations. The computational approach implements the software package FDS® 6.7.4 along with a post-processing visualization module (Smokeview) to simulate the smoke dispersal processes for determining the unsteady distributions of temperature and visibility during emergency concourse fires. The interfacial temperature between the lower air layer and upper smoke layer is employed to estimate the smoke layer height, as guided by NFPA-92B. The FDS predictions agree reasonably well with the measured fire plume temperatures at the heights of 7.0 m and 13.0 m above the fire source from the available literature in the time duration of 600 s for model verification. FDS calculations are then extended utilizing the validated computational model to explore the effects of the control area, exhaust rate and station size on the smoke spreading progressions. The simulated results reveal the effectiveness of installing static barriers to restrict smoke dispersal within a specific control space; however, the implementation of suitable mechanical exhaust system is required to extract the dense smoke out of the concourse. For the scenario of a high volume MRT underground station, the design adopting the smoke control area of 20 m × 15 m in conjunction with the exhaust rate of 15 m3/s can attain clear visibilities for emergency evacuation. However, the simulations show the inappropriateness of arranging the same design layout of control area and exhaust rate as safety measures of underground fires for a medium volume station.

Machine learning prediction of groundwater heights from passive seismic wavefield

SUMMARY Most of water reservoirs are underground and therefore challenging to monitor. This is particularly the case of karst aquifers which knowledge is mostly based on sparse spatial and temporal observations. In this study, we propose a new approach, based on a supervised machine learning algorithm, the Random Forests, and continuous seismic noise records, that allows the prediction of the underground river water height. The study site is a karst aquifer in the Jura Mountains (France). An underground river is accessible through an artificial shaft and is instrumented by a hydrological probe. The seismic noise generated by the river is recorded by two broadband seismometers, located underground (20 m depth) and at the surface. The algorithm succeeds in predicting water height thanks to signal energy features. Even weak river-induced noise such as recorded at the surface can be detected and used by the algorithm. Its efficiency, expressed by the Nash–Sutcliffe criterion, is above 95 per cent and 53 per cent for data from the underground and surface seismic stations, respectively.

Damage and failure of underground subway stations under different soil constraint conditions.

Investigations from past earthquakes have shown that underground subway stations can suffer excessive deformation under strong seismic loads, leading to the damage of critical components and the collapse of structures. This study presents the results of finite element analyses on the seismic damage of underground subway stations installed under different soil constraint conditions. The plastic hinge distribution and damage characteristics of cut and cover double-storey and three-storey subway stations are analyzed using the finite element method software ABAQUS. Combined with the static analysis results of the column sections, a discriminant method for bending plastic hinges is presented. The numerical results show that the collapse of the subway stations begins with the failure of the bottom columns' bottom sections, which leads to the bending of the plates and the destruction of the whole structure. The bending deformation at the end section of columns has an approximatively linear relationship with the inter-storey drift ratio, and the change in soil conditions shows no apparent influence. The sidewall deformation behavior varies significantly under different soil conditions, and the bending deformation at the bottom section of sidewalls increases along with an increase in the soil-structure stiffness ratio at the same inter-storey drift deformation level. The sidewall bending ductility ratio of the double-storey and three-storey stations at the elastic-plastic drift ratio limit increases by 61.6% and 26.7%, respectively. In addition, the fitting curves between the component bending ductility ratio and inter-storey drift ratio based on the analysis results are also presented. The findings may provide a helpful reference for the seismic performance evaluation and design of underground subway stations.

Indoor Air Quality Assessment of Metro Stations Based on the Optimal Combination Weight and Improved Fuzzy Comprehensive Evaluation

Aair quality issues and respiratory diseases have become issues of particular concern since the outbreak of the COVID-19 pandemic. The indoor air quality of crowded places such as underground metro stations has received growing attention from passengers and staff, thus requiring both qualitative and quantitative assessment. However, the traditional fuzzy comprehensive evaluation is ineffective in this respect. Therefore, this paper proposed the method of optimal combination weight and improved fuzzy comprehensive evaluation to assess the air quality. First, subjective weights were calculated with the multiple-input weighted precedence chart and analytic hierarchy process; objective weights were computed using the entropy weight and exceedance multiple methods. Second, the moment estimation theory was introduced for the optimal combination of these weights. Results show that the optimal combination weighting method achieves the minimum relative deviation. Moreover, in the traditional fuzzy comprehensive evaluation, the air quality is generally classified based on the maximum membership, and the evaluation is inapplicable when the validity (K0) is less than 0.5. Therefore, the concept of confidence was introduced herein for improvement. Finally, the optimal combination weight and improved fuzzy comprehensive evaluation is proved to be the most reasonable in comparison with the traditional fuzzy comprehensive evaluation and indoor air quality index. This study not only suggests a good method to assess the indoor air quality of metro stations but also provides references for decision makers.

The Ontario Line, another milestone in developing Toronto's public transit system

AbstractThe new Ontario Line is one of four priority transit projects announced by the province of Ontario in 2019 for the Greater Toronto Area (GTA). It will be a 15.6 km stand‐alone rapid transit line that will run through the city from Exhibition/Ontario Place in the southwest, through the heart of downtown Toronto, all the way to the Ontario Science Centre in the northeast. Over half of the route (9 km) is planned to run underground through new tunnels, with the remainder running along elevated and at‐grade rail corridor sections of track. Fifteen new stations are proposed, whereby eight are planned as deep underground structures. Most of these underground stations will be built in the downtown core, with numerous connections to the broader transit network of the GTA, including GO Transit rail services, the Toronto Transit Commission's (TTC) existing subway Lines 1 and 2, the Line 5 (Eglinton Crosstown LRT) currently under construction, as well as numerous bus and streetcar routes. The expected project benefits of Ontario Line are as follows: A faster and more reliable access to rapid transit system with more than 227,500 people living within walking distance to the new line. Reduction in crowding of existing Line 1 subway. Up to 47,000 jobs accessible by transit in 45 min or less for Toronto residents. Economic and community growth along the future transit line and significant reduction in traffic congestion and greenhouse gases by providing alternative transportation options. The Ontario Line is currently being delivered through a number of contracts with different procurement approaches.

An adaptation resilience assessment framework for key components of prefabricated underground stations

Prefabricated underground stations (PUS) have become an important aspect of resilient cities. Adaptability to local emergency restoration is a critical target for PUS to achieve resilience after disasters. For this purpose, this study constructed a PUS adaptation resilience assessment framework (PUS-ARAF) with three modules: (1) A PUS key component vulnerability function was proposed to analyze its morphology. (2) A ‘Resilience performance - recovery Time - restoration Cost’ assessment process was established to analyze local emergency restoration. (3) A dynamic assessment was proposed to quickly obtain PUS adaptive schemes for key components. A case study was performed based on the Shenzhen PUS and the results indicated that (1) the Joint-region-weak-link scheme alleviated brittle damage on PUS large-span structures and achieved 0.97 bearing and 0.96 energy absorption capacities of continuous-section beam, (2) local emergency restorability exhibits conditional function characteristics with local factors. Threshold-compliant schemes demonstrate easy adaptation to local restorability at minimal cost. (3) PUS-ARAF developed local adaptive schemes with minimum restoration time and cost, and (4) the final PUS adaptive scheme preferred a light-asset strategy and was applied to the Shenzhen PUS. The PUS-ARAF provides adaptive schemes and local-adaptive life-cycle resilience strategies for PUSs.