Tunnel Type Research Articles

Analysis of Excavation Parameters on Face Stability in Small Curvature Shield Tunnels

This study investigates the face stability of small curvature shield tunnels during excavation and its relationship with various excavation parameters. The stability of the excavation face is critical to the safety and efficiency of underground construction projects. Despite the increase in the use of small curvature shield tunnels in urban areas, research works on this type of tunnel are limited and the existing literature focuses only on straight shield tunnels. This study addresses this research gap through numerical simulations, analyzing the effects of different excavation parameters such as jacking force, cutting speed, and soil conditioning on face stability. The results of the study show that the excavation parameters significantly affect face stability. The findings can be used to optimize the performance of small curvature shield tunnels and support their continued development in urban areas.

Overall Resilient Evaluation of Surrounding Rock of In-Service High-Speed Railway Tunnel Based on Information Fusion-Improved Fuzzy Matter-Element

Once the high-speed railway tunnel is put into use, its resilience will determine the possibility of permanent safety of the tunnel due to the closure of the structural space of the high-speed railway tunnel in service. Resilience theory is introduced into a risk analysis of operating high-speed rail tunnels to improve the ability to respond to risks in operating high-speed rail tunnels and to relieve the aging phenomenon caused by changes in the tunnel with time. First, an evaluation framework for the safety resilience of existing high-speed railway tunnels is constructed. Starting from the attributes of resilience such as resistance, adaptability, and resilience, and considering the characteristics of high-speed railway tunnels, protective measures, emergency management measures, and other factors, we fit the risk factors and probability of accident type of the high-speed railway tunnel and establish a tunnel safety resilience evaluation index system with 10 indexes. Secondly, the method of information fusion is used to combine subjective weighting and objective weighting. Then, the comprehensive weight of the evaluation index is obtained based on the principle of minimum discriminant information. Thirdly, the system resilience evaluation model based on the TOPSIS improved fuzzy matter-element is constructed to determine the classification criteria of resilience. On this basis, based on the temporal and spatial variability of the ductile tunnel, the concepts of ductile transition and ductile attenuation are introduced and the tunnel toughness optimization model is established to suppress the attenuation situation, enhance the transition ability, and then improve the system resilience level. On this basis, an optimal lifting scheme is obtained. Finally, taking Ai-Min tunnel of Ha-Mu high-speed railway as the engineering background, the flexibility of the resilience system is calculated, and the resilience grade (3) of the rock system surrounding the tunnel is obtained. Combined with the numerical model, improvement measures for specific tunnel facilities are proposed. The results show that the Ai-Min tunnel system has a general ability to resist external intrusion and prevent disasters, and the resilience level is general. It should focus on improving the resilience level of the transition index. The resilience evaluation results of the evaluation model are consistent with the actual situation of the project.

A Study on the Formation Mechanism and Calculation Method of Surrounding Rock Pressure in Shallow-buried Loess Tunnel Considering the Influence of Vertical Joints

Vertical joints have significant effects on the stability of shallow-buried loess tunnel. Due to the presence of vertical joints distributed widely in loess, the formation mechanisms of surrounding rock pressure on shallow-buried loess tunnel and its computational method are far different from those in other types of soil tunnel. In this study, the distribution characteristics of surrounding rock pressure in shallow-buried loess tunnel were investigated, and discrete element software 3DEC was used to analyze the formation mechanism and development process of surrounding rock pressure in loess tunnel under the influence of joints. We correlated the stratum deformation characteristic with the frictional force caused by the mutual dislocation between joints, and revised the semi-empirical method (Chinese Code methods) in China. The results show that the measured data of radial surrounding rock pressure of shallow-buried loess tunnel are generally between 0–600 kPa, and 80% in the range of 0–200 kPa. The surrounding rock pressure increases with the burial depth, while the distribution of lateral pressure coefficient is relatively discrete. The existence of loess vertical joints (LVJs) aggravates the uneven distribution of the vertical pressure above the tunnel, and the reduction of the lateral earth pressure coefficient at rest under the influence of joints leads to an increase in pressure near the arch shoulder, these two constitute the essence of the joints action on the surrounding rock pressure. The surrounding rock pressure of the shallow-buried loess tunnel reaches the peak stress at about 0.5D from the tunnel face (D is the tunnel span), which is about 1.04–1.32 times of the initial stress. After the excavation of the upper step, the stress of the tunnel crown monitoring point decreased to about 60% of the initial stress. Compared with ignoring the influence of joints, the time of reaching the peak stress at the arch shoulder monitoring point is earlier, and the final stress release degree is smaller. The comparison of the analytical results (proposed method) with the numerical results and the field data exhibits good agreement, proving the proposed method's correctness.

FECC: DNS tunnel detection model based on CNN and clustering

As the basic service of the network, the Domain Name System (DNS) is almost never blocked by the firewall. DNS tunnel takes advantage of this feature of DNS service to achieve barrier-free communication between the internal network and the external network, thereby implementing malicious network activities such as data theft and Command & Control (C2) control. As an intrusion means, DNS tunnel constitutes a serious threat to network security. At present, some research work on DNS tunnel detection is implemented based on manual features, which are “explicit” features. DNS tunnels can specifically circumvent these “explicit” features as they are designed, rendering detection methods ineffective. Additionally, the quality of these manual features also relies heavily on expert knowledge. The features extracted by the detection method based on convolutional neural network (CNN) have the characteristics of “implicit” that are not easily circumvented by DNS tunnels. However, the homogeneity and exclusivity of features are not considered in the existing research works that only perform the model training for classification tasks on datasets with limited sample types. This can cause the model to fail when detecting variants or new types of DNS tunnels. This paper proposes a novel DNS tunnel detection model, called FECC (Feature Extraction CNN and Clustering), to effectively detect various DNS Tunnel traffic. FECC takes the payload of the transport layer as input without preprocessing. The model uses a CNN-based module to extract features, then the homogeneity and exclusivity of features are evaluated based on the clustering method. FECC uses a cluster-based loss function to optimize the model parameters, which greatly improves the detection rate of the model for both classification tasks and unknown types of DNS tunnels, and further reduces the false positive rate. We have deployed a variety of DNS tunnel tools in the laboratory environment and constructed multiple datasets for sufficient comparison experiments. The experimental results show that FECC is a very effective DNS tunnel detection model.

The Effect of Tibial Tunnel Drilling Technique on Retained Intra-Articular Bone Debris Following Anterior Cruciate Ligament Reconstruction

To assess the effect of tibial tunnel drilling technique (retro-drilled bone socket vs full tibial tunnel) on the presence and grade of postoperative, intra-articular bone debris following primary hamstring anterior cruciate ligament (ACL) reconstruction. This was a retrospective cohort study of primary hamstring autograft ACL reconstructions performed by 2 surgeons. Two blinded independent reviewers assessed the presence and length of retained intra-articular bone debris on the immediate postoperative lateral radiograph. Debris was graded according to a predefined 5-point ordinal grading system: grade 0 (no debris) to IV (severe debris). Results were analyzed according to the type of tibial tunnel; retro-drilled socket or full tibial tunnel using Kappa statistics and the Mann-Whitney U test. Sixty-five patients undergoing primary hamstring ACL were included (39 tibial socket: 26 full tibial tunnel). Bone debris was observed among the tibial socket technique in 29 of 39 instances (74.3%), compared with 14 of 26 (53.8%) instances for the full tibial tunnel technique (P= .09). Where there was measurable debris present, the tibial socket group had a mean length of bone debris of 13.7 ± 6.2 mm as compared with the full tibial tunnel, 10.0 ± 4.7 mm (P= .165). There were significant differences in bonedebris gradings between the 2 treatment groups, with tibial sockets having an overall greater grade (P= .04). A difference in the presence of, or length of, retained bone debris on the postoperative lateral radiograph was not demonstrated between the retro-drilled bone socket and full tibial tunnel techniques. However, when bone debris was present, greater grades of debris were seen in the retro-drilled socket group. III, retrospective, comparative study.

A Comprehensive Review of Tunnel Detection on Multilayer Protocols: From Traditional to Machine Learning Approaches

Tunnels, a key technology of traffic obfuscation, are increasingly being used to evade censorship. While providing convenience to users, tunnel technology poses a hidden danger to cybersecurity due to its concealment and camouflage capabilities. In contrast to previous studies of encrypted traffic detection, we perform the first measurement study of tunnel traffic and its unique characteristics and focus on the challenges and solutions in detecting tunnel traffic among traditional and machine learning techniques. This study covers an almost twenty-year research period from 2003 to 2022. First, we present the concepts of two types of tunnels, broad and narrow tunnels, respectively, as well as a framework for major tunnel applications, such as Tor (the second-generation onion router), proxy, VPN, and their relationships. Second, we analyze state-of-the-art methods from traditional to machine learning applications to systematize tunnel traffic detection, including HTTP, HTTPS, DNS, SSH, TCP, ICMP and IPSec. A quantitative evaluation is presented with five crucial indicators applied to the detection methods and reviews. We further discuss the research work based on datasets, feature engineering, and challenges that have are solved, partly solved and unsolved. Finally, by providing open questions and the potential directions, we hope to inspire future work in this area.

The time-dependent grout buoyancy behavior based on cement hydration mechanism

The grout buoyancy has a great influence on the segment during synchronous grouting of shield tunnel. Traditionally, the large buoyancy leads to certain types of tunnel distresses, such as convergence deformation, differential settlement, cracks, and water leakage. This paper made a detailed study on the time-dependent grout buoyancy behavior. The hydration heat test and LF-NMR test were carried out. Then the four periods of hydration rate curve were revealed, and the evolution rules of gel water, capillary water and free water were also obtained. The time-dependent grout buoyancy was tested by self-designed equipment, and the theoretical formula of grout buoyancy considering w/c ratio and time was proposed. The indoor test results were compared with the theoretical solution. The theoretical formulas could effectively predict the size and variation rules of buoyancy. The indoor test results showed that variation trend of cement grout buoyancy is consistent with the hydration rules. The buoyancy mainly exists in the initial period and the induction period, and decreases sharply to zero before the acceleration period. The initial setting moment is the one in which hydration rate is the largest.

Experience in the Treatment of Breast Cancer Using Tunnel Type Linear Accelerator

Purpose: Describes the features of dosimetric planning for breast cancer and conducts statistics analysis of the radiation treatment planning results, while taking into account 2.5 years of work experience on the Halcyon linear accelerator at the Irkutsk Regional Cancer Center.
 Materials and methods: Varian Halcyon tunnel type linear accelerator and Varian TrueBeam C-arm linear accelerator were used for breast irradiation. Treatment planning was performed in the Eclipse planning system, Acuros dose calculation algorithm. The experience of using the specified equipment and developments in the field of radiation treatment planning using the Halcyon system are presented.
 Results: Developed an approach to planning breast radiation at the Halcyon linear accelerator. A retrospective analysis of 84 radiation treatment plans on linear accelerators of various types was carried out. Breast treatment plans for Halcyon linear accelerator have equal dosimetric parameters in comparison to the TrueBeam treatment plans.
 Conclusion: Linear accelerator Halcyon can be used for treating breast cancer if staff understands specifics of treatment planning and treatment delivery.

Two New Methods for Defining Shut-In Pressure in Hydraulic Fracturing Tests

Hydraulic fracturing is one of the most common methods to determine in situ rock stress. The interpretation of the shut-in pressure to determine the minor principal stress is an important element of this method, and many different methods to interpret shut-in pressure have been studied and developed throughout the years. Each method has its advantages and disadvantages. With more than 50 years of research and development within the rock stress measurement field, especially in HF, SINTEF has established two practical ways of defining shut-in pressure. These methods are independent and termed zero flow and water hammer. The zero flow method has been used by SINTEF in more than 130 projects over the last 30 years. The methods clearly differ from the other methods as they are based on singular events in the development of pressure/flow versus time which enables us to read the shut-in pressure directly during testing. In this paper, a comparison is made between different methods for interpretation of shut-in pressure, including 12 existing methods and the 2 SINTEF methods. Comprehensive laboratory tests were performed, and a field test was selected from SINTEF’s database for demonstration and comparison of the methods. The SINTEF methods have been developed mainly for use in hard rock environment where the rock is a jointed aquifer and with low permeability. The application of the two methods has traditionally been hydroelectric power development, different types of tunnel, and cavern projects, and also in mineral mining. The methods have not been used in deep petroleum applications such as oil wells or offshore in porous rock types.

Kernel broken smooth particle hydrodynamics method for crack propagation simulation applied in layered rock cells and tunnels

Understanding the cracking process of layered tunnels requires a high-fidelity method. Improved smooth particle hydrodynamics (SPH), termed kernel broken SPH (KBSPH), was implemented to simulate the crack propagation and deformation of layered rock cells and field layered tunnels with dip angles of 0°–90°, and the results were compared with those of the laboratory tests. Three attempts, including the bedding angle, interlayer distance, and lateral pressure coefficient, were made to investigate the crack propagation and deformation of layered tunnels. Finally, the pros and cons of the KBSPH method applied in the rock field were compared with those of other methods. The results indicate that the KBSPH can explicitly reproduce crack propagation by improving the kernel function with a totally damaged symbol, and the deformation responses have been captured reasonably. We infer that this method is effective and rapid in crack propagation and large deformation simulation for other types of rock tunnels.

Comparative Clinical Evaluation of Trapezoidal, Envelope, and Tunnel Type Coronally Advanced Flap in the Treatment of Gingival Recession: A Network Meta-Analysis of Randomized Clinical Trials.

This study evaluated the efficacy of trapezoidal coronally advanced flap (tCAF), envelope coronally advanced flap (eCAF), and coronally advanced tunnel flap (TUN) in treating gingival recession (GR) through a network meta-analysis. Eligible articles from the PubMed, Embase, and Cochrane Library databases published up to September 2020 were selected to identify randomized controlled trials (RCTs) on tCAF, eCAF, and TUN treatments. Sample size, treatment time, and outcome measures including complete root coverage (CRC), root coverage esthetic score (RES), and other data were extracted from the article, and integrated analysis was conducted. In total, 10 RCTs met the inclusion criteria, involving 310 patients. Direct meta-analysis showed no significant differences in CRC among the three surgical methods; A significant difference was seen for RES, with TUN worse than tCAF (weighted mean difference: -0.73; 95% CI: -1.44, -0.02; P = .045). The network meta-analysis showed no statistical significance in the cross-comparison of tCAF, eCAF, and TUN. However, eCAF had the most significant effect on improving CRC (SUCRA = 69.2) and RES (SUCRA = 85.0). eCAF has the best prognosis in the treatment of GR, followed by tCAF and TUN. This may influence the surgeon's treatment choice, as eCAF may be more effective in root coverage procedures.

Seismic Response of Mountain Tunnels by Comprehensive Analysis Methods and Feasible Aseismic Measures

In mountainous area, earthquake is an inevitable factor during the construction of tunnel. Earthquake can cause great damage to faults and mountain slopes, and at the same time, the deformation and failure of mountain tunnels are closely related to faults and landslides. This study analyzes the impacts of faults and landslides on the mountain tunnel by numerical modelling, model test and field investigation, and discusses the corresponding engineering countermeasures. Mountain tunnel through fault tends to be damaged severely because it may be shorn by fault dislocation. However, the fractured tunnel may undergo even severer damage due to earthquake wave. Various factors, including earthquake wave, condition of surrounding rock, width of fault, relative position of fault and tunnel, fault friction velocity, fault activity and lining section type, affect the seismic performance of tunnel through fault. In addition, buffer layer, grouting, shock absorption gap, sectional tunnel lining with flexible joints, fiber reinforced concrete lining, and ultra-excavating are all available aseismic or anti-dislocation measures. The damage mode and degree of landslide to tunnel are related to the type of tunnel, and the different relative positions of the tunnel and the sliding surface controls damages. Landslide prevention and control engineering measures mainly include weight loss, drainage, construction of retaining works, improvement and reinforcement of soil and rock properties of sliding zone, etc.

CARBON FOOTPRINT OF A CONCRETE TRANSPORT STRUCTURE - A DEEP TUNNEL

The research object of this scientific work is the massive concrete structures of underground low-deep transport tunnels, reinforced with steel and non-metallic composite reinforcement. Circular-section tunnels with the frame nominal diameters of 5, 10 and 15 m are considered. The subject of the research study is the assessment of the averaged carbon footprint in both types of the constructive solution throughout their entire life cycle. The presented research is due to the need to implement the European Climate Law (the European Green Agreement. At the same time the Paris Agreement (2016) recommends to stop producing and using carbon steel in construction by 2030. The ecological impact of both types of transport tunnels is expressed in the form of carbon footprint, as the equivalent of carbon dioxide emissions, which is calculated separately for each stage of their existence in accordance with the current European Codes, including the recommendations of the proprietary methodology. To determine the required sizes of the tunnels concrete frames and their reinforcement, the numerical routine (B3) experiment was carried out in PLAXIS software complex in accordance with the current regulations. Averaged according to three different diameters and generalized carbon dioxide emissions during the life cycle of the reference structure (type 1) and proposed one (type 2) of the underground transport tunnel with the length of 1 m.p. were, respectively, 15.97 t СО2 eq and 11.551 t СО2 eq, i.e. decreased by almost 1.4 times. The conducted research made it possible to analyze the carbon dioxide emissions into the atmosphere, to systematize the existing factors and impact factors of the specified building on the environment, and to determine the ways of their reduction. The possibility and expediency of using basalt-plastic reinforcement instead of steel in monolithic concrete structures, incl. transport tunnels, according to the criterion of reducing greenhouse gas emissions are proved. Keywords: carbon footprint, carbon dioxide emissions, underground transport tunnel, monolithic heavy concrete, steel and non-metallic composite reinforcement, construction life cycle, stage, information group (module).

Direct generation of finite element mesh using 3D laser point cloud

An approach for the finite element (FE) mesh generation of tunnel structures considering the lack of detail, low automation, and intermediate link transformation in the FE mesh generation of tunnels based on the 3D laser point cloud is presented in this paper. To this end, we acquired the tunnel point cloud model using terrestrial laser scanning or mobile laser scanning, and uniform nodes from the raw point cloud using a clock simulation extraction algorithm we developed. In addition, we assign topology information to these nodes. Further, we generated an FE model of the tunnel structure suitable for numerical simulation analysis using Abaqus. We applied the developed method to three types of tunnels; the mesh satisfied the evaluation standards of practical engineering applications. We examined the impact of mesh size and used an engineering example to confirm the method's accuracy. Finally, we provide recommendations for future research considering the future trend of FE mesh generation based on the 3D laser point cloud and its improvements.

Lead selenide microcrystals fabricated by the pulsed laser welding technique employed as 6G technology microwave resonators and as MOS capacitors

PbSe microcrystals are fabricated by the pulsed laser welding technique in Ar atmosphere within 2 min. The microcrystals showed cubic structural phases of PbSe in addition to tetragonal SeO2. PbSe microcrystals exhibited layered structure composed of 200 nm thick layers. Electrical characterization on these crystals (Ag/PbSe/Ag) revealed tunneling type current-voltage characteristics. Large resistive response to an imposed ac signal in the microwave frequency domain has been shown. In addition, the cutoff frequency (fco) spectra displayed fco value larger than 100 GHz nominating the devices for 6G technology applications. Moreover, investigations on the current conduction mechanism have shown the preferred current conduction by quantum mechanical tunneling accompanied with correlated barrier hopping. On the other hand, measurements of the capacitance-voltage characteristics in the frequency domain of 1.0–100 MHz showed performance of the Ag/PbSe/Ag structures as a metal-oxide- semiconductors (MOS) devices suitable for energy storage at ultrashort times.

Enhanced Optical and Electrical Interactions at the Pt/MgSe Interfaces Designed for 6G Communication Technology

AbstractMagnesium selenide thin films are coated onto glass and semitransparent Pt substrates (nanosheets) by the vacuum evaporation technique under a vacuum pressure of 10−5 mbar. The effect of Pt nanosheets of thicknesses of 100 nm on the structural, compositional, optical, and electrical properties of MgSe is explored. It is found that platinum nanosheets enhance the light absorbability in the visible and infrared ranges of light. They slightly redshift the energy bandgap and decrease the dielectric constant. The strong interaction between Pt and MgSe increases the electrical conductivity by five orders of magnitude. Pt forms shallow impurity levels in the energy bandgap of MgSe allowing the tunneling process at the Pt/MgSe interfaces. Practically, a Pt/MgSe/Pt tunneling type device is fabricated and tested by the microwave impedance spectroscopy technique. It is found that Pt/MgSe/Pt devices can exhibit resonance–antiresonance and negative capacitance effects which are important in electronic circuits as parasitic capacitance cancelers, signal amplifiers, and noise reducers. In addition, evaluation of the cutoff frequency spectra has shown the ability of using the Pt/MgSe/Pt devices as microwave resonators appropriate for 5G/6G technologies. A cutoff frequency larger than 70 GHz can be achieved by imposing ac signal of amplitude of 0.10 V.

Study on the Influence of Internal Water Pressure on the Internal Force of Circular Hydraulic Tunnel Lining

The internal water pressure condition influences the internal force of the circular hydraulic tunnel lining. However, calculating the lining’s internal force of this type of tunnel still lacks practical theory. Based on the modified routine method and the theory of structural mechanics, the internal stress model of the tunnel section is established in this paper. The general calculation formula of lining internal force is deduced by considering arbitrary water level height and different water conveyance pressures. The formula is used to calculate the internal force of the lining under the action of internal water pressure and the influence laws of water level height and water conveyance pressure are explored, respectively. In addition, case analysis was carried out for several typical projects. The results show that the maximum internal force of the lining increases with the increase of water pressure and inner radius and the maximum internal force is in a fixed special position when the water is conveyed under pressure. When the water is conveyed without pressure, the internal force of the lining will increase with the increased water level. However, the maximum bending moment and axial force will reduce at the special water level. This calculation theory considering different working conditions of internal water pressure solves the calculation problem of the internal force of a circular hydraulic tunnel. It improves the design theory of tunnel structure and provides a theoretical basis for this type of tunnel’s structural design and safe operation.

How To Identify The Quality Figs?

Fig production is carried out in a very limited number of countries in the world, and accordingly, the number of countries producing dried figs is quite low. In this study, a small scale tunnel type greenhouse model dryer was designed and manufactured. In this study, the process of drying figs with hot air was carried out by using a combination of uninsulated greenhouse and collector system. Sarılop fig variety was chosen as the food to be dried. The experiments were carried out in Aydın in August 2021. Drying parameters were determined for figs. In addition, the figs offered to the market throughout the province were examined, the practices that should be done to prevent drying damage in figs were determined, and the answer to the question of how to understand quality figs was sought. In the preparation of the study, the studies of the provincial directorate of agriculture, TÜİK reports, visual and printed documents were also examined.

Design and Manufacturing of Wind Tunnel for Turbine Impeller Airfoil Testing

In this study, the design of a wind tunnel was carried out to observe airflow through an airfoil, streamlines and turbine blades. To accommodate this, in this study a design was made of an open return wind tunnel. In this case, an open circuit wind tunnel type will be made because the construction is simpler and the manufacturing costs are relatively cheaper compared to the closed circuit wind tunnel type. The Wind Tunnel is designed with Open CLosed Wind Tunnel (OCWT) type. The OCWT is designed to consist of fan and housing, diffuser, test section, contraction, honeycomb. The OCWT design uses an operating fan to circulate air into the test section. The maximum air speed in the Test Section is 5 m/s with a flow that is closed to laminar. The recommended diffuser has a dimension of 50 cm on the side that is attached to the test section and 52 cm on the side facing the fan with an inclination angle of 1.79o. The driver uses a 16 inch exhaust fan with a power of 74 W to make the flow in the Test Section stable at a speed of 2 m/s.

Research on the Safety Thickness of Tunnel Outburst Prevention in Water-Rich Fault Fracture Zone Based on Janssen’s Theory

In the construction of tunnel in water-rich fault fracture zone, when the thickness of outburst prevention is insufficient, it is very easy to cause water and mud inrush engineering accident. Therefore, it is very necessary to study the safety thickness of outburst prevention for this type of tunnel. In this paper, the expression of in situ stress in water-rich fault fracture zone is derived based on Janssen’s theory. Two mechanical models of outburst prevention rock mass are established, and according to the shear balance theory, the calculation formula for the safe thickness of outburst prevention is determined and the parameter sensitivity analysis is carried out. Finally, it is verified by engineering examples and numerical simulation. The results show that: (1) the calculation formula of outburst prevention thickness proposed in this paper is more perfect and shows good prediction effect for deep- and shallow-buried tunnels; (2) the greater the angle α between tunnel axis and fault zone and the dip θ of fault fracture zone, the smaller the critical safety thickness of outburst prevention and the safer it is for tunnel construction; (3) when the fault fracture zone inclines inward relative to the tunnel face, the gravity of the rock mass in the fault zone will lead to an increase in the safety thickness of outburst prevention, and reinforcement measures should be taken during actual construction.