Tunnel Operation Research Articles

Room-temperature single-electron tunneling in highly-doped silicon-on-insulator nanoscale field-effect transistors

From the viewpoint of high- (room-) temperature operation of donor-based single-electron transistors, we make a comparative study of nano-scale silicon-on-insulator transistors with phosphorus-doped channels for two dopant-concentration regimes: N D ≈ 1 × 1018 and 2 × 1020 cm−3. We experimentally show that the high-N D devices can provide room-temperature single-electron tunneling operation owing to a large tunnel-barrier height, while operation temperature is limited to about 100 K for the low-N D devices. Numerical simulations of random donor-atom distributions indicate that donor clustering plays a dominant role in the formation of quantum dots, and suggests that clusters comprising of more-than-three donors are responsible for room-temperature operation.

Overall Instability Failure Mechanism and Monitoring Strategy Research of the Shallow Tunnel under Unsymmetrical Pressure during Operation Period

Aiming at the safety of tunnel operation, based on the investigation and statistical analysis of a large number of operating tunnel diseases, comprehensively considering the interaction between the surrounding rock and the structure, this paper establishes the failure criteria for surrounding rocks and lining materials by using numerical limit analysis and theoretical analysis methods, analyzes the overall stability and instability failure mechanism on the shallow tunnel under unsymmetrical pressure during the operation period by using the strength reduction method in light of the operation safety of the tunnel, proposes the reasonable monitoring strategy, and also constructs monitoring index system. The analysis and research results show that the tunnel structure is affected by bias pressure due to the asymmetry of the terrain. The probability of disease in the bias pressure tunnel under asymmetric terrain conditions is significantly higher than that of the general terrain. The shallow tunnel under unsymmetrical pressure has experienced three development stages from shear failure to overall instability, including rock mass fracture and sliding, structural damage, and overall instability, which can be divided into eight processes. During operation, the key monitoring indicators of surface deformation are the subsidence and deformation of the slope top and the horizontal displacement of the slope itself, followed by the monitoring of the uplift and deformation at the bottom of the slope. Meanwhile, close attention should be paid to the structural stress states in the sliding direction and perpendicular to the sliding direction of the lining structure, which demonstrates that the principal compressive stress in the sliding direction is more sensitive than the principal tensile stress in perpendicular to the sliding direction and should be listed as the key monitoring and early warning indicators of the structural stress.

Ship fire modelling and evacuation simulation in navigation tunnel

Navigation tunnels are an essential part of inland shipping networks and play a vital role in enhancing the efficiency of navigation. Ships require a significant amount of time to pass through a navigation tunnel owing to safety speed limitations. If a ship fire accident happens in a confined space inside a navigation tunnel, people on board the ship cannot evacuate quickly on account of the high freeboard of the ship. The accumulated fire smoke poses a significant risk to human lives and can even be fatal. Currently, research on navigation tunnels are rather few, none of them has discussed the safety evacuation under ship fire scenarios. In this study, the Gou Pitan navigation tunnel is used as an example, the safety assessment of evacuation is realized by the simulation and calculation of safety egress time, then, a general method to quantitatively assess the safety of evacuation during ship fire accidents in navigation tunnels is proposed based on the analysis results. This study fills the gaps in the relevant research, and the assessment results can be used to develop the ventilation strategies during emergency evacuations, furthermore, provide a theoretical reference for the safe operation of navigation tunnels.

Study on the Influence of Cracks on the Mechanical Performance of Tunnel Lining Structure Based on Fracture Mechanics Theory

The problem of tunnel lining cracking is becoming more and more common. The existence of cracks changes the stress state of lining structure and has an adverse impact on the safety of lining structure. In this paper, the mechanical properties of tunnel cracked lining structure are studied. Based on the theories of structural mechanics and fracture mechanics, the performance indexes of cracks in the arch waist of tunnel secondary lining are studied with the reference of stress intensity factor. The numerical simulation calculation is carried out. Finally, the XFEM extended finite element method is used, the crack damage of secondary lining under different crack depths is demonstrated and analyzed, and the theoretical value is compared with the numerical value. The results show that, for the cracked model (the crack depth is 12 cm), the stress and displacement at the arch waist increase greatly compared with the uncracked model and are the most significant with the increase of crack depth. In the initial stage of crack development, the growth of stress and displacement of the structure is not obvious, and the small change of crack depth in the later stage can also cause great growth of stress and displacement. Compared with the uncracked model, when the crack depth is 3 cm, the maximum vertical stress increases by 4.3 times and the maximum settlement increases by 1.3 times. When the crack depth is 18 cm, it increases by 21.2 times and 2.94 times, respectively. The research results can provide a theoretical basis for the prevention and treatment of cracks in the arch waist of tunnel secondary lining during tunnel operation.

Study on the Design of Variable Lane Demarcation in Urban Tunnels

In order to alleviate the influence of low-speed vehicles on tunnel safety, this paper discusses the setting method of variable lane boundaries in urban tunnels. VISSIM simulation software is used to analyze the influence of low-speed vehicles on tunnel traffic flow when lane changes are allowed and when lane changes are prohibited. The results show that the influence of low-speed vehicles on the average speed of traffic flow in urban tunnels is the greatest, and the influence of low-speed vehicles on the average speed of traffic flow can be significantly alleviated when lane changes are allowed in the lane dividing line. When the speed of low-speed vehicles is 40 km/h and the variable lane is set, the average delay time is reduced by 30–50%. The existence of low-speed vehicles significantly increased the average delay time of the local lane, and the lower the vehicle speed and the greater the road traffic volume, the longer the average delay time. When the speed of low-speed vehicles is 40 km/h and the traffic volume is 1200 pcu/h, the traffic density of the right-hand lane decreases by 43.5% after the variable lane is set. While lane changing is prohibited, the presence of low-speed vehicles causes a backlog of vehicles in the rear of the lane, which leads to a significant increase in traffic density. Setting lane-changing permits can alleviate the impact of low-speed vehicles on traffic flow. The research results can provide a scientific basis for the operation and management of urban tunnels.

Prediction of gas leakage and dispersion in utility tunnels based on CFD-EnKF coupling model: A 3D full-scale application

Natural gas compartment accommodated in utility tunnels is beneficial in meeting the pressing demand of energy supply and sustainable urban environment. However, the leaking gas characterized by flammable and explosive can pose a huge threat to the safe operation of the utility tunnel. When an unexpected gas leakage accident happens in the actual situation, the prior information associated with the leakage source is commonly unclear or unknown. Therefore, the absence of an available tool for reasonable leakage and dispersion prediction in the above scenario precludes the timely and appropriate emergency response treatment. In this study, a three-dimensional source term estimation (3D-STE) model with the combination of the computational fluid dynamics (CFD) and ensemble Kalman filter (EnKF) algorithm is proposed to achieve spatiotemporal gas concentration prediction and gas emission source estimation. In the proposed approach, the observation data can be incorporated into the gas dispersion simulations continuously, thus the simulation results can be revised by the observation data and the source term estimation of gas leakage can be achieved by employing the EnKF algorithm. A twin experiment is employed to validate the effectiveness and practicability of the proposed model. The results show that the proposed model can revise the prior errors in the gas leakage rate significantly and obtain an accurate prediction of gas concentration distribution as well as gas leakage rate. A feasible framework is also proposed serving as a good paradigm for the 3D-STE model application. This study helps for consequence assessment and emergency response of gas leakage accidents in utility tunnels.

Influence of different visual guiding facilities in urban road tunnel on driver’s spatial right-of-way perception

Urban road tunnel construction is becoming ever more prevalent, and traffic safety in tunnel operation is even more important. This study evaluates the influence of different visual guiding facilities on drivers’ spatial right-of-way perception by combining quantitative and qualitative methods in order to provide a basis for traffic safety optimization in the tunnel. Simulation scenes were designed for six common types of visual guiding facilities as comprising no facility (baseline), horizontal strips, edge markers, LED arch, vertical stripes, and combination (multiple) facilities. An eye tracker was used to obtain eye movement data of subject drivers exposed to various scenes. After each driving test, psychological feeling of the subjects in tunnel driving, and their ratings of alignment and contour guidance of various facilities were obtained by questionnaires. The research results showed that setting locations and facility types have a great impact on drivers’ glance location and glance duration. When horizontal stripes, edge markers, LED arch and vertical stripes were set separately, alignment guidance and contour guidance performance were found to vary in inverse proportion. Horizontal stripes and edge markers are the preferred and necessary facilities, which are conducive to ensuring longitudinal and horizontal rights-of-way. LED arch and vertical stripes are also good supplements to spatial right-of-way. The combination of these 4 types of facilities can provide multi-level alignment guidance and contour guidance functions, which is beneficial to traffic safety in the tunnel.

Thermomechanical Coupling Analysis of the Lining Structure of the Tunnel Entrance in Cold Regions Based on Peridynamics

To explore the effect of frost heaving of the tunnel entrance in cold regions, this paper carries out a thermomechanical coupling analysis based on peridynamics (PD), combines PD with finite-element method (FEM) into a numerical model, and verifies the feasibility of the proposed model. On this basis, we selected frost heave amount as the quantitative index, discussed the evolution law of the energy field in the lining structure of the tunnel entrance in cold regions, and analyzed the stress of the lining structure, as well as the expansion and distribution laws of lining cracks, under different frost heave amounts. The results show that: The difference of frost heave amount indirectly brings changes to the system’s energy field. With the growth of frost heave amount, the thermal potential and strain would increase. During the changes, the thermal potential and strain energy of the system are both positively correlated with frost heave amount. The degradability of tunnel lining increases with the frost heave amount of the lining. A high density of cracks can be observed at the foot and waist of the arch, most of which are tensile cracks. With frost heave amount as the main temperature reference, this research explores the degradation state of the tunnel entrance in cold regions, which greatly facilitates the maintenance, repair, and safe operation of tunnels.

A Novel Method for Tunnel Digital Twin Construction and Virtual-Real Fusion Application

Tunnels play important roles in integrated transport infrastructure. A digital twin reproduces a real tunnel scene in virtual space and provides new means for tunnel digital maintenance. Aiming at the existing problems of video fragmentation, separation of video and business data, and lack of two- and three-dimensional linkage response methods in tunnel digital operation, in this paper, we propose a novel method for tunnel digital twin construction and virtual-real integration operation. Firstly, the digital management requirements of tunnel operations are systematically analyzed to clarify the purpose of digital twin construction. Secondly, BIM technology is used to construct a static model of the tunnel scene that conforms to the real tunnel main structure. Thirdly, a three-dimensional registration and projection calculation method is proposed to integrate tunnel surveillance video into a three-dimensional virtual scene in real time. Fourthly, multi-source sensing data are gathered and fused to form a digital twin scene that is basically the same as the real tunnel traffic operations scene. Finally, a management model suitable for digital twins is discussed to improve the efficiency of tunnel operations and management, and a tunnel in China is selected to verify this method. The results show that the proposed method is helpful to realize the application of two- and three-dimensional linkages of tunnel traffic smooth, accident rescue, facility management, and emergency response, and to improve the efficiency of tunnel digital management.

Predicting earth pressure balance (EPB) shield tunneling-induced ground settlement in compound strata using random forest

The prediction and control of the ground settlement induced by shield tunneling in compound strata is a crucial challenge for tunnel excavation. In this regard, a finite element model for the analyses of ground surface settlement induced by earth pressure balance (EPB) tunneling was established and validated by the field test. The influence of single influence factors, such as rock proportion in the face, support pressure, and tunneling angle, on the surface settlement above the tunnel face was systematically studied. To investigate the joint influence of different factors on ground deformation mechanism, the multi-factor analysis based on field data and the multiple regression (MR) method was conducted. However, the prediction accuracy of the MR method was limited. Therefore, a prediction approach of shield tunneling-induced settlement in compound strata based on a random forest (RF) was developed. Tunnel geometry, geological features, and operation parameters were investigated as input variables in the RF model to achieve this goal. The applicability effect of the RF-based method was proved by utilizing two data sets (i.e., the settlement ahead of tunnel face and final settlement). The results indicated that the prediction accuracy of shield tunneling-induced settlement in compound strata by the RF-based model is higher than the MR method. The relative importance analysis of variables indicates that advance rate, the cover depth of the tunnel ring, and pressure in the chamber were the most influential features for the settlement ahead of the tunnel face, while the thrust of the cutter head and the grout quantity were the most significant variables for the settlement after the segment assembling is completed. Overall, the conducted study could provide a helpful reference for the efficient excavation of EPB tunnels across compound strata.

Vibration characteristics of hard rock cutterhead under spatial distribution load

During the actual operation of the full-face tunnel boring machine (TBM), the vibration of the mainframe system is very strong, leading to the failure of key parts. Therefore, the vibration characteristics of TBM Cutter head under the maximum thrust condition are analyzed by ANSYS finite element software, and the effects of Cutter head panel thickness, Cutter head baseplate thickness, and support plate thickness on Cutter head vibration are analyzed. Subsequently, the optimal solution of the system is obtained by analyzing the data with orthogonal tests. It provides a reference for vibration reduction and parameter matching of Cutter head.

Effects of concrete materials on the vibration of the adjacent tunnel and surroundings by DEM and experiment

Concrete material can reduce the disturbance of train vibration to adjacent tunnels during the operation of near-distance twin tunnels. This paper adopts the discrete element method (DEM) and experimental model (scaled by 1:20) to study the influence of the train vibration at the speed of 120 km/h on the static and dynamic characteristics of the adjacent tunnel's liner and sleeper. The region between the twin tunnels was set as the concrete zone (CZ) to explore the effect of train vibration waves. The distance between twin tunnels is set to 0.25 D, where D (6.2 m) is the diameter of the tunnel. Foam brick (FB) is the similar materials of CZ in similar experiment. The DEM and similar experiments obtained similar results. The CZ (FB) can effectively block the propagation of the train vibration waves in T1, thus reducing the disturbance to the T2 liner and sleeper. Next, the CZ with four thicknesses and six heights are discussed with DEM, and it is found that thickness and height have a significant influence on the isolation effect of CZs, so the size should be selected according to actual engineering needs. This study provides a reference for studying the vibration reduction effect of CZs on adjacent tunnels during train operation.

Study on auxiliary operation control of machine learning in multiobjective complex drainage system.

Recently, urban waterlogging prevention and treatment of black-odorous rivers have become a social concern and the upgradation of drainage system and the development of river runoff pollution control projects have accelerated. The use of deep tunnels to upgrade old drainage systems and achieve pollution control-related engineering designs has complicated the drainage system operation control. The traditional operation control mainly relies on human experience or model simulation. This study provides a perspective of machine learning for controlling the operation of the drainage system and exploring whether the operation suggestions regarding facilities in this system can be given in real time while relying only on real-time data and avoiding the complex model simulation process. Herein, five drainage systems were used as examples: the initial water level of a pipeline, key point water level flow, pump station front pool water level, and most unfavorable point water level were selected as relevant variables and four machine-learning discrimination methods were used for to analyze the weir-lowering operation of a deep tunnel. This study found that the average error rate of the linear discrimination method was <10%, thereby exhibiting satisfactory performance. This study provides insights for improving the operation of complex drainage systems.

Ground Settlement Due to Tunneling in Cohesionless Soil

By the year 2035 it is estimated that Delhi and Mumbai will become two of the most populous cities around the globe. The massive population growth rate has led to the rise of land scarcity, urbanization, and industrialization and developments for rapid transit systems have made accordingly. Modern rapid transit systems comprise Metro rails and subways etc., and increase underground-construction activities. Nowadays, the tunnel-construction process heavily relies on massive machineries such as tunnelling-boring machines (TBM) and operations that produce great hindrance in the soil mass resulting in ground settlement at the surface. This study aimed to address these issues through small-scale laboratory experiments and further amplification to real-valued problems utilizing numerical methods. A cubic box of edge length 1 m made up of mild steel was generated to simulate a tunnelling operation and aluminum-made lining were used to simulate concrete tunnel linings. A finite element-based numerical investigation was done for a 2D elastoplastic numerical tunnel model with dimensions of 42 m × 42 m. Analysis was carried out on Optum G2 software. The analyzed variations in lining shapes of lining included circular, horseshoe, arch, elliptical, and square. Results showed that elliptical-shaped linings experienced the least ground settlement and these are recommended for places where surface settlement may cause major damage. It is also recommended that square-shaped linings should not be used in such situations due their higher settlement values.

Use of BIM for the optimized operation of road tunnels: Modelling approach, information requirements, and exemplary implementation

AbstractIn 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.

Experimental analysis of suppression effects of crosswise arranged porous iron-nickel materials on the natural gas explosion in utility tunnels

Natural gas pipeline in utility tunnels has been leading to great concern because of potential hazards characterized by flammability and explosives, which could pose a grave threat to the safe operation of utility tunnels and even surrounding facilities. Therefore, revealing the dynamic process of natural gas explosion in utility tunnels is quite important for the consequence analysis and risk assessment, especially in such complex scenarios with various facilities. In this study, a kind of porous material with low cost (porous iron-nickel materials) was selected and crosswise arranged to investigate its explosion-proof effects on the natural gas explosion in utility tunnels. The results demonstrate that porous iron-nickel materials have obvious suppression effects on the gas explosion process. The maximum overpressure decreases from 0.3898 Mpa to 0.2778 Mpa and the maximum flame front velocity decreases from 66.67 m/s to 37.51 m/s. It is also found that the inhibition effect of porous materials on explosion overpressure and fame front velocity increase with the increase of the number of holes in porous materials. This study is helpful to consequence assessment and risk analysis of natural gas explosion accidents in utility tunnels.

Identifying the outlier in tunnel monitoring data: An integration model

Structural health monitoring (SHM) system based on the Internet of Things is an important method to evaluate the safety of tunnel operation through the real-time monitoring data analysis. Identifying the outlier in SHM data is a non-trivial task but it is challenging for the tunnel engineers because the measurements are quite complicated with the characteristics of time series, unlabeled, high-dimensional, inter-correlations between variables, etc. To detect the outliers, an integration model is developed based on the independent data analysis from the Probabilistic, Proximity-Based (global), Proximity-Based (local), Linear Model and Outlier Ensembles. The model is examined with the shuttle data set in the University of California Irvine (UCI) database and its precision rate is up to 94.5%, highlighting the favorable performance in identifying the outliers. This method is thus applied to the outlier detection of the SHM data in the Nanjing Yangtze River tunnel. 6698 data sets collected from SHM are evaluated and 270 groups of outliers are identified effectively. By eliminating these outliers, comparisons between the proposed integrated model and the single model (i.e. IForest, ABOD, KNN, LOF) are further conducted to discuss the model performance based on the regression analysis. Results show that the integrated model is better than the single model and it possesses the great potential to detect the outliers in SHM system.

Технология прокладки тоннелей в массивах с неоднородностями с использованием вспомогательной конструкции

The article considers an innovative method of penetrating inhomogeneities encountered in the path of the trace laid microtunnel. The authors have developed a technology for sinking microtunnels in inhomogeneities using an auxiliary structure consisting of piles immersed in inhomogeneity throughout the project route of the microtunnel. This technology makes it possible to pass microtunnels in inhomogeneities without opening the surface and without using technologies to strengthen or freeze the array, which makes it possible to work in densely populated areas. The authors make a comparative assessment of the proposed innovative technology and the traditional technology of changing the project route of the microtunnel. The technology proposed by the authors is developed on the basis of an experiment using the methods of field tests and laboratory studies. Models of metal and reinforced concrete piles and a mock-up of the tunnel microshield AVN-1500 with the following sections of the lining were used for conducting field tests. In relation to the laying of underground workings in loose soils with the use of tunneling equipment, it is proposed to use the technology of driving inhomogeneities, including the creation of an auxiliary structure made of piles immersed in the array. Based on the results of the comparison of the necessary equipment and the cost of work, the conclusion about the technical and economic rationality of the proposed technology is formulated. According to the authors, the technology of tunneling in arrays with inhomogeneities using an auxiliary structure allows not only to provide the necessary strength and durability of the array, but also to significantly reduce the cost of financial resources. In conclusion, the authors formulate directions for further research that will improve the safety of tunneling operations in densely populated areas.

Vulnerability assessment of freeway network considering the probabilities and consequences from a perspective based on network cascade failure.

Freeway networks are vulnerable to natural disasters and man-made disruptions. The closure of one or more toll stations of the network often causes a sharp decrease in freeway performance. Therefore, measuring the probability and consequences of vulnerability to identify critical parts in the network is crucial for road emergency management. Most existing techniques only measure the consequences of node closure and rarely consider the probability of node closure owing to the lack of an extensive historical database; moreover, they ignore highways outside the study area, which can lead to errors in topological analysis and traffic distribution. Furthermore, the negative effects produced by the operation of freeway tunnels in vulnerability assessment have been neglected. In this study, a framework for freeway vulnerability assessment that considers both the probability and consequences of vulnerability is proposed, based on the perspective of network cascade failure analysis. The cascade failure analysis is conducted using an improved coupled map lattice model, developed by considering the negative effects of tunnels and optimizing the rules of local traffic redistribution. The perturbation threshold and propagation time step of network cascade failure are captured to reflect the probabilities and consequences of vulnerability. A nodal vulnerability index is established based on risk assessment, and a hierarchical clustering method is used to identify the vulnerability classification of critical nodes. The freeway network of Fuzhou in China is utilized to demonstrate the effectiveness of the proposed approach. Specifically, the toll stations in the study area are classified into five clusters of vulnerability: extremely high, high, medium, low, and extremely low. Approximately 31% of the toll stations were classified as the high or extremely high cluster, and three extremely vulnerable freeway sections requiring different precautions were identified. The proposed network vulnerability analysis method provides a new perspective to examine the vulnerability of freeway networks.

Femtosecond Laser Electronic Excitation Tagging Velocimetry in a Mach 6 Ludwieg Tube

Nonintrusive velocity measurements using femtosecond laser electronic excitation tagging (FLEET) were conducted at 1 kHz for both air and nitrogen flows in a Mach 6 Ludwieg tube under static pressure conditions. The signal from air and nitrogen were compared in freestream conditions and with a blunt cone model (7 deg half-angle). The long-laser time series operation relative to the facility operation time allowed the characterization of the mean velocity over the entire tunnel operation. The measurement uncertainty for both air and nitrogen FLEET were thoroughly examined. Our finding shows that the measured freestream velocity differed by from that of the compressible flow calculations. Additionally, the velocity near the leading bow shock was measured at six and three locations in nitrogen and air, respectively, to resolve the large velocity gradient at several locations along the shock layer. The velocity results for the freestream and bow shock were averaged in space and time.