Effects of the solid curtains on natural ventilation performance in a subway tunnel

Solid curtains can be installed in subway tunnels for the promotion of air ventilation in ventilation ducts in association with the piston effect caused by a running train. With an aim to analyze the effects of solid curtains on duct ventilation performance in a subway tunnel, the current study adopts the tunnel and subway train geometries which are exactly the same as those in a previous model tunnel experiment, but newly incorporates two ventilation ducts connected vertically to the tunnel ceiling and two solid curtains placed at an upstream position of a duct near the tunnel inlet and at a downstream position of another duct near the tunnel outlet, respectively. A three-dimensional CFD model adopting the dynamic layering method for tracking the motion of a train, which was validated against the reported model tunnel experiment in a previous study, is employed to predict the train-induced unsteady airflows in the subway tunnel and in the ducts. The numerical results reveal that the duct ventilation performance in a subway tunnel strongly depends on the operation of the solid curtains. The suction mass flow of the air through the duct near the tunnel inlet and the exhaust mass flow of the air through the duct near the tunnel outlet are increased considerably in the case with the solid curtains in comparison with those in the case without the solid curtains.     

Effects of vent shaft location on the ventilation performance in a subway tunnel

A computational analysis of a ventilation system in a subway tunnel is carried out by solving 3D Reynolds-averaged Navier–Stokes equations for train-induced unsteady flow using the sharp interface method as the model for the moving boundary of an immersed solid. The ventilation performance is evaluated depending on the location of the vent shaft by analyzing the ventilating flow rate through the shaft and the feature of the flow field in the subway tunnel around the shaft. It is found that the optimum location of the vent shaft with respect to maximizing ventilation performance lies near the station.     

Numerical study on the optimization of smoke ventilation mode at the conjunction area between tunnel track and platform in emergency of a train fire at subway station

To cope with fires in a subway station, ventilation systems are usually installed, which includes an air supply system and a smoke exhaust system. In case of a train fire, the operation of these ventilation systems needs to be studied in order to get optimal control of smoke propagation and provide better environmental conditions for personnel evacuation. In this paper, CFD simulations are carried out by Fire Dynamics Simulator (FDS) to study the effectiveness of different ventilation modes in case of a train fire in a subway station. The temperature and visibility contours are computed as to compare the performance of various ventilation modes for subway stations with full-seal Platform Screen Door (PSD) or half-height safety door. Results show that appropriate activation of the air supply system can improve the efficiency of the ventilation system in smoke control, and vice versa. It is better to activate the lobby air supply system and meanwhile close the platform air supply system. As for the exhaust system, it is necessary to activate the platform exhaust system and the Over Track Exhaust (OTE) system, and it is better to deactivate the Under Platform Exhaust (UPE) system. The optimization strategy of the ventilation mode for subway stations with full-seal PSD is similar to that for subway stations with half-height safety door. With the help of the additional smoke barrier, smoke propagation in a subway station can be well controlled. The results in the paper may serve as a useful reference for the smoke control design in case of subway train fires.     

Experimental and numerical analyses of train-induced unsteady tunnel flow in subway

To analyze the unsteady three-dimensional flow in the subway tunnel caused by the passage of a train, both experimental and computational studies have been conducted. The experimental analysis of train-induced unsteady flow is conducted on a 1/20 scale model tunnel and the pressure and air velocity variations with time are presented. The three-dimensional unsteady numerical analysis using the sharp interface method for the moving boundary of an immersed solid was carried out for the same geometric configurations as the experimental analysis. The predicted numerical model results show good agreement with the experimental data.     

Influences of the train-wind and air-curtain to reduce the particle concentration inside a subway tunnel

Subways are used widely for public transportation in major cities and require efficient ventilation systems to maintain indoor air quality in the subway tunnel. A subway tunnel was investigated numerically and experimentally to reduce the particle concentration in subway tunnels. The subway tunnel is 54-m long, 1.65-m high, and 2.5-m wide. The subway tunnel is one-quarter scale of a real subway tunnel. The tunnel has two U-type mechanical ventilation shafts. The steady three-dimensional airflow in the tunnel was analyzed using ANSYS CFX software to solve the Reynolds-averaged Navier–Stokes equations. The airflow in the tunnel and shafts was observed numerically using the train-wind and air-curtain. The effects of the train-wind, air-curtain, and electric precipitator were examined experimentally. The ventilation performance in the subway tunnel was observed with respect to the particle concentration in the tunnel. The numerical results suggest proper operating conditions for experimental analysis of the particle concentration. The average velocity of the airflow increases in the shaft when the velocity of the air-curtain increases. The particle concentration at the dust monitoring device after ventilation shaft 1 was reduced significantly in the tunnel when the air-curtain and train-wind were operated.     

浅谈地铁隧道中通风排烟存在的问题及对策

针对目前国内地铁站台、隧道设置的通风和排烟设施的情况,分析了地铁站台、隧道的通风和排烟存在的问题,并提出了整改措施,指出科学设置防排烟设施以及事故状态下合理进行防排烟处置,对于减少人员伤亡和财产损失具有重要意义。     

Influence of the slope in the ventilation semi-transversal system of an urban tunnel

The covering of a section of the Inner Belt roadway (“Ronda del Mig”) in Barcelona gives rise to an urban tunnel of great length (1535 m). The tunnel is divided into two independent parallel galleries and its orientation is North–South, with a 2% upward slope towards the North. Although normal ventilation is achieved with jet fans, between the two galleries there is an interior passage for smoke extraction, in case of fire, through exhaust openings on both sides of this passage. Therefore, the tunnel has a semi-transversal ventilation system for fire incidents.The behavior of the smoke generated during those possible fire incidents in the traffic galleries was simulated with a commercial code, FLUENT^®, which allows a three-dimensional multispecies Navier–Stokes unsteady simulation. The mesh of each tunnel was made with about 250,000 triangular base prismatic cells. The simulated fire had a thermal power of 30 MW and the time step was set to one second, while the simulation covered 15 min.Special emphasis was put on the influence of the tunnel slope on the smoke’s behavior in each gallery. Simulation results showed that the fans’ capacity established in the project specifications was not enough to extract the smoke of a fire with the simulated power. A significant percentage of the smoke was aspirated through the exhaust openings but the rest continued rising to the tunnel portal due to the slope. This created a great risk mainly in the descending gallery with opposite traffic direction. For a more efficient extraction it was determined that the exhaust sections should be opened upward of the fire’s location. The standard opening, at both sides of the fire, reduced the capacity to extract smoke due to clean air aspiration from the lower portal.     

Prediction of smoke back-layering length under different longitudinal ventilations in the subway tunnel with metro train

Due to the small width and the large train blockage ratio in subway tunnel, the smoke back-layering will be different from that in the wider road tunnel with small vehicle blockage ratio. In the train blockage region of tunnel, the velocity of longitudinal ventilated air-flow interacting with the back-flowed smoke gas is different from that in the upstream tunnel without train blockage. Then the back-flowed smoke gas might be prevented in the train blockage region with higher ventilation velocity, otherwise it would be stopped in the upstream tunnel without train blockage but with lower ventilation velocity. They were taken into consideration separately and an equivalent fire source was introduced by dividing the dimensionless heat release rate of fire source into two parts in the cases where the smoke back-layering length is longer than metro train length. A series of full-scale numerical simulations are carried out with FDS to investigate the smoke back-layering length in subway tunnel with different train lengths and longitudinal ventilation velocities. The simulation results indicate that the influence of metro train length on the smoke back-layering is great and cannot be ignored any more. A global correlation model is proposed based on the dimensionless analysis and simulation results.     

CFD simulation and optimization of the ventilation for subway side-platform

To obtain the velocity and temperature field of subway station and the optimized ventilation mode of subway side-platform station, this paper takes the evaluation and optimization of the ventilation for subway side-platform station as main line, builds three dimensional models of original and optimization design of the existed and rebuilt station. And using the two-equation turbulence model as its physics model, the thesis makes computational fluid dynamics (CFD) simulation to subway side-platform station with the boundary conditions collected for simulation computation through field measurement. It is found that the two-equation turbulence model can be used to predict velocity field and temperature field at the station under some reasonable presumptions in the investigation and study. At last, an optimization ventilation mode of subway side-platform station was put forward.     

Statistical model for the volume rate reaching the end of ventilation duct

Auxiliary ventilation is used to ventilate dead-ends of the drivages, and the most common method employed is to use auxiliary fans and ducting. In order to provide a safe and comfortable environment, it is necessary to provide sufficient air to the working areas. The optimum design of auxiliary ventilation systems may be difficult owing to the methods used in the design of such systems that require complex calculations. In this study, by evaluating data gathered from Turkish Hardcoal Enterprises, a predictive model of the volume flow rate reaching the end of a leaky ventilation duct for a simple auxiliary ventilation system was developed using multiple regression analysis. The independent variables that enter the regression were chosen as duct diameter, fan flow output, fan operating pressure, frictional pressure drop, duct length, duct resistance, and resistance coefficient of leakage paths. The coefficient of determination (R²) obtained for the predictive model was 0.931, and the residual analysis indicated that the model was statistically acceptable. Also, by using the two-sample t-test, it was shown that the developed regression model was consistent with the results obtained from another data set not included in the derivation of the presently developed regression model.     

某地铁隧道道床隆起原因分析

结合隧道所处特殊地理位置、岩土层分布特点、矿山法施工影响及地下水等因素,从工程地质、水文地质角度对某地铁隧道道床突发隆起原因进行分析,探讨了工程实例中事故发生的主要原因,并总结了类似工程施工中的注意事项。     

地铁隧道工程中的风险研究

针对地铁隧道工程的特点,对南京地铁和杭州地铁等出现的事故进行了论述,并结合国内外风险管理经验及研究成果,对部分地铁隧道中常见的风险进行了分析,以期为隧道工程的安全、经济建设奠定基础。     

地铁盾构区间隧道水平近距离洞内加固技术

以苏州轨道交通一号线桐泾路站-广济路站区间为背景,详细介绍了在盾构隧道近距离施工的情况下采取的洞内加固和保护措施,并通过各种监测表明,这些措施能够满足工程实际的需要。     

水电站无压尾水洞引风热湿交换特性的现场测试

对映秀湾水电站无压尾水洞引风过程中的室外空气温湿度、尾水洞出口空气温湿度、尾水进出口温度、引风量等参数进行了测试。测试结果表明,夏季运行时无压尾水洞对引入空气有良好的降温除湿效果;在无压尾水洞足够长的条件下,尾水洞末端引风参数主要受尾水温度的影响,而受室外空气参数的影响很小,尾水洞出口空气接近对应尾水温度的饱和状态。     

地铁隧道火灾人员疏散与烟气控制

在分析目前国内外地铁隧道火灾人员疏散方式的基础上，建议采用提高疏散效率且基本不增加投资的侧向疏散平台加联络通道的疏散方式，同时分析了隧道烟气控制的有关因素，给出了典型隧道烟气控制的临界风速(危急空气流速)。     

Deformation and mechanical characteristics of tunnel lining in tunnel intersection between subway station tunnel and construction tunnel

Deformations and stress distributions in tunnel intersection areas are more complicated than those in common tunnels. The literature on deformations and stress distributions in tunnel intersections, in which the intersecting tunnel is in a different section, is limited. The Shangxinjie subway station in Chongqing, China, was selected to investigate the deformation, stress and plastic zone responses of a tunnel intersection using numerical simulations. Based on the numerical results, the scopes of influence with respect to the deformation, stresses and possible failure modes of the tunnel lining were further studied. The numerical results show that the deformation in a section close to the tunnel intersection was larger than the deformations in distant sections. Compared with the common section, the crown settlement reached the maximum value at the tunnel intersection, and the maximum rate of increase was approximately 28%. The range of the plastic zone at the tunnel intersection was much larger than that in the other areas, and it was mainly located in the side wall and tunnel crown. In the longitudinal direction, the lengths of the scopes of influence were 2.4 B and 1.6 B with respect to the deformation and stress, respectively. The magnitudes of the internal forces in the longitudinal and circumferential directions were almost equal. The bending moments of the tunnel lining within 135° and 225° significantly changed, but the axial force decreased dramatically. Tensile and compressive failures may occur at the tunnel intersection and in a section 5 m away. Locally thickening the supporting structures is suggested to improve the stability of the tunnel.     

Effect of ventilation duct as a particle filter

This paper discusses the effect of ventilation duct as a particle filter by modeling particle deposition in ventilation ducts, which is the reason that ventilation ducts could “filter” particles. An Eulerian model is employed to predict the particle deposition velocity onto the wall and floor from fully developed turbulent flow in ventilation ducts [Zhao B, Wu J. Modeling particle deposition from fully developed turbulent flow in ventilation duct. Atmospheric Environment 2006;40:457–66], while an empirical equation is proposed to predict the particle deposition velocity onto the ceiling combined with experimental data and, another empirical equation by McFarland et al. [Aerosol deposition in bends with turbulent flow. Environmental Science and Technology 1997;31:3371–7] is used for predicting the particle penetration through the bends, which are hard to analyze by theoretical method.     

基坑开挖对地铁隧道的影响分析

结合工程实例,采用现场监测和数值计算的方法对九沙大道5号箱涵基坑开挖施工进行了分析研究,结果表明：数值计算和现场监测两者比较吻合,同时隧道结构现场监测竖向位移最大1.49 mm,收敛变形最大1.80 mm,研究结果对类似工程实践具有指导意义。     

浅议地铁区间隧道堵漏注浆处理

结合具体工程实例,介绍了地铁区间隧道漏水治理方法及堵漏注浆的参数,阐述了聚合物水泥砂浆的具体施工步骤,提出了注浆技术要求以积累注浆加固施工经验,使注浆效果达到理想要求。     

地铁隧道钢筋混凝土裂缝的治理

有效控制混凝土裂缝的发生、发展,是提高地铁隧道耐久性的关键。阐述了混凝土裂缝的种类,从收缩裂缝、温度裂缝、不均匀沉降裂缝等方面论述了裂缝产生的原因,并从工程设计、材料、施工、养护等方面提出了裂缝控制的措施与方法。对既有隧道的混凝土渗漏,根据不同情况,采取有针对性的治理方案进行治理,保障了结构的安全运营。