Tunnel Safety Research Articles

The influence of dimming-induced luminance change on driving safety in tunnels

Although dimming the light in tunnels brings salient benefits to energy saving, the effects of dimming-induced luminance changes on driving safety have been rarely explored. Adopting the visual performance experiment, the present study investigated the impacts of the dimming-induced luminance change rate (V) on the safety of driver’s perception, judgment, and operation in the threshold zone of the tunnel under different seasons and weather conditions. The results show that the reaction times (RTs), pupil area change rate (vp), and blink frequency (fb), increased with the increase of V. When the luminance before the beginning of dimming (L) was higher, drivers reacted faster and stood a lower level of the mental load and fatigue. Compared with decreasing the luminance through dimming, when increasing the luminance through dimming, the present study found that each of the visual performance indices was about 10% lower, and the changes with V became smaller. Based on the safety thresholds of RT, vp, and fb, the present study obtained the thresholds of V which can meet the safety requirements of driver’s perception, judgment, and operation. Finally, a theoretical model between the thresholds of V and L was developed, and this model will shed light on the control of V in the threshold zone of the tunnel under different seasons and weather conditions.

Validation of a Driving Simulator for Road Tunnel Behavioural Studies

Introduction. According to European regulations, road tunnel safety is strategic in the management of national and international road corridors. Although the accident rate is lower in tunnels than on open roads, the severity of crashes in tunnels is higher due to the presence of hard lateral obstacles and limited space in case of lane departure. Driving simulation studies can support design decisions to assess the impact of any safety improvement albeit driving simulators must be validated to understand how the experimental results relate to real driving conditions. Method. This study deals with the behavioural validation of the fixed base driving simulator of the RSDS Lab for safety studies for tunnels. Field speed and lateral position data for vehicles were collected by image analysis of video sequences collected from the CCTV cameras in five sections of the Fréjus tunnel (Italy-France). The tunnel was faithfully modelled in the virtual scenario, and the same data were collected by extracting records at the same cameras’ stations. Thirty-five participants were involved in a between-subject experiment. Fifteen drivers with Italian B licenses drove a car, and twenty professional drivers with Italian C and/or D licenses drove a heavy truck. Results and Conclusions. Normality tests for data distributions and t-tests for the comparison between real and simulated data were conducted. The simulator achieved the relative validation for truck speeds (with values observed in the simulation always lower than those observed in real driving), and absolute validation with regard to truck lateral position. Opposite outcomes were obtained for cars, with absolute validity for speed and relative validity for lateral position. The relative-absolute validation of the driving simulator enables us to establish how experimental outcomes can be generalized to understand the impact of any safety countermeasure.

Time-Varying Response Analysis of Surrounding Rock Construction Mechanics of a Double-Arch Tunnel without a Middle Pilot Tunnel and Suggestions for Tunnel Construction

Abstract This research carries out the model test and numerical simulation, studying the time-varying response regularity of surrounding rock construction mechanics. The purpose was to ensure the construction safety of a double-arch tunnel without a middle pilot tunnel and to prevent rockburst or large deformations of surrounding rock in a stress concentration areas. To resist shear deformation of the steel arch of the first tunnel, during construction of the secondary lining of the lower step of the following tunnel near the side of the first tunnel, shear reinforcement is added to form a shear wall. To resist the stress of upward uplift in the inverted arch area, the spacing of steel reinforcements in the inverted arch is encrypted to reduce disturbance to the supporting structure. To reduce disturbance to the first tunnel caused by the blasting construction of the following tunnel, this article carried out the SHPB test on field rock samples and suggests that the reserve 2 m width of the surrounding rock (the lower heading of the following tunnel near the side of the first tunnel) is mechanically broken.

Investigation of the Effect of Tunnel Geometry on Deformations in Shallow and Stratified Rock Formation

Tünel içindeki deformasyonlar, üst yapıdan gelen sürşarj yükü, aşırı yükleme, kayaç veya zemin biriminde oluşan içsel gerilmeler ile diğer faktörlerin bir sonucu olarak ortaya çıkar. Tünel içi deformasyon ölçümü, tüneldeki plastik şekil değiştirmenin büyüklüğünü belirleyebilmek için önemlidir ve tünel güvenliğinin izlenmesinde önemli bir safhayı oluşturur. Bu çalışmada, dört tabakalı bir kaya formasyonunda ve yeraltı suyu etkisinde bulunan, at nalı veya yumurta şeklinde tasarlanan, NATM (Yeni Avusturya Tünel Açma Metodu) tekniği ile kademeli olarak açılacak olan tünellerin üç boyutlu ve doğrusal olmayan davranışları sonlu elemanlar yöntemi ile analiz edilmiştir. Kazı adımlarına göre farklı yükleme koşullarına maruz kalan taç ve tünel çevresinde meydana gelen kalıcı deformasyonlar ayrıntılı olarak incelenmiştir. Ayrıca her iki tünel geometrisinde, bütün kazı aşamalarında tünelin kritik kesitleri boyunca oluşacak olan kalıcı şekil değiştirmeler, deformasyon eğrileri sayesinde göreli olarak karşılaştırılmıştır. Sığ ve tabakalı kaya ortamında tasman ve konverjans miktarının azaltılmasında, tünel geometrisinin at nalı tipi yerine yumurta şeklinde seçilmesinin daha avantajlı olduğu tespit edilmiştir.

Thermo-mechanical analysis of fire effects on the structural performance of shield tunnels

Investigating fire effects is a continuing endeavour in the research and practice communities concerned with the design and safety of shield tunnels. This paper aims to provide a comprehensive model for the assessment of structural safety of a shield tunnel segmental ring exposed to fire. A thermo-mechanical model for assembled shield tunnel structure in fire is developed to provide a basis for a holistic analysis by incorporating tunnel lining segments and longitudinal joints, as well as improved predictions for the temperature, stress and deformation distributions in the tunnel structure. Validation of the numerical results against experimental data shows satisfactory agreement. Parametric studies are subsequently conducted to investigate the effects of spalling, buried depth and cooling-off phases on the fire behaviour of the shield tunnel. The results show that the damage and failure of a tunnel lining structure under high temperature are mainly due to the combined action of internal thermal expansion force and thermal stress. Spalling leads to the loss of a key “insulation” layer of a tunnel lining structure. On the other hand, the constraint of strata on the tunnel structure under high temperature not only restrains the deformation of key parts of the structure, but also helps offset the adverse effect of load on the structure through elastic resistance.

Reliability Enhancement Driven by ANN for Lighting Control System in Highway Tunnels

Compared with open roadways, traffic safety in highway tunnels requires more attention to build smoothly transitioned and well-coupled light environments for drivers to alleviate visual discomfort so as to achieve a balanced sense of driving safety and comfort. In this study, in order to overcome the drawbacks of existing tunnel lighting control modes that disregard the color temperature of natural light characteristics and collaborative influence of color temperature and luminance of natural light on tunnel lighting quality, one artificial neural network (ANN) model is designed and trained to simulate one physical lighting control system that takes into consideration color temperature and luminance simultaneously. In this model, multiple parameters of discrete and continuous types of input layer and output layer are synergistically analyzed. The model was also trained with quantities of field data from one tunnel in service and includes one hidden layer with 10 neurons. The simulation results showed that this model obtains a high degree of fitness with inside luminance and 100% recognition rate with inside color temperature in the threshold zone, which conforms to the regulation strategy of actual lighting control systems with high confidence. The proposed model will greatly enhance the reliability and sustainability of the lighting system during its normal operation, which can also support other lighting scenarios due to its flexibility and scalability with multiple-input and multiple-output (MIMO) capabilities.

Evaluation of Void Defects behind Tunnel Lining through GPR forward Simulation.

Voids, a common defect in tunnel construction, lead to the deterioration of the lining structure and reduce the safety of tunnels. In this study, ground-penetrating radar (GPR) was used in tunnel lining void detection. Based on the finite difference time domain (FDTD) method, a forward model was established to simulate the process of tunnel lining void detection. The area of the forward image and the actual void area was analyzed based on the binarization method. Both the plain concrete and reinforced concrete lining with various sizes of air-filled and water-filled voids were considered. The rationality of the model was verified by measured data. It was observed that the response mode of voids can be hyperbolic, bowl-shaped, and strip-shaped, and this depends on the void's width. Compared with the air-filled voids, water filling increases the response range of the voids and produces a virtual image. Although the diffracted wave caused by a steel bar will bring about significant interference to the void response, the center position of the voids can be accurately located using 3D GPR.

Safety-Risk Assessment for TBM Construction of Hydraulic Tunnel Based on Fuzzy Evidence Reasoning

Due to multiple factors influencing the construction safety of TBM hydraulic tunnels, risk assessment is a critical point of a construction management plan to avoid possible risks. In this paper, a safety-risk evaluation index system of TBM construction for hydraulic tunnels is built based on the identification and analysis of possible sources of risk in techniques, geologic, equipment, management, and accidents. Considering the influence of factors such as the experience level and the expertise of decision makers, a combination assignment method of index weights is proposed based on binary semantics. On the basis of a fuzzy normal distribution used as the subordinate function distribution of fuzzy evaluation levels, the subordinate function distribution of fuzzy evaluation levels under multi-level intersection situations is introduced, and a comprehensive evaluation model of safety risks for TBM tunnel construction is built. The validity and practicality of the evaluation model is examined with the combination of a long-distance water conveyance tunnel project. Results show that the construction safety-risk of the TBM hydraulic tunnel project belongs to the middle-high level, and the safety accident risk belongs to the low level. The study provides guidance of evaluation and control of risks for this tunneling construction being successfully completed.

A detection method of urban underground geological anomalies in the United Kingdom based on feature fusion

Engineering geological conditions include the nature of rock and soil, geological structure, landform, hydrogeological conditions, and adverse geological processes. Among them, faults, fissures, folds, karst, and lithology changes seriously affect the safety and construction cost of mountain tunnels, hydraulic tunnels, and other projects. For this reason, a new method based on feature fusion is proposed to detect the geological anomalies in London and Sheffield. It established a 3D raster data model oriented to attribute information modeling and visualization of urban underground space to obtain geological data. Based on this acquired data, authors adopted the feature-level fusion extraction method based on the multi-attribute geological abnormal body to extract, fuse, fill and surface the multi-attribute data of underground space geological data. Smooth processing can realize the detection of abnormal geological bodies in underground space. It has been proved that this method can be used in geological data display, feature extraction, feature fusion, and abnormal physical examination.

Integrated waterproofing evaluation method for longitudinal joints of shield tunnel subjected to extreme surcharge: Numerical analysis and experimental validation

Sufficient waterproofing performance is critical to ensure a normal operation and safety of tunnels, and certain safety margin is essential to cope with uncertain external loads. This study proposes a novel methodology for evaluating the waterproofing performance of shield tunnels subjected to extreme surcharges, by integrating an analytic derivation, numerical analysis, and experimental validation. First, the analytical derivations of stresses at longitudinal joints and a finite element (FE) model for calculating the internal forces of tunnel linings under external loads are established; these are subsequently combined to compute the gasket deformation. Then, the stress–deformation curve of the gasket is fitted by a material-scale FE model to evaluate the contact stress against the underground water pressure. Finally, the methodology is validated via measurements from a full-scale experiment. The results help establish that the presumptions derived from the proposed method are consistent with the experimental results. It is also anticipated that the waterproofing performance would reach the actual failure point at the approximate 4–7 m depth of the equivalent dumped soil, which is remarkably consistent with the on-site observations in the Shanghai Metro tunnel. This study provides an efficient and economical method in terms of engineering applications, with emphasis on the importance of structural analysis in the waterproofing evaluation.

Freezing Damage to Tunnels in Cold Regions and Weights of Influencing Factors

Concrete materials are widely used in tunnel engineering. In China, the cold regions have gradually become the main area for highway and railway construction. Affected by high altitude, low temperature, turbulent wind, and other conditions, freezing damage, such as tunnel icing, occurs in concrete materials, which seriously affects the quality and operational safety of tunnels in cold regions. Therefore, it is necessary to carry out a quantitative analysis of various factors affecting freezing damage to protect concrete materials in tunnels. This paper summarizes various freezing damage phenomena in tunnels in cold regions and divides them into three types: water seepage and hanging ice type freezing damage, lining interface type freezing damage, and tunnel foundation ice accumulation type freezing damage. Based on the qualitative evaluation of each factor, the affiliation of each factor was divided. Then, the influence weight of each factor on freezing damage was obtained through the analytic hierarchy process, and then each factor was ranked. This study is helpful to the selection of anti-freezing measures for tunnels in cold regions.

Fire tests with lithium-ion battery electric vehicles in road tunnels

Alternative propulsion technologies, including battery-electric vehicles, are becoming increasingly prevalent. Whilst such vehicles remain a small overall proportion of the vehicle fleet, the combined impact of government policy and technological advances in alternative fuels is expected to accelerate the increase in their numbers in coming years.As a result of these changes, the nature of tunnel safety risk (including the risk of fire) is expected to change over time. The risk implications associated with such vehicles thus requires more detailed consideration. This entails evaluation of incident consequences with particular attention being paid to the impact of fire characteristics and toxic emissions on tunnel users and to the need for specific emergency intervention strategies.In the past, concerns were voiced with respect to the fire safety of the new energy storage device (battery) and the possibility of more difficult firefighting conditions. This resulted in a series of investigations concerning the safety aspects of batteries and battery electric vehicles. However, most of the tests performed merely dealt with battery cells or battery packs. To date, publicly available tests involving actual vehicles remain relatively rare. In 2018, the Austrian Government commissioned a research project concerning the effect of incidents with battery electric vehicles on tunnel safety. This project encompassed fire tests of passenger cars, simulations for heavy duty vehicles, and the impact of incidents with such vehicles on the safety of tunnel users and the tunnel structure.In a series of fire tests, the heat-release and production of (toxic) substances has been evaluated. The burning behaviour of vehicles with different energy storage technologies (i.e. Li-ion batteries, Diesel) was monitored and compared to each other. The heat-release rate and emission of (toxic) substances was measured, and different fire-fighting methods were applied during each test.This paper will focus on the aspect of full-scale fire tests of passenger cars performed in a road tunnel. It should be emphasized that the battery-electric vehicle fire tests presented here were the first of their kind under real road tunnel conditions. This concerns the fire behaviour, but also some new approaches to fighting a BEV fire. All previous tests reported in journals were either carried out in fire halls or only concerned individual battery modules.

Influence of multiple random variables on the safety of cracked tunnels under earthquake action

To explore the mechanical properties of cracked lining subjected to seismic loads based on wave theory and the extended finite element method, the dynamic viscoelastic boundary of a seismic wave and equivalent nodal force load were generated by MATLAB programming software to establish a simulation model of cracked lining structure. The internal force state change law of the lining structure was studied by varying the crack depth, crack length, secondary lining thickness, and other parameter values (including the layout between multiple cracks). Also, the safety factor of the lining crack section was obtained, and the functional relationship between the safety factor and parameter variables was established. Results show that the crack depth and secondary lining thickness were the main factors affecting the internal force of the crack section. Based on the least square method, the calculation formula and 95 % confidence interval between the minimum safety factor (Kmin) and each parameter of the crack section were obtained. Meanwhile, the Kmin prediction model was obtained via multiple nonlinear regression. When the crack depth value was 30 % of the lining thickness value, Kmin reduced 2.5 times. At 57 % crack depth of the lining thickness, the Kmin was less than the specification value, indicating that the lining structure’s safety reserve was low. Compared with the arrangement of the vertical distribution of the two cracks, the stress concentration generated when the two cracks were arranged in parallel would more likely affect the structure adversely. The findings can provide a reference for the safety study of cracked tunnels.

Effectiveness Evaluation of Optical Illusion Deceleration Markings for a V-Shaped Undersea Tunnel Based on the Set Pair Analysis Method and the Technique for Order Preference by Similarity to Ideal Solution Theory

To improve traffic safety in undersea tunnels, the speed control effect of optical illusion deceleration markings (OIDMs) in V-shaped undersea tunnels and their applicability to drivers were explored. In this study, UC-Win/Road software was used to build a simulation scenario, and the V-shaped Jiaozhou Bay undersea tunnel in Qingdao, China, was selected as the simulated road section. Four kinds of OIDMs were selected as the research objects. According to the physiological and psychological response characteristics of drivers to the visual recognition process of OIDMs and vehicle driving parameters, three primary and six secondary evaluation indices were identified. The analytic hierarchy process-entropy weight method was applied to assign weights to each evaluation index in combination, and a comprehensive evaluation model based on the set pair analysis method and the technique for order preference by similarity to ideal solution was constructed to comprehensively evaluate the effectiveness of the OIDMs based on the ternary coefficient and the comprehensive evaluation index. To verify the accuracy of the model, the data of the three secondary evaluation indicators with larger weight coefficients were statistically analyzed, and the results showed that the results of the statistical analysis of the data were consistent with the results of the model test. In the entrance section of the tunnel, the combination of white inverted fishbone deceleration markings and red warning pavement has the highest comprehensive evaluation index of γ A1 = 0.9611. In the downhill section of the tunnel, the white variable-spacing inverted fishbone deceleration markings have the highest comprehensive evaluation index, γ B1 = 0.9644.

Building “common knowledge” when responding to major road tunnel incidents: an inter-organisational focus group study

PurposeMajor incidents in tunnel environment will pose several challenges for the emergency service organisations in terms of heat, visibility and lack of experiences from working in confined environments. These aspects, in turn, could pose challenges to establish collaboration. This study aims to contribute to the field of collaborative tunnel responses by exploring how “common knowledge” (Edwards, 2011) is built by the emergency services organisations, that is, what the organisations consider important while working on a potentially common problem, and their motives for the interpretations and actions if a major tunnel incident occurs.Design/methodology/approachParticipants from the road traffic control centre, emergency dispatch centre, emergency medical service, rescue service and police were included in the study. Data from four focus group sessions was analysed using thematic analysis.FindingsThe study revealed that the tunnel environment presents specific aspects of how common knowledge was produced related to lifesaving and safety. The themes structuring mechanisms to reduce uncertainty, managing information for initial priorities, aligning responsibilities without hampering each other's work and adjusting actions to manage distance, illustrated how common knowledge was produced as crucial aspects to a collaborative response. Organising management sites, grasping and communicating risks, accessing the injury victims, was challenged by the confined environment, physical distances and imbalance in access to information and preparedness activities in tunnel environments.Originality/valueThis study offers new insights of common knowledge, by illustrating a motive perspective on collaborative responses in tunnel incidents. Creating interoperability calls not just for readiness for action and tunnel safety, but also training activities acknowledging different interpretations and motives to further develop tunnel responses.

Non-linear FE investigation of subsurface tunnel with gfrp protection against internal blast

The contribution of subsurface tunnels in the present time is imperative. However, in the past few decades they have become a target to explosives and terrorist attacks. Considering the strategic importance and susceptibility of tunnels in case of internal explosion, the blast mitigating design has become very critical. In this work, a novel concept involving the use of glass fiber reinforced polymer (GFRP) layer to strengthen the reinforced concrete (RC) tunnel lining against these incidents has been introduced. Metro underground tunnels exposed to internal blast with two different surrounding soil conditions are investigated. The analysis is done using explicit 3D-Finite Element (FE) method. A comparative study towards the damage due to explosion of different trinitrotoluene (TNT) charges is executed. It is observed that the application of GFRP layer reduces the displacement and stress values at key points in tunnel and ground surface under different explosive charges and soil conditions. Also, there is a reduction in the tunnel damage as well as the risk of long-term geotechnical effects in soil. Thus, GFRP may be effectively utilized as an additional layer to improve the resistance of RC tunnel against blast instead of designing an uneconomical rigid structure. Consequently, the present study contributes towards the safety and blast mitigation design of RC tunnels.

TBM penetration rate prediction ensemble model based on full-scale linear cutting test

Accurate and effective prediction of TBM penetration rate (PR) is significant for ensuring TBM tunneling safety, improving tunneling efficiency and optimizing construction cost. Establishing a prediction model is usually an effective method to solve this critical problem. The type of TBM penetration rate prediction models can be divided into two categories: theoretical models and empirical models. Each model has its advantages, but there are also shortcomings. To make the advantages of the two models complement each other and further improve the accuracy and application scope of the prediction model, this paper proposes a prediction ensemble model of PR based on a full-scale linear cutting test and machine learning algorithm. A semi-theoretical TBM penetration rate prediction model is established through the full-scale linear cutting test and the rock-breaking analysis of granite and sandstone with different strengths. Based on the XGBoost intelligent algorithm, an empirical model of the penetration rate prediction is also established. On this basis, the Bagging algorithm combines these two models to form an ensemble prediction model of TBM penetration rate. We collected rock mass and operational parameters in the Hangzhou Second Water Source Water Transfer Channel Project to verify the semi-theoretical, empirical, and ensemble models, respectively. The results show that the three models' prediction errors are all less than 15%, and the ensemble model has a smaller error of 10.2%. This result confirms that the ensemble model can effectively improve prediction accuracy and has good engineering applicability.

Investigation on the Deformation of Segment Linings in Cross-Fault Tunnel Considering the Creep Behavior of Surrounding Rock during Construction-Operation Period

Time-dependent deformation of surrounding rocks during construction and service directly affects the structural safety of hydraulic tunnels. Specifically, the creep effect on the cross-fault diversion tunnels is particularly significant. In recent years, a variety of research has focused on the impact of creep on operating cross-fault diversion tunnels. However, there is a lack of consideration for the creep phenomenon during the construction-operation period. This study proposes a simulation method of segment linings deformation of cross-fault diversion tunnel combining deformation monitoring, creep constitutive identification, and creep during construction operation. According to the measured time-displacement data of the surrounding rock, the suitable creep constitutive model is selected by a regression-comparison method. Subsequently, the three-dimensional numerical model of the cross-fault tunnel is established, with the tunnel excavation and long-term creep calculation carried out under the creep effect of the surrounding rock. In addition, the intelligent inversion model was adopted to obtain the basic parameters of the surrounding rock. The results show that fault directly affects the rock mass characteristics near the fault. The radius of influence is about one time the tunnel diameter from the fault. The vertical deformation of segment linings of the vault and inverted arch tends to be subsidence when the fault is above the tunnel; however, the trend is inverse when the fault is under the tunnel. This work gives targeted engineering suggestions and provides a scientific basis for designing and constructing diversion tunnels under complicated geological structures.

Intelligent Edge Computing Detection Vehicle and Detection Method Based on Tunnel Lining Concrete

In recent years, with the rapid development of tunnel construction in China, the length of tunnels has continued to increase, and the consequent tunnel disease detection has attracted more and more attention from maintenance departments. Among many diseases, lining cracks are the most common, which directly reflect the stress of the lining, which is very important for the study of tunnel diseases. In view of the current detection status and detection requirements, this article has carried out research work on a vehicle-mounted tunnel lining crack detection system based on image processing. Due to the grayscale difference between the cracks on the lining surface and the lining background, these differences lead to significant crack edge features and relatively stable detection. Therefore, this article designs an intelligent edge algorithm system for cracks on the lining surface to detect the edges of the image, extract the edges of cracks, and remove useless interference information in the lining background. The experiment proves that the paired sample t-test can find that after the experiment is over, the P value of different edge detection operators for global threshold segmentation is less than 0.05, which has a significant difference. The Canny, Deriche, and Lanser filters are relatively strong, and the extracted crack edge noise is relatively small. Finally, the parameter values of the crack image are calculated, and the calculated values of the crack parameters provide a scientific and reliable basis for tunnel safety evaluation.

Study on the long-term performance of shield tunnel passing through the gas-bearing strata

When the shield tunnel passes through the gas-bearing strata, gas and water leakage may occur depending on the sealing performance of the segment joints. This process involves the complex multiphase seepage flow phenomenon in unsaturated soil. In this study, a fully coupled solid-liquid-gas model of the GIL Utility Tunnel was established to investigate the influence of the high-pressure gas on the mechanical properties of the tunnel segments and joints. The constitutive model of the Extended Barcelona Basic Model was implemented to simulate the effect of the seepage process on soil deformation. The results show that significant upward displacement occurred in the gas reservoir and its overlying strata, and the maximum displacement reached 30 mm. In addition, during the leakage of the gas and the water, an increase in the average soil effective stress was observed. It would induce a reduction in the suction and expansion of the yield surface. The tunnel tended to be stable from 20 years onwards, thus the soil deformation due to the water leakage only occurred at the early stage. In addition, the joint opening under the most unfavorable internal force combination was 0.69 mm, and the corresponding bolt stress was 119.5 MPa, which is below the yield limit. The results of this study help to understand the influence of high-pressure gas on tunnel safety and the sealing performance of the joints.