Tunnel End Research Articles

Scaled Model for Studying the Propagation of Radio Waves Diffracted from Tunnels

One of the major challenges in designing a wireless indoor–outdoor communication network operating in tunnels and long corridors is to identify the optimal location of the outside station for attaining a proper coverage. It is required to formulate a combined model, describing the propagation along the tunnel and the resulting diffracted outdoor pattern from its exit. An integrated model enables estimations of the radiation patterns at the rectangular tunnel exit, as well as in the free space outside of the tunnel. The tunnel propagation model is based on a ray-tracing image model, while the free-space diffraction model is based on applying the far-field Fraunhofer diffraction equation. The model predictions of sensing the radiation intensity at the tunnel end and at a plane located at a distance ahead were compared with experimental data obtained using a down-scaled tunnel model and shorter radiation wavelength correspondingly. This down-scaling enabled detailed measurements of the radiation patterns at the tunnel exit and at the far field. The experimental measurements for the scaled tunnel case fit the theoretical model predictions. The presented model accurately described the multi-path effects emerging from inside the tunnel and the resulting outdoor diffracted pattern at a distance from the tunnel exit.

Analyses of the Ground Surface Displacement under Reinforcement Construction in the Shield Tunnel End Using the Artificial Ground Freezing Method

There are stringent requirements on the vertical movement of a ground surface when using artificial ground freezing method to reinforce a shield tunnel in a city. This paper focused on the tunnel of Nanjing Metro Line Two between Yixianqiao and Daxinggong. Based on the discrete element thermo-mechanical coupling theory, the horizontal freezing reinforcement project was numerically simulated. The numerical results of the soil temperature field and displacement field are approximately compatible with the field measurements. When the tunnel was frozen for 40 days, an effectively frozen soil wall was created and satisfied the construction requirements. During the freezing construction, both frost heave and thaw settlement obviously occurred. Above the tunnel, the vertical deformation of the ground surface was symmetrical about the center of the tunnel and decayed towards the ends. The maximum vertical displacement of ground surface frost heave was 8 mm, and the maximum vertical displacement of ground surface thaw settlement was 18 mm. Increasing the depth of the tunnel embedment can result in a decline in ground surface displacement. The study serves as a viable means of predicting ground surface displacements.

Investigation of shock waves reflected at the end of a Hyperloop tube

In this study, a Hyperloop pod travelling beyond the Kantrowitz limit in a tunnel of finite length was studied using analytical methods and computational fluid dynamics simulations. Impact on a pod of a shock reflected off the tunnel end wall was observed, resulting in an instantaneous 35% increase in drag across a range of blockage ratios. After impact, further reflections of shocks resulted in continuous drag increase to a peak of 230%. The temperature at the tunnel wall was estimated to rise 26.5 K due to the increase in absolute pressure upstream of the pod. Multiple tunnel-end geometries were proposed to dissipate or delay an incident normal shock and to reduce the transient forces on the pod upon reflected shock impact. We found that a short expanded section at the tunnel end reduced the shock pressure rise by 44%, with small improvements demonstrated by a radial baffle-inspired geometry.

Application of Numerical Simulation Technology in New Intelligent Reinforcing Method of Shield Tunnel End in Seaside Environment

The instability of the soil at the shield end is an important safety hazard in shield tunnel construction. In loose and weak strata, the risk of instability and damage is higher, and the loss is greater. In this paper, the instability and failure of the end soil in loose and weak strata are studied. To ensure the smooth start and arrival of the shield and avoid engineering accidents such as end soil instability, surface subsidence, landslides, etc., during the construction process, this paper summarizes the commonly used reinforcement technology and characteristics of the shield in and out of the tunnel. Through numerical simulation, the influence of the thickness of the added solid on the formation and diaphragm wall is analyzed. It is found that the reinforcement effect increases with the increase in thickness of the added solid, but the change rate becomes smaller and smaller. The indoor triaxial test is used to find out the physical and mechanical properties of loose sand and soft clay. The biaxial compression numerical model is built with PFC2D (Particle Flow Code 2D PFC 6.0), and the wall constraint type is improved. With the help of the PFC biaxial test, the influence of model parameters on the macroscopic properties of the simulated material was analyzed. The research has certain reference values for the actual construction of the project.

Study on the Effects of Artificial Trapezoidal Freezing Soil Mass on the Stability of Large-Diameter Shield Tunnel Portal

The shield tunnel end reinforcement is important in the water-rich sandy strata. In this paper, a trapezoidal freezing soil mass was proposed to reinforce the shield tunnel end, and the reinforcement effects were evaluated based on the Wuhu River-Crossing Tunnel. Firstly, the influences of the freezing soil mass geometric dimensions on the stability of the tunnel portal were analyzed. Then, displacements of the tunnel portal with different trapezoidal freezing soil masses were simulated. Finally, the trapezoidal freezing soil mass was applied in the Wuhu River-Crossing Tunnel. The results show that the portal’s stability is improved significantly with increased freezing soil mass longitudinal length if the length is less than the tunnel diameter. The lower side of the trapezoidal freezing soil mass has a greater influence on the tunnel portal stability than the upper side. The trapezoidal freezing soil mass is more effective than the rectangular freezing soil mass for the Wuhu River-Crossing Tunnel end reinforcement. The trapezoidal freezing soil mass is a good choice for the shield tunnel end soil reinforcement in water-rich sandy strata. This study provides a freezing reinforcement method for the large-diameter shield tunnel end, which provides guidelines for similar engineering.

Mitigation of the pressure fluctuation arising from high-speed train intersection in tunnels using enlarged tunnel ends

Intense pressure fluctuations generated by the intersection of high-speed trains (HSTs) in a tunnel are unfavourable for the comfort of passengers and the safety of HSTs and tunnel facilities. This study numerically investigated the mitigation principle of the pressure fluctuation impacted upon HSTs using the enlarged tunnel end with taking into account the total tunnel length and the unit number of HSTs. Moving model tests were also performed to validate the numerical method based on the unsteady RANS equations and RNG k-ε turbulence model. The numerical results show that the enlarged end of a tunnel can manifestly alleviate the negative pressure induced by the train intersection and the length ratio of the optimal length of the enlarged section to the total length is in the range of 0.26–0.28. The optimal length of the enlarged section can be implemented by synchronising the contact of the derived waves with the train intersection. Moreover, the increase in the marshalling number of HST augments the mitigation effect of the enlarged section. This study gives insight into the mitigation of the pressure fluctuation in tunnels and can provide valuable data and a theoretical basis for the tunnel design when considering the aerodynamic effect of HST intersection.

Numerical simulation of overpressure loads generated by gas explosions in utility tunnels

Studies of overpressure loads are essential to mitigate the potential hazards of public safety induced by gas explosion accidents. Based on the computational fluid dynamics (CFD) code FLACS, numerical models of gas explosions in large-scale tunnels were developed and verified by comparing with testing data. Numerical simulations of gas explosions in confined and side-vented utility tunnels were carried out. The effects of the venting condition, gas cloud volume, and ignition position were analyzed and discussed. It is found that gas explosions in utility tunnels can be divided into three stages according to the pressure and flame development, i.e., the combustion-induced rise stage, oscillation rise stage, and oscillation decline stage. The pressure oscillation is significant, and a side vent near the tunnel end can reduce the peak pressure by 42~78% and the oscillation peak by 35~87%. The peak pressure, oscillation peak, and duration of oscillation rise stage varied significantly with the gas cloud volume. When the premixed gas cloud is ignited at the 1/4 L, the peak pressure and oscillation peak reach the maximum of 1242.5 kPa and 490.4 kPa for confined cases, which are one time higher than those of side-vented cases. What is more, based on the equivalent single degree of freedom (SDOF) approach in the elastic range, the dynamic effects of gas explosions in utility tunnels are figured out, and suggestions for engineering practice are proposed.

Comparison of female and male behavior in the elevated gradient of aversion.

The elevated gradient of aversion (EGA) is an apparatus for investigating the exploratory behavior of rats in 3-min sessions, consisting of three different sections of the same size: tunnel, closed arm, and open arm. Factorial analyses have defined three factors: exploration, impulsivity, and self-protection. In general, male rats are placed in the tunnel end and tend to hesitate leaving this starting point. Then, they hesitate leaving the tunnel and entering the closed arm, which they explore and tend to avoid entering the open arm or even just stick their head in and not enter it at all. Since females were not used for this test and are reported to be more explorative than male rats, the present work aimed to compare the behavior of male and female rats in the EGA. Thirty male and 34 female Wistar rats were submitted to 3-min sessions in the EGA. In general, results indicated that females were different from males: they explored more (Factor 1 - Exploration), are more impulsive (Factor 2 - Impulsivity), and are less anxious/fearful (Factor 3 - Self-protection). These results confirmed the results of other studies obtained with other apparatuses and show that females exhibit higher locomotion than males and are less anxious/fearful.

Assessing the effects of a novel biostimulant to enhance leafminer resistance and plant growth on common bean

The leafminer Liriomyza trifolii is one of the major insects that affect Phaseolus vulgaris production worldwide. Novel and safe biobased stimulator compound (BSTC) with micronutrient-amino acid chelated compounds was developed from natural compounds and was used for foliar spray of P. vulgaris. Treated plants showed significantly increased in quality and productivity as well as significant reduction in leafminer infestation by close the tunnel end resulting in larvae suffocation and death. BSTC contains chemical composition that has important function in inducing immunity and resistance against insects, enhance plant growth and production. Also, HPLC showed that the assembled BSTC is rich in nucleobases than yeast extract (> 56 fold). Aminochelation zinc enhanced the rate of absorption of nutrient compounds and could participate in safe biofortification strategy. The expression of plant defense related genes under BSTC treatment revealed strong correlations between the transcription rates of defense related genes. Based on binding energies and interacting residues of six vital insect proteins, the best-docked complexes was obtained with disodium 5′-inosinate, delphinidin 3-glucoside and hyperoside. Obtained findings indicate that the foliar application of BSTC can enhance plant growth and productivity, uptake of important elements, expression of defense related genes and inhibit insect essential genes.

A Modified Elastic Plate Model for the Thickness of Reinforced Soil of Shield Tunnel End

The soil body of the shield end could be unstable and should be reinforced, and its thickness affects the stability and economy of engineering. The existing elastic thin plate model was too conservative for design. A modified elastic plate model was proposed for the calculation. Based on elastic finite element analysis data, optimal fitting was conducted for the proposed elastic model, and the coefficients of the model were obtained. A case study showed that the elastic thin plate model is too conservative when used to calculate the thickness of the reinforced soil body. The actual reinforced thickness in practice is between the values of the elastic thin plate model and the modified elastic plate model.

Characterization of Cebama low-pH reference concrete and assessment of its alteration with representative waters in radioactive waste repositories

Concretes, mortars and grouts are used for structural and isolation purposes in radioactive and nuclear waste repositories. For example, concrete is used for deposition tunnel end plugs, engineered barriers, mortars for rock bolting and injection grouts for fissure sealing. Despite of the materials anticipated functionality, it is extremely important to understand the long-term material behaviour in repository environments. A reference concrete and mortar for the Cebama project based on a cement, silica and blast furnace slag ternary blend were designed and characterized in different laboratories with multiple experimental methods (XRD, XAS at the Fe and Cl K-edges, SEM-EDX, 29Si and 27Al MAS-NMR, TG-DSC, MIP and Kerosene porosimetry) and techniques (punch strength tests). The reference concrete enabled comparison of results from different institutes and experimental techniques, unifying the individual results to more comprehensive body. The Cebama reference concrete and mortar were designed to have high durability and compatible formulation with respect to an engineered barrier system in clay or crystalline host-rocks, having pore solution pH significantly lower than traditional concretes. This work presents main results regarding their characterization and alteration in contact with representative waters present in radioactive waste repositories. Pore solution pH of the matured reference concrete was 11.4–11.6. The main hydrated phases were C–S–H and C-A-S-H gels with a Ca:Si ratio between 0.5 and 0.7 and an Al:Si ratio of 0.05. Minor phases were ettringite and hydrotalcite. Iron(III) could be in the C–S–H phases and no Cl-bearing solid phases were identified. Connected porosity and pore size distribution was characterized by MIP observing that, as expected, the size of the pores in the hydrated cement phases varies from the micro-to the nanoscale. Connected porosity of both materials were low. Compressive strength of the concrete was 115 MPa, corresponding to traditional high-performance concrete. Degradation of these materials in contact with different waters mainly produce their decalcification and enrichment in Mg for waters containing high amount of this element, like the clay waters.

KORONER ARTER BAYPAS OPERASYONLARINDA OTOLOG VENA SAFENA MAGNA ÇIKARILMASINDA ENDOSKOPİK, TÜNEL VE STANDART YÖNTEMİN KARŞILAŞTIRILMASI

Objective: Autologous vena saphena magna is the most common bypass material used in coronary artery surgery. It is generally prepared with a long medial leg incision, and so healing problems are often observed. In this study, we aimed to compare endoscopic, classical and tunnel techniques in saphen harvesting. Material and Method: Fourty patients, who were selected randomly and retrospectively, were included in the study. Endoscopic saphen harvesting was performed on 10 patients, the tunnel technique was performed on 15 patients and the classical method was performed on 15 patients. Postoperative hospital stay, antibiotics, additional antibiotic requirement, upper leg size, hematoma, open care time, culture antibiogram, incision size, complication site, cost, postoperative complaints, median vena saphena magna harvesting time, vena saphena magna length, closed dressing time, elastic bandage time, drenaige amount, postoperative pain scores (Visual Analogue Scale-VAS) were all factors compared regarding saphen insicion site. Results: In tunnel end endoscopic procedures; insicion length, postoperative pain, major complication rate, incision closure time, the sutur material reqired for closing incisions were lower than the classical technique group. Moreover, the level of patients’ satisfaction was increased due to perfect cosmetic results and ease of early mobilization. Conclusion: Comparing classical saphen harvesting techniques with endoscopic and tunnel methods, it was found that incision problems, length of hospital stay, sutur material amounts, incision closure time, incision length and postoperative pain were detected in lower numbers in endoscopic and tunnel methods. Depending on these factors, the patient’s mobilization time was shortened. According to these results, the superiority of the endoscopic and tunnel methods compared to the classical method should be considered.

Simulation of Intermediate Channeling by Nanoscale Confinement

Confinement of active sites and reaction intermediates in a physical tunnel is one example of intermediate channeling found in natural reaction cascades. The study of transport properties and their impact on kinetics of these confined systems provides a pathway for implementing confinement strategies in integrated and intensified catalytic systems. In the present study, the effect of geometric, kinetic, and transport parameters on intermediate channeling via confinement is studied via a continuum model in which two reaction sites are confined within a physical tunnel. One site generates an intermediate species that is consumed at the second site to form a product, where the process efficiency may be quantified by product yield. Key geometrical parameters include distance between sites, distance between sites and the tunnel end, and tunnel conical angle. Maximizing the distance between sites and the tunnel end and minimizing the tunnel diameter are demonstrated to be effective approaches to maximizing prod...

Effect of Boundary Conditions in Segmental Lining Model on its Sectional Force

Nowadays, underground construction becomes popular as the demand for infrastructure in urban areas increases. To develop underground space in an urban area, it is important to investigate ground surface settlement and damage to existing neighbouring structures. Consequently, 3D finite element method (FEM) continuum models have been developed. This paper introduces a 3D FEM continuum model, which can consider, longitudinal joints, circumferential joints, and nontension boundary between lining and ground, and examines the effect of boundary condition at the tunnel end and ground stiffness on the lining behavior (i.e., bending moment, axial force, normal effective earth pressure, and segment displacement) in the case of staggered building. As a result, it was found that the boundary condition at the tunnel end does not significantly affect the sectional force, except for the axial force in the case of soft soil; The two-ring model provides the safe side results from the viewpoint of segment design; and it can be adopted for segmental lining design and lining behavior simulation.

Using Submucosal Tunneling Endoscopic Resection to Treat Submucosal Tumor

Introduction: This video shows the submucosal tunneling endoscopic resection (STER). Today, endoscopic submucosal dissection (ESD) is increasingly used for superficial esophageal cancers and esophageal submucosal tumors (SMTs),1,2 but the surgical area in the esophagus is limited and the esophageal adventitia is very thin. As improved ESD technology, STER can reduce risk of postoperative gastrointestinal (GI) tract leakage and secondary infection.3 Method: This was a 56-year-old patient who found it difficult to swallow since November 23rd 2013. Then, she went to hospital and had a computer tomography (CT) scan and endoscopic ultrasonography; both of them showed there was an SMT in the middle segment of the esophagus. The patient had no other symptoms besides dysphagia, and the blood routine examination is regular. On December 4th 2013, we decided to use STER to treat this lesion. After a short anesthesia induction, we found there had been a lesion of about 1.5×1.5 cm with smooth surface in the middle segment of the esophagus, 21 cm far from the incisor. Then, we made the submocosal injection of diluted indigo carmine to locate the SMT. Next, a fluid cushion was obtained using an injection needle 5 cm proximal to the SMT, and a 2-cm longitudinal mucosal incision was made using the electric knife at the esophageal mucosa as the entry point. With the electric knife, a submucosal longitudinal tunnel was created between the submucosal and muscular layers. We made the tunnel end 1–2 cm distal to the tumor to ensure a satisfactory endoscopic view and enough space to work. In the tunnel, we resected the SMT under direct endoscopic visualization safely and completely. After removing the SMT, hemostatic clips were used to close the tunnel and the STER ended. Results: The pathology shows that the lesion was a spindle cell tumor and has no lymph node metastasis. The patient woke up in half an hour after STER and was discharged 3 days after the endoscopic resection. Also, she was seen 1, 2, and 4 weeks after this resection with no symptoms to report. Conclusion: To treat the SMT in the esophagus, the surgical area is limited and the esophageal adventitia is very thin for ESD. STER provides enough work space for the surgeon and reduces the infection and bleeding during the resection of the lesion. There is no conflict of interest of any kind in relation to this article between Shilun Cai, Yunshi Zhong, and Liqing Yao. Runtime of video: 8 mins 29 secs

Societal application of geophysics as an aid to a rescue operation at Jaipur

Geophysical techniques are normally employed to explore the subsurface and determine the anomalies but they are always much larger in dimension. However, a very precise measurement was needed to pin point a misaligned horizontal tunnel made at 47 m depth to intercept an old bore well and rescue a four year child fallen accidently on 9th November at Jagatpura village in Jaipur, India. Due to the greater depth and presence of iron casing, electric power, etc., no equipment could work to determine the orientation of the tunnel that has lost its direction. The dimension of the site and many other constrains didn’t allow conventional geophysical methods to be used. An innovative method was then designed and successfully applied, which determined 1.92 m deviation of the tunnel end point to the east from the old bore well. The digging was redirected accordingly and the bore well was intercepted. This paper describes the theoretical background, forward simulations and the field experiment of the newly designed geophysical method.

Study on Earthquake Damage Characteristic on Mountain Tunnel and Analysis

This paper collects earthquake damage data and research on tunnel in recent years(Wenchuan earthquake,Ms 8.0;Yushu earthquake, Ms 7.1, Chi-Chi Earthquake,Ms 7.6 and so on). Damage patterns and characteristics of mountain tunnels in severe earthquake region are classified: Slope failure near tunnel portal; Spalling and collapse of tunnel portal and end wall; Lining collapse; Longitudinal and transverse cracks of lining; Slant and transverse fracture of lining; Sheared off lining in fault region; Steel frame damage of primary support; pavement or bottom cracks. The damage mechanisms are analyzed and some proposals are put forward for tunnel rehabilitation and new tunnel construction: It is suggested that in strong earthquake areas, a comprehensive aseismic design should be conducted considering tunnel portal structure and slope. Line selection should avoid or reduce passing through active faults and avoid placing tunnels too close to slope faces when planning future tunnels. The paper provides a reference for seismic design and construction procedures of tunnel.

Influence of Ventilation Tube Rupture from Fires on Gas Distribution in Tunnel

The ventilation tube was an important equipment in tunnels. Although the ventilation tube used in most coal mines was hard to ignite, it can be destroyed by fires. Based on numerical simulation methods, the influence of ventilation tube rupture locations on gas distribution has been investigated when fires happen. The results show that when the ventilation tube ruptured, the flow rate of the ventilation tube increased as the distance between the rupture location and the tunnel end increasing. In addition, when the distance increased to a certain value, “the second vortex” appears but its scale decreased as the fire intensity increasing. When at the same rupture location, the maximum gas concentration increased first and then decreased as the fire intensity increasing. When the ventilation tube ruptured, the coal gas distribution shows an “up-down” –“left-right”-“uniform” pattern from the tunnel end to the outlet, and whether the second vortex appeared or not is a critical factor on deciding the detailed gas distribution in the former part of the tunnel.

Influence of Ventilation Tube Rupture from Fires on Secondary Catastrophes in Tunnel

Based on the 3-D tunnel model, the influence of ventilation tube rupture, its locations and the draught fan stopping working on second catastrophes has been investigated when fires happen. The results show that when the ventilation tube ruptured, “the second vortex” appears and the gas concentration shows “up-down” –“left-right”-uniform distribution from the tunnel end to the outlet. When the tube broken position is larger than 30 m, the volume where the gas concentration is between 5%∼16% increases first and then decreases as the fire intensity increases and it reaches to its maximum value when the fire intensity equals to 400kW. But due to low temperature, this will not induce to gas explosion. The coal gas and smoke show an evident layered distribution and concentration on the tunnel roof after the fan shut down. When fire intensity is 1200kW, gas explosion will not happen but the secondary catastrophes will appear when the fire intensity is further increased.

Queue Size Determines the Width of Tunnels in the Formosan Subterranean Termite (Isoptera: Rhinotermitidae)

We present a model of tunnel excavation by termites that requires no pheromone labeling of soil or work sites, but instead relies on tactile interactions and individuals who actively orient their movement. Potential termite excavators moved from the tunnel origin towards the distal end of the tunnel and formed a queue behind those termites at the digging face. Delayed termites excavated soil laterally from the tunnel wall at a position governed by their position in the queue of termites. By examining excavation under artificially induced conditions of longer and shorter queues of termites at the tunnel end, we showed that tunnel width increased with increased queue size and the rate of lateral excavation in a process we termed “digging pressure.”