Roadway Tunnel Research Articles

The damage and response of some underground structures by the 2023 February 6 Great Turkish Earthquakes and some considerations

Two successive disastrous earthquakes occurred on February 6, 2023 in the province of Kahramanmaraş of Türkiye. These earthquakes resulted in loss of more than 50.000 lives and several cases of serious damage to various engineering structures. Some roadways and railway and underpass tunnels were also damaged by the earthquakes as a result of heavy shaking as well as faulting. In addition, many rockfalls occurred at the portals of railway and roadway tunnels. The faulting caused quite severe damage at the railway tunnel near Ozan village. The concrete lining of the new Erkenek tunnels ruptured at several places. The damage in the new Erkenek twin tunnels may be related to mass movements caused by heavy ground shaking as well as an inclined geological structure together with low overburden next to a valley. Sinkholes of man-made and natural cavities occurred in several locations including urbanized areas. In this study, the authors describe the damage to underground structures by the doublet Kahramanmaraş earthquakes with some detailed analyses of Erkenek tunnels. Furthermore, the causes of the damages are described and their implications on the seismic design of underground structures are discussed. The observations indicated that underground openings crossing by faults and fracture zones may be enlarged to accommodate relative slips along faults and fracture zones. Furthermore, the ductility of support should be high in such zones in order to prevent brittle failure, which may have very disastrous effects. In addition to man-made underground structures, natural underground rock structures may be damaged or sinkholes may be caused by earthquakes as observed in the 2023 Kahramanmaraş earthquakes. The computational results clearly explain why the valley-side of one of the tunnels was more damaged compared to that of the mountain-side tunnel. It is also noted that some of the sinkholes in the earthquake region can be explained using some techniques available in literature.

Experimental investigation of the effect of using expanded polystyrene geofoam and geogrid in different forms on vertical earth pressure on high-filled cut-and-cover roadway tunnel

Experimental investigation of the effect of using expanded polystyrene geofoam and geogrid in different forms on vertical earth pressure on high-filled cut-and-cover roadway tunnel

Deformation Analysis of a Roadway Tunnel in Soft Swelling Rock Mass Based on 3D Mobile Laser Scanning

Deformation Analysis of a Roadway Tunnel in Soft Swelling Rock Mass Based on 3D Mobile Laser Scanning

Advancing Shallow Tunnel Construction in Soft Ground: The Pipe-Umbrella Box Jacking Method

The development of modern cities has often led to increased traffic congestion and limited usable space. One effective solution to these problems is to construct roadway tunnels, which can expand urban space and alleviate traffic congestion. However, building large underpass tunnels in urban areas, especially in soft ground, presents technical challenges owing to its extensive environmental disturbance. The pipe-umbrella box jacking method offers a promising solution to these challenges as this method does not require breaking the ground from the surface or disrupting surface traffic. This study reviews the key techniques of the pipe-umbrella box jacking method for constructing large rectangular tunnels with small burial depths in soft ground. The study focuses on three main technical issues: pipe umbrella installation, soil face excavation, and box jacking control. Furthermore, two tunnel projects in Shanghai, China, are presented as case studies to showcase the construction challenges and countermeasures during box jacking tunneling with pipe-umbrella. Practical construction experience has revealed that the installation of the pipe umbrella before box jacking serves as an effective method of ground pre-support. However, its performance can be influenced by factors such as pipe installation deviation and inter-pipe connection design. Both open-face steel grid extrusion (SGE) shields and closed-face earth pressure balanced (EPB) shields can be used for soil excavation during box jacking, with different work modes resulting in distinct ground deformation patterns. Additionally, lubrication grouting has been found to effectively reduce friction resistance and affect vertical ground deformation. The study also examines the lessons learned from case studies and proposes optimization measures. This study can serve as a valuable reference for the tunneling industry, providing insights into the pipe-umbrella box jacking method and its application in constructing large rectangular tunnels in soft ground.

Characterization and apportionment of carbonaceous aerosol emission factors from light-duty and heavy-duty vehicle fleets in Maharashtra, India

This study aims to investigate the characteristics of carbonaceous aerosols and estimate emission factor (EF) based on roadway tunnel measurements, from two distinct vehicular fleets: an all light-duty vehicle (LDV) fleet, and a mixed fleet of 80% LDV and 20% heavy-duty vehicle (HDV). Carbonaceous content (organic carbon: OC and elemental carbon: EC) in total fine particles (PM2.5) accounted for 41% ± 6.8% in LDV fleet and 48% ± 7.2% in mixed fleet. While higher volatile OC dominated in the LDV fleet emissions, in mixed fleet, lower volatile OC and EC emissions dominated due to the presence of higher HDV and super-emitter (SE) fractions which led to significantly higher optically active absorbing aerosols. Reconstructed HDV fleet EF was higher than LDV fleet by 36 times (PM2.5), 19 times (OC) and 51 times (EC). Our findings emphasize the significance of implementing vehicle inspection and maintenance programs, coupled with decarbonization of HDVs to mitigate on-road vehicular emissions in India.

DEVELOPMENT OF A MACHINE VISION SYSTEM FOR DAMAGE AND OBJECT DETECTION IN TUNNELS USING CONVOLUTIONAL NEURAL NETWORKS

Abstract. Tunnel inspection, i.e. detection of damages and defects on concrete surfaces, is essential for monitoring structural reliability and health conditions of transport facilities, thus providing safe and sustainable urban transportation infrastructures. In this study, an innovative visual-based system is developed for damage and object detection tasks in roadway tunnels based on deep learning techniques. The main components of the developed Machine Vision System such as industrial cameras, flash-based light sources, controller, the synchronization unit and corresponding software programs are designed to collect high-resolution images with sufficient quality from dimly lit tunnel environments in normal traffic flows with an operating speed of 30–50 km/h. Unlike recent studies, the training data includes multiple types of damage such as cracks, spalling, rust, delamination and other surface changes. Furthermore, 10 classes of common tunnel objects including traffic signs, traffic cameras, traffic lights, ventilation ducts, various sensors and cables are labeled for object detection. As state-of-the-art Convolutional Neural Networks, DeepLab and U-Net are trained and evaluated using accuracy metrics for image segmentation. The results highlight the most important parameters of the discussed Machine Vision System as well as the performance of DeepLab and U-Net for object and damage detection.

Objective-level resilience assessment of circular roadway tunnels with reinforced concrete liners for vehicle fire hazards

A framework is presented to quantify the objective-level resilience of reinforced concrete liners of circular tunnels when exposed to enclosed vehicle fire hazards. By assessing the loss of functionality due to fire-induced damage, the framework enables a decision-basis evaluation of the efficiency of various fire mitigation methods for specific tunnel conditions. In this study, the fire-induced damage of concrete tunnel liners due to strength loss and spalling is stochastically simulated and classified based on typical post-fire repair procedures and damage evaluation. The resilience assessment is conducted using Monte Carlo Simulation in combination with a fast-running tool for calculating the thermal impact from vehicle fires on the inside surface of the tunnel liner (developed by the authors in previous work). The proposed approach accounts for uncertainties associated with both the vehicle fire (particularly the combustion energy) and the tunnel conditions (i.e., geometry, dimensions, and the presence of longitudinal ventilation and/or fixed fire-fighting systems (FFFS)). A parametric case study is used to quantitatively demonstrate the effectiveness of FFFS for reducing post-fire losses of tunnel functionality. Other parameters such as tunnel dimensions, traffic restrictions for vehicles with heavy fire hazard risk, and installation or upgrade of the tunnel ventilation system show somewhat less effectiveness for reducing fire-induced damage.

Injury-Based Surrogate Resilience Measure: Assessing the Post-Crash Traffic Resilience of the Urban Roadway Tunnels

Crash injuries not only result in huge property damages, physical distress, and loss of lives, but arouse a reduction in roadway capacity and delay the recovery progress of traffic to normality. To assess the resilience of post-crash tunnel traffic, two novel concepts, i.e., surrogate resilience measure (SRM) and injury-based resilience (IR), were proposed in this study. As a special kind of semi-closed infrastructure, urban tunnels are more vulnerable to traffic crashes and injuries than regular roadways. To assess the IR of the post-crash roadway tunnel traffic system, an over-one-year accident dataset comprising 8621 crashes in urban roadway tunnels in Shanghai, China was utilized. A total of 34 variables from 11 factors were selected to establish the IR assessment indicator system. Methodologically, to tackle the skewness issue in the dataset, a binary skewed logit (Scobit) model was found to be superior to a conventional logistic model and subsequently adopted for further analysis. The estimated results showed that 15 variables were identified to be significant in assessing the IR of the roadway tunnels in Shanghai. Finally, the formula for calculating the IR levels of post-crash traffic systems in tunnels was given and would be a helpful tool to mitigate potential trends in crash-related resilience deterioration. The findings of this study have implications for bridging the gap between conventional traffic safety research and system resilience modeling.

Mobile measurement of vehicle emission factors in a roadway tunnel: A concentration gradient approach

Tunnels are the preferred experimental environments for estimating vehicle emission factors (EFs) under real-world driving conditions. In this study, online measurements of traffic-related air pollutants (including CO2, NOX, SO2, O3, particulate matter [PM], and volatile organic compounds [VOCs]) were conducted using a mobile laboratory in the Sujungsan Tunnel in Busan, Korea. Mobile measurements generated concentration profiles of the target exhaust emissions inside the tunnel. These data were used to produce a zonation of the tunnel, i.e., mixing and accumulation zones. There were differences between the CO2, SO2, and NOX profiles, and a starting point that was free from ambient air mixing effects could be set at 600 m from the tunnel entrance. The EFs of vehicle exhaust emissions were calculated using pollutant concentration gradients. The average EFs for CO2, NO, NO2, SO2, PM10, PM2.5, and ∑VOCs were 149,000, 380, 55, 29.2, 9.64, 4.33, and 16.7 mg km−1·veh−1, respectively. Among the VOC groups, alkanes contributed more than 70% of the VOC EF. Mobile measurement-derived EFs were validated using the conventional EFs from stationary measurements. The EF results from the mobile measurements matched those from the stationary measurements, while the absolute concentration differences between them implied complex aerodynamic movements of the target pollutants inside the tunnel. This study demonstrated the usefulness and advantages of applying mobile measurements in a tunnel environment and indicated the potential of the approach for observation-based policymaking.

Correlating Air Pollution Concentrations and Vehicular Emissions in an Italian Roadway Tunnel by Means of Low Cost Sensors

There is an increasing scientific interest in studying vehicular traffic pollution in road tunnels. This is due both to the interest in evaluating the effect that the different polluting gases can have on the driving style of motorists and also to the hypothesis that tunnels could be considered as closed systems in which the vehicular traffic–pollution correlation is easier to study because it is more easily separated from other effects. In this work, a system of low-cost IoT sensor nodes for the detection of carbon monoxide (CO), nitrogen dioxide (NO2), ozone (O3), particulate matters (PM1, PM2.5, PM10), relative humidity (RH) and temperature (T) has been installed in an Italian tunnel, where vehicular traffic has been measured and classified for type of vehicles. The results of the measurement campaign, which lasted 3 months, from April to June 2022, allowed us to state that road tunnels actually behave like closed and isolated systems in which pollution may be directly correlated to the traffic volume and type. Furthermore, data show that quite high values of the major pollutants are observable in the tunnel in comparison to the external environment. As such, IoT sensor nodes may contribute to a distributed measuring approach on the road tunnel system mechanics assessment including, as an example, the operational impacts of forced ventilation.

Exploration of road closure time characteristics of tunnel traffic accidents: A case study in Pennsylvania, USA

With the increase of roadway tunnels, tunnel traffic accidents are also increasing. Compared with open roadways, road closures caused by traffic accidents in the tunnel have greater influences on traffic operations, as tunnels are often the key junctions of the roadway network. With the traffic accident data of Pennsylvania from 1997 to 2020, this study is designed to identify the features and trends of road closure time due to tunnel traffic accidents. First, features of tunnel and non-tunnel traffic accidents are compared from the perspectives of accident consequences, environmental factors, risky driver behavior, and vehicle features. The data confirms that tunnel traffic accidents are more likely to lead to road closures than non-tunnel ones. Besides, tunnel traffic accidents are mainly consisted of rear-end and hit-fixed-object collisions with many speeding cases. Then, a Negative Binomial model is built to statistically identify the factors significantly influencing the road closure time, which is recorded as non-negative integer in the data. The estimation results indicate that collision type, accident severity, road type, driving under the influence, the involvement of heavy trucks, and the number of involved vehicles could significantly influence the road closure time, whereas lighting, road condition, speeding, and area are insignificant. Finally, based on the research findings, some countermeasures are proposed to reduce the road closure time caused by tunnel traffic accidents.

Numerical simulation study of the contact relationship between the external supporting arch and the surrounding rock in a soft rock roadway

To develop an effective research tool for special contact behaviors observed in the field measurements of large deformation roadway to simulate the radial separation and circumferential friction sliding contact between the supporting arch and the surrounding rock, especially in the process of arch yielding. In view of the fact that the traditional method unable to achieve both the yield of the arch and the contact behavior with the surrounding rock, as well as the practicality of the engineering. The improved numerical simulation approach is constructed through additional development of FLAC3D. The yield criterion of the supporting arch was embedded in the modified Liner element via the FISH language programming, and the separable arch-rock interaction module is realized. Taking an actual mining roadway tunnel as the simulation object, three simulation schemes adopting the newly improved approach and the original methods were carried out respectively, and verified by the field measured data. The results show that: (1) the bending moment and axial force at the yielding moment of the supporting arch change from independent to related after modification, and the computed deviation of the arch model caused by the shortcomings of the original Liner element were effectively suppressed; (2) the surrounding rock controlling and the supporting arch stress results in the modified model scheme are closer to the actual; and (3) the modified Liner element is proved effective to simulate the supporting arch by the responses of supporting forces curves and relative displacement of the supporting arch and surrounding rock. The analysis shows that the improved numerical simulation approach is much more reliable to simulate the contact relationship between the supporting arch and the surrounding rock.

On-road vehicular emission characterization from the road-tunnel measurements in India: Morphology, emission factors, and sources

In India, there is very limited data on vehicular emission characterization in real-world driving conditions and the contribution of non-exhaust vehicular emissions to ambient particulate matter (PM) is still unanswered. Furthermore, there are no real-world emission factors (EFs) for the PM constituents. Thus, this study aims to characterize the trace elements and metals, and black carbon (BC) in PM2.5 and PM10 from the light-duty vehicles (LDVs) and mixed vehicular fleet with significant contribution of heavy-duty vehicles (HDVs) through road-tunnel measurements. Real-world EFs were estimated for the measured PM chemical constituents. Further, source apportionment was carried out to find the plausible sources and their contribution to total PM2.5 and PM10 road traffic emissions. Air pollutant and traffic measurements were conducted at two roadway tunnels: Eastern Freeway tunnel (FT; only LDVs) and Kamshet-I tunnel (KT; 80% LDVs & 20% HDVs) in Mumbai, India covering both peak and off-peak traffic hours. Major elements (Al, Ca, Fe, K, Mg, and Na) constitute 90─93% of total measured elemental concentrations in both PM2.5 and PM10 road traffic emissions. Overall, the elemental concentrations were higher for the HDV-dominant fleet than the LDV-fleet for both PM2.5 and PM10. Similarly, BC was higher for the HDV-dominant fleet which is corroborated by the morphological analysis. The measured BC, trace elements and metals EFs in this study were higher than those reported than previous road tunnel studies with similar vehicle composition indicating the presence of high-emitting vehicles in this study. The dominant proportion of PM2.5 road traffic emissions was from the tailpipe (52%) followed by brake wear (30%) and vehicular driven resuspended road dust (18%). Whilst, resuspended road dust (63%) was identified as the major source of PM10 traffic emissions followed by vehicular exhaust (28%) and brake wear (9%). With the potential increase in the share of electric and hybrid vehicles in the vehicular fleet, the relative contribution of non-exhaust emissions to the airborne PM will be more significant. Hence, there is an imminent need to regulate non-exhaust vehicular emissions.

Performance-based evaluation of exposed electrical conduit for severe fires in roadway tunnels

This paper numerically investigates the thermal impact of vehicle fire hazards on exposed electrical conduits in roadway tunnels. By modeling the fire and subsequent heat transfer to the conduit, the analysis results provide performance-based design guidance for allowable temperature increases before the conduit and its contents fail. The computationally efficient Confined Discretized Solid Flame (CDSF) model (previously developed by the authors) is used to calculate the heat flux imparted to the tunnel conduit from the enclosed fire. A simplified finite element model is used to calculate the subsequent thermal response of the conduit piping. Envelopes of conduit temperature increase, as well as exposure duration, are developed for a range of vehicle fire intensities that are enclosed in two- and three-lane circular tunnels. By accounting for overall traffic volume and truck traffic percentage, the limiting criteria for conduit temperature increase during standard experimental testing can be associated with a return period or a probability of exceeding an expected temperature. Sensitivity analyses are performed to examine the influence of conduit size and material, conduit location, tunnel ventilation conditions, average annual daily traffic, and traffic composition.

Experimental research on deformation failure process of roadway tunnel in fractured rock mass induced by mining excavation.

Deformation failure of roadways in fractured rock can lead to large-volume collapse and other engineering accidents. Failure mechanisms in fractured rock are complex and poorly understood, so to explore this issue, we simulated fractured rock masses using physical model tests in combination with numerical computations. A set of experimental techniques for roadway excavation under jointed surrounding rock included a mixed pouring–bricking method and a roadway excavation device, which can reproduce the structural characteristics of the prototype and replicate the excavation conditions of the roadway. Stress distribution characteristics of the roadway, from loading to excavation, were obtained based on strain monitoring and image acquisition, and the process of roadway deformation and failure was described in detail. A series of numerical simulations were conducted to investigate the deformation failure mechanisms of roadways under different excavation conditions. Results indicate that the deformation failure modes of roadways including collapse, rock burst, and floor heaving that were similar regardless of depth. Deformation failure modes of the roadway were determined by rock mass structure, and the deformation intensity was determined by geo-stress. Model testing and numerical simulation were consistent; hence, findings provide a theoretical basis and technical guidance for roadway engineering in fractured rock masses.

The Elizabeth River's New Immersed Tube Tunnel

The Midtown Tunnel Project team had to design safe, yet economical slope geometries for the subaqueous dredge slopes for a new roadway tunnel using immersed tube construction techniques. The design of safe slopes for this project was of paramount importance, because a dredge slope failure could cause complete failure of the existing adjacent immersed tube, sloughing slopes would create a costly maintenance issue during construction, and divers and equipment would be working within the dredge prism.

Study on Dominant Frequency Attenuation of Blasting Vibration for Ultra-Small-Spacing Tunnel

The middle rock pillar in ultra-small-spacing tunnels is significantly narrow, and the stability of the primary support and lining are easily influenced by the blasting vibration wave from an adjacent tunnel. Therefore, understanding the vibration frequency characteristics is essential for the blasting vibration control. Based on the blasting works on a double-track roadway tunnel (Jiuwuji tunnel in Guizhou, China), this study investigates the dominant frequency attenuation in the preceding tunnel with the middle rock pillar spacing ranging from 4.0 m to 9.4 m. The results show that the ranges of the dominant frequency distributions on the primary support and lining are widely within 200 Hz, but there are varieties in their propagation laws. The distribution of the dominant frequencies on the primary support is broader than that on the lining; and the dominant frequencies are concentrated on a specific range when the lining is far from the blast face beside a particular value, which is not present on the primary support. As the presence of cavity and changing medium between the lining and the primary support, it made a significant contribution to the filtering the vibration waves. Furthermore, on the primary support, the high-frequency part of the vibration waves attenuates rapidly with distance, and then, the practical prediction equations describing dominant frequency attenuation were proposed. The comparison on frequency characteristics per delay for the millisecond delay blasting shows that multiple delay sequences blast contributes to a multi-structured amplitude spectrum of blast vibration waves; and the varies of the equivalent explosion sources dimensions and numbers of free surfaces in each blast delay resulting in diverse vibration waveforms. Finally, the dominant frequencies determined by different methods were compared, and the results show a nonlinear relationship between the ZCFs and DFs. The above research conclusion expands the understanding of blasting vibration in tunnel engineering, particularly in the frequency distribution.

Numerical Simulation of the Evacuation Process in a Tunnel during Contraflow Traffic Operations

The purpose of this numerical research is to assess the evacuation process in a tunnel under the contraflow condition. Numerical simulations utilizing FDS+Evac codes associated with a fire dynamic simulator (FDS) model simulating a fire scenario are used to simulate evacuation and to predict the impact of a 100 MW fire scenario on the occupants inside the tunnel. Traffic and passenger conditions are based on real data from a tunnel in the UK. Two fire loads, 100 MW and 5 MW, are studied to represent an HGV and a passenger car fire. The 100 MW fire source, caused by an unexpected heavy good vehicle (HGV) catching fire, is located in the middle of the tunnel and at 20% of tunnel length to study the effect of fire source location on the usage of emergency exits and tenability thresholds. The dimensions and the inclination angle of the existing roadway tunnel are 1836 m (L) × 7.3 m (W) × 5 m (H) and 4%, respectively. It should be noted that the 4% inclination of the tunnel causes asymmetry propagation of smokes thus the visibility of the downstream and upstream from the fire behave differently. The maximum needed time to evacuate using all egress, the amount of fractional effective dose and visibility at the human’s height are analyzed. Simulation results indicate that when a realistic worst-case fire scenario is modeled, all evacuees can survive before the combustion gases and heat influence their survivability.

Traffic-based quantitative risk analysis of structural fire damage to roadway tunnel linings

This paper demonstrates a quantitative risk analysis (QRA) approach of fire-induced damage to the reinforced concrete linings in roadway tunnels. Large fire events associated with buses and heavy goods vehicles are the focus of this study because their impact on the tunnel linings is structurally significant versus fires from smaller vehicles. The proposed approach accounts for stochastic variations of fire severity and frequency (based on traffic volume and the percentage breakdown by vehicle type) as well as the consequences (structural and economic) of thermal exposure to tunnel linings. The probabilistic distribution of fire size is developed using available weight-in-motion data, and combustible vehicle mass is correlated with the peak heat release rate using published test data and forensic reports. The heat transfer from the vehicle fire to the tunnel linings was modelled by a fast-running computational tool that was previously developed by the authors. Fire-induced damage to the tunnel linings is categorized into three levels of progressive strength reduction and cracking potential. Economic impacts are calculated in terms of estimated repair costs. The proposed approach enables informed decision making for the design or renovation of tunnel fire protection by quantifying the loss potential for severe fire hazards in a given tunnel.

CONSTRUCTION OF ATAL TUNNEL

Atal tunnel is the world’s longest highway tunnel at an altitude of about 10,000 feet from the Mean Sea Level (MSL). It was formerly known as the Rohtang tunnel and was renamed after India’s former prime minister Atal Bihari Vajpayee. The length of the tunnel is 9.02 Km. It is also the longest bi-directional, single tube roadway tunnel of India and a project of great strategic importance. It is built with modern technologies and specifications in the Pir Panjal Range of Himalayas. The construction method for this tunnel is based on the philosophy of NATM. During construction of this tunnel, the team faced many challenges, unexpected difficulties like sudden collapse, ingress of water from pores of rocks etc. The team overcame such difficulties by solving the challenges using different methods. This paper will briefly give an overview of the strategic importance of the tunnel, geology of the site, construction technologies implemented, challenges faced during constructions and how the team overcame those.