Underground Metro Station Research Articles

Основные факторы, влияющие на сходимость расчётных и фактических значений деформаций существующих зданий

A study of the interaction between an underground structure and the soil mass in which it is located is based on mathematical modelling by means of geotechnical software packages. Possible settlement of the foundations that support the foundations of buildings located within the influence area of underground construction is normally calculated with the PLAXIS software package. The actual settlements of these buildings when compared to the simulation results show differences in a wide range from 3 to 75%. Specific values are predetermined by the method of excavation support and the adopted technology of works. The paper analyses the ratio of actual and calculated (by different models, including the Coulomb-Mohr model and various modifications of the Hardening Soil Model as the most frequently used in our country and, therefore, analysed most thoroughly in respect of their advantages and drawbacks) deformations of existing buildings during underground works carried out in the vicinity. Factors influencing the deformations are considered. Numerical discrepancies for different methods and in different soils (sand, loam, clay) are given. Possible reasons for discrepancies are formulated. The deviations are strongly influenced by the adopted calculation scheme. A corresponding study on a detailed level required mathematical modelling, which was carried out using the example of excavation of a construction pit for the entrance hall of the Butyrskaya underground metro station in Moscow and a nearby building.

Evaluation of comfort perception of passengers in urban underground metro stations

Indoor thermal comfort levels in underground metro platforms and trains in Chennai metropolitan city are assessed in the present research study to determine the comfort perception of passengers. The field measurements were conducted in 7 underground metro stations during summer (Mar-Jun 2019) and winter seasons (Dec 2019 - Feb 2020). The thermal comfort of metro passengers is investigated through environmental parameters and a subjective survey. Results indicated that the percentage of unacceptability in metro platforms is in the range of 36.7–98.8%, while inside the metro trains it is less than 12%. This indicates the efficiency of the in-train air-conditioning systems compared to metro platforms. Good agreement is found between the findings of the thermal comfort investigation and the comfort perception of passengers. A linear and very strong positive correlation is found between operative temperature and the percentage of passengers dissatisfied. No relation is found between the metro stations' indoor and outdoor thermal conditions. Thus, it is inferred that internal factors such as the functioning of stations, operation of metro trains, and high density of passengers contribute significantly to indoor heat generation. During both seasons, the thermal conditions in all metro stations surpassed the ASHRAE-55 and ISO7730 guidelines. Stations with low passenger traffic are maintained with high operative temperatures to save energy costs. Based on the prevailing thermal conditions and ASHRAE recommendations of operative temperature, a Predicted Percentage of Dissatisfied (PPD) value of up to 40% could be deemed a thermal comfort metric that can be acceptable in underground metro stations.

Exploring the Applicability of Building Energy Performance Certification Systems in Underground Stations in China

To improve the energy efficiency of underground metro stations, and in view of the absence of a comprehensive energy performance evaluation system for underground stations, this study introduced building Energy Performance Certification (EPC) tools into underground stations and conducted a comparative analysis of their applicability. The findings indicated that due to the unique characteristics of underground stations, China’s current EPC system was inapplicable to them. Specifically, (1) for basic items, although evaluation methods were available, due to the limited energy use data for the statistical method, the self-reference method was preferred, but its calculation encountered issues with missing reference values; (2) for prescribed items, the emphasis should be placed on the energy efficiency requirements of energy use systems rather than those of the thermal performance of envelopes; (3) for alternative items, the energy recovery measures related to the heat dissipation of trains and the piston wind should be addressed. Furthermore, a case study was conducted for verification of the proposed energy evaluation method, and the EPC system was updated based on the results of the comparison. The authors hope that this study will help improve China’s energy evaluation methods for underground stations and serve as a reference for expanding the EPC system to include public transportation buildings.

Evaluation of the concentration of suspended particles in underground subway stations in Tehran and its comparison with ambient concentrations

Subway lines are responsible for 20% of the total passenger traffic in Tehran. Particulate matter is one of the most important major pollutants in subway stations and increasing their concentration leads to numerous health consequences for passengers and subway employees. This study aims to investigate the concentration of PM10 and PM2.5 in four underground metro stations and compare them with the concentration of these particles in the open air. Seasonal sampling (April 2018 - April 2019) of particulate matters was conducted in the middle months of all four seasons for one week in the middle months of each season at peak traffic times from 8am to 12am, at three locations (entrance, middle, and exit in each station) and also at outside ambient of each station. The results are then compared with the relevant standards. The main sources of suspended particulate matter in the underground subway stations were due to passenger traffic, train piston pressure, floor cleaning, maintenance operations, wheel-rail wear and braking, and the performance of the ventilation system in the subway station. The results of the monitoring measurements in this study showed that the annual average concentrations of PM10 and PM2.5 in the four underground subway stations were 68 μg/m3 and 47 μg/m3 and in the outdoor ambient around these stations were 42 and 29 μg/m3, respectively. Also, this study showed that in the four underground subway stations, the annual average concentrations of PM10 and PM2.5 were 1.5-1.7 times higher than those in the outdoor ambient, respectively.

Air quality in underground metro station commuter platforms in Singapore: A cross-sectional analysis of factors influencing commuter exposure levels

The metro is a major component of public transport systems in urbanized cities and may expose commuters to indoor air pollutants. We examined how commuter exposure to indoor air pollutant levels varied with the characteristics of underground metro stations. We carried out a national study of 41 commuter platforms from 39 randomly selected underground stations in Singapore. We used generalized linear models to assess the variability of air pollutant concentrations with station characteristics. We computed commuter-weighted pollutant-specific station rankings to inform mitigation priority. PM2.5 (mean = 24.1 μg/m3) and PM10 (mean = 26.9 μg/m3) concentrations across commuter platforms were generally lower than those found outdoors while platform CO2 levels (mean = 608.1 ppm) were 1.7 times those outdoors. More stations exceeded the WHO 24-h mean exposure guidelines values for PM2.5 (n = 30, 73%) than for PM10 (n = 4, 10%). PM2.5, PM10 and CO2 levels were lowest in stations on the Circle, North-East and Downtown lines. PM2.5 and PM10 concentrations at platforms were positively associated with their outdoor concentrations. Mean CO2 concentration levels at platforms were the highest during commuter rush hours. Longer train arrival intervals were associated with lower CO2 levels. PM2.5 and PM10 levels in stations were negatively associated with the depth of the commuter platforms. Commuter volumes influenced the priority ranking of mitigation measures. Underground metro stations exhibited high variability and dependence on station characteristics as well as outdoor ambient pollutant levels. Our study findings suggest that any required improvements in ventilation and station design should be focused on PM2.5 exposure reduction and prioritized according to both indoor air pollutant levels and commuter volumes to provide the largest extent of commuter benefits.

Wind tunnel modeling experiments on airflow characteristics of underground metro station with sunken squares

Building airflow characteristics can affect the indoor air environment, thereby affecting indoor air quality and building energy consumption. In recent years, the sunken square has increasingly designed and applied to underground transportation hub systems, because of their special advantages, such as improving the ventilation and lighting of the underground space, blurring the feeling of the ground and underground and improving the quality of the space. However, at present, there are few systematic and comprehensive researches on the airflow characteristics of the sunken squares to the underground metro station. In this study, the wind tunnel modeling experiment and the particle image velocity (PIV) technology are comprehensively used to study the influence of the sunken square on the airflow characteristics of the underground metro station, the influence of the sunken square on the flow field distribution and air exchange rate of underground metro station are obtained. The dimensionless average wind velocity at the large openings of the sunken square is 0.053-0.18, and the air exchange rate of the underground metro station is changed with the number and the relative positions of sunken squares. Conclusions of this research could provide useful reference to the design of airflow characteristics for underground buildings.

Multi-LOD BIM for underground metro station: Interoperability and design-to-design enhancement

Underground metro stations as essential large-scale infrastructures that ease the traffic congestion on the overcrowded urban surface should be thoroughly designed, constructed and maintained. Building information modelling (BIM) has been increasingly employed for project design authoring, construction monitoring and operation management to promote digital engineering. Geotechnical design engaging numerical modelling techniques is an indispensable process for underground construction projects. These cross-disciplinary processes employing heterogeneous applications are yet to be coordinated in an efficient way, and thus improved interoperability can streamline the processes and optimise engineering design. This paper proposes an extension to the primary standard for openBIM data exchange – the Industry Foundation Classes (IFC) to facilitate wider adoption of BIM in underground infrastructure design, construction and management. Then a multiple level-of-detail (LOD) metro station BIM model is introduced to represent information at distinct levels of geometric and semantic richness required for varying application scenarios. Finally, we suggest a workflow underpinned by heuristic techniques, as an intermediate solution, to enhance the interoperability between a BIM authoring tool and a numerical modelling program for geotechnical analysis, and exemplify the workflow with the State Library Station of Melbourne. The proposed workflow offers an automated error-free, design-to-design solution, and hence enables the efficient exploration of design scenarios and construction optimisation before IFC is adopted by geotechnical modelling software.

Research on Comprehensive Evaluation of the Operation and Maintenance Status of Urban Deep Metro Station

With the rapid development of urban metro system, the operation and maintenance status of urban metro station has received increasing attention. The operation and maintenance status of urban subway stations involve various factors including structure, equipment, and environment, which are difficult to be accurately evaluated directly. On the other hand, as the burial depth of metro station increases, disaster-triggering factors become increasingly complex and diverse, which enhances the difficulty of evaluating the operation and maintenance status. A new method is proposed herein to realize the comprehensive evaluation of the operation and maintenance status of urban deep metro stations. Firstly, the evaluation indexes needed for evaluation are selected by referring to a large number of literatures, combined with many relevant specifications and standards, and based on some existing index selection principles. According to the selected indexes, an evaluation index system of operation and maintenance status of underground metro station is established. Then, based on the established evaluation index system, a comprehensive evaluation method for the operation and maintenance status of urban deep metro station is developed by combining the analytic hierarchy process (AHP) and relevant information aggregation methods. This method is characterized by considering the functions with prominent defects with the use of weighted geometric average (WGA) and variable weight methods. Finally, the proposed evaluation scheme is applied to guide the maintenance of China’s deepest metro station. The proposed comprehensive evaluation method will promote the in-time management and maintenance of urban deep metro station.

Rectification of Ground Water Leakage During Metro Tunnel Operation

It has been more than 20 years since the Taipei Metro Danshui Line of Taipei City was put into commercial operation and, the tunnels and underground metro stations experience structural aging along with possible deterioration of structural components, which can result in water seepage and sand ingress. In an effort to avoid any adverse influences on the metro operation, including possible passenger safety issues and potential damage to adjacent third-party buildings, Taipei Metro conducted a comprehensive maintenance management program including daily inspection patrols. This paper describes a rectification case of sealing underground water leakage using a controlled low pressure continuous grouting technique, the double-packer grouting. The retrofit work was conducted while the metro remains in normal operation with no interruption. Details of the rectification and instrumentation works are described in this paper. As a result of this retrofit work, the strength of the site stratum has been improved considerably, and the potential structural aging process has been delayed with an improved water tightness. Service life of the underground structure is expected to be extended. The double-packer grouting method proved to be adaptable to relevant underground retrofitting projects.

Assessment of exposure to airborne aerosol and bio-aerosol particles and their deposition in the respiratory tract of subway metro passengers and workers

This research paper presents an investigative study of airborne aerosol particles (PM2.5) and bio-aerosol particles (bacteria and fungi) inside subway metro stations and their deposition dose in the respiratory tract of exposed passengers and workers. In this study, aerosol monitoring and bio-aerosol sampling were conducted along the metro line and inside metro stations to determine the daily average exposure levels of passengers and workers. The deposition of aerosol and bio-aerosol particles in the respiratory tract of healthy adult males and females was calculated using Multipath Particles Dosimetry Model. The exposure assessment revealed that exposure to fine airborne particles (<1 μm) was dominant; more than 40% of total aerosol deposition and 10–16% of bio-aerosol deposition were found in the pulmonary region of the respiratory tract. Higher deposition dose of particles was observed in males in comparison to females. In the journey along the metro line, a high deposition dose was found during in-train travel and in the underground metro station. Severalfold higher deposition doses were found in the respiratory tract of subway metro workers due to the longer exposure duration. Recent studies have confirmed the spread of COVID-19 virus through airborne particles of size <2.5 μm and airborne transmission was found to be significantly more in indoor spaces. Thus, it is critical to study the exposure levels and deposition dose of fine airborne particles in the human respiratory tract to assess the possible health risks and devise ways to maintain a healthy metro environment.

Measuring and modeling moisture environment in underground metro stations during commissioning stage: A case study

Due to the humid underground environment, underground metro stations often have internal condensation issues, especially during the commissioning and initial operation phases, and these issues will have a negative impact on the equipment operation and building life. This study aims to solve the issue by 1) identifying common areas with condensation risks based on on-site measurements and numerical simulation methods, and 2) proposing effective dehumidification solutions for the moisture control of stations. By on-site investigating the characteristics of the station’s moisture environment and numerical assessing the effects of two different dehumidification strategies, it has been found that 1) for Tianjin, during most times in summer, the air temperature of the station in the commissioning phase was maintained relatively stable, but with significantly changing humidity; 2) the relative humidity on the platforms was higher than 80% for almost 30% of the testing time, and the surface of the upper structure of platform doors having a high risk of condensation; 3) the dehumidification effect of industrial dehumidifiers was found to be better than that of increasing exhaust air volume. The authors hope that the research could aid the decision on dehumidification strategies and provide guidance for further moisture control in underground stations. Practical Application This article analyzed the moisture environment of the underground metro stations in the commissioning phase and conducted a numerical approach to assess the condensation risk. Potential dehumidification solutions including increasing the exhaust air volume and using industrial dehumidifiers have been proposed, and their effects have been investigated and compared. The authors hope that this research can aid the decision on dehumidification strategies for facilities maintenance and provide a guidance to further moisture control in underground stations.

Reasonable Clear Spacing for Large-SpanTwin Tube Four Track Underground Metro Station in Steep Dip Rocks

Reasonable Clear Spacing for Large-SpanTwin Tube Four Track Underground Metro Station in Steep Dip Rocks

Assessment of Train Noise at Platforms in Underground Metro Stations

Abstract Metro has become one of the most used means among public transit due to its advantages such as mass transit capacity, safety, fast speed, and comfort. Despite its benefits, workers and passengers ride the metro daily, and they are continuously being exposed to a high level of noise. Noise exposure has been related to various health-related issues. This paper presents an evaluation of the acoustic environment at the station’s platform and studies factors affecting the platform’s noise levels. Greater Cairo Metro Line 1, 2, and 3 have been selected as a case study. The result indicates that noise levels are unacceptable compared with the international standards of noise exposure as the highest measured noise level at station platforms was 93.93 dB(A). Regarding the rolling stocks type, the L Aeq was different from one type to another, with a range of 2.28 to 6.5 dB(A). The L Aeq on the underground platforms station was 11 dB(A) higher than on the surface stations regarding the station type. For underground stations, the L Aeq on curved platforms higher than the straight platforms when a train arrived, stop and go from the station with a range of 2.7 to 4.9 dB(A). Regarding the station platform dimension, the L Aeq on the underground platforms with a 5 m width is higher than the one with a 3 m width by 3 dB(A).

Influences of the optimized air curtain at subway entrance to reduce the ingress of outdoor airborne particles

It is of great significance to control the air quality of underground metro stations, especially considering their poorly ventilated environments. Existing literature mainly focuses on the removal and control of underground pollutants and seldom pay attention to the ingress effects of atmospheric pollutants (e.g., from the burning of fossil fuels, exhaust gas of vehicles, etc.) diffusion through the entrances/exits. In this study, we aim to study the reducing effects of integrated air curtain and exhaust systems on atmospheric airborne particles entering into the metro stations. Validated turbulent models were adopted for numerical simulations. The associated effects of air curtain velocity, exhaust velocity, and atmospheric wind speed were investigated. Four different installation locations of the air curtain were considered. Subsequently, monitoring, Artificial Neural Network, and air purification methods were proposed for the optimal design of integrated air curtain and exhaust system. It is concluded that an integrated air curtain and exhaust system can improve the interception efficiency on particles around 40% compared with no measure taken at the subway entrance, or it can be increased about 20% compared with only using an air curtain system (no exhaust vent) at the entrance.

Enhancing underground development users’ health through facilities management: a study of the underground metro system in Hong Kong

The ever-rising global population poses a great challenge for cities to accommodate additional citizens in limited land space. As such, many high-density cities were transforming the mind from “build higher” to “dip deeper”. However, most of the existing underground space were built with inadequate consideration of user’s health. Thus, this study aims to enhance underground users’ health using an integrated Facilities Management-Health (FM-H) model. A questionnaire survey study was conducted in 4 underground metro stations in Hong Kong, which resulted in 120 valid survey responses. Based on the extensive literature review, the survey was designed to cover eight FM factors: thermal comfort, indoor air quality, ventilation, visual comfort, noise level, greenery, wayfinding support, and immediate access, and four health indicators: physical health, emotional exhaustion, depersonalization and claustrophobia stress. Pearson’s correlation and multiple regression modelling were adopted to investigate the associations between FM and users’ health. The results indicate that, even though all FM factors were found to have a significant impact to at least one health indicator, thermal comfort and wayfinding support were found to have impacted on three health indicators respectively. This sheds light to the importance of needing further investigation into these two FM factors in underground studies.

Behaviour of an underground metro station for different constitutive models - A study on the influence of Mohr-Coulomb and other advanced constitutive models using PLAXIS 2D for the proposed Chennai Metro Rail Phase 2 project

The Phase 2 of the proposed Chennai Metro Rail Project contains underground stations of depths below ground varying from 20m for a 2 level station to 32m for a 4 level station. Diaphragm walls have been chosen for the purpose of earth retention during construction stage and also to be a part of the permanent structure. The centre part of the stations is constructed using top-down methodology and the ends of the station which are used for the purpose of TBM launching and retrieval activities are constructed using either bottom-up or top-down methodologies. The behaviour of the part of the station constructed using top down sequence will be different from the part constructed using bottom up sequence. The current study focusses on the comparison of the influence of the various constitutive models available in the FEM software package PLAXIS 2D such as the basic Mohr-Coulomb model and advanced models such as Hardening soil model and Hardening soil small strain stiffness (HSS) models on the bending moments, shear forces of the diaphragm walls, ground deformations, strut forces etc. This comparative study has been performed on both the top-down and bottom-up sequences and for the different ground conditions along the proposed second phase metro rail alignment in Chennai region of India.

Assessing the Quality of Architectural Works in Underground Metro Stations in Egypt Via Six Sigma Methodology

The research is trying to find a new suitable strategy to assess the quality of Architectural works in the underground Metro Stations. Due to the important role which these stations play in crowded cities as Cairo. Applying six-sigma methodology as it based on rational analysis can achieve a fruitful success in construction field as it succeeded in the industry. This strategy not only can assess the quality level of Architectural works in the underground Metro Stations but also can discover its defects to ignore it in the upcoming stations. That will eliminate the unnecessary cost and will raise the values of the stations by achieving the high quality level. In addition, it will contribute in developing this great project.

Prefabrication technology for underground metro station structure

Serious social and environmental issues associated with large-scale metro construction such as long construction periods, considerable environmental effects, large resources consumption, and labour force shortage were overcome using fully prefabricated technology for the construction of metro station structures; this technology was first researched and developed in Changchun, China. Thus far, six prefabricated metro stations on Changchun Metro in China have been constructed using this new technology, and it is expected to be applied and to gain popularity in other cities. This paper provides a comprehensive introduction to the main research and contributions of this new prefabrication technology. The paper covers mechanical properties of the newly developed “grouted mortise-tenon joint”, the first static and dynamic research on the mechanical behaviour of prefabricated structure system, mechanical characteristics of the newly proposed lightweight closed-cavity thin-walled components, and waterproofing technology of prefabricated structures. Further, the paper also discusses the application of these research achievements. In addition, the technical, economic, and social benefits achieved using this technology are examined. The research and development of this technology for constructing metro stations is of great significance in promoting prefabricated technology in the field of underground structures.

Applying Value Engineering Technique Using Building Information Modeling at Underground Metro Station

Applying Value Engineering Technique Using Building Information Modeling at Underground Metro Station

Planning and Scheduling of Underground Metro Station Box Using MSP Software

Planning and Scheduling of Underground Metro Station Box Using MSP Software