Tunnel Operation Research Articles

Of the pandemic

Wind tunnel operators have balanced availability and safety measures to guarantee the availability of facilities during the pandemic

Analysis of Optimal Internal Water Pressure During The Operation Period of Ultra-long Water Tunnel

At present, the per capita shortage and imbalance of water resources are the basic national conditions of China, water-conveyance tunnel can solve some this problems. Because the tunnel project is a covert project, people cannot accurately know the operation of the project in advance, and can only basically know the operation state of the tunnel through the existing test means, thus bringing certain blindness to the tunnel operation management. This paper takes the Qiandao Lake Water Distribution Projec as an example, the stability of surrounding rock under different internal water pressure is analyzed and studied by using numerical simulation, and an optimal internal water pressure is obtained, which provides some guidance and suggestions for tunnel operation management and ensures the security of operation.[1][2][3][4][5]

NON-STATIONARY TRANSMISSION OF HEAT AND HYGROSCOPIC MASS BETWEEN VENTIIATION FLOW OF METRO AND SURROUNDING MINING MASSIF

According to modern technologies of construction and operation of transport tunnels, it is assumed in the present work that drainage of water does not occur inside the membrane in the area of reinforced coating of the tunnel and here takes place a non-stationary process of transfer of hygroscopic mass (moisture) together with а similar process of heat transfer between the ventilation stream and the surrounding mining massif. Thus, we have to deal only with the sorption mass content in the pores of the massif and the water in the explicit form in the tunnels can only be in exceptional cases as local sources and therefore, their influence on the ventilation flow should be considered separately. The paper provides results of mathematical modeling of heat and mass transfer processes as well as graphs and nomograms, which can be used to define non-stationary coefficients of the heat and mass transmission required for thermal physics calculation of underground ventilation. The additional flows initiated by the Soret and Dufour effects usually strengthen the main flows, but in practice one can find a case where it is not necessary to take into account the effect of additional flows. Based on the analysis of processes, the criteria that determine the numerical value of these show the case when accounting for additional flows of Soret and Dufour is mandatory. The marked effects can be ignored when 106 Lα=1.

A fluid-solid coupled modeling on water seepage through gasketed joint of segmented tunnels

The water leakage at segment joints of underwater shield tunnels has always been the major concern and trouble to be dealt with in tunneling practices, not only for its threat to the durability and safe operation of tunnels but also for its difficulty to check the leaking process directly in the joints either on-site or in the laboratory test. In order to explore the water leakage mechanism of the segmented tunnel, a Coupled Eulerian-Lagrangian based model considering water flow and large deformation of rubber gasket was developed to simulate the whole process of water seepage through the gasketed joint. A series of numerical modelings were conducted to investigate the seepage pattern and the stress variation during the seepage process, and the dynamic waterproof performance of gasket was investigated. Then, the numerical modeling results were verified against the laboratory test data to prove the reliability of the proposed numerical method. Finally, a formula quantifying the relationship between the waterproof capacity and joint deformations was established, and the critical joint deformation sets were derived from the formula. It was found that the water has an impact effect on the gasket during seepage, which is up to 4 times the initial contact stress. The pressurized water must overcome a cluster of seepage stress barriers to form a seepage path through the gasketed joint. And therefore, the waterproof performance over the length of the gasket-gasket interface is changing and fluctuating with the seepage process, with higher values at both ends of the interface and lower values in the middle. Based on a comprehensive analysis, the critical joint deformation sets (joint opening, joint offset) are recommended for the design and construction of Qiongzhou Strait Tunnel (a planned deep-water shield tunnel in Hainan Province, China) to meet the long-term waterproof capacity of 2 MPa. It is suggested that the assembly accuracy of the segments and gaskets as well as the adhesion of gaskets to joint groove should be strongly guaranteed during the construction process.

Analysis and Prediction of Long-Term Settlement of Metro Shield Tunnel in Saturated Sand

Based on the existing monitoring data, this paper uses the matured data method to analyze, predict the long-term settlement of the subway shield tunnel, and comprehensively analyzes the long-term settlement of the subway shield tunnel in the saturated sand layer of Zhengzhou. Logical curve model, etc. is used to separately predict the long-term settlement of the Zhengzhou metro shield tunnel. Combining the prediction results to summarize the characteristics of the prediction model, a prediction model suitable for the long-term settlement of the subway shield tunnel in the sandy soil area represented by Zhengzhou is obtained, which can be used for the operation of the Zhengzhou subway tunnel. Management and similar engineering projects provide a certain reference basis.

15N natural abundance of vehicular exhaust ammonia, quantified by active sampling techniques

Vehicular exhaust has been identified as an important ammonia (NH3) emission source in urban areas using the stable isotope tracer technique (δ15N); however, its δ15N signature remains poorly constrained due to difficulties in concentrating and speciating NHx (NH3 + particulate NH4+). In this study, we deployed two active sampling techniques, MCIs (Multi-nozzle Cascade Impactor sampler; “particle-gas” order) and CCSCs (ChemComb Speciation Cartridge sampler; “gas-particle” order), to collect vehicular exhaust NHx in a long urban tunnel in Shenyang, China, and quantified the 15N from the collected NH3 and NH4+. While no significant difference in tunnel NH3 concentrations between the two samplers was observed (n = 21), the δ15N-NH3 was slightly higher using the MCIs (6.3 ± 1.6‰) compared to the CCSCs (4.8 ± 2.3‰) during the tunnel operation period. This minor absolute difference of 1.5 ± 2.8‰ may derive from denuder-saturation used within the CCSCs that lead to NHx speciation ambiguity, which also caused significant δ15N-pNH4+ differences between the two sampling approaches. Our results suggest that both active samplers can well characterize the δ15N-NHx in the ambient environment, but the “particle - gas” sampling approach performs better in elevated NH3 concentration environments. We recommend that the δ15N value of 6.3‰ is used as the isotope end member for vehicle NH3 when performing NH3 source apportionment.

Use of saturation diving technique for tunnel boring machine cutterhead intervention in the Tuen Mun–Chek Lap Kok Link Sub-sea Tunnel Project, Hong Kong

The entire Tuen Mun–Chek Lap Kok Link (TM-CLKL) was commissioned on 27 December 2020 and it comprises a 9km-long dual 2-lane carriageway between Tuen Mun and North Lantau, Hong Kong. Construction of the 5km-long sub-sea tunnels was carried out by two 14m diameter Tunnel Boring Machines (TBMs). The tunnel alignment for the TM-CLKL sub-sea tunnel section is in mixed ground condition with the first 500 m in mixed geology of slightly to moderately decomposed granite and completely decomposed granite (CDG), followed by soft ground condition with CDG, alluvial sand, alluvial clay and marine deposit. This mixed ground geology requires regular TBM cutterhead interventions to change the worn-out cutting tools during the tunnelling operation. As the tunnel alignment is up to 55 m below the sea level with the deepest seabed level at -21 mPD, in order to maintain the cutting face stability during the intervention, the intervention pressure could be up to 6 bars. This paper describes different techniques used for TBM interventions under the sea such as trimix bounce mode and saturation mode that appears first time in Hong Kong under a high hyperbaric pressure to change the worn-out cutting tools at the TBM cutterhead.

Outlier Detection Transilience-Probabilistic Model for Wind Tunnels Based on Sensor Data.

Anomaly Detection research is focused on the development and application of methods that allow for the identification of data that are different enough—compared with the rest of the data set that is being analyzed—and considered anomalies (or, as they are more commonly called, outliers). These values mainly originate from two sources: they may be errors introduced during the collection or handling of the data, or they can be correct, but very different from the rest of the values. It is essential to correctly identify each type as, in the first case, they must be removed from the data set but, in the second case, they must be carefully analyzed and taken into account. The correct selection and use of the model to be applied to a specific problem is fundamental for the success of the anomaly detection study and, in many cases, the use of only one model cannot provide sufficient results, which can be only reached by using a mixture model resulting from the integration of existing and/or ad hoc-developed models. This is the kind of model that is developed and applied to solve the problem presented in this paper. This study deals with the definition and application of an anomaly detection model that combines statistical models and a new method defined by the authors, the Local Transilience Outlier Identification Method, in order to improve the identification of outliers in the sensor-obtained values of variables that affect the operations of wind tunnels. The correct detection of outliers for the variables involved in wind tunnel operations is very important for the industrial ventilation systems industry, especially for vertical wind tunnels, which are used as training facilities for indoor skydiving, as the incorrect performance of such devices may put human lives at risk. In consequence, the use of the presented model for outlier detection may have a high impact in this industrial sector. In this research work, a proof-of-concept is carried out using data from a real installation, in order to test the proposed anomaly analysis method and its application to control the correct performance of wind tunnels.

Initial ground stress field regression analysis and application in an extra-long tunnel in the western mountainous area of China

The understanding of the initial ground stress field in a deep and long tunnel can help to optimize the support structure design and reduce the occurrence of collapse and other failures in tunnel construction and operation periods. Daxiangling Tunnel is a deep and long tunnel under multiple faults condition, many collapses, rock bursts, and large deformations occurring during construction. This paper presents a study of initial ground stress field regression analysis in Daxiangling Tunnel. A three-dimensional geomechanical model with faults is established first, which satisfies the deformation compatibility equation at the fault location. Then, according to the superposition principle, the distribution of regional stress field under the fault condition is obtained by the method of partition inversion. The results show that the distribution of the ground stress field in the Daxiangling Tunnel areas is mainly tectonic stress. The horizontal stress in the area is greater than the vertical stress, and the extreme value appears at the maximum excavation depth. Owing to fault extrusion shear, the stress relaxation exists in the stratum near the fault. The regression analysis results are generally consistent with the measured results, and the relative error is controlled within 10%. However, owing to the boundary effect of the finite element model, the regression stress values near the tunnel entrance and exit are distorted. This can be corrected by applying a mathematical statistical method to obtain the initial stress field of the Daxiangling tunnels with higher applicability.

Design analysis of GOS-HEFET on lower Subthreshold Swing SOI

Due to various kind of Band-To-Band Tunneling (BTBT) operation, Heterojunction Tunnel Field Effect Transistors (HEFETs) are widely used in ultralow power applications. Anyhow, circuit complexity is a major issue in case of HEFET based memory development because of their uncomfortable size. Device scaling is a better way to eliminate such kind of issues for HEFET based memory development. Thus, development of Gate-oxide Overlapped Source-HEFET (GOS-HEFET) with lower Subthreshold Swing (SS) based Silicon on Insulator (SOI) is proposed to achieve perfect scaling in this work. Tunneling operation is done with the help of Si-based tunnel devices which are considerably lower than that of MOSFETs. Tunneling rate is enhanced by small bandgap material (Germanium (Ge)) in the source (S) while the ambipolar leakage is minimized by wide band gap material (Silicon (Si)) in the channel. Here, Ge is mainly utilized to dope the source region of P type transistor while Si is used to dope the drain (D) region of N type transistor. Moreover, the tunneling rate of BTBT is enhanced by the geometric alignment of the P and N type transistors with the gate oxide/semiconductor interface. Based on this procedure, five different kinds of SRAM (6 T, 7 T, 8 T, 9 T and 10 T) memory cells are designed. The proposed GOS-HEFET with lower SS on SOI design is implemented using SILVACO TCAD and TANNER CMOS technology. Then, power performance for different temperatures of the proposed method is compared with conventional HEFET based SRAM memory cells.

Justification of the use of a vegetal additive to diesel fuel as a method of protecting underground personnel of coal mines from the impact of harmful emissions of diesel-hydraulic locomotives

Equipment with diesel engines is used in all mining enterprises. Monorail diesel transport is of great importance in coal mines, as it facilitates the heavy labor of workers when transporting materials and people, fixing mining workings, refueling and repairing equipment, which leads to an increase in the speed of tunneling operations. Reducing the concentration of harmful gases from diesel-hydraulic locomotives at the workplaces of coal mine locomotive drivers can be ensured by the use of additives to diesel fuel that reduce the volume of harmful gas emissions during the operation of diesel-hydraulic locomotives. Additive ester-based on vegetal oil in the amount of 5 mass % in a mixture with hydrotreated diesel fuel reduces the concentration of carbon monoxide by 19-60 %, nitrogen oxides by 17-98 %, depending on the operating mode of the engine, the smoke content of the exhaust gases is reduced to 71 %. There is an improvement in working conditions at the workplace of the driver of a diesel-hydraulic locomotive by the chemical factor due to the reduction of the class of working conditions from 3.1. to 2.

Green and sustainable tunnel maintenance activities scheduling under uncertainty

The maintenance of tunnel infrastructure is fundamental to the reliability, safety, and efficiency of tunnel operations. However, environmental deterioration has dramatically changed maintenance scheduling of tunnel infrastructure. Therefore, the trade-off between maintenance cost and environmental impact is crucial when formulating maintenance schedules. This paper extends the preventive maintenance scheduling problem (PMSP) from three perspectives: social impact, environmental impact, and unexpected maintenance over the entire planning horizon. We then propose a stochastic bi-objective integer programming model to minimize the total cost and CO2 emissions of tunnel maintenance over the entire planning horizon. The model is applied to a case study developed for the Dalian Road Tunnel in Shanghai. A scenario-based method is adopted to account for uncertain failures. A hybrid algorithm using particle swarm optimization (PSO) and genetic algorithm (GA) is proposed to solve the model in realistic large-scale environments. Extensive numerical experiments are performed to verify the effectiveness of the proposed model and the efficiency of the proposed algorithm. Some meaningful management implications are revealed based on the experimental results.

Anti-Collision Systems in Tunneling to Improve Effectiveness and Safety in a System-Quality Approach: A Review of the State of the Art

Tunnelling and underground construction operations are often characterized by critical safety issues mainly due to poor visibility and blind spots around large vehicles and equipment. This can lead to collisions between vehicles or between vehicles and pedestrians or structural elements, causing accidents and fatalities. To improve the OS&H conditions, it is important to investigate the possible introduction of innovative techniques and technologies to reduce the occurrences and consequences of shared spaces (spaces used by both vehicles and pedestrians). For this reason, research was conducted to investigate the possible use of different technologies of anti-collision systems in tunnelling operations. First, to achieve this goal, an extensive review of the literature was carried out in accordance with the PRISMA statement to select the current techniques and technologies used by general anti-collision systems in civil and mining construction sites. Then, the operating principles, the relative advantages and disadvantages, combinations, and costs were examined for each of these. Eight types of systems and many examples of applications of anti-collision systems in underground environments were identified as a result of the analysis of the literature. Generally, it was noted that the anti-collision techniques available have found limited application in the excavation sites of underground civil works up to the present day, though the improvement in terms of safety and efficiency would be considerable.

Modelling the construction and long-term response of Göta Tunnel

This paper presents a benchmark of a rate-dependent constitutive model for soft soils, implemented in a 2D finite element code, against the response of an instrumented excavation in sensitive clay: Göta Tunnel in Gothenburg. The monitoring data, which comprise time-series of pore water pressures, displacements, earth pressures and strut forces, provide valuable insights of the time-dependent response during the construction period. The long-term response, in terms of the ongoing settlement rates, is assessed using remote sensing data. The results of the numerical simulations demonstrate that the constitutive model, Creep-SCLAY1S, is capable of capturing the observed response. The trends of vertical and horizontal displacements are captured well until the stage of dewatering, and the evolution of pore pressures and earth pressures is computed with high accuracy, excluding peaks in the measurement values arising from pile and rock anchor installation. Most importantly, the results demonstrate that the rate-dependent model enables to model the complete service life of the tunnel, from construction of the excavation to the tunnel operation, with one unified model parameter set. Furthermore, the comparisons highlight the importance of assessing installation effects both in the choice of construction methods and modelling.

Reliability evaluation for ventilation system of gas tunnel based on Bayesian network

The ventilation system is the only channel for gas exchange inside and outside the gas tunnel. Therefore, it is very important to evaluate its reliability for the safe operation of the gas tunnel. In this paper, the ventilation system of gas tunnel in Songjiang District of Shanghai City is taken as the study object, a fault tree model of the ventilation system is established, and a corresponding evaluation model of Bayesian network is formed according to the mapping rule. The fuzzy probability obtained from the fuzzy set theory and the multi-layer expert judgment is taken as the prior probability, the reliability evaluation of the ventilation system was carried out. Finally, the hierarchical management measures of the ventilation system are formulated. The results are as follows: (1) The main risk sources of the ventilation system include the third party damage, system aging, design defect and misoperation. (2) The aging of exhaust fan and no emergency and alarm function seriously reduce the reliability of the ventilation system. (3) The events with high sensitivity and promoted index to the failure of the ventilation system are completely consistent and concentrated on the system aging and design defect. (4) The aging of lines, exhaust fan and alarm instruments are the most likely evolution paths of the failure of the ventilation system. (5) At present, the reliability level for the ventilation system of gas tunnel in Songjiang District of Shanghai City is level IV, and it can run safely.

Diagnostics of condition of soil lying in the foundation of sewer collectors and metro tunnels by crosshole sounding method in urban underground space

Non-destructive geophysical crosshole sounding method can be used to control and monitoring the condition of natural and improved soils. This work studies the application of the crosshole sounding method to determine the condition of soils lying in the foundations of sewer collectors and tunnels. The investigation uses crosshole sounding apparatus APZ-1 developed by LLC “Geodiagnostika”. The study considered the results of crosshole sounding of soils at the site of the reconstruction of the Church of The Icon of the Mother of God “Joy of All Who Sorrow” and on the section of buried metro tunnels between “Lesnaya” and “Ploschad Muzhestva” stations in St. Petersburg (Russia). The author postulates that crosshole sounding provides the most accurate information about the foundation soils for making a decision on strengthening them for trouble-free operation of sewer collectors and tunnels.

Research on the Construction Technology of Tunnel Internal Air Circulation Purification under High-Quality Air Quality

As the traffic volume increases, the air quality in the tunnel decreases. In order to ensure the health of the tunnel staff and the safety of tunnel operation, and to better play the role of the duty room in the tunnel, through the test and analysis of the tunnel ventilation and environment, it is proposed to take the air in the tunnel and circulate the purification and the roots blower to send and exhaust air. The design scheme combining methods effectively solves the design problems of small air volume and high air pressure of the air purification system in the tunnel, and has reference significance for the safe operation of similar long road tunnels.

On Inflow to a Tunnel in a Fractured Double-Porosity Aquifer.

Inflow to a tunnel is a great public concern and is closely related to groundwater hydrology, geotechnical engineering, and mining engineering, among other disciplines. Rapid computation of inflow to a tunnel provides a timely means for quickly assessing the inflow discharge, thus is critical for safe operation of tunnels. Dewatering of tunnels is another engineering practice that should be planned. In this study, an analytical solution of the inflow to a tunnel in a fractured unconfined aquifer is obtained. The solution takes into account either the spherical or slab-shaped matrix block and the unsteady state interporosity flow. The instantaneous drainage water table and anisotropic hydraulic conductivities of the fractures network are also considered. Both uniform flux and uniform head boundary condition are considered to simulate the constant head boundary condition in the tunnel. The effects of the hydraulic parameters of the fractured aquifer on the inflow variation of the tunnel are explored. The application of the presented solution to obtain the optimum location and discharge of the well to minimize the inflow to a tunnel is illustrated.

System design and experimental verification of an internal insulation panel system for large-scale cryogenic wind tunnel

With the rapid development of aerodynamics for high speed aircraft, the flight experiments need to be carried out under ultra-high Reynolds number condition to simulate actual high-speed flight conditions, which puts forward higher requirements for the wind tunnel. Reynolds number increases rapidly as the decrease of the flow temperature because the viscosity of the working gas decreases and the density increases. As a result, a pressurized tunnel at cryogenic temperature can provide real-flight Reynolds numbers. Therefore, cryogenic wind tunnel is one of the best testing facilities to rech ultra-high Reynolds number. The thermal insulation system is crucial for the design and operation of the cryogenic wind tunnel. In this paper, the features of an internal insulation system for the cryogenic wind tunnel are firstly highlighted in comparison with traditional insulation systems. The internal thermal insulation system for the cryogenic wind tunnel is discussed. In order to evaluate the thermal insulation performance, the heat transfer calculation for a typical wind tunnel region with the diameter of two meters is carried out using finite element method based on the analyses of the heat transfer conditions. The averaged heat load from the environment is obtained to optimize the liquid nitrogen consumption during the wind tunnel operation. The thickness of the panel should be 150 mm to reach the design target of averaged heat flux 60 W/m2. Meanwhile, the typical region is constructed according to the new internal insulation system. Cryogenic test is conducted and it is proven that the new internal insulation system could efficiently prevent the environment heat flow and ensure the normal operation of the cryogenic wind tunnel.

Prediction of drilling rate index from rock strength and cerchar abrasivity index properties using fuzzy inference system

Rock drillability characteristic is one of the important properties for mining and tunneling operations. The rock drillability can be determined by using the drilling rate index (DRI) for engineering applications. The present study attempts to develop a practical and convenient DRI estimation model by using rock strength and abrasivity properties. For this purpose, fuzzy inference system (FIS) being an accurate prediction model was applied to predict DRI by using experimental data obtained with 37 different rocks. The predictive FIS based on experts knowledge by taking mechanical and abrasivity properties as input parameters was created on MATLAB. This structure was carried out by using Mamdani extraction method. DRI values obtained experimentally and estimated from the FIS model were compared. This comparison is given with statistically reliable (R2=0.9277) results. In order to prove the validity of the FIS model for DRI prediction, a validation process has been performed by using test data as well. The performance determination coefficients (R2) are found as 0.9513 by using test data. As a result, it was found that DRI values can be predicted very efficiently and accurately with the proposed prediction method.