Tunnel Operation Research Articles

Study on aerodynamic pressures caused by double-train tracking operation in a metro tunnel

The continuous construction of extra-long metro tunnels and the shortened departure intervals enable double trains to simultaneously drive in the same tunnel direction to be possible. Transient pressure changes induced by trains passing through tunnels have a remarkable influence on the structural safety of tunnels. In this study, pressure waves generated by single and double trains passing through the tunnel are both explored by numerical simulation. The accuracy and feasibility of the simulation method of double train tracking operation is verified by comparison with the small-scale experimental research. Based on the verified simulation method, the pressure wave and its propagation characteristics in the aforementioned two situations are investigated. Variation of transient pressure on the surface of the train and tunnel are compared and analyzed. Results show no obvious difference on the generation and propagation mechanism of pressure waves between the two typical situations. However, the propagation of the pressure wave is found to be more complicated in the double train tracking mode. More concretely, in the double train tracking mode, the maximum transient pressure P-max, minimum transient pressure P-min, and the peak-to-peak value of transient pressure ΔP on the first train surface are observed to be same as those in the single train condition, whereas those of the second train denote different values. The transient pressure at different positions in the tunnel and the waveform after the second train entering the tunnel are different compared to that in the single train condition, while the peak value exhibits insignificant difference. Moreover, the maximum pressure, minimum pressure, and maximum peak-to-peak pressure occur inside tunnel denote no obvious difference in the two typical scenarios.

Intelligent monitoring and residual analysis of tunnel point cloud data based on free-form approximation

With the rapid development of urban rail transit and the aging of transportation infrastructure, the demand for shield tunnel disaster detection is about to break out. Most of the traditional monitoring methods require considerable manpower and time costs, which cannot satisfy the increasing requirements of tunnel operation and maintenance. Free-form model construction and deviation mechanism analysis are investigated in this paper to monitor the geometric deformation information of shield tunnels quickly and accurately. A method for identifying geometric features of tunnel sections based on the free-form B-spline approximation is proposed. The innovation of this paper lies in the intelligent recognition of common interference targets by the residual classification method. Furthermore, various Root Mean Squared Error (RMSE) distributions are investigated, which successfully realizes and verifies the clustering analysis of certain point cloud features.

Research on Abnormal Event Classification of Expressway Tunnel based on Security Control

Based on the perspective of tunnel traffic safety operation and control and the human, vehicle, road, and environment system in tunnel operation process, adopting event tree analysis method according to the different influencing factors, generation mechanism and performance characteristics of tunnel abnormal events, this research propose abnormal event classification tree diagram. According to the current abnormal event management and control mechanism in China, the administration departments and disposal facilities associated with different types of abnormal events in expressway tunnel operation are sorted out, which can provide decision-making support for the rapid treatment of abnormal events and realize intelligent control of tunnel.

Aerodynamic Analysis of a scaled UHBR Fan

In the frame of the CA3ViAR Clean Sky 2 (Composite fan Aerodynamic, Aeroelastic, and Aeroacoustic Validation Rig), the main objective is to design a low-speed (low-transonic) fan typical of a future large aircraft UHBR engine, in terms of aerodynamic shaping as well as structural design and analysis to make sure the test article experiences aerodynamic and aeroelastic instabilities in an expected way during wind tunnel (WT) operations. Eventually, open access to all the produced models will be provided, with the objective to establish an “open test-case” for the whole European scientific community, unique in the engine fans landscape. A preliminary fan stage design is presented in this paper, details about the aerodynamic design process and the results of the CFD analysis of the stage are shown. The present UHBR fan design fulfils the initial aerodynamic requirements and represents the starting point for the structural and aeroelastic analysis within the multidisciplinary design process employed to design the final CA3ViAR fan stage.

The control system design and study for continuous supersonic wind tunnel

As the first continuous supersonic wind tunnel in China, Mach number and total pressure are the most important flow field parameters of the wind tunnel, how to precise control and rapid and stable adjustment of total pressure and Mach number is the key in the design and construction of the wind tunnel control system. By analyzing the principle of parameter control of the wind tunnel flow field and the coupling relationship of each adjustment methods, the construction of continuous supersonic wind tunnel control system is constructed, and the solution measure of each key technical problem is given. The total pressure is precisely controlled by the segmented variable parameter fuzzy PI control algorithm, and then the wind tunnel operation control process design is carried out. Finally the wind tunnel blowing test is verified. The result shows that the accuracy of total pressure accuracy is better than 0.05%, the Mach number accuracy is better than 0.167 3, all the flow field parameter is greatly better than the design index, which proves that the design idea proposed in this paper is effective and can provide reference for the design and debugging of continuous supersonic wind tunnels.

The preliminary design of a scaled Composite UHBR Fan for a wind tunnel test campaign

The ambition of the CA3ViAR project is to design an open test case fan that experiences instability mechanisms, which are representative for ultra-high bypass ratio (UHBR) fans of civil aircrafts, and to perform a comprehensive experimental investigation to measure aerodynamic, aeroelastic and aeroacoustic performance in a wide range of operational conditions. Experimental tests will be performed in the Propulsion-Test-Facility (PTF) of the Institute of Jet Propulsion and Turbomachinery (IFAS) of Technische Universität Braunschweig, Germany. The final objective of the project is to provide an open test case for the entire research community, with geometries, numerical and experimental results to establish a new reference for composite UHBR fan design. This will support the development of new methods and tools for the development of safer, lighter and more efficient composite fans for greener UHBR engines. In this work the preliminary design of the low transonic fan (LTF) to be used as test article, whose main requirement is to be operated in a safe and controlled way in conditions of aerodynamic and/or aeroelastic instability during wind tunnel operations, is presented. More in particular, consolidated aerodynamic design, strategy adopted to drive the structural design, flutter analysis taking into account acoustic reflection at the intake, dynamic and stress analyses, as well as aeroacoustic measurement optimization are presented and discussed. The preliminary mechanical design of composite blades and the rotor hub, together with the rotor instrumentation and related studies to embed sensors in the composite blades, are also part of this article, and complemented by manufacturing trials and demonstration tests give the full picture of all the project activities up to the preliminary design review.

Mechanism and Application of Blasting Technology Using Phase-Difference Vibration Mitigation on Adjacent Railway Tunnel

The blasting vibration velocity is a widely used controlling index for the safety assessment of tunnel structures. How to reduce the impact of blasting vibration on the operation of adjacent railway tunnels is worth studying. In this paper, the initial phase-difference of blasting using phase-difference shock absorption is derived from the propagation theory of the blasting stress wave. When the initial phase-difference is Δφi = ±(2n + 1)π (n = 1, 2, 3, …), the peak particle velocity (PPV) in the tunnel structure is decreased to the minimum. On the basis of blasting theory using phase-difference shock absorption, the blasting parameters were designed for the No. 2 drainage tunnel excavated which adjacent a railway tunnel from Guiyang to Changsha, and it carried out 4 times blasting tests. It was found that the PPV of the railway tunnel structure in X, Y, and Z directions reduced by 64.6%, 66.25%, and 81.26%, respectively, which compared with the conventional blasting with the same total quality. Meanwhile, the amount of overbreak and underbreak can be controlled within 5%. The results show that the effect of blasting technology using phase-difference vibration mitigation is obvious, which is able to match with the design requirements for the tunnel excavation contour. The blasting technology using phase-difference vibration mitigation can be achieved via controlling the blasting time interval accurately. Moreover, it is beneficial for enriching and developing the blasting vibration control technology.

Damage Model and Experimental Study of a Sand Grouting-Reinforced Body under Seepage

Grouting is a reinforcing method commonly used in underground engineering. The grouting-reinforced body is in saturated groundwater, which is due to long-term seepage, resulting in reinforcing performance attenuation. This is a guarantee for the safe operation of the underground structure’s long life cycle that obtains the performance attenuation law of the grouting-reinforced body under the action of seepage. This paper uses primitive to describe the mechanical properties of grouting-reinforced body under seepage erosion, establishing the damage mechanics model of grouting-reinforced body under seepage, designing deterioration experimental of grouting-reinforced body under seepage, studying the mechanism of the permeation water pressure on the permeability of the grouting-reinforced body, and obtaining the variable of the grouting-reinforced body damage variable with the permeation water pressure. Studies have shown that seepage effects have a “sudden jump” phenomenon in the process of grouting-reinforced body erosion, and the limit damage of grouting-reinforced body is 0.15~0.19. The relationship between the permeability and damage variables of grouting-reinforced body under seepage are verified, and the quantitative relationship of grouting-reinforced body between permeation pressure, time and damage variables are obtained. This research is of great importance for improving the deterioration theory under seepage and ensuring the long-term safety of tunnel operations.

Successfully managing Covid-19 on tunnelling operations for the Thames Tideway Tunnel, UK

The Covid-19 pandemic had a huge impact on the way the UK population lived and worked during 2020. This paper explores the challenges faced while boring the west section of the Thames Tideway Tunnel in London, UK, with particular focus on the first national lockdown that began in March 2020. It discusses how the reduction in personnel triggered closure of the site, the technical challenge of safely stopping a tunnel boring machine for extended periods of time and the practical difficulties of creating a Covid-safe environment in a challenging space. This case study can be used to inform other underground construction projects coping with coronavirus.

Monitoring and Analysis of Geotemperature during the Tunnel Construction

High geotemperatures are encountered during tunnel construction in areas with complex geological structures, which can seriously affect personnel and equipment in the process of tunnel construction and operation. The Nige tunnel, a deep-buried extra-long tunnel, was selected to monitor the geotemperature during construction. The air, rock, and water temperatures during the tunnel construction were measured at the tunnel face, and the actual temperatures of the rock or water body at the tunnel face were measured by advanced drilling. The variation trends of the water temperature, air temperature, and flow of water with the tunnel mileage were analyzed. The differences in three measured rock temperatures in three advanced drillings were revealed. The results showed that the Nige tunnel had a maximum water temperature of 63.4 °C, maximum rock temperature (Rock T) of 88.8 °C, and maximum air temperature (Air T) of 56.4 °C. Increasing trends of the air, rock, and water temperatures with the tunnel’s horizontal distance and the buried depth (vertical depth) were obvious, and the geotemperature gradient was approximately 7.6 °C per 100 m. Additionally, the variation laws of the construction ambient temperature with time in a complete construction cycle showed four stage characteristics, and each stage presented different mathematical relationships. These findings will provide guidance for the construction of high geotemperature tunnels in future.

Impact of dust loads in long railway tunnels: In-situ measurements and consequences for tunnel facilities and operation

Reliable information concerning rail tunnel dust emissions dependent on parameters such as train type, train speed, operating conditions, etc. is quite rare. Thus, in order to quantify the effect of heavy metals on the environment, specific data is needed when designing air filtration systems inside the tunnel, or in carrying out environmental assessment studies. Detailed investigations were therefore carried out in a test installation in an Austrian rail tunnel. In order to be able to use these data for the long railway tunnels currently under construction, train-specific emission factors were determined. It was found that emissions from freight trains are up to 6.68 times higher than those from passenger trains. Bulk freight transport in open cars produces the highest emissions, while the short regional passenger trains exhibit the lowest emission levels. Chemical analysis of the samples came up with a mass fraction of 60% related to metals, of which, iron is the dominating component. Based on these findings, maintenance intervals for high quality dust filters were derived.In addition, the knowledge gained on train type-dependent emission factors greatly helps to improve upon the very poor data now used in environmental studies, particularly when determining railway particulate matter emissions.

Measurement of indoor environmental parameters and analysis of the condensation phenomenon in urban utility tunnels

Condensation is a major issue in the safe operation of utility tunnels. To address the condensation problem, the indoor air temperature, relative humidity (RH) and surface temperature in an urban utility tunnel in Jining were continuously measured, and the condensation conditions were surveyed and analysed. The results indicated that under natural ventilation conditions, the air temperature in the comprehensive cabin varied from 23.4°C to 24.5°C, the RH fluctuated between 86.4% and 95.3%, and the corresponding air dew point temperature (DPT) remained in the range of 22.2°C–22.9°C. The surface temperature of the water supply pipeline ranged from 17.8°C to 18.5°C, which was far lower than the DPT in the tunnel, resulting in serious condensation. A water supply pipeline with an anti-condensation design was developed based on environmental test data. A 25-mm-thick rubber plastic sponge insulation layer was used to thermally insulate the water supply pipeline, preventing further dew condensation. Furthermore, mechanical ventilation had little effect on reducing the RH in the tunnel and may actually cause dew condensation; therefore, a ventilation control mode was proposed in this study. These results are expected to provide basic data for further research and reference for the safe management of utility tunnels.

Підвищення енергетичного потенціалу вугілля при відпрацюванні малопотужних запасів шахт Західного Донбасу

Purpose. Development and generalisation of a set of key elements for a non-waste technology concept of mining high-quality coal from thin coal seams, based on the processes of backfilling the mined-out space with waste rocks from stope and tunnelling operations. Methods. A comprehensive methodical approach, containing the systematisation and generalisation of the constituent elements of a non-waste coal mining technology based on the implementation of theoretical studies and substantiations, is used in the research. Findings. The main hypothesis of a new approach to non-waste coal mining has been formed, in which the priority is not only the process of leaving the maximum waste rock volume in underground cavities, but also its use to form backfill mass, thereby improving the geomechanical conditions for mining thin coal seams. A wide range of mining tasks has been formulated and systematised for using a non-waste coal mining technology. The conditions for the harmonious functioning of the proposed conceptual scheme of a non-waste coal mining technology within the extraction field boundaries have been determined and substantiated. The conceptual foundations for the functioning of a new highly efficient non-waste technology for mining high-quality thermal coal from thin coal seams have been developed. Originality. The scientific novelty is in revealing the mechanism for the effective logistic functioning of rock-transport systems for the accumulation of waste rocks in the underground space using a non-waste technology of coal mining from thin coal seams. Practical implications. The research results can be used in planning non-waste technological schemes for mining the coal with an increased energy potential.

КОНЦЕПТУАЛЬНІ ЗАСАДИ СТВОРЕННЯ БЕЗВІДХОДНОЇ ТЕХНОЛОГІЇ РОЗРОБКИ ТОНКИХ ВУГІЛЬНИХ ПЛАСТІВ

Purpose. Development and generalization of a set of key elements for a non-waste technology concept of mining high-quality coal from thin coal seams, based on the processes of backfilling the mined-out space with waste rocks from stope and tunneling operations. Methods. A comprehensive methodical approach, containing the systematization and generalization of the constituent elements of a non-waste coal mining technology based on the implementation of theoretical studies and substantiations, is used in the research. Findings. The main hypothesis of a new approach to non-waste coal mining has been formed, in which the priority is not only the process of leaving the maximum waste rock volume in underground cavities, but also its use to form backfill mass, thereby improving the geomechanical conditions for mining thin coal seams. A wide range of mining tasks has been formulated and systematized for using a non-waste coal mining technology. The conditions for the harmonious functioning of the proposed conceptual scheme of a non-waste coal mining technology within the extraction field boundaries have been determined and substantiated. The conceptual foundations for the functioning of a new highly efficient non-waste technology for mining high-quality thermal coal from thin coal seams have been developed. Originality. The scientific novelty is in revealing the mechanism for the effective logistic functioning of rock-transport systems for the accumulation of waste rocks in the underground space using a non-waste technology of coal mining from thin coal seams. Practical implication. The research results can be used in planning non-waste technological schemes for mining the coal with an increased energy potential. Keywords: non-waste technology, waste mine rocks, backfill, selective mining, stope, drifting face, transportation.

Risk Evaluation of Urban Integrated Pipe Corridor Operation and Maintenance Based on Improved AHP‐CIM Model

In order to scientifically and objectively evaluate the risk in the operation and maintenance process of the urban integrated pipe corridor, and then prevent the occurrence of urban integrated pipe corridor operation and maintenance accidents, this paper combines AHP analysis and CIM model to propose a new model for the risk assessment of pipe corridors: AHP‐CIM model, and uses the model to conduct a verification of the operation and maintenance risk evaluation of the Beijing Tongzhou Canal Core Area North Ring Tunnel Integrated Pipe Corridor. Using a combination of qualitative and quantitative methods, the risk factors in the operation and maintenance process of the integrated urban pipe corridor were first identified and their weights determined, and then the CIM model was used to calculate the probability distribution of the levels of risk factors at each level of the hierarchical model, and finally the risk assessment set of the risk probability distribution of this integrated pipe corridor was obtained. The results show that the overall O&M risk level of this integrated pipe corridor is high, and its probability is 69.47%.

Study on Drivers’ Visual Load Features in Lighting Environments of Interior Zones of Extra‐Long Tunnels over 10 km

In extra‐long road tunnels (>10 km), the interior zone accounts for 95% of the total tunnel length. Driving for an extended period in the interior zone of such a tunnel in a monotonous and dimly lit environment causes heavy visual loads for drivers and undermines the safe operation of tunnels and driving comfort. This study investigated the changing patterns of drivers’ visual loads while driving through road tunnels. In a real vehicle experiment, the pupil diameter, fixation duration, electroencephalogram power spectral density, standard deviation of normal to normal, and root mean square of successive differences were used as indicators of drivers’ visual loads. By comparing the differences in psychological and physiological parameters in tunnels of four different lengths, this study discovered the changing pattern of drivers’ visual loads in the interior zone of extra‐long tunnels and merged multi‐source information of various indicators based on the entropy evaluation model to obtain comprehensive visual load values for drivers. The experiment revealed that as the tunnel length increased, the changing patterns of the drivers’ visual load indicators diverged. In particular, the driver’s tension levels began to spike after 180s of driving. The comprehensive visual load values of drivers, combined with the change features of multiple indicators, provide a more accurate and complete assessment of visual loads. The analysis of drivers’ visual load features can provide a theoretical basis for measures to optimise the lighting environment of the interior zone of extra‐long tunnels over 10 km.

Study on the Koshibu Dam sediment bypass tunnel operation based on sediment transport monitoring in upstream reaches

SBTs (sediment bypass tunnels) are a leading technique to mitigate reservoir sedimentation. SBTs consist of a tunnel connecting the upstream and downstream reaches of a dam and diverts sediment-laden flood directly during flood events. A difficulty in operating SBTs is to reduce sediment inflow into the reservoir effectively, and simultaneously sustaining dam functions such as flood mitigation and hydropower generation. To optimize the problem in controlling the timings required in opening and closing the gates in the SBTs, which are governed by the hydrograph and inflow sediment data. Despite many studies on SBT operations considering hydrograph, there are few of those on the temporal change of sediment inflow. Ultimately, this study aims at improving SBT operations by understanding sediment inflow from upstream reaches using an indirect bedload monitoring system called an impact sensor. For this study, the Koshibu River basin was chosen because impact sensors are already placed in several locations around the basin including inside of the SBT. This observation has revealed the amount of transported sediment during each season in a year, are shown with relations between hydrograph and sediment inflow, and the spatial transient of sediment transport peak levels. According to these observations, desirable rules for SBT operations are suggested.

Analysis of the use of transformable elements in intelligent tunnel ventilation systems

All main and auxiliary equipment in the tunnel with an intelligent ventilation system are designed to ensure the safety. These systems “talk” and “listen” to each other, make decisions to switch on/off certain system(s) or part(s) thereof and duly inform the tunnel operator, who is authorized to the centralized control of all systems of necessity. The present article uses the numerical models to assess the efficiency of the transformable elements ensuring safe operation of the tunnels. The idea of their use is based on an artificial increase of the tunnel aerodynamic resistance by means of a flexible element, which will hamper the dissemination of combustion products, but not the movement of people through the tunnel and will help isolate clean and polluted air masses. Such resistance will be used to swiftly divide the tunnel carriageway into smaller sections what will help extinguish the fire as early as at its initial stage, prolong the evacuation time and save lives during the strong uncontrollable fires. As for the compact transformable element, it can be used in both, the operating and the planned tunnels, as it in practice does not reduce the volume of valuable underground space.

Comparison of different damping materials during train vibration at twin tunnels by similarity experiment and DEM

To reduce the disturbance of train vibration to adjacent tunnels during the operation of near-distance twin tunnels, three reduction methods are proposed. In this paper, the vibration mitigation effects of steel plate (SP), concrete zone (CZ), and double liner (DL) on their tunnels and adjacent tunnels during train vibration are compared by scale model and discrete element method (DEM). The distance between twin tunnels is 0.25 D, where D (6.2 m) is the diameter of the tunnel. The results show that CZ can produce a good vibration isolation effect on the first tunnel (T1) and second tunnel (T2). At the same time, SP has a good vibration isolation effect on the liner and surroundings of T2 but has the potential to increase the dynamic characteristics of T1 surroundings. The vibration mitigation effect of the DL on T1 and T2 is the same, and the ratio of weakening effect is about 30%–50%. In summary, the most recommended vibration isolation method in practical engineering is CZ. This study provides a reference for studying the vibration mitigation effect on adjacent tunnels during operation.

Research on prediction method of section convergence and deformation of shield tunnel in operation period based on deep learning

Presently, the tunnel construction of China is changing from “mainly construction” to “equal emphasis on construction and maintenance”. In this context, tunnel structure inspection, monitoring, and maintenance technologies have developed rapidly. However, the effective use and in-depth mining of massive data has always been the most difficult point in this field. Based on deep learning technology, this paper carries out in-depth mining of the multi-source data of the tunnel structure, so that the convergence and deformation of the section during the operation of the shield tunnel is predicted in a short time. Taking the Nanjing Yangtze River shield tunnel project as an example, the indicators are screened based on the fluctuations of the pair wise correlation coefficients of all monitoring indicators. And based on the Keras (a high-level neural network API) framework, a short-term prediction model of the convergent deformation of the shield tube section at this location is established. The results show that the model successfully predicts the convergence of the tunnel section in the next 10 days, and the prediction accuracy reaches 93.6 %. The short-term prediction of key sections and the near warning sections is realized, so as to prevent it in advance.