Urban Traffic Tunnel Research Articles

Probabilistic model for predicting fire casualties in an urban traffic tunnel

Fire accidents could result in severe casualties in an urban traffic tunnel due to the concentration of users and narrow space. However, fire casualties could not be easily predicted due to the complicated evacuation environment and uncertainty in personnel distribution. This paper proposes a probabilistic model to predict the fire casualties in an urban traffic tunnel with only natural ventilation, considering the effects of the thermal and carbon monoxide distribution, in addition to the arrangement of various vehicles. First, the general framework of the probabilistic model was put forward and the methods to analyze the fire scenario, evacuation process, casualty criteria, and probability curve were introduced in details. Then, a case study based on a three-lane traffic tunnel was conducted, and the effects of maximum heat release rate on probabilistic curve of fire casualties were discussed. The results showed that the fire casualty increased with the maximum heat release rate. Besides this, when the distance between fire source and evacuation exit was reduced to 150 m, the impact of maximum heat release rate would decrease significantly. This study made notable contributions toward evaluating the personnel loss in tunnel fire and laid a foundation for assessing and improving the resilience of tunnel.

Improving the management of tunneling operations in urban areas of Vietnam

Nowadays, in Vietnam's major cities, making use of underground space (tunnels) in road traffic is necessary, especially at river crossings or at complex intersections with high traffic density. However, there have been many problems in the operation, exploitation and maintenance of traffic tunnels due to damages such as cracks in the tunnel shell, water infiltration, flooding, fire and explosion, causing traffic insecurity, which needs to be further considered and perfected, especially the safety of people and vehicles traveling through the tunnels. The drafting of management procedures for tunnel works has some limitations in the operation process, because the tunnel operation process contains many potential risks that can lead to risks affecting the function, the existence of the work and the damage to human life and property, the cost and time for the maintenance. This article focuses on perfecting the management process of tunneling operations in order to contribute to ensuring stability, longevity, workability and efficiency when operating tunnels in general and urban traffic tunnels in particular.

Theoretical Analysis of Rock Blasting Damage in Construction of Tunnels Closely Under-Passing Sewage Box Culverts

With the large-scale construction of urban traffic tunnels in China, it has become common to underpass existing buildings and structures such as sewage box culverts and pipelines using the drilling-blasting method. How to analyze accurately the blasting damage of surrounding rock and reasonably determine the safe distance between tunnel and box culvert or pipelines is an urgent issue to be solved. In this paper, the Cowper-Symonds plastic kinetic hardening model was improved using both rock initial damage degree and damage modification coefficient considering rock residual strength. The proposed model was implemented into LS-DYNA. The proposed damage model was used to evaluate the blasting construction of rock tunnels closely under-passing sewage box culverts. The results of numerical simulation using the proposed damage model shows that the blasting damage range of rock with a damage degree of more than 0.5 very significantly reduces from 1.0 m to 0.3 m as the spacing between the box culvert and the tunnel increases from 1.0 m to 4.0 m, and the evolution process of rock blasting damage can be well-presented. Moreover, the safe distance between tunnel and box culvert in blasting construction can be reasonably determined to be no less than 4.0 m. The findings in this paper could be significant for guiding the blasting construction of rock tunnels closely under-passing sewage box culverts.

Numerical study on fire-induced smoke temperature characteristics in small curvature radius UTLT-like tunnels under emergency state

Extensive studies have usually focused on an ordinary single straight or large curvature radius tunnel fire. However, the curvature effect of small curvature radius curved tunnel on the fire-induced smoke temperature characteristics still needs to clarify. Therefore, a three-dimensional transient computational fluid dynamics (CFD) fire model for small curvature radius urban traffic link tunnel (UTLT)-like tunnel was established to understand the scope and extent of curvature effect on the fire-induced smoke under emergency state. The results show that, in the curved tunnel area, small curvature radius or large critical ventilation velocity results in stronger centrifugal force of the fire smoke, readily destabilizing the fire smoke downstream of the fire source. Compared with large radius of curvature and straight tunnels, due to the greater resistance of curved walls in small curvature radius tunnel, the length of smoke back-layering is longer. Simultaneously, the temperature of the high-temperature smoke on the outer wall of the ceiling cross section is higher than the inner wall. Prediction mathematical models for the maximum temperature and longitudinal temperature profiles were further developed by taking the curvature and ventilation velocity effect, which is basically consistent with experimental and simulated results.

Full-scale experimental investigation on smoke spreading and thermal characteristic in a transversely ventilated urban traffic link tunnel

Transverse ventilation system is an effective method to control the smoke propagation in tunnel fires. In the current research, 14 full-scale burning tests were conducted in an urban traffic link tunnel in Chongqing, China. Temperature and velocity profiles, as well as the smoke stratification characteristics affected by the transverse ventilation were successively explored. Results underlined that 1) Fire location and air supply system have limited influence on the induced air velocity while the induced air velocity slightly decreased as heat release rate increased. When more smoke outlets were activated, the induced air velocity increased; 2) Ceiling temperature was very sensitive to the fire location, smoke extraction, and air supply system. A distinct temperature decrease was observed when (a) the fire moved closer to the outlet; (b) more outlets were activated; (c) supply vents near the fire were opened; 3) Thermal stratification could be well predicted by the temperature quotient proposed by Newman. Considering the transverse ventilation, the relationship between temperature ratio ΔTcf/ΔTavg and Froude number Fr accounting for the transverse ventilation was modified based on the present measurements.

Demonstration and Analysis of Urban Traffic Tunnel Expansion Project Adjacent to Buildings

With the increasing number of urban underground construction projects, the evaluation of the influence of tunnel expansion on building foundation is one of the important factors to be considered in the project. In this paper, the deformation of the upper structure and the deformation pattern of the upper structure were analyzed, and the two-dimensional finite element model was built based on the case of Chongqing Jiefangbei Underground Ring Road Expansion Project Scheme. Comparative analysis of the deformation and changes in stress of the two tunnel expansion construction schemes of full-frame support and bolt suspension was performed, and the safety, rationality and feasibility of the bolt suspension scheme was confirmed through project safety analysis. It is hoped that this paper will serve as a reference for similar projects in the safety control technology of tunnel construction process.

Research on Deformation Control Indicators and Standard of Urban Traffic Tunnel Construction Adjacent to High-rise Building

The biggest environmental problem caused by the construction of tunnels adjacent to high-rise buildings is the settlement of buildings. The paper analyzes the influence of tunnel excavation on the deformation of the superstructure and the deformation mode of the superstructure. It introduces the indicators and standards for the construction control of tunnel adjacent to the building at home and abroad. Combined with the Yuzhong tunnel project under construction in Chongqing, the main monitoring indicators and control standards of the Yuzhong Tunnel passing through the main buildings are given after comprehensive analysis and considerations, which provide a reference for the deformation control indicators of similar urban traffic tunnels adjacent to high-rise buildings.

Experimental study on the performance of hybrid ventilation system combining forced longitudinal flow and shaft natural ventilation in tunnels

The hybrid ventilation system combining forced longitudinal flow and shaft natural ventilation has the advantages of both ventilation strategies; for example, it can discharge buoyant smoke through the nearest downstream shaft and can actively constrain backlayering flow. A series of brine-water experiments were conducted to investigate the effects of the longitudinal velocity and shaft dimensions on the performance of the hybrid ventilation system in urban traffic tunnels. A light attenuation technique was used to obtain the width-averaged density distribution in the entire tunnel. Subsequently, ventilation efficiency and the backlayering length were easily determined. The results indicated that the extraction efficiency of the buoyant fluid decreases with increasing longitudinal velocity, particularly when the ventilation shaft is short and the longitudinal velocity is large. Moreover, the existence of a stable backlayering flow is useful for improving the extraction efficiency. For ordinary urban traffic tunnels that allow only passenger cars to pass through, the optimal height and width of the ventilation shaft were determined to be 9 and 7 m, respectively. From the results of the backlayering length and extraction efficiency, we observed that the acceptable longitudinal velocity corresponding to the optimal shaft dimensions approximately varies from 1.8 to 2.3 m/s. The study can provide useful information for the design of such hybrid ventilation systems in urban traffic tunnels.

An experimental study on the influence of local loss on ventilation characteristic of dividing flow in urban traffic link tunnel

In order to deeply study the local ventilation loss coefficient of the bifurcation structure in urban traffic link tunnel, a scale 1:50 model with bifurcation structure was designed and constructed based on the Xiamen Haicang undersea tunnel. The ventilation characteristics and local ventilation loss coefficient are studied for the bifurcation structure through a model experiment. The results show that the length-to-height ratio at the bifurcation structure has a significant influence on the local loss coefficient. When the split ratio is greater than 0.5, the local loss coefficient of direct flow will decrease with the increase of this ratio, however it will increase when the split ratio is less than 0.5. The local loss coefficient of split flow will just decrease with the increase of the length-to-height ratio. The local loss coefficient of direct flow and split flow will decrease during the process of increasing the bifurcation angle from 10° to 20°. When the bifurcation angle is increased from 160° to 170°, the local loss coefficient of direct flow is independent of the bifurcation angle. The results clarify the influence law of the bifurcation structure on the local loss coefficient and provide the reference for the ventilation design in urban traffic link tunnel.

Study on the heat insulation performance of fire water curtain applied to the connecting passage

It provide a reference for the design of the heat insulation system of the connecting passage of the urban subway traffic tunnel, carry out 1:3 scale model experimental, discussion on the coupling of artificial ventilation and heat insulation water curtain, thermal radiation and temperature change in two tunnels. The results show that the heat insulation water curtain has good heat insulation effect under the coupling of ventilation and water curtain. However, ventilation will cause turbulence of air flow in the connecting passage, and the hot water curtain is easy to drift. Therefore, it is suggested to reduce the ventilation speed as much as possible without backflow of fire smoke, to reduce its impact on the thermal insulation water curtain.

Research on the evaluation model of deep foundation pit supporting structures in urban traffic tunnels

Research on the evaluation model of deep foundation pit supporting structures in urban traffic tunnels

Research on the evaluation model of deep foundation pit supporting structures in urban traffic tunnels

In order to improve the building mechanics performance of the foundation pit supporting structure of urban traffic tunnel and guide the engineering design and construction, the evaluation model of the deep foundation pit supporting structure of urban traffic tunnel is proposed based on mechanical anchoring and linear mechanical loading. The mechanical anchoring method is used to load the support structure of deep foundation pit of urban traffic tunnel. The constitutive relation of dynamic node of deep foundation pit supporting structure of urban traffic tunnel under moving load is constructed, and the tangent elastic modulus of supporting structure of deep foundation pit of tunnel is calculated according to equivalent stress-strain relation. Thus, the mechanical evaluation and optimisation design of deep foundation pit supporting structure of urban traffic tunnel are realised. The test results show that the mechanical loading performance of the model is good for the design of the deep foundation pit supporting structure of urban traffic tunnel, and the load capacity of the supporting structure is improved, and the engineering design of the foundation pit supporting structure is optimised.

Traffic-related air pollution induces non-allergic eosinophilic airway inflammation and cough hypersensitivity in guinea-pigs.

The pathogenesis and pathophysiology of eosinophilia-related chronic cough such as non-asthmatic eosinophilic bronchitis and cough variant asthma are still not clear. This study is to examine the potential role of traffic-related air pollution (TRAP) in eosinophilic inflammation and cough responses. Non-sensitized guinea-pigs were exposed to TRAP in an urban traffic tunnel or kept in a filtered air environment for 7 or 14days. Reflexive cough was measured using citric acid and allyl isothiocyanate (AITC) challenges, respectively. Spontaneous cough counting was determined using audio recording and a waveform analysis. Airway inflammation was evaluated using differential cells in bronchoalveolar lavage fluid (BALF) and lung histopathology. To further elucidate the relationship between airway inflammation and cough hypersensitivity, a subgroup of those exposed for 14days received a dexamethasone treatment. Compared to reflexive cough count (mean (95% confidence interval) in 10minutes) provoked by the AITC challenge for the unexposed animals (3.1 (1.7-4.5)), those were increased significantly following both the 7-day (12.0 (6.8-17.2), P<0.01) and the 14-day (12.0 (6.4-17.6), P<0.01) TRAP exposure. The effect provoked by the citric acid challenge was more profound following the 14-day exposure (26.0 (19.5-32.5) vs 3.8 (1.5-6.0) for the control, P<0.001). TRAP exposures enhanced spontaneous cough events, caused a significant increase of eosinophils and neutrophils in BALF and resulted in a dramatic eosinophilic infiltration in submucosal layer of trachea and bronchus, which can be inhibited significantly by dexamethasone treatment. TRAP exposures induced cough hypersensitivity and non-allergic eosinophilic inflammation of airways in guinea-pigs. This study highlights the potential mechanisms of eosinophilia-related chronic cough that can be induced by traffic-related air pollution.

Combining diverse driving forces for smoke control in complex urban traffic link tunnels (UTLTs) using one-dimensional flow modelling

Urban traffic link tunnels (UTLTs) could become increasingly more complex because they incorporate both looped main tunnels and multiple branch tunnels. In such a complex tunnel structure, smoke control in the event of fire becomes more difficult than that in conventional simple tunnels due to the enhanced flow interactions among various branches. Moreover, there are still no specific smoke control guidelines for such complex tunnels. Furthermore, the use of a single smoke control method could be inapplicable or even unaffordable in UTLTs because the complicity of the configuration and the interaction between the flow of different branches. In this paper, hybrid ventilation modes which combine diverse flow driving forces are proposed for smoke control in UTLTs. The hybrid modes could exploit the advantages of each of the constitutive modes. Three-dimensional numerical simulations are performed to show the benefits of combining diverse driving forces. Then, a one-dimensional flow modelling approach was employed to investigate the efficiency of three hybrid modes. The results demonstrate that proper matching of various driving forces is crucial for effective application of the hybrid modes. This paper provides a new route for UTLT smoke control and also demonstrates the advantages of one-dimensional flow modelling in such designs.

Designing a Two‐Floor Urban Traffic Tunnel by Using NATM Tunneling Method in Tehran Alluvium with Shallow Overburden under Modares Highway

Designing a Two‐Floor Urban Traffic Tunnel by Using NATM Tunneling Method in Tehran Alluvium with Shallow Overburden under Modares Highway

Research on Influence and Prediction Model of Urban Traffic Link Tunnel curvature on Fire Temperature Based on Pyrosim--SPSS Multiple Regression Analysis

The underground space, also known as the “fourth dimension” of the city, reflects the efficient use of urban development intensive. Urban traffic link tunnel is a typical underground limited-length space. Due to the geographical location, the special structure of space and the curvature of the tunnel, high-temperature smoke can easily form the phenomenon of “smoke turning” and the fire risk is extremely high. This paper takes an urban traffic link tunnel as an example to focus on the relationship between curvature and the temperature near the fire source, and use the pyrosim built different curvature fire model to analyze the influence of curvature on the temperature of the fire, then using SPSS Multivariate regression analysis simulate curvature of the tunnel and fire temperature data. Finally, a prediction model of urban traffic link tunnel curvature on fire temperature was proposed. The regression model analysis and test show that the curvature is negatively correlated with the tunnel temperature. This model is feasible and can provide a theoretical reference for the urban traffic link tunnel fire protection design and the preparation of the evacuation plan. And also, it provides some reference for other related curved tunnel curvature design and smoke control measures.

Experimental study on thermal and smoke control using transverse ventilation in a sloping urban traffic link tunnel fire

A set of full-scale experiments was conducted to study thermal and smoke control strategies using transverse ventilation system in a sloping urban traffic link tunnel (UTLT). Results showed that it is not the case that the slower the smoke spread longitudinally, the better the smoke being controlled. For transverse ventilation, within the smoke extraction compartment, the faster the smoke spread to the exhaust vents the faster the smoke being extracted from the tunnel. More importantly, the operation of the exhaust and supply vents for transverse ventilation in real time should take the effect of tunnel slope into consideration. For tunnel with a slope going uphill from upstream to downstream, supplying air from the downstream is recommended while supplying air from the upstream or directly to the fire located smoke compartment should be avoided. Additionally, for a given total smoke exhaust volume flow rate, increasing the number of exhaust vents is an effective way of controlling the smoke layer interface height. For the kind of tunnel as studied at hand, open the exhaust vents in the fire located compartment and its downstream smoke compartment is recommended.

How Fear Responses of Fight, Flight and Freezing Interact With Right Hemispheric Deficits in the Prediction of Anti-Social Behavior: Proposing A New Process Model of Hemispheric Asymmetry

In order to deeply study the local ventilation loss coefficient of the bifurcation structure in urban traffic link tunnel, a scale 1:50 model with bifurcation structure was designed and constructed based on the Xiamen Haicang undersea tunnel. The ventilation characteristics and local ventilation loss coefficient are studied for the bifurcation structure through a model experiment. The results show that the length-to-height ratio at the bifurcation structure has a significant influence on the local loss coefficient. When the split ratio is greater than 0.5, the local loss coefficient of direct flow will decrease with the increase of this ratio, however it will increase when the split ratio is less than 0.5. The local loss coefficient of split flow will just decrease with the increase of the length-to-height ratio. The local loss coefficient of direct flow and split flow will decrease during the process of increasing the bifurcation angle from 10° to 20°. When the bifurcation angle is increased from 160° to 170°, the local loss coefficient of direct flow is independent of the bifurcation angle. The results clarify the influence law of the bifurcation structure on the local loss coefficient and provide the reference for the ventilation design in urban traffic link tunnel.

One-dimensional analysis for optimizing smoke venting in tunnels by combining roof vents and longitudinal ventilation

A hybrid mode that combines both longitudinal ventilation and natural roof venting is proposed for thermal and smoke control in tunnel fires. This hybrid strategy creates safe environments at the upstream side of the fire and shortens the smoke spreading distance at the downstream side, if the longitudinal ventilation and roof smoke venting are well cooperated. It is advantageous to the urban traffic tunnels that are adjacent to other underground facilities. The pressure rise of the longitudinal ventilation system and the geometrical parameters of the roof vents are the two key factors affecting the effectiveness of the proposed hybrid mode. The heat and smoke convection patterns under this hybrid mode are investigated with both a one-dimensional hydraulic analysis method and numerical simulations. The simulation results demonstrate that the smoke can be exhausted by the roof vents downstream of the fire, and thus, the gas temperatures downstream of the vents can be significantly decreased. The maximum deviation between the theoretical smoke exhaust rate and simulation result is approximately 17%, indicating the analytical model and numerical simulation results are in good agreement. The one-dimensional analysis method and the equations associated with it can be directly used to optimize the design parameters.

Performance evaluation of longitudinal and transverse ventilation for thermal and smoke control in a looped urban traffic link tunnel

The complex structure of the urban traffic link tunnel (UTLT) exacerbates fire accident risk and increases the difficulty of smoke control, especially for a UTLT with looped tunnel systems. The applicability of the traditional tunnel smoke control methods, e.g., transverse ventilation and longitudinal ventilation, needs further investigation for UTLTs. Experiments were conducted in a small-scale model to investigate the effectiveness of both two ventilation modes for a looped UTLT. In a longitudinally ventilated UTLT, the critical velocities, as the minimal air velocities for preventing smoke infiltrating into the regions upstream of the fire and entering the downstream tunnel branches that are adjacent to the smoke discharge route, should be guaranteed. Multiple operational modes of longitudinal ventilation could be feasible for achieving the desired performance of smoke control. For transverse ventilation, both the effects of the exhaust flow rate and the air supply rate are investigated. To confine the smoke in the tunnel branch where fire occurs, an effective exhaust flow rate could be twice the smoke production rate. Forced air supply could be unnecessary for a UTLT due to the abundance of natural air supply routes. Longitudinal ventilation leads to lower smoke flow temperatures than transverse ventilation does in UTLTs.