Traffic Tunnel Research Articles

Calculation and analysis of shear resistance of segment ring joint with shear pin

In order to get the effect of shear pins between segments on the shear resistance of segment girth joints. Take the Maliuzhou traffic tunnel project of Zhuhai which with super large diameter and Marine Composite strata as the research object, the longitudinal shear stiffness of tunnel shear considering the shear rigidity of shear pins was obtained through the finite element shear experiment of segment ring. By comparing the calculation results of shear pin and non shear pin between segment ring connections, the conclusion that shear pin setting can effectively decompose and transfer shear force and control the dislocation between segment ring blocks is obtained. The study can be used as reference for the design and construction of shield tunnel.

Influence of Short Distance Super-large Diameter Shield Tunneling on Existing Tunnels in Sea Areas

In oder to find out the influence of large diameter shield tunneling on the existing tunnel under the condition of compound strata in the sea area, taking the Maliuzhou traffic tunnel as the research background, numerical simulation and field test were combined to get the regulation of the additional internal force and deformation of the existing tunnel caused by the shield tunneling. Analysis of the data showed that: the shield construction caused the secondary additional internal force; The moment of the vault was most affected by the tunnel excavation; The axial force of the arch bottom was most affected by the excavation of the tunnel. The deformation of arch waist near excavation tunnel was more affected by tunnel excavation than that of the other side. Combined with the construction experience, the influence of the tunnel close-distance construction on the existing tunnel was within the control range, which could ensure the normal construction.

Insights into organic-aerosol sources via a novel laser-desorption/ionization mass spectrometry technique applied to one year of PM<sub>10</sub> samples from nine sites in central Europe

Abstract. We assess the benefits of offline laser-desorption/ionization mass spectrometry in understanding ambient particulate matter (PM) sources. The technique was optimized for measuring PM collected on quartz-fiber filters using silver nitrate as an internal standard for m∕z calibration. This is the first application of this technique to samples collected at nine sites in central Europe throughout the entire year of 2013 (819 samples). Different PM sources were identified by positive matrix factorization (PMF) including also concomitant measurements (such as NOx, levoglucosan, and temperature). By comparison to reference mass spectral signatures from laboratory wood burning experiments as well as samples from a traffic tunnel, three biomass burning factors and two traffic factors were identified. The wood burning factors could be linked to the burning conditions; the factors related to inefficient burns had a larger impact on air quality in southern Alpine valleys than in northern Switzerland. The traffic factors were identified as primary tailpipe exhaust and most possibly aged/secondary traffic emissions. The latter attribution was supported by radiocarbon analyses of both the organic and elemental carbon. Besides these sources, factors related to secondary organic aerosol were also separated. The contribution of the wood burning emissions based on LDI-PMF (laser-desorption/ionization PMF) correlates well with that based on AMS-PMF (aerosol mass spectrometer PMF) analyses, while the comparison between the two techniques for other components is more complex.

Experimental and numerical analysis of flow field and ventilation performance in a traffic tunnel ventilated by axial fans

To investigate air flow in longitudinally ventilated traffic tunnels, a scaled model of a typical road-traffic tunnel with an appropriate ventilation system based on axial ducted fans, is designed and built in the Lab. The focus of this paper is the airflow in a bi-directional traffic, two-lane tunnel. At the scale ratio of approx. 1:20, at 20.52m length it represents ? 400m of a realscale tunnel. The model consists of two parallel tunnel tubes, where the main tunnel (with a hydraulic diameter of ???1 ? 0.4m) has the geometry of a scaled road traffic-tunnel. The second tunnel (???2 ? 0.16m) has a smaller size and is circular in cross-section, used only to simulate airflow towards an evacuation tunnel tube. Thus the two tunnels are connected by the evacuation passages, equipped with adjustable escape doors. By a combination of experimental and numerical work, the air flow-field and the performance of the ventilation system are investigated. The velocity field and its turbulence properties exiting the fans were determined experimentally using hot-wire anemometry. These data were further processed to be used in the tunnel flow computations by CFD. The efficiency of momentum transfer (????, Kempf factor) of the longitudinal tunnel ventilation is determined. The effect that the imposed boundary conditions and the level of their detail, have within a CFD computation of tunnel airflow, with respect to accuracy, velocity distribution and computed ????. Finally a traffic-loaded (traffic ?jam?) case of flow is studied through experiment and CFD. The difficulty in assessing the required thrust of the plant in traffic-jam tunnel conditions is discussed, and the ventilation efficiency is estimated. Based on later results, the two limiting shapes of axial velocity distribution with respect to height above the road, in this type of tunnel and traffic, are estimated. The last result can be used as a realistic boundary condition (as inlet b.c. and/or initial condition) for numerical studies of flow and fire scenarios in such tunnels with the traffic load critical for design.

Channel Characteristics of Rail Traffic Tunnel Scenarios Based on Ray‐Tracing Simulator

The tunnel scenario is a major rail communication scenario. In this paper, the radio channel characteristics of tunnel scenarios with different carrier frequencies, different distances between the transmitter (Tx) and receiver (Rx), and cross sections are simulated with a ray‐tracing tool. Key parameters such as path loss, Rician K‐factor, root mean square (RMS) delay spread, and angular spread are studied. According to the results, higher frequencies introduce larger path loss and the presence of the vehicle body increases the path loss by about 35 dB in the scenario; at the same time it will also cause the fluctuation and instability of the path loss. Besides, the influence of reflections from the side walls is significant on radio propagation. The channel experiences more severe fading in a narrow tunnel compared with others.

Simulation of emergency events with fire in virtual road tunnels

Road emergency events are very dangerous, especially if they happen in tunnels. If such an event occurs with the presence of fire, self-evacuation is the most important. From experience from catastrophic events in Alpine tunnels, people can only have a few minutes to rescue. It was also reason that a lot of changes in technology and safety tunnel equipment have been legislatively adopted. Then if we want to help rescue people, we need experienced tunnel operators, who know the principles of tunnel ventilation control with fire and smoke. This paper is about simulation of emergency events in virtual tunnel of Tunnel Traffic & Operation Simulator (Simulator) and about simulations of smoke stratification on the basis of Computer Fluid Dynamics (CFD) models.

Urban Organic Aerosol Exposure: Spatial Variations in Composition and Source Impacts.

We conducted a mobile sampling campaign in a historically industrialized terrain (Pittsburgh, PA) targeting spatial heterogeneity of organic aerosol. Thirty-six sampling sites were chosen based on stratification of traffic, industrial source density, and elevation. We collected organic carbon (OC) on quartz filters, quantified different OC components with thermal-optical analysis, and grouped them based on volatility in decreasing order (OC1, OC2, OC3, OC4, and pyrolyzed carbon (PC)). We compared our ambient OC concentrations (both gas and particle phase) to similar measurements from vehicle dynamometer tests, cooking emissions, biomass burning emissions, and a highway traffic tunnel. OC2 and OC3 loading on ambient filters showed a strong correlation with primary emissions while OC4 and PC were more spatially homogeneous. While we tested our hypothesis of OC2 and OC3 as markers of fresh source exposure for Pittsburgh, the relationship seemed to hold at a national level. Land use regression (LUR) models were developed for the OC fractions, and models had an average R2 of 0.64 (SD = 0.09). The paper demonstrates that OC2 and OC3 can be useful markers for fresh emissions, OC4 is a secondary OC indicator, and PC represents both biomass burning and secondary aerosol. People with higher OC exposure are likely inhaling more fresh OC2 and OC3, since secondary OC4 and PC varies much less drastically in space or with local primary sources.

Traffic Tunnel Management in Cloud-based Flow Security System

Considering the increasingly serious problem of Internet security recently, Cloud-based Flow Security System(CFS) has been built as a solution to the Internet security application, providing convenient and effective application and content level security for enterprise users by means of cloud services. Under the CFS system, this paper developed custom function modules to achieve unified management of network nodes and GRE tunnel between the nodes, management of the switch data forwarding, and real-time monitoring of the state of the tunnel in the control platform, accomplished the design scheme of combining the load balancing algorithm with the unified management of the tunnel, realized the efficient allocation of the network nodes in the large-scale network environment and improved the network flexibility.

The mechanism of hysteretic ground settlement caused by shield tunneling in mixed-face conditions

Shield is used more and more widely, such as coal mine roadway, hydropower tunnel, traffic tunnel and so on. But Tunneling with a tunnel boring machine (TBM) may cause inevitable ground subsidence. Though over the world numerous researches have been conducted for surface settlement induced by TBM in soft ground, the researches of surface settlement induced by TBM in a sandy cobble stratum are limited and a comprehensive study of the mechanism of delayed settlement induced by TBM in a sandy cobble stratum is unavailable. A ground stable state or surface settlement can be determined based on real-time monitoring data for surface dynamic subsidence. Subsequently, TBM tunneling parameters can be adjusted to accommodate various geological conditions. A sand-pebble-soil matrix is a typical heterogeneous material. The macro-mechanical performance of this matrix significantly differs from any material. In a general situation with a low water level and minimal disturbance, a stratum can stabilize by itself for a long period of time. Considering the characteristics of the stratum, ground loss can be divided into two phases: immediate settlement, which tends to stabilize, and delayed settlement, which tends to occur in sand-cobble strata, where settlement develops at a much slower rate than in single-medium strata. Monitoring data is not sufficient to guide the construction in the case of delayed settlement. Cobble-soil matrix can be treated as a spatial structural system that is constituted by single granular soil, aggregates of granular soil and pebble grains. Based on Particle Flow Code in 2 Dimensions (PFC2D), the mechanical characteristics of the matrix and the TBM tunneling process were numerically simulated. Movements of the pebble grains were traced and recorded in real time. The model addressed the mechanism of surface collapse from the perspective of mesomechanics. According to the model, a matrix formed self-stabilizing arch that overlies an underground cavity seems gradually wear out with expanding the cavity and eventually penetrating to the ground surface. The law of ground movement and the formation mechanism of ground subsidence in TBM advancement were investigated. The main factors that affect surface subsidence are the speed of advancement, the underground water level and the supporting period. In the numerical analysis, the surface-loss lag was reproduced and the field monitoring data were verified. The findings of this study provide a new method for investigating ground subsidence in similar strata.

Static design of steel-concrete lining for traffic tunnels

Article summarizes the results of research focused on the structural design of traffic tunnel linings that have been achieved in the framework of a research project TE01020168 that supports The Technology Agency of Czech Republic. This research aim is to find and develop a process for design structure parameters of tunnel linings. These are now mostly build up by a shotcrete technology. The shotcrete is commonly endorsed either with steel girders or steel fibres. Since the installation a lining structure is loaded while strength and deformational parameters of shotcrete start to rise till the setting time elapses. That’s reason why conventional approaches of reinforced concrete are not suitable. As well as there are other circumstances to step in shown in this article. Problem is solved by 3D analysis using numerical model that takes into account all the significant features of a tunnel lining construction process inclusive the interaction between lining structure with rock massive. Analysis output is a view into development of stress-strain state in respective construction parts of tunnel lining the whole structure around, including impact on stability of rock massive. The proposed method comprises all features involved in tunnel fabrication including geotechnics and construction technologies.

Measures for the reduction of sinter formations in tunnels

A considerable part of the maintenance costs of tunnel structures is related to the inspection, maintenance and repair of the drainage system. The drainage system of tunnels is frequently clogged with Calcium precipitates. Cleaning and water conditioning are costintensive for operating companies. Apart from the direct costs associated with inspection, maintenance and repair works of the drainage system indirect costs are generated, such as by the blocking of the tunnel while inspection, maintenance or repair or by the reduction of the permitted operation speed. Sintering and clogging of the drainage systems is mainly caused by dissolution of cement minerals in concrete and mortar and/or by inadequate design and construction of the drainage system and/or grubby workmanship. With long-term studies and in-situ experiments in Austria traffic tunnels the specific input factors for sinter mechanism have been identified and appropriate counter measures could be defined. In particular modified mix designs for shotcretes and mortars have proven to bring a significant beneficial effect. By means of constructional measures and by the application of hardness stabilizers a further reduction of hard deposits inside the drainage system is achievable. The paper will deal with the specific aspects and will propose adequate counter measures.

Thermal load of the final lining of traffic tunnels

The final lining of mined tunnels using NATM is connected with the need to ensure long-term durability of the construction. The interaction between the secondary lining and surrounding rock mass is ensured by contact with the primary lining. Static load depends already on the interaction between tunnel lining and rock mass. Loading is given by geotechnical conditions, the size of the excavation, construction progress and very important is weather conditions. In this paper presents the results of long-term temperature measurements of the final lining of traffic tunnel. Measurement at selected tunnel pass over ten years. The monitoring results should be available for future design of the final lining of tunnel construction.

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.

Diffraction Characteristics of Small Fault ahead of tunnel face in coal roadway

Small fault ahead of the tunnel face in coal roadway is the important hidden hazard factor of coal and gas outburst accidents. The study of small fault prediction has important practical significance, which is the urgent demand of coal mine safety production. The diffraction of breakpoint can be used to identify the fault. However, unlike surface seismic exploration, the diffraction is with approximately horizontal incidence when the advanced detection is carried out in the roadway. The common advanced detection system is mainly as the reference of traffic tunnel, without considering the influence of low-velocity coal seam. Considering the influence of an acoustic wave of the roadway cavity and channel wave of the coal seam, the advanced detection model of small fault ahead of tunnel face is established. Diffraction advanced observation system in which sources located in front of tunnel face is constructed, and the numerical calculation of the high-order staggered-grid finite difference is carried out. The simulation results show that: Compared with the data collected by reflection observation system, in seismic records acquired by diffraction observation system, the suppression effect of acoustic wave is appeared. The diffracted P-wave of the breakpoint of component X is clear with strong energy and short-wave group. Multiple diffractions of the breakpoint are not found, but the multiple diffraction of tunnel face endpoint is obvious. The difference between breakpoint diffraction and multiple diffractions of the endpoint is clear, and diffracted P-wave of the breakpoint is easy to identify. The multiple reflected channel wave between the fault and the tunnel face is very obvious, and the reflected channel wave of small fault is so hard to identify. Migration results show that the imaging resolution of diffracted P-wave of small fault is higher than the reflected channel wave, and breakpoint location of imaging is consistent with the actual model.

Pressures on the lining of a large shield tunnel with a small overburden: A case study

The pressure on a tunnel lining is an important issue in shield tunnel design, because it is related to the safety and durability of the lining. There is an increasing need for short (about 1km) but wide traffic tunnels in parts of China near rivers. In order to satisfy the gradient requirement of the road over such a short distance, the depth of the overburden is inevitably very shallow. The non-uniform distribution of the pressure on the lining of this kind of tunnel may result in damage to the tunnel segments. However, little published research is available on this topic. In this study, in-situ monitoring was carried out to measure the pressure on the lining of a large cross-river shield tunnel (diameter D=11.36m) with a shallow overburden (0.7 D) in silty-sandy ground. A pad type earth pressure gauges and pore-water pressure gauges were used to measure the pressures on the tunnel lining, including the tail brush pressure, grouting pressure, earth pressure and pore-water pressure. The time history and the distribution of pressures on the lining during tunnel construction and post-construction were obtained. A comparison between the measured values and theoretical values was carried out. This showed that the tail brush pressure had a considerable effect on the segments while the shield machine was passing through. Non-uniform tail brush pressures caused cracking and water leakage in the concrete segments. The maximum pressure induced by the backfill grouting was twice that of the theoretical earth pressure. However, the non-uniformity of the backfill grouting induced pressure was not as great as that induced by the tail brushes. In the silty-sandy ground, the earth pressures were generally stable 24 h after segment assembly. The final stable values were close to the total overburden pressure, particularly at the tunnel crown. The pore-water pressure generally was equal to the hydrostatic pressure and accounts for a large proportion of the total earth pressure.

Fire Spread Models and Tunnel Traffic & Operation Simulator

The computer simulation of fire spread based on modelling of complex processes related to fire by Computer Fluid Dynamics CFD theory should be a significant contribution to increase of safety of road tunnels. This paper is about instant project aimed at creating simulation models of formation and spread of fires in the road tunnel. The simulations will be compared with real in-situ measurements of fire scenarios suggested by customer organization in two road tunnels. Within the project, Tunnel Traffic and Operation Simulator, as unique facility at University of Žilina will be extended by visualizations of smoke stratification in the virtual tunnel tube.

Ventilation performance and pollutant flow in a unidirectional-traffic road tunnel

To develop a reliable method for modeling fire case scenarios within the road tunnels and observing the effects of the skewed velocity, experimental and numerical approach is used. Experimental results obtained from a laboratory tunnel model installation, are used to define geometry and boundary conditions. The result for the overall ventilation performance is compared to the available cases, for empty tunnel and stationary bi-directional vehicle traffic. For a unidirectional traffic road tunnel, in traffic loaded conditions, with a ventilation system based on axial ducted fans, the numerical simulation is used to determine the flow and temperature fields, the ventilation efficiency (efficiency of momentum transfer), and to assess the shape of the velocity distribution. The effect that a skewed velocity distribution can have on the resulting thermal and pollutant fields (CO2), smoke backlayering and stratification, is evaluated using numerical simulations, for the model-scale tunnel fire conditions. The effect of two possible limiting shapes of the velocity distribution, dependent only on the location of the fire with respect to the nearest upstream operating fans, is analyzed. The numerical results for a fire are scenario are a starting point in assessing the feasibility of a laboratory model fire-scenario experiment, what is planned as the next step in this research.

Gas-Particle Partitioning of Vehicle Emitted Primary Organic Aerosol Measured in a Traffic Tunnel.

We measured the gas-particle partitioning of vehicle emitted primary organic aerosol (POA) in a traffic tunnel with three independent methods: artifact corrected bare-quartz filters, thermodenuder (TD) measurements, and thermal-desorption gas-chromatography mass-spectrometry (TD-GC-MS). Results from all methods consistently show that vehicle emitted POA measured in the traffic tunnel is semivolatile under a wide range of fleet compositions and ambient conditions. We compared the gas-particle partitioning of POA measured in both tunnel and dynamometer studies and found that volatility distributions measured in the traffic tunnel are similar to volatility distributions measured in the dynamometer studies, and predict similar gas-particle partitioning in the TD. These results suggest that the POA volatility distribution measured in the dynamometer studies can be applied to describe gas-particle partitioning of ambient POA emissions. The POA volatility distribution measured in the tunnel does not have significant diurnal or seasonal variations, which indicate that a single volatility distribution is adequate to describe the gas-particle partitioning of vehicle emitted POA in the urban environment.

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.

Experimental evaluation of the heat flux induced by tunnel fires

Traffic tunnel closures are highly undesirable and some of the lengthiest are attributed to structural failures. Historical data shows that these failures are closely linked to fire. Furthermore, the parameters necessary for proper thermo-mechanical analysis of structural members are poorly defined or absent from literature. The energy transferred to the structure (i.e. heat flux) is the fundamental parameter for determining structural performance in fire. However, current research focuses on identifying heat release rates and temperature histories which are difficult to use for structural analyses. In this study, full-scale experiments were undertaken on passenger vehicles resulting in heat fluxes between 20 and 70kW/m2. The analyses show fire duration is linked to a vehicle’s mass and small vehicle fires can be scaled as a function of the ratio between the tunnel diameter and the characteristic height of the desired vehicle. Appropriate design values are outlined for engineers to undertake informed thermo-mechanical analyses to minimise the risk of structural tunnel failure in fires.