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[Objective] There are many characteristics of the box culvert tunnel, such as large section, slow construction progress and instability excavation face.[Method] Based on the project of shallow buried tunnel section of Luzhou Avenue in Binhu Science City of Hefei City, this study used limit equilibrium theory, Mohr-Coulomb strength criterion and full overburden weight theory to carry out theoretical derivation, and combined with large-scale three-dimensional fine numerical model to study the limit support pressure of excavation face. [Result] The results show that : it proposed a simple calculation method for the limit support pressure of the excavation face of large-section box culvert tunnel under the action of pipe curtain. Based on this, according to the calculated value of Bishop slice method, the error was very small. Compared with the calculated value of the limit support pressure proposed in this paper, which proves the accuracy of the method. Through the establishment of three-dimensional numerical model of pipe curtain box culvert construction, it is found that the surface s ment and the displacement of the longitudinal axis of the excavation face gradually decrease with the increase of the support pressure and tend to be stable. When the support pressure exceeds the static earth pressure, the upper soil is subjected to strong extrusion, and the excavation face state is easy to be inverted S shape. [Conclusion] The above results can be used as a reference for related projects. [ABSTRACT FROM AUTHOR]

Conceptual pre-estimation of road tunnel costs is a vital yet challenging process during feasibility studies due to the prevailing underground uncertainties and risks. Most existing cost estimation approaches are deterministic, probabilistic methods are limited to a single cost examination. This paper introduces a probabilistic model for pre-estimating road tunnels life-cycle costs. It aims to capture their inherent uncertainty holistically, thus enabling more reliable decision-making at a project's early stages. The proposed model is developed in three steps: multiple regression analysis, fitting distribution, and Monte-Carlo simulation. The first step unveils the correlations between independent and dependent variables, while the other two steps return the probabilistic descriptions of cost drivers and life-cycle costs. Civil engineering, electromechanical works costs, energy consumption, and operation & maintenance costs are determined as the model's output variables. A real-world database of 32 dual-bore road tunnels with a total length of 55 km is used to develop probability distributions within reasonable confidence intervals and a sensitivity analysis was performed utilizing tornado charts. The results can assist public authorities and managers in estimating the probability of a specific life-cycle cost and making appropriate decisions in accordance with their risk tolerance. [ABSTRACT FROM AUTHOR]

This paper presents a specific 3D computational fluid dynamics model to quantify the effects of the combustion of asphalt road pavement on user safety in the event of a fire in a bi-directional road tunnel. Since the consequences on tunnel users and/or rescue teams might be affected not only by the tunnel geometry but also by the type of ventilation and traffic flow, the environmental conditions caused by the fire in the tunnel under natural or longitudinal mechanical ventilation, as well as congested traffic conditions, were more especially investigated. The simulation results showed that the combustion of the asphalt pavement in the event of a 100 MW fire, compared to the case of a non-combustible road pavement, caused (i) an increase in smoke concentrations; (ii) a greater number of users exposed to the risk of incapacity to escape from the tunnel; (iii) a more difficult situation for the firefighters entering the tunnel upstream of the fire source in the case of natural ventilation; (iv) a higher probability of the domino effect for vehicles queued downstream of the fire when the tunnel is mechanically ventilated. [ABSTRACT FROM AUTHOR]

Given the role of road tunnels in a road network, it is relevant to quantitatively assess their resilience due to disruptive events. In this respect, the travel speed of traffic flow, as a metric of resilience, in the event of traffic accidents in road tunnels has been scarcely used. This represents a gap of knowledge that this paper intends to fill. For the purpose, the research method applied involves the development of a traffic macro-simulation model, and the analysis of results using the average travel speed and its spatial profile as a resilience metric. Particularly, we have evaluated the resilience of a twin-tube motorway tunnel when a traffic accident occurs in a tube. The findings showed how the best functionality level of the system, expressed in terms of average vehicles' speed, with its related greatest resilience index, is associated with the partial closure of the disrupted tube rather than the complete one. Further benefits might be obtained by activating Variable Message Signs (VMSs) that alert only the Heavy Goods Vehicles (HGVs) to exit the motorway before entering the tunnel and to use an alternative itinerary identified in the nearby transportation network. In this respect, we found that by means of the activation of VMSs as a traffic control strategy, the resilience index increased by about 7–17% when the traffic accident caused the partial closure of the disrupted tube for 1–3 h. Improvements might also be achieved by rapidly opening the two traffic by-passes at the tunnel portals that allow for the use of the adjacent undisrupted tube for two-way traffic. The unavailability of an alternative itinerary in the nearby transportation network along which to re-route the HGVs is also examined, finding a reduction in the functionality conditions of the system. The results obtained might serve as a support tool in the choice of functional recovery strategies in the case of the temporary partial or complete block of a tunnel tube due to a traffic accident. [ABSTRACT FROM AUTHOR]

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This paper presents a specific 3D computational fluid dynamics model to quantify the effects of the combustion of asphalt road pavement on user safety in the event of a fire in a bi-directional road tunnel. Since the consequences on tunnel users and/or rescue teams might be affected not only by the tunnel geometry but also by the type of ventilation and traffic flow, the environmental conditions caused by the fire in the tunnel under natural or longitudinal mechanical ventilation, as well as congested traffic conditions, were more especially investigated. The simulation results showed that the combustion of the asphalt pavement in the event of a 100 MW fire, compared to the case of a non-combustible road pavement, caused (i) an increase in smoke concentrations; (ii) a greater number of users exposed to the risk of incapacity to escape from the tunnel; (iii) a more difficult situation for the firefighters entering the tunnel upstream of the fire source in the case of natural ventilation; (iv) a higher probability of the domino effect for vehicles queued downstream of the fire when the tunnel is mechanically ventilated.

After a long planning and approval phase, the main construction work on the A26 Linz motorway began at the beginning of 2019. The new A26 road section, large parts of which are underground, will not only significantly relieve the existing inner‐city traffic routes around Linz, but will also provide an additional Danube crossing in the form of a suspension bridge with a span of over 300 m. The main elements of the first Phase of construction are the Danube Bridge and two underground branches, north and south of the Danube, with excavated cross‐sections of up to 400 m2 and ramp tunnels with tight curves. The planning of an inner‐city construction project requires the comprehensive and careful consideration of the protection of the local residents with regard to the effects of noise and vibration. It also needs the impact of the construction work on the existing traffic routes to be reduced as much as possible. The material excavated from the Freinberg tunnel and the Danube South junction must be transported away via the Danube waterway. The project‐specific framework conditions, such as the very high number of tunnel portals, the sound reflections within the Danube valley and the low overburden require considerable measures to reduce their impact during the construction phase. [ABSTRACT FROM AUTHOR]

The small town of Weyer is located in Upper Austria on the B121 Weyerer Straße. The B121 leads through the historic market square of Weyer, which is characterised by confusing bottlenecks that can only be passed in one lane. For decades, these bottlenecks have caused congestion, mainly due to heavy traffic. For residents, the burden of air pollution and noise is high. The roads department of the Upper Austrian Government has been planning the construction of a bypass for many years. Construction finally started in the summer of 2022. The Weyer bypass construction lot is 1.2 km long and includes the construction of two NATM tunnels, a vertical escape shaft, a bridge over the river Dürnbach, two roundabouts, and one traffic junction. The tunnel construction works are carried out in urban areas, in loose material with little overburden and partly under existing buildings. These boundary conditions make the project a challenge for all involved at every stage. [ABSTRACT FROM AUTHOR]

Fire is one of the most dangerous types of an accident that might happen to a ship, highly harmful to the crew as well as to the ship itself, high temperature, toxic vapours and gases are created (generated) by the combustion of a combustible material. In addition to human casualties, a material damage was also included in the fire. Therefore, a significant role of the fire protection is timely notification of fire, enabling the quick intervention, the damage reduction and engagement of people and equipment. The possibilities of fire protection improvement are carefully studied by the authors on RO-RO ships. The aim is to point out the importance of fire protection preventive measures. The analysis of the article is based on the road tunnels fire alarm system and the possibilities of application on RORO ships. The authors have been suggesting the use of an optical sensor cable in garages on RO-RO ships as the main type of fire alarm system detectors. [ABSTRACT FROM AUTHOR]

A 3D Computational Fluid Dynamics (CFD) model was set up to investigate the effects of the longitudinal slope on the risk level of users in naturally ventilated unidirectional road tunnels in the event of a fire accident. These tunnels, which in general do not require any mechanical ventilation system, have a length

A 3D Computational Fluid Dynamics (CFD) model was set up to investigate the effects of the longitudinal slope on the risk level of users in naturally ventilated unidirectional road tunnels in the event of a fire accident. These tunnels, which in general do not require any mechanical ventilation system, have a length <1 km and their natural ventilation is due to the difference of pressure at the portals and/or the piston effect of the unidirectional traffic flow. Fire accidents related to vehicles characterized by different maximum Heat Release Rates (HRRs max), situated at different locations from the entrance portal of the tunnel, were simulated by varying the longitudinal slope (i), as well as by applying both a positive and negative pressure difference (ΔP) between the entrance and exit portals to also consider any adverse wind conditions, or neglecting that (i.e., ΔP = 0). The combined effects of Peak Hourly Volumes (PHVs) were also investigated in the Quantitative Risk Analysis (QRA), which based on a probabilistic approach, considered as a risk indicator the annual cumulative frequency (F) of having a certain number of potential fatalities (N). The longitudinal profiles of temperature, radiant heat flux, toxic gases concentrations, and visibility distance upstream of the burning vehicle along the escape route (i.e., sidewalks) are reported and compared with the acceptability limits to verify if the environmental conditions are tolerable for user safety while escaping from the tunnel towards the entrance portal or the emergency exit located in the middle of the tunnel length. The results showed that the number of dangerous scenarios for user safety increased in the event of adverse wind (i.e., ΔP < 0) and/or negative gradients (i.e., i < 0). The QRA indicated the combinations of i, ΔP , and PHV for which the annual cumulative frequency (F) of having a given number of potential fatalities (N) was not acceptable. By providing additional points of knowledge in the field of fire safety engineering, this paper might serve in the design of the vertical alignment of naturally ventilated tunnels with a length <1 km, as well as in the strategies of management and traffic control. • The paper investigates user safety in the event of fire in road tunnels, a computational fluid dynamics modeling is set up. • The effects of the longitudinal slope, pressure difference between the tunnel portals, and traffic volume are considered. • The results show that the worst scenarios are for adverse wind and negative gradients. • The number of dangerous scenarios for user safety increases in the presence of adverse wind and negative gradients. • For a given pressure difference and/or longitudinal slope, the risk level for users increases with the traffic volume. [ABSTRACT FROM AUTHOR]

After a long design and approval process, the construction works for the first phase of the A26 started in 2019. The A26 not only relieves the central part of the road network of the city of Linz but also allows the river Danube to be crossed by means of a bridge: a 300 m long bridge, anchored in the rock slopes forming the banks of the Danube. The elements of the first phase are the Danube bridge and the two underground motorway junctions, Danube North and South, with excavation cross‐sections of up to 400 m2 and the tight radii of the motorway on‐ramps. Besides these conditions, urban planning requirements such as the protection of residents against immissions caused by noise and vibration, and the increased negative impacts resulting from the traffic during construction have an effect on the construction works. The excavated material from the tunnel is transported off site by ship. The existing rock mass requires excavation by means of the drill‐and‐blast method. The project‐specific boundary conditions such as the high number of portals, the noise‐reflecting effect of the "Danube gorge" and the low overburden require substantial measures to limit and monitor the immissions. [ABSTRACT FROM AUTHOR]

With the proliferation of tunnels in mountainous and intricate landscapes, the design of tunnel lighting has emerged as a crucial factor in curbing tunnel-related accidents and bolstering driving safety. This study employed scaled experiments and integrated human eye luminance adaptation curves to refine tunnel lighting configurations. The investigation revealed that the incorporation of high-light-transmittance sunshades within tunnels effectively diminished external luminance, thereby the alleviating the 'black hole effect'. From an economic perspective, adopting a tunnel lighting model with sunshades can achieve up to a 30% reduction in annual electricity costs. This study presents innovative strategies and methodologies for optimizing tunnel lighting design, offering valuable insights for future tunnel construction and lighting design endeavours. [ABSTRACT FROM AUTHOR]

Road tunnels might be exposed to Boiling Liquid Expansion Vapor Explosion (BLEVE) due to the transportation of liquified gas tankers passing through road tunnels. An efficient and accurate prediction of the response of road tunnels under internal BLEVEs can facilitate the reliable BLEVE-resistant design and risk assessment of road tunnels. This study introduces an advanced deep-learning model that employs a Transformer-based architecture with a modified self-attention mechanism, termed as Self-Attention Modified Transformer (SAMT), to predict BLEVE-induced support rotation of tunnel structure, which is a common criterion in assessing reinforced concrete structure damage to blast loads. Unlike the Transformer with the traditional self-attention mechanism, the proposed SAMT effectively aggregates global information across all variables while mitigating undue dependencies among uncorrelated variables. Consequently, the proposed SAMT is better suited for processing tabular data with uncorrelated variables. The feasibility and advantages of the proposed SAMT are verified by extensive data generated using calibrated numerical models of box-shaped road tunnels subjected to internal BLEVEs. By comparing the performance of the proposed SAMT with the non-modified Transformer network (FT-Transformer) as well as two other typical deep learning networks, i.e., Multi-layer Perceptron (MLP) and Residual Network (ResNet), it is found that the SAMT offers higher prediction accuracy and robustness than the other three models in predicting BLEVE-induced support rotations of box-shaped road tunnels. The study demonstrates that the proposed SAMT is an effective tool for the prediction of BLEVE-induced support rotations of road tunnels. • An improved Transformer-based deep learning model (SAMT) is proposed. • The SAMT features a modified self-attention mechanism. • BLEVE-induced response of road tunnel is predicted by using SAMT. • Advantages of the SAMT model are demonstrated. [ABSTRACT FROM AUTHOR]

The drainage system is a core element of tunnel construction and operation. Frequently, natural as well as technical boundary conditions lead to the deposition of scales (especially calcium carbonates) in the drainage system. As a preventive measure – in contrast to post‐depositional cleaning procedures – the use of scale inhibitors to treat the drainage water (hardness stabilisation) is an option. 'Green inhibitors' are tailored green organic substances that delay or prevent scale formation when added in small concentrations. Moreover, green inhibitors can change the material consistency of scale deposits (soft sinter). An additional advantage of their use is the good environmental compatibility compared to conventional inhibitors. Suitable test procedures can be used to select a substance or product and evaluate or optimise its dosage. The application of polyaspartic acid or polysuccinimide products as ecologically harmless and readily biodegradable agents has proven advantageous in tunnel structures. The choice of liquid or depot stone conditioning essentially depends on the scaling mechanism, in addition to the technical considerations, flow rates and water chemistry. Regarding discharge to existing receiving water bodies, the inhibitor concentration in the water can be measured and controlled by DOC analysis and fluorescence spectroscopy. This article presents contemporary and tunnel‐specific case studies. [ABSTRACT FROM AUTHOR]

Scale formation in water drainage systems occurs in diverse forms. In tunnel drainage systems in particular, calcium carbonate deposition can significantly impair water discharge, resulting in costly maintenance work and tunnel closures. This review paper presents and discusses the state of knowledge as well as the current challenges regarding scale formation in tunnel drainage systems in terms of typification, parameters controlling formation, such as hydrochemistry, interfacial phenomena, microbial activity, and countermeasures, such as appropriate adaptation of construction materials, drainage design, inhibitor use and cleaning. Detailed knowledge of the case‐specific scale formation environment and the scaling capacities of the waters provides the basis for the tailored development and evaluation of suitable strategies for successfully reducing maintenance efforts and tunnel closure. For this purpose, time‐ and site‐resolved monitoring of the composition of the solid phases, waters and the tunnel atmosphere during the implementation of the construction project and during the operation of the tunnel is paramount. [ABSTRACT FROM AUTHOR]

A field test was carried out in Koralmtunnel in order to enhance process understanding and to optimize the drainage system in a tunnel section that is complex in terms of hydrochemistry, water inflow and mineral (calcareous scale, iron ochre) and biological (microbial mats) deposits. The field test comprised three test fields with different system components and flow characteristics. The development of critical waters and deposits was recorded by continuous measurements of relevant water and air parameters by means of autonomous sensors/data loggers. Furthermore, the components were "forensically" examined with respect to scale formation. The experiments show the crucial importance of gas exchange (CO2, oxygen ingress), filling level (flow geometry/regime), residence time of waters and water‐air interaction in the drainage system. The type, material consistency, and amount of scale and biofilms depend significantly on specific gradients. Floating scale crusts formed in stagnant sections, biofilms and iron ochre deposits of soft consistency formed at higher flow rates. Seepage packs and siphons turned out to be potential sediment traps with decreasing flow‐through with no access. Drainage hoses and dimpled membranes tend to be beneficial because they can prevent air exchange at relatively high flow rates. High CO2 partial pressure within these components (measured and modeled) inhibits carbonate precipitation. The drainage system is locally designed as a series of direct cross‐drains with simple flow paths, restricted air exchange, precautionary cleaning access, and optional water hardness stabilization (liquid conditioning). [ABSTRACT FROM AUTHOR]

The unknown subsurface conditions in tunnelling projects have led to their management with many uncertainties. From these uncertainties, we can mention the geological condition of the tunnel route and the time and costs required for construction. In order to significantly reduce these uncertainties, techniques that have a high predictive power must be used. For this purpose, in this study, an autoregressive model was used to reduce the uncertainties related to geology and construction time and cost in tunnelling projects. A comparison between the predicted results and the actual values through several statistical indices showed the high-performance prediction of the autoregressive model in the prediction of tunnel resources. Also, three input parameters affecting tunnel construction time and costs, such as RQD, groundwater, and RMR, were considered. The sensitivity analysis of these parameters on the time and cost of tunnelling projects was investigated through mutual information test (MIT). The groundwater was the most effective parameter on the tunnel's time and cost. [ABSTRACT FROM AUTHOR]

Unthinkable just a few years ago, the precise laser‐scanning survey of a kilometer‐long tunnel in one day by one operator has become possible. This article describes how 261 scans were taken with a RIEGL VZ‐400i laser scanner to digitize the Zentrum am Berg (ZaB) research tunnel with millimeter resolution. The data has been automatically registered during the acquisition process within the instrument. After applying multistation adjustment, a block adjustment postprocess step, the high accuracy of the point cloud with respect to a network of 35 retroreflective bireflex targets has been approved. For further applications such as analysis, simulation, or visualization, a homogeneous 3D‐meshed surface model has been created automatically from the point cloud representing an as‐built 3D documentation of the tunnel. [ABSTRACT FROM AUTHOR]

Tunnel surveys making use of photogrammetric three‐dimensional (3D) tunnel reconstruction reach resolutions in the millimeter range. Classical big data visualization approaches display point clouds only, neglecting this considerable resolution difference between structure and texture. The article suggests a data structure that separates structural and textural resolution by a regular grid on the unwrapped design surface for 3D, combined with a UV mapping technique as regularly used in computer graphics. For real‐time rendering of huge multiscale data sets, the result of photogrammetric commercial‐off‐the‐shelf reconstructions is transformed into a proprietary hierarchical data structure. It facilitates to only load currently relevant parts of the tunnel surface from the hard drive, and only upload and render currently adequate levels‐of‐detail onto the graphics card for seamless exploration of high‐resolution geometric and image 3D tunnel data of arbitrary length. The solution allows for smooth interactive analysis and annotation such as crack identification and mapping, inventory, deformation assessment, and dimensional measurements. Aspects of data generation are addressed and information is given about the data structure, showing examples from entire tunnel 3D representations to demonstrate the smooth behaviour of the real‐time rendering of huge data volumes in various scales on standard graphics hardware. [ABSTRACT FROM AUTHOR]

Building information modelling (BIM) is a frequently discussed topic in tunnelling since it promises less loss of information and reduced lifetime cost of underground infrastructure. There is still some way to go as standardisation in this sector is immature, the implementation of three‐dimensional (3D) BIM models is developed for pilot cases of tunnelling only, and data transfer between software tools is a challenge. The long linear structures of tunnels make a specific approach of parameterised and adaptive modelling necessary to meet the requirements of repetitive construction elements and the natural differences of forecast and actual excavation conditions. This approach renders the matching of construction elements in the model and service items feasible for determining quantities for the tender and billing in tunnel projects. In this article, we show that only 57 % of service items can actually be linked to a physical item in traditional two‐dimensional (2D) design and highlight the need to consider how to incorporate these items into a BIM model. We also use a case study to propose an approach for parameterised and adaptive modelling of repetitive construction elements and show a way of a continuous data transfer from the forecast tunnelling class distribution via 3D BIM modelling to a billing software without data loss. [ABSTRACT FROM AUTHOR]

This paper presents the results of an experimental investigation which was carried out with the purpose of assessing the performance-related properties of self-compacting cement-bound mixtures to be employed in pavement foundations in road tunnels. The mixtures contained a significant quantity of recycled components and function-specific additives. Characteristics of the mixtures, which were produced in a concrete batch plant, were studied by means of laboratory and field tests. Investigated properties included flowability, compressive strength, resilient modulus and bearing capacity. It was found that mixtures prepared with a cement dosage of up to 100 kg/m3 possess the required properties of flowability, strength and stiffness. On the contrary, mixtures with higher cement dosages (150 and 200 kg/m3) fail to meet all the performance-related requirements as a result of their high long-term strength which jeopardises excavatability. Obtained results also highlighted the effects of the different components on the properties of the mixtures and led to the definition of acceptance criteria which can be adopted in actual construction works. [ABSTRACT FROM AUTHOR]

Background: One of the major topics related to the very long tunnels is dark hole effect. This is a common phenomenon caused by the sunlight reflected from the surroundings of the tunnel to the eyes of drivers and the lack of sufficient light at the tunnels' entrance, which decreases the contrast of barriers inside the tunnel and also makes it difficult to see potential obstacles at the entrance. The result is an increased risk of traffic accidents in these tunnels. Therefore, the aim of this research is to subjectively assessment the safe rate of lighting in one of the very long tunnels located in the province of Ilam. Methods: To subject evaluation the safe rate of lighting at the tunnel entrances, two parameters of the average luminance of tunnel entrance and equivalent luminance are required. In this study, Luminancemeter device model S3 was used to measure the average luminance of tunnel entrance. Then, to calculate the equivalent luminance, a YASHICA108 camera with a 35 mm lens was photographed at a distance between the tunnel entrance and a safe stopping point, and then the Holliday polar diagram was used to calculate equivalent luminance (accordance with the standard CIE88-2004). Results: In this study, the average luminance at tunnel's entrance was equal to 17 , the luminance was equal to 127.5 Using the ADRENAL equation, the quality of lightening at the tunnel entrance was less than 1. Conclusion: Comparison of the results obtained from the healthy and safety rate of lighting levels at the tunnel's entrance with the De Boer mental scale indicated that a dark hole effect occurs at the entrance of the tunnel under investigation and the light sources installed at the entrance of this tunnel did not have the sufficient ability to inhibit the dark hole effect.

In the operating phase of a road tunnel, not only maintaining or increasing the availability in the network but the economic optimization regarding the life cycle costs of the structure are also important priorities. A consistent application of the Building Information Modelling (BIM) methodology can theoretically make a useful and targeted contribution, as it provides a complete digital model of the structure with all installed elements and the information required for the operator tasks. In the research project FE https://doi.org/15.0623/2016/RRB "Building Information Modeling (BIM) in Tunneling," the Institute of Tunneling and Construction Management and the Institute of Computing in Engineering (both Ruhr University Bochum) in cooperation with BUNG Ingenieure AG developed the basics for a BIM‐based operating model of road tunnels with funding from the Federal Highway Research Institute commissioned by the Federal Ministry of Transport and Digital Infrastructure. In the article, the results of the research are presented on the basis of specific use cases of a BIM‐based operation and maintenance management. [ABSTRACT FROM AUTHOR]

In the past decades, Norwegian tunnelling has undertaken a major digital development in all operations from planning to the excavation phase. The breakthrough is driven by digital contract requirements from forward‐leaning clients and innovative industrial stakeholders, aiming for ever more efficient, quality‐oriented and risk‐reducing operations. A formal milestone documenting this development was the publication of Digitalisation in Norwegian Tunnelling in 2019. From 2019, most contracts of new infrastructure tunnels must deliver a level 3 Building Information Modeling (BIM) model. Control systems for drilling jumbos are fully digitalised. All drilling must be monitored and documented with Measurement While Drilling techniques. Via cloud servers, the drilling information is interpreted and delivered live to face engineers for decision support. Sensors are used to monitor rock grouting flow and pressure in each drill hole. Digital electronic detonators with exact delay time are used for blasting. Geotechnical mapping is carried out on field tablets. High‐resolution scans with RGB imaging must be carried out on the exposed rock surface and after rock support/linings. The next step is to utilise all the collected data to a higher degree by advanced analysis with machine learning (ML) and similar techniques for automation and optimisation. This study reviews and exemplifies the digital focus and achievements in core operations in Norwegian tunnel excavation. [ABSTRACT FROM AUTHOR]

This study complements our previous work with a simultaneous analysis of user safety and road tunnel resilience. We developed a computational fluid dynamics (CFD) model and simulated the corresponding egress process to evaluate the risk level of users exposed to different types of fire, such those which might occur on the undisrupted lane of a partially closed tube tunnel due to a traffic accident, or in the adjacent tube when used for two-way traffic in the case of the complete closure of the tube involved in the accident. The CFD results showed that: (i) better environmental conditions were found with the partial closure of the tube rather than the complete one; (ii) additional benefits can be achieved by activating variable message signs (VMSs) that suggest an alternative itinerary for heavy good vehicles (HGVs) only; (iii) safety issues for human health may arise only in the case of a 100 MW fire, occurring during the complete closure of the tube and the use of the parallel one for two-way traffic. The findings of the CFD simulations were subsequently used to perform a quantitative risk analysis (QRA) based on a probabilistic approach. The findings of the QRA were found to be consistent with those obtained by the tunnel resilience analysis. In particular, the lowest risk level for user safety was found with the partial closure of the tube instead of the complete one, and by activating the VMSs to redirect HGVs only towards an alternative itinerary. This finding was found to correspond to a higher resilience index of the tunnel (i.e., a lower resilience loss due to a traffic accident occurring in a tube). This study increases our knowledge on certain relevant aspects of the operating conditions of tunnels and can serve as a possible reference for tunnel management agencies (TMAs) in their choice of the most appropriate arrangement to recover the functionality of a tunnel taking into account both user safety and resilience at the same time. [ABSTRACT FROM AUTHOR]

During the renovation of the Gotschna Tunnel from 2019 to 2020, prefabricated elements made of Compex were used for the first time as a deformable yielding zone in the invert zone. The client, construction management, construction company and supplier of the compressible elements worked closely together to implement the design specifications. Consequently, the expectations of the special building material in terms of the production quality of the prefabricated elements and handling on the construction site were more than met. The parties involved in the construction thus see potential for further applications and further developments of Compex. [ABSTRACT FROM AUTHOR]

Tunnel geothermal systems hold the potential to promote decarbonization of the building heating and cooling sector. They can be integrated into existing infrastructure, resulting in low additional costs. In addition, these systems have large contact areas with the ground leading to larger heat fluxes. However, tunnel geothermics is relatively unknown and rarely used. Thus, the objective of this study is to provide an overview of the two primary tunnel geothermal system types as well as their application and potential. Open hydrothermal systems use the tunnel drainage water as a heat source, whereas closed absorber systems harness the heat flux from the subsoil and the warm tunnel interior via heat exchangers. The evaluation of the global application of existing and planned tunnel geothermal systems shows that all open systems are currently located in mountainous regions with a thick rock overburden. In contrast, closed absorber systems are mostly installed in urban tunnel infrastructures. The spatial distribution of geothermal tunnel systems has a focus in central Europe with Switzerland, Germany and Austria being the countries with the highest number of installed systems. Finally, this study also presents a brief summary of existing methods to determine the geothermal potential of tunnels. [ABSTRACT FROM AUTHOR]

We have developed a traffic simulation model to quantitatively assess the resilience of a twin-tube motorway tunnel in the event of traffic accident or fire occurring within a tube. The motorway section containing the tunnel was investigated for different possible scenarios including its partial or complete closure. The functionality of the road infrastructure, in the case of an accident in one of the two tubes (each tube presents two lanes with unidirectional traffic under ordinary conditions), was assumed to be recovered both by using the remaining undisrupted lane of the tube interested by the disruptive event (only one lane is closed) and reorganizing the traffic flow by utilizing the adjacent tube for bi-directional traffic (both lanes are closed). The effects of an alternative itinerary individualized in the corresponding open road network were also examined. The level of functionality of the system during the period in which the tube is partially or completely closed was computed as the ratio between the average travel time required to reach a given destination from a specific origin before and after the occurrence of the disruptive event. The resilience metrics were assumed to be resilience loss, recovery speed, and resilience index. The best scenario was found to be the partial closure of the tube in contrast to the complete one. However, in order to contain the negative effects on the functionality of the motorway section due to the complete closure of the tube, it is worth highlighting how the traffic by-pass before the entrance portal of the closed tube should be open in a very short time by the tunnel management team to allow for the quick use of the adjacent tube for bi-directional traffic. An additional improvement, with reference exclusively to passenger cars traveling through the adjacent unblocked tube, might be obtained by activating the variable message signs, located at a sufficient distance from the motorway junction before the entrance portal of the closed tube, in order to suggest an alternative route to heavy good vehicles (HGVs) only. Whereas, when the alternative itinerary is used by all vehicles traveling towards the blocked tube (i.e., both passenger cars and HGVs), this redirectioning of the motorway traffic flow was found to be characterized by an excessive travel time, with it therefore not being advisable. The results obtained might be useful as a decision-making support tool aimed at improving the resilience of twin-tube tunnels. [ABSTRACT FROM AUTHOR]

This paper aims to develop a mathematical model using Petri nets to simulate the traffic flow inside the road tunnel. First, a new modular Petri net theory is used; the modeling approach shown in this paper for modeling a specific road tunnel can also be applied for the other tunnels (reusable modules). Second, since the traffic inside road tunnels is intrinsically continuous, the roads are segmented to make the processes discrete; the segments become the basic building block of road tunnel models. Third, the modular Petri net theory and the modular Petri net model are implemented using the software GPenSIM to model and analyze real-life road tunnels. [ABSTRACT FROM AUTHOR]

This paper discusses the concept and the practical experiences of excavating an under‐river crossing with a slurry shield (D = 13.45 m) to construct a single‐tube road tunnel. Unstable sand and gravel as well as harder chalk zones in the invert area combined with high groundwater pressure require the tunnel face to be actively supported at all times. Over long stretches the overburden to the river bed is only around 0.5 D, which means that a delicate balance has to be struck between achieving the minimum support pressure required to stabilise the tunnel face while at the same time preventing blow‐out. An innovative segment sealing system with integrated expanding insert combined with a push‐fit dowel system achieves a high degree of protection from moisture and voids. The evacuation and rescue concept for the single‐tube road tunnel is based on a refuge running under the carriageway. This evacuation channel is accessed via staircases in recesses at the side. Ground freezing is used to stabilise the sand during excavation of the recesses at around 4 bar water pressure. [ABSTRACT FROM AUTHOR]

The Stockholm bypass (E4 Förbifart Stockholm) is being built by the Swedish Transport Administration (Trafikverket) – the office responsible for transport infrastructure in Sweden. The project aims to improve connections between the regional town centres and reduce congestion on the main urban roads. The route, which runs mainly underground, employs numerous contractors and has a planned construction period of 14 years, preceded by a 10‐year planning phase. This article looks at three projects: the FSE 61 Akalla Interchange, the FSE 309 Lovön Interchange and in particular, the FSE 613 Akalla Tunnel. The Akalla Tunnel is driven as a conventional full‐face excavation with pre‐grouting and supported with rock bolts and steel‐fibre‐reinforced shotcrete. The tunnel excavation is followed by the interior work comprising precast concrete walls, a suspended membrane reinforced with shotcrete, ceiling foundations and the carriageway structure. [ABSTRACT FROM AUTHOR]

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The approx. 3 km long twin‐tube Rudersdorf tunnel is part of the Fürstenfeld Motorway S7. In addition to jet grouting and steel pipe umbrella sections, the excavation is mainly carried out according to the NATM. After the contract had been signed, the contractor proposed a value engineering concept including a stepped (almost) full excavation with a short ring closure. This concept avoids jet grouting sections and reduces sections with steel pipe umbrellas and the temporary top heading invert. A fair risk transfer between both contractual partner enables the full technical and economic potential of the project to be released and guarantees a win‐win situation. The modified construction methodology consequently also requires a change of tasks and responsibility for the contractual partners for the project. This paper highlights the main topics of the contractual modifications required and explains the handling of the ground risk with examples. [ABSTRACT FROM AUTHOR]

A quantitative risk analysis (QRA) concerning dangerous goods vehicles (DGVs), including also vehicles for the transport of liquid hydrogen (LH2TVs), running through unidirectional motorway tunnels was performed. An event tree was built, and a wide parametric analysis based on different geometric and traffic characteristics of tunnels was carried out. The effects of the annual average daily traffic (AADT) per lane, the tunnel length (L), the percentage both of heavy goods vehicles (HGVs) and DGVs (for a given 7% of LH2TVs) were investigated. The results in terms of social risk, as expressed by F/N curves and the expected value (EV), show an increased risk level with the presence of the hydrogen transported, and with certain F/N curves that might also lie above the acceptability limit. This means that additional safety measures should be implemented in order to reduce the risk level or that, alternatively, appropriate strategies of traffic control systems should be taken. A statistical modeling for developing a predictive method of the EV is also performed. The outcomes show that the regression coefficients have the signs expected. In particular, the EV increases with the tunnel length (L), the AADT, and the percentage both of HGVs and DGVs. However, the magnitude of estimated coefficients indicates that the expected value EV increases more with the traffic (AADT per lane, HVGs, or DGVs) than the tunnel length. The application of the approximate method might help the Tunnel Management Agencies (TMAs) in making quick decisions, at a preliminary stage, about temporarily allowing, forbidding or limiting the circulation of DGVs and/or LH2TVs through tunnels; and subsequently investigating in greater depth the potential hazards due to the transport of hydrogen in the worst cases individualized. [ABSTRACT FROM AUTHOR]

The present work represents the second and final part of a twofold study aiming at the definition and validation of an integrated methodology for the analysis and modeling of road tunnel ventilation systems. A numerical approach is presented, based on the Finite Volume integration of the 1D mechanical and thermal energy conservation equations on a network of ducts, representing the ventilation system of the 11.6 km long Mont Blanc Tunnel. The set of distributed and concentrated loss coefficients, representing dissipation of mechanical energy by friction in each part of the ventilation system, is calibrated against a rich experimental dataset, collected throughout a dedicated set of in situ tests and presented in the first part of the work. The calibration of the model is carried out by means of genetic optimization algorithms. Predictions of the flow field using the calibrated parameters are in remarkable agreement with the experimental data, with an overall RMS error of ± 0.27 m/s, i.e. of the same order of the accuracy of the measurement probes. Further validation against a selection of field data recorded by the tunnel monitoring and control system is brought forward, highlighting the robustness and potential general applicability of the proposed approach.

The Artificial Ground Freezing (AGF) has demonstrated its versatility as an effective approach for both temporary ground stabilization and ground water control in almost all types of saturated soils. This paper describes the use of a closed circuit freezing system in the construction of four cross passages. The passages connect 4.8 km long twin road tunnels that have recently been constructed at depths of up to 60 m under Suez Canal in Ismailia, Egypt. The paper starts by describing the ground conditions at the locations of the cross passages and by presenting the results of laboratory tests conducted on unfrozen, frozen and thawed soil specimens. The main design criteria considered in designing the freezing works are discussed and the freezing and cross passages construction works are described. The frozen body was carefully monitored during the freezing process and construction of passages. Records of the adopted monitoring program are presented and discussed. Significant observations that contribute to effective planning of future freezing works are also presented. [ABSTRACT FROM AUTHOR]

We performed Computational Fluid Dynamics (CFD) modeling, and simulated a people evacuation process from a tunnel in the event of a fire, for evaluating the potentialities of using, as a temporary safety measure, an emergency vehicle equipped with a micronized water system for contrasting the fire growth phase. The structure investigated is a one-way road tunnel with only natural ventilation, and with a length less than 1000 m. The tunnel is assumed at present to be affected by refurbishment works for making it comply with the minimum safety requirements of the European Directive 2004/54/EC. In particular, it is considered that it has not yet been provided with hydrants, and with the sidewalks and the emergency exit which are still under construction. This means that users are forced to use the road carriageway for escaping from the tunnel if a fire occurs. The CFD findings have shown that the use of the micronized water system might lead to a significant improvement in the environmental conditions along the escape route since the tenability limits of temperature, radiant heat flux, CO and CO2 concentration were found to be better satisfied. Additionally, the visibility distance was shown to increase, even though it was found to be higher than the acceptable threshold value only in a few cases. However, the quantitative risk analysis based on a probabilistic approach, which was combined with a method currently used in Europe for assessing the risk due to the transit of only dangerous goods, shows that the final cumulative F-N curves related to the micronized water system always lie below those without the mentioned system, and in addition, they are always contained within the limits of the ALARP region. It is to be stressed that our paper might represent a reference in showing the effectiveness of the micronized water system as a temporary safety measure. However, it is desirable that the Tunnel Management Agencies accelerate the refurbishment works for making road tunnels definitively safer for users in a short period of time. [ABSTRACT FROM AUTHOR]

Tunnels are nowadays key elements in transport networks worldwide. To achieve a safe and efficient operation, a proper integration and design of Mechanical, Electrical and Intelligent Transportation Systems is required. Among these systems, tunnel ventilation is one of the most critical ones from the Fire Life Safety perspective, being smoke control to maintain safe conditions during self-evacuation and rescue operations one of its main objectives. Traditionally tunnel ventilation systems are sized following a deterministic approach. Designers, based on requirements and design criteria from Standards and Recommendations, focus on a limited number of fire scenarios and design parameters to reach a solution considered acceptable from a fire safety perspective. This paper proposes the use of a probabilistic approach to assess, in terms of probability of failure, the capacity of a tunnel ventilation system for fire scenarios. The model applied in the proposed process uses a 1D steady state model based on pressure losses, where critical design variables are considered random (unlike with the deterministic approach) to calculate a failure probability associated to an installed ventilation thrust. A case study example is used to analyse results using both, the traditional deterministic approach and the proposed probabilistic one. Results obtained with the deterministic approach show how, under the same design requirements, tunnels with similar characteristics allow different safety margins for the capacity of the ventilation system. These results are confirmed numerically using the probabilistic approach by evaluating failure probabilities. To avoid this, the paper proposes the use of the probabilistic approach to allow a definition of an equivalent uniform safety margin (to achieve a certain probability of failure) which would be of significant help for designers, administrations and tunnel operators. It is not the aim of the study to define the limit for the probability of failure or to characterise the design variables, but to present a useful tool with which important conclusions about the design criteria can be obtained. [ABSTRACT FROM AUTHOR]

The knowledge of the flow field inside road tunnels under normal operation, let alone fire conditions, is only approximate and partial. The reason is that while the full three-dimensional, unsteady problem is out of reach of numerical methods, on the other hand accurate measurement of the airflow in road and railway tunnels constitutes an extremely demanding task. The present work, structured as a twofold study, takes up the challenge and proposes an original integrated experimental and numerical approach for the analysis and modeling of flow inside a road tunnel and its ventilation systems, aiming at defining a methodology for the creation of “digital twins” of the system itself, on which advanced ventilation and smoke control strategies can be tested and fine-tuned. In this first part, an innovative experimental facility for the continuous acquisition of the longitudinal velocity profile along the whole length of a road tunnel has been designed and built. The facility consists of a survey rake with five bidirectional vane anemometers, which is mounted on a small electric vehicle that can travel through the tunnel at constant speed. This paper reports the design procedure of the measurement facility, with particular focus on the conception and realization of the vehicle carrying the survey rake. Results of the first experimental campaign carried out under the 11611 meters long Mont Blanc road tunnel are presented to corroborate the validity of the approach adopted and the accuracy of the measurement chain.

The study is based on the Dartford-Thurrock Crossing tunnel, Kent, UK. It analyses the impact of the tunnel closures necessary for monitoring the flow of Dangerous Goods Vehicles and Abnormal Load Vehicles as per The European Agreement concerning the International Carriage of Dangerous Goods by Road regulations. A traffic simulation model is developed using PTV Vissim software, based on real-world Dartford Crossing traffic data and validated against independent Motorway Incident Detection and Automatic Signalling data. The autonomous driving implementations of Dangerous Goods Vehicles and Abnormal Load Vehicles, defined as per CoEXist project in the PTV Vissim software, are compared against the conventional vehicles traffic simulations. The results show that if the tunnel closures are reduced to two or less per hour then significant improvements in road congestion and travel time are observed. Furthermore, the benefits of autonomous Dangerous Goods Vehicles and Abnormal Load Vehicles are observed in improving traffic queues and travel times, given that the Dartford Crossing tunnel is appropriately equipped with intelligent communication technologies. The study shows that even with a small proportion of Connected and Autonomous Vehicles, the movement of road traffic can largely be influenced.

This study complements our previous work with a simultaneous analysis of user safety and road tunnel resilience. We developed a computational fluid dynamics (CFD) model and simulated the corresponding egress process to evaluate the risk level of users exposed to different types of fire, such those which might occur on the undisrupted lane of a partially closed tube tunnel due to a traffic accident, or in the adjacent tube when used for two-way traffic in the case of the complete closure of the tube involved in the accident. The CFD results showed that: (i) better environmental conditions were found with the partial closure of the tube rather than the complete one; (ii) additional benefits can be achieved by activating variable message signs (VMSs) that suggest an alternative itinerary for heavy good vehicles (HGVs) only; (iii) safety issues for human health may arise only in the case of a 100 MW fire, occurring during the complete closure of the tube and the use of the parallel one for two-way traffic. The findings of the CFD simulations were subsequently used to perform a quantitative risk analysis (QRA) based on a probabilistic approach. The findings of the QRA were found to be consistent with those obtained by the tunnel resilience analysis. In particular, the lowest risk level for user safety was found with the partial closure of the tube instead of the complete one, and by activating the VMSs to redirect HGVs only towards an alternative itinerary. This finding was found to correspond to a higher resilience index of the tunnel (i.e., a lower resilience loss due to a traffic accident occurring in a tube). This study increases our knowledge on certain relevant aspects of the operating conditions of tunnels and can serve as a possible reference for tunnel management agencies (TMAs) in their choice of the most appropriate arrangement to recover the functionality of a tunnel taking into account both user safety and resilience at the same time.

This paper provides an analysis of the evacuation process in a road tunnel in the event of a fire, using the example of the tunnel under the Luboń Mały mountain currently being constructed on Expressway S7's Lubień - Rabka-Zdrój section. As fires are the largest and most dangerous events occurring in road tunnels, it is important to predict the evacuation process as early as at the design stage. The study described here used numerical modelling to simulate evacuation, which made it possible to determine the required safe evacuation time of all tunnel users in a fire. On the basis of the parameters of the tunnel under Luboń Mały, numerical studies were performed for four different fire scenarios, three of which assumed various fire locations with the currently designed two traffic lanes. The fourth variant accounted for the planned extension of the roadway to include three traffic lanes. Eventually, four numerical models were developed involving various fire ignition locations and numbers of potential tunnel users. The values of initial-boundary conditions used in the simulation, such as movement speed during evacuation, shoulder breadth and pre-movement time, were specified on the basis of experimental data for an evacuation performed in smoke conditions in the Emilia tunnel in Laliki. The results lead to the conclusion that if the time of reaching critical conditions in the tunnel is not shorter than 5 minutes 40 seconds for the current design state and 5 minutes 47 seconds for three lanes, the distribution of evacuation exits in the tunnel under Luboń Mały will ensure safe evacuation. [ABSTRACT FROM AUTHOR]

We have developed an appropriate Computational Fluid Dynamics (CFD) model for assessing the exposure to risk of tunnel users during their evacuation process in the event of fire. The effects on escaping users, which can be caused by fire from different types of vehicles located in various longitudinal positions within a one-way tunnel with natural ventilation only and length less than 1 km are shown. Simulated fires, in terms of maximum Heat Release Rate (HRR) are: 8, 30, 50, and 100 MW for two cars, a bus, and two types of Heavy Goods Vehicles (HGVs), respectively. With reference to environmental conditions (i.e., temperatures, radiant heat fluxes, visibility distances, and CO and CO2 concentrations) along the evacuation path, the results prove that these are always within the limits acceptable for user safety. The exposure to toxic gases and heat also confirms that the tunnel users can safely evacuate. The evacuation time was found to be higher when fire was related to the bus, which is due to a major pre-movement time required for leaving the vehicle. The findings show that mechanical ventilation is not necessary in the case of the tunnel investigated. It is to be emphasized that our modeling might represent a reference in investigating the effects of natural ventilation in tunnels. [ABSTRACT FROM AUTHOR]