Tunnel Operation Research Articles

Heat hazard control in excavation engineering: Numerical simulation of heat transfer characteristics of high temperature tunnel with movable thermal insulation layer

• The use of movable thermal insulation layer (MTIL) in excavating tunnels was proposed. • The thickening of the air layer causes the temperature to rise. • The longer MTIL reduces the thermal insulation capacity. • The moving grid is used to dynamically simulate the MTIL and heading face. The current mine mining has entered the kilometres stage where the high geothermal has become a key factor limiting the tunnel excavation and operation. During the auxiliary ventilation of the mine, the heat exchange between the fresh air and the surrounding rock is serious and cannot meet the cooling demand. Therefore, thermal insulation must be adopted to control the heat transfer. However, the heat exchange between tunnel excavation area and operation area is different, so it is not economical to carry out full tunnel insulation. In order to optimize mine insulation technology and save construction cost, this paper proposes and verifies the feasibility of using movable thermal insulation layer (MTIL) for partial insulation of the excavation tunnel. The dynamic process of tunnel excavation and MTIL following is simulated by using a moving grid method. The results show that MTIL can effectively preserve the air cooling capacity and enhance the ventilation cooling effect. In addition, the thickness of the air layer is proportional to the convective heat flux of the surrounding rock. Whether to install the overall insulation layer and thermal conductivity have little effect on the insulation effect, but the best insulation layer length is 6–8 m. This study provides theoretical and technical support to improve the thermal environment of deep mine excavation work.

Development and study of a constructive solution for a single-track railroad tunnel for a high-speed railway line, with the account of aerodynamic processes

The materials presented in the article will be used in the dissertation submitted in partial fulfillment of the requirements for the degree of Ph.D. in Engineering Science. The article provides information on the construction and operation of a railroad tunnel for a high-speed railway line, it is noted that generally single-track railroad tunnels are constructed on new railway lines. A development review of existing methods for reducing and compensating aerodynamic pressure and ways of its regulation is given, and its advantages and disadvantages are analyzed. A new design solution description that helps to reduce the intensity of the aerodynamic effect is presented, the principles of its operation and the main hypothesis are described, and advantages over existing solutions are shown. The study materials of the aerodynamic state of the «tunnel-train» system, obtained from the numerical simulation results by the methods of computational fluid dynamics, are presented. An analysis of the change in aerodynamic pressure for various parameters of the passage of a train in a tunnel has been carried out, and the «tunnel-train» system state assessment has been given. The main attention is paid to the influence degree of the train speed, the cross-sectional areas ratio, and tunnel and train lengths. The numerical modeling results were evaluated by the aerodynamic pressure drop values, by the nature of the aerodynamic state of the «tunnel-train» system, by the nature of the air flows, and by its speed trajectories. The obtained results are presented in tabular and graphic forms, and results analysis is carried out. The effectiveness of a new design solution for a tunnel for a high-speed railway line in solving the problem of mitigating aerodynamic pressure is shown, and the rationality of the engineering solution is substantiated. The constructive solution of the tunnel for a high-speed railway line has the potential to reduce material consumption and improve the technical and economic characteristics of the structure and can be used in the design and construction for further efficient operation of perspective high-speed railway lines in modern conditions, with the account aerodynamic phenomena.

Mechanisms of trace water vapor desublimation over airfoil in transonic cryogenic wind tunnels

Cryogenic wind tunnels can provide a larger operating Reynolds number compared to conventional ones. However, the internationally known “moisture contamination problem” resulting from the residual trace water vapor desublimation in the cryogenic wind tunnel may affect the accuracy of the aerodynamic data. Due to extreme difficulties in experiments, the detailed trace water desublimation characteristics remain unrevealed. An Euler–Euler two-phase flow model based on classical nucleation theory and a droplet growth model were established to predict the trace water vapor spontaneous desublimation in the nitrogen flow over airfoil in a transonic cryogenic wind tunnel. The proposed model was validated by experimental data obtained from the literature and showed good agreements. The verified model was applied to 0.152-m National Advisory Committee for Aeronautics 0012 airfoil in a Langley 0.3-m transonic cryogenic wind tunnel under a series of operating conditions. The simulated results reveal that the water vapor desublimation process in a transonic cryogenic wind tunnel can be divided into two patterns by a critical region. In pattern I, over the upper critical total temperature, the water vapor desublimates quickly during the rapid expansion of gas flow over the airfoil surface. In pattern II, below the lower critical total temperature, the water vapor is sufficiently supercooled and desublimates completely into small ice particles in the free-stream flow. For pattern I, the desublimation characteristics were analyzed in detail, and the influences of the desublimation process on the aerodynamic data were quantitatively evaluated, which can provide theoretical guidance for the practical operation of transonic cryogenic wind tunnels.

The Damage Deterioration Mechanism of Tunnel Structure under the Effect of Thermo-Mechanical Coupling and Its Maintenance

The effect of thermo-mechanical coupling is a key factor that needs to be fully considered during the construction, operation, and maintenance of tunnels in high ground temperature areas so that measures could be taken to reduce the frequency of damages and accidents. However, research methods and theoretical results for tunnel support structures under high temperature conditions and layered soft rock environment are insufficient, therefore, to fill in this research blank, this paper aims to study the damage deterioration mechanism of tunnel structure under thermo-mechanical coupling effect and its maintenance. In the second chapter, this paper gave a diagram showing the coupling mechanism of several physical fields, including the stress field, the seepage field, and the temperature field, and proposed control equations for the coupling of these fields during the damage deterioration process of the tunnel structure. In the third chapter, this paper applied two yield failure criterions, namely the Mohr-Coulomb criterion and the maximum tensile stress strength criterion to the analysis of the evolution of compression shear failure and tensile failure, and built scientific evolution equations for the permeability coefficient and the thermal conductivity coefficient. At last, experimental results verified the effectiveness of the constructed model and the analysis method.

The mechanical properties of concrete in water environment: A review

The service performance of concrete structures in a water environment differs from that in a normal environment. An accurate evaluation of the mechanical properties and service status of wet concrete is related to the reliable design and safe operation of concrete structures, e.g., hydraulics, marine engineering, bridges, and tunnels. To promote the application of new and high-performance concrete to complex water environments and grasp the future development trend, the research progress on the service performance of concrete in water environments was reviewed worldwide. Starting from the internal water content of concrete, the existing research is combed, the influence of water content, water pressure, and loading rate on the static and dynamic characteristics of concrete in a water environment is summarized, and the influence mechanism is analyzed. The literature review demonstrates that the static compressive strength of wet concrete is lower than that of dry concrete; however, the elastic modulus improves. With an increase in the strain rate, the compressive strength of wet and dry concretes improves, and the rate sensitivity of the wet concrete is greater than that of the normal concrete. Pore structure characteristics mainly affect the static strength of the wet concrete. The improvement in the dynamic strength of the wet concrete is caused by the combined effect of the concrete rate sensitivity, “Stefan” effect, and water pressure.

Sensitivity Assessment of Electrically Doped Cavity on Source Junctionless Tunnel Field-Effect Transistor-Based Biosensor

The tunnel field-effect transistor (TFET) has emerged as a promising device for biosensing applications due to band-to-band tunneling (BTBT) operation mechanism and a steep subthreshold swing. In this paper, an electrically doped cavity on source junctionless tunnel field-effect transistor (ED-CS-JLTFET)-based biosensor is proposed for label-free detection of biomolecules. In the proposed model, the electrically doped concept is enabled to reduce fabrication complexity and cost. In order to create a nano-cavity at the source region, some portion of the dielectric oxide of the polarity gate terminal is etched away. To perceive the presence of biomolecules, two important properties of biomolecules, such as dielectric constant and charge density, are incorporated throughout the simulation. The sensing performance of the proposed ED-CS-JLTFET-based biosensor has been analyzed in terms of transfer characteristics, threshold voltage and subthreshold swing. In addition, the sensitivity of the proposed biosensor has also been analyzed with respect to different fill factors (FFs), varying nano-cavity dimension and work-function of the control gate. It is found from the simulated results that the proposed ED-CS-JLTFET-based biosensor offers higher current sensitivities with neutral, positively charged and negatively charged biomolecules of [Formula: see text] (at k [Formula: see text]), [Formula: see text] (at [Formula: see text] and [Formula: see text] C[Formula: see text]cm[Formula: see text]) and [Formula: see text] (at k [Formula: see text] and [Formula: see text] C[Formula: see text]cm[Formula: see text]), respectively.

Thermo-hydro-mechanical behaviour of geothermal energy tunnel in different ground conditions

Energy tunnel is attracting increasing attention because it provides an innovative and efficient approach to harvest geothermal energy. Most of the previous studies focused on its thermal performance and little attention was paid to the thermo-hydro-mechanical behaviour during the operation of energy tunnel, such as lining deformation and ground movement. To address this problem, a numerical model that can simulate the coupled thermo-hydro-mechanical behaviour was developed in this study and verified by a field test. Then, comprehensive parametric studies were conducted to investigate the effects of key soil properties and states (i.e. permeability, thermal conductivity, coefficient of thermal expansion (CTE), elastic modulus, Poisson’s ratio and tunnel burial depth) on the mechanical responses of energy tunnel and surrounding soils under cooling. It is found that: (1) CTE and elastic modulus among the above parameters are the most influential parameters for ground settlement and normal stress from soil to lining, respectively; (2) The thermally induced change in normal stress highly depends on the burial depth, with a percentage change of 24% for a shallow tunnel and 5% for a deep tunnel. Based on the guidelines of tunnel management, the thermally induced ground settlement is a more critical aspect than the lining deformation.

Bending Performance of the Steel Longitudinal Joint for Quasi-Rectangular Pipe-Jacking Tunnels

Pipe jacking is a special tunneling method for installing underground pipelines or tunnels with the minimum surface disruption. Longitudinal pipe-to-pipe joints are important for tunnels with the pipe-jacking technique. The longitudinal joint generally adopts the socket type, that is, a bell-and-spigot joint, designed for use with gaskets work well for jacking. The joints should have sufficient bearing surfaces to transmit the required axial thrust and have the ability to resist lateral forces from ground movements during tunnel construction and operation. This paper focuses on the mechanical performance of the longitudinal joint of the superlarge cross section quasi-rectangular pipe-jacking tunnel under the action of local bending moments caused by lateral forces. A full-scale ultimate bending test of the local joint specimen was carried out to study its bearing mechanism, ultimate bearing capacity, and failure mode. Numerical simulations were then employed to analyze the performance of the joint specimen and were verified by the experimental results. The damage evolution process and bearing mechanism changes of the joint specimen were analyzed by numerical simulations. The results show that the bell part contributes much more to the bending of the joint than the spigot part. The bolt contributes little to the bearing capacity and stiffness of the joint but plays a role in positioning the pipe to pipe in the installation. The bending failure of the joint is characterized by weld fractures between the longitudinal rib and its flange next to the V-groove weld at the bottom of the bell part. The V-groove weld connecting the bottom of the spigot part and the bell part primarily affects the bending capacity of the joint.

Anwendung von Grünen Inhibitoren zur Härtestabilisierung in Tunneldrainagen

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

Study on the performance of the new composite thermal insulation lining for the railway operational tunnel in cold regions

In railway tunnels located in cold regions, frost damage is constantly emerging, which seriously affects the safety of railway tunnel operations. While having general thermal insulation effects, thermal insulation measures developed in previous studies have not solved the problem of frost damage in operational railway tunnels. To fill this gap, this paper puts forward a new composite thermal insulation lining. Firstly, through numerical simulation, this new composite thermal insulation lining was verified to have better mechanical properties and insulation effects than general steel plate thermal insulation lining. The fast construction method of thermal insulation lining is proposed to have excellent construction efficiency and great economic and social benefits. According to field monitoring data, the outer surface temperature of the lining reached about 5 °C in winter after the new composite thermal insulation lining was added, which fundamentally inhibited the formation of ice and effectively avoided frost damage. At the coldest moment in time, the temperature of the secondary lining was about 9 °C higher than without thermal insulation lining. In summary, compared with existing anti-freeze technology, the new composite thermal insulation lining has better thermal insulation capacity, can be constructed faster, and offers clear economic benefits.

Research on the movement law and traffic safety zoning of spalled blocks in the linings of high-speed railway tunnels

Recent years have brought to notice the spalling and falling off problem of the lining of high-speed rail tunnels, which is dangerous for traffic safety. In this study, a three-dimensional spalled block–train–tunnel–air gas–solid coupling calculation model was built using FLUENT numerical simulation software. This model was used to simulate the trajectory characteristics of the spalled blocks under the operating condition of a high-speed rail at a speed of 300 km/h. The spatial movement characteristics of the block falling from the lining under four influencing factors, namely, block's geometric size, density and positions and train's speeds were analyzed. During the operation of the train, the lateral displacement of the spalled block decreases with the increase of the density of the spalled block, increases with the increase of the vehicle speed, and first increases and then decreases with the increase of the geometric size of the spalled block. Considering the above influencing factors comprehensively, the safe area and dangerous area in the tunnel are divided depending on whether the traffic safety was threatened by the falling of the spalled blocks from tne tunnel lining. The results show that the area 4.5 m away from the ground is a dangerous area where the tunnel operation and maintenance need to be paid attention to. Meanwhile, it is recommended to install the auxiliary equipment in a safe area to avoid the peeling off of the surrounding lining and thereby threatening train-driving safety.

Deformation and Failure Mode Analysis of the Tunnel Structure Based on the Tunnel-Related Landslides Cases

When the tunnel passes through the slope area, once the slope stability changes or landslide disasters occur, large additional stress, deformation, or cracking are easily caused in the tunnel, which results in high risk to the tunnel operation. The deformation and failure mode of the tunnel induced by different types of tunnel-related landslides are different. However, there is no systematic classification of tunnel structure deformation and the failure mode in the tunnel-related landslides systems. By investigating the typical cases of tunnel diseases caused by landslide in China, this study analyzes the relationship between the tunnel-related landslide types and tunnel disease characteristics. It also summarizes five typical tunnel deformation failure modes and corresponding deformation characteristics and determines the relationship between tunnel-related landslide types and deformation failure modes. This study can provide a technical support for the identification of landslide types through the tunnel deformation characteristics in practical engineering applications. Finally, it provides a reference for tunnel location selection, the design of tunnel structure, and the treatment of landslide in landslide areas.

Exploratory Research on Drainage Structure of Highway Tunnel Based on Reducing the Risk of Crystallization Blockage

Crystal blockages of tunnel drainage systems severely undermine the tunnel lining structure and operation safety. In order to reduce the risk of crystal blockages of tunnel drainage systems, the distribution of highway tunnel defects was identified through a field survey, indoor test, and literature analysis, and an optimization method of tunnel drainage structures was proposed. The research suggested the following: (1) Lining water leakage and construction joint water leakage were the most common defects in the tunnel drainage system of Renhua–Xinfeng Expressway and Yingde–Huaiji Expressway in Guangdong Province, accounting for 60% and 32% of total defects, respectively. The number of defects that occurred in the drainage system of the tunnel was larger in the granite formation, with the number of road seepage and inspection chamber crystallization incidents reaching 2.5/km and 2.8/km, respectively. (2) The groundwater was mainly alkaline with a pH value of 8~12, Ca2+ (107 mg/L) was the cation with the largest ion concentration, and HCO3− (165 mg/L) was the anion with the largest ion concentration. The crystals in the tunnel drainage system were predominantly square, spindle, and rhombic calcite and aragonite composed of CaCO3, mixed with a small amount of sediment. (3) To reduce the risk of crystal blockages of the tunnel drainage system and ensure tunnel lining structure safety, a threefold optimization measure was proposed, namely, setting one-directional drainage pipes between the cable trench and the roadside blind drainage ditch, applying “π” type anti-crystallization drainage water-stop belts at the circular construction joints in the secondary lining, and both increasing the slope of the transverse drainage pipe and using an anti-crystallization drainage pipe. The research results will play an important role in guiding the design, construction, and maintenance of highway tunnel drainage systems in China.

İÇ GÜVENLİKTE YER ALTI, TÜNEL VE MAĞARA OPERASYONLARI İLE YÖNETİMİ

Underground, tunnels and caves are places that are frequently used by terrorists, organized crime organizations and smugglers in cities, rural areas and borders of countries. Especially in recent years, law enforcement's use of reconnaissance and surveillance technologies such as unmanned aerial and land vehicles has increased the desire of organizations to use underground, tunnels and cave environments as an asymmetric advantage. Underground, tunnels and caves are cavities that are either spontaneously formed in nature or built with human resources, which are used for the purpose of maintaining security or life. The homogeneity of the physical environments of these places makes it meaningful to mention underground, tunnels and caves together. Securitization of these environments in order to prevent crime and terrorist activities has become a priority internal security approach for law enforcement. Within the scope of the study, firstly, the importance of underground, tunnels and caves in terms of internal security was investigated. Subsequently, the conditions affecting the underground, tunnel and cave operations were determined. Finally, answers were sought to the questions of how underground, tunnel and cave operations were carried out and managed. The purpose of this study is to define the management method in underground, tunnel and cave operations in terms of internal security in Turkey today. The study was carried out on a theoretical basis by making a literature review. As a result of the study, it was emphasized that a separate technology should be used for each of the exploration and surveillance, cover and protection, firepower and communication needs in underground, tunnel and cave operations. Subsequently, it has been decided that the operation units should manage their operations in accordance with the planning, preparation, execution and evaluation phases.

Design, steady performance and wake characterization of a scaled wind turbine with pitch, torque and yaw actuation

Abstract. This paper describes the design and characterization of a scaled wind turbine model, conceived to support wake and wind farm control experiments in a boundary layer wind tunnel. The turbine has a rotor diameter of 0.6 m and was designed to match the circulation distribution of a target conceptual full-scale turbine at its design tip speed ratio. In order to enable the testing of plant-level control strategies, the model is equipped with pitch, torque and yaw actuation and is sensorized with integrated load cells, rotor azimuth and blade pitch encoders. After describing the design of the turbine, its steady-state performance and wake characteristics are assessed by conducting experiments in two different wind tunnels, in laminar and turbulent conditions, collecting wake data with different measurement techniques. A large-eddy simulator coupled to an actuator-line model is used to develop a digital replica of the turbine and of the wind tunnel. For increased accuracy, the polars of the low-Reynolds-number airfoil used in the numerical model are tuned directly from measurements obtained from the rotor in operation in the wind tunnel. Results indicate that the scaled turbine performs as expected: measurements are repeatable and consistent, and the wake appears to have a realistic behavior in line with expectations and with a similar but slightly larger scaled model turbine. Furthermore, the predictions of the numerical model are well in line with experimental observations.

Modified Burgers model of creep behavior of grouting-reinforced body and its long-term effect on tunnel operation

Grouting has been widely employed to mitigate geohazards in underground projects (e.g., the tunnel). However, few studies have focused on the effects of the creep behavior of a grouting-reinforced body on the stability of tunnel operation. In this study, the curtain grouting-reinforced Nanshibi tunnel was adopted as an example to explore this issue. More specifically, uniaxial compressive creep tests were firstly performed to study the time-dependent behavior (i.e., the creep behavior) of the grouted specimen. Then, the improved nonlinear Burgers model was proposed to characterize the observed creep behavior of the grouted specimen. Finally, a numerical simulation of the tunnel operation post grouting was conducted using the newly-proposed nonlinear Burgers model. The following results were obtained: (1) The creep behavior of the grouted specimen under different loadings undergoes three stages: decaying creep, steady creep, and accelerated creep. The steady creep rate is attributed to the homogeneity of the grouting-reinforced body. (2) The nonlinear Burgers model can reasonably quantify the creep behavior of the grouting-reinforced body. (3) The creep behavior of the grouting circle of the tunnel has a significant influence on the tunnel deformation and thus the lining safety. More specifically, the tunnel deformation exhibits nonlinear growth and mainly occurs at the vault and inverted arch. Furthermore, owing to the shape of the lining structure, the arch spring is most vulnerable to cracking under the eccentric tension state. The improved creep model is proved to more accurately predict the structural deformation of a curtain grouting-reinforced tunnel. As such, it can help devise grouted-tunnel maintenance strategies for long-term safety.

Sequence of Factors Affecting Stability of Tunnel Exit Section in Low Temperature Rain and Snow Weather

When the vehicle is only affected by road conditions and its own speed, in the low temperature rain and snow weather. In order to clarify the order of the importance of each influencing factor at the exit section of the tunnel on the driving stability, this article uses the analytic hierarchy process to sort them. The results show that the order of importance is: Friction coefficient μs > driving speed ν (m/s)> circular curve radius R (m), longitudinal slope i (%). According to the sorting results, targeted safeguard measures can be provided for the tunnel design, operation and use process.

Countermeasures for the Maintenance Management of Expressway Bridges and Tunnels

In order to improve the maintenance of expressway bridges and tunnels as well as to maximize the utilization rate of expressway bridges and tunnels, this paper studies the countermeasures for the maintenance management of expressway bridges and tunnels. Through theoretical analysis, this paper expounds the problems existing in the maintenance management of expressway bridges and tunnels as well as proposes corresponding solutions to these problems. By implementing the countermeasures for the maintenance management of expressway bridges and tunnels, it is possible improve the maintenance effect of expressway bridges and tunnels as well as ensure the smooth and safe operation of expressway bridges and tunnels.

Propagation of carbon monoxide in road tunnels in case of fire by considering the critical velocity, backlayering and gradient factor

The optimal use of transit potential is viewed as one of the basic means under the Economic Development Strategic Plan for Georgia with a primary emphasis on the modernization and development of the transport infrastructure. In this regard, the construction and improvement projects for the main and auxiliary highway structures are planned and carried out successfully across the country, with the construction of over 50 road tunnels in the country being one of the components. The sustainability and safe operation of the tunnels is the criterion for the successful implementation of such complex projects. As a result, it is critical to evaluate all risk factors for the safe operation of road tunnels as objectively as possible [1].

Life-saving problems during fire in road tunnels

One of the main risk factors for the safe operation of tunnels, according to the design solutions of Georgian road tunnels, is the possibility of fire initiation with relevant negative consequences. The report will discuss the fire development scenarios under the ground based on the results of numerical modeling, as well as the recommendations for training and raising awareness of fire service personnel and rescuers depending on fire capacity, tunnel geometry, location and other factors, which will be applicable to the safe operation of transport tunnels and the survival of fire in the event of a fire.