Single Tunnel Research Articles

Zoning of mutual influence of approach rock tunnels based on a safety factor

For multiple approach tunnels, the construction of the new tunnel near the existing tunnel modifies the state of stresses and movements around the existing tunnel in an area called the “influence zone”. In this study, new method is developed to optimize the relative position of approach tunnels and guide their design via the zoning of mutual influence of the approach tunnels based on a safety factor. The strength reduction method is applied to calculate the global safety factor of multiple approach tunnels in limit state. According to quantitative laws of variation in the safety factor from single tunnel to multiple tunnels, the strong influence, weak influence, and no influence have been zoning to guide the design and construction of approach tunnels. By changing the relative position of the new tunnel complex, the safety factor and failure shapes of the tunnel complex in several cases are obtained through numerical simulation. The results are based on dividing the influence zone of approach construction of the new tunnel complex. Combining the influence zone with failure shapes, the relative position of the tunnel complex is optimized. Special support countermeasures for weak tunnel complex parts and parameters of support are initially determined.

Exchange field determination in a quantum dot spin valve by the spin dynamics

We develop the theory of the electron transport through quantum dot weakly coupled to ferromagnetic leads with noncollinear magnetization directions, that has been studied in recent experiments. One can observe much richer transport behavior of the canted quantum dot spin valves, as compared to single magnetic tunnel junctions, that relies on the possibility to generate a nonequilibrium accumulated spin on the quantum dot and the presence of the exchange interaction between dot and electrodes, depending on system parameters such as gate and bias voltages, the charging energy, an asymmetry of the tunnel couplings, and the external magnetic field. We demonstrate that one can extract information about spin dynamics on quantum dot from the dc current–voltage characteristic even at the linear response, and detect the exchange field similarly to the FMR (ferromagnetic resonance) experiment. This exchange field can be widely used in nano-spinelectronics, as a local field controlled by the gate or bias voltages also at high temperatures.

Drainage-induced ground response in a twin-tunnel system through analytical prediction over the seepage field

Leakage-induced hydraulic and ground responses in a twin-tunnel system are analyzed via the proposed analytical solution on the seepage field. The seepage continuity conditions are rigorously satisfied at the interface between the ground and the tunnel lining, in terms of both water pressure and seepage velocity. The analytical solution is verified by comparing the results of numerical simulations. A detailed parametric analysis is carried out to explore the effect of tunnels’ spatial layouts and degraded waterproof facilities on leakage-induced hydraulic and ground response, including head decline, water inflow and ground surface settlement. Our results show that the often used single tunnel model tends to overestimate the pore pressure on the lining along with water inflow into the tunnel, and underestimate the leakage-induced ground settlement.

An Analytical Solution for 2D Dynamic Structure-Soil-Structure Interaction for Twin Flexible Tunnels Embedded in a Homogeneous Half-Space

The interaction between subway tunnels is investigated by using a 2D analytic model of a twin tunnels system embedded in a homogenous half-space. The closed-form analytical solution for tunnel displacement response is derived through the wave function expansion method and the mirror method, and the correctness of the solution is verified through residuals convergence and comparison with the published results. The analysis focuses on the effects of tunnel relative stiffness on tunnel–soil–tunnel interaction. Tunnel relative stiffness has a great influence on tunnel displacement response. For small tunnel relative stiffness, tunnel displacement amplitude can be enlarged by 3.3 times that of single rigid tunnel model. The response of the tunnel–soil–tunnel interaction system depends not only on the distances between tunnels but also on the frequency of the incident wave and the incident angle. The strength of the interaction between the tunnels is highly related to the tunnel spacing distance. The smaller the distance between tunnels, the stronger the interaction between them. When the distance between tunnels reaches s/a = 20, the interaction between tunnels can be ignored. It is worth pointing out that the seismic design of underground tunnels should consider the interaction between tunnels when the tunnel distance is small.

Biomechanical comparison of two medial patellofemoral ligament reconstruction techniques: Quadriceps tendon fixation versus single-tunnel patella fixation with gracilis autograft did not differ in load to failure and stiffness

BackgroundThe purpose of this study was to evaluate the ultimate failure load and stiffness of two patellar fixation techniques for medial patellofemoral ligament (MPFL) reconstruction: (1) quadriceps tendon fixation (QT), (2) single tunnel (STG) patella fixation with gracilis autograft. MethodsA total of 16 fresh-frozen cadaveric knees (eight matched pairs) were randomized into two groups (QT vs. STG). The MPFL reconstructions were subjected to cyclic loading for 10 cycles to 30 N and then tested to failure at a constant displacement rate of 15 mm/min using a materials-testing machine (MTS 810 Universal Testing System). Failure mode, ultimate failure load and stiffness were recorded for each cadaveric specimen. ResultsThere was no significant difference in mean ultimate failure load among groups (P = 0.35). The STG group failed at a mean ultimate load of 190.04 N [standard deviation (SD) 23.18] and the QT group failed at 206.24 N (SD 37.99).The STG group had a mean stiffness of 21.38 N/mm (SD 1.44). This was not significantly higher than the mean stiffness value achieved for the QT group at 20.36 N/mm (SD 1.3) (P = 0.19). In the QT group all reconstructions failed due to tendon rupture at the patella attachment. The reason for failure in the STG group was the graft–suture connection. ConclusionsThis cadaver study showed no statistically significant difference in biomechanical performance of the evaluated patella fixation techniques, in terms of maximum load to failure and stiffness. Both techniques are reliable in terms of biomechanical properties and could offer additional surgical solutions.

Experimental investigation on the smoke back-layering length in a branched tunnel fire considering different longitudinal ventilations and fire locations

Most previous works concentrated on the smoke back-layering length in traditional single tunnel fires, whereas very few studies have been performed related to the smoke back-layering length(L) in a branched tunnel fire. In the present paper, a series of fire tests were performed in a 1/10 scale branched tunnel to investigate L under various longitudinal ventilation velocities (v), heat source locations(d) (the distance between the heat source centerline and junction) and heat release rate (HRR). The smoke back-layering length and smoke temperature for various conditions are obtained and analyzed. The results are summarized as follows: With longitudinal ventilation velocity increasing to large enough, the smoke back-layering phenomenon will be observed and the maximum smoke temperature tends to deflect downstream. The larger the v and the farther the heat source is to the intersection, the smaller the L is. The dimensionless smoke back-layering length L/H is proportional to gHQ˙/ρ0cpT0v3A, which is consistent with Thomas's work. Whereas, due to that the smoke will split in intersection of branched tunnel, the proportional coefficient increases from 0.467 to 0.754, which is less than that in traditional single tunnels in previous work. Moreover, a revised relation is proposed to describe the smoke back-layering length in branched tunnel fires considering the longitudinal ventilation and fire location.

Design and Investigation of F-shaped Tunnel FET with Enhanced Analog/RF Parameters

In this manuscript, a novel physically doped single gate F-shaped tunnel FET is simulated and optimized. The designed configuration is well optimized and analyzed for different source thickness, source length, drain length with different lateral tunneling lengths between the source edge and gate dielectric. Also, we optimized some stand-points like threshold voltage, ION to IOFF current ratio, ambipolar conduction range, sub-threshold swing and various capacitance to rectify the analog/RF performance of single gate F-shaped TFET. Regarding this, we concurrently optimize the lateral tunneling length between source and gate with optimization of source thickness. The variation in lateral tunneling length, the potential and strength of electric field at fixed Vgs voltage is varied which leads to effective change in the ON-current, average sub-threshold swing, and turn ON-voltage. Another side, as well as the source thickness vary, the electric field variation takes place near the edge of source, which leads to variation in the ON-current and ON-voltage. The performance parameters of single gate F-TFET is compared with single gate L-TFET, which is the incentive of this submitted work. The optimized single gate F-TFET have 0.30 V turn ON-voltage with 7.4 mV/decade average sub-threshold swing and high Ion/Ioff ratio approx 1013. Besides, a significant reduction in parasitic capacitance is beneficial to enhanced RF performance with better controllability on channel.

Influence of single tunnel and twin tunnel on collapse pattern and maximum ground movement

Particle Flow Code in Two Dimensions (PFC2D) was used in order to examine the influence of single tunnel and twin tunnel on the collapse pattern and maximum ground movement. Since first PFC was calibrated by the experiments, the results obtained were rendered by a uniaxial test. Further, a rectangular model with dimensions of 100 m ˟ 100 m containing both the central tunnel and twin tunnel was built. The center of the single tunnel was placed 25 m under the ground surface, and its diameter changed from 10 m to 35 m with an increment of 5 m. The center of the twin tunnel was situated 25 m under the ground surface, and its diameter was changed from 10 m to 30 m with an increment of 5 m. For measurement of the vertical displacement, one measuring circle with a 2 m diameter was opted on the ground surface above the tunnel roof. The average of the vertical movement of discs covered in these circles was determined as a ground settlement. A confining pressure of 0.01 MPa was applied on the model. The uniaxial compression strength was 0/09 MPa; the results obtained depicted that the tunnel diameter controlled the extension of the collapse zone. Also the vertical displacement at the roof of the tunnel declined by decreasing the tunnel diameter. The ground settlement increased by increasing the tunnel diameter.

Impact of Tunnel Groups on Pupil Diameter of Drivers on Mountainous Freeway in China: A Real-World Driving Study

A real-world driving experiment was performed in the Wen-Ma section of the G4217 Rong-Chang Freeway situated in the Sichuan Province to investigate the impact law of the pupil diameter of drivers in tunnel groups on the mountainous freeway. The eye-movement data of drivers were collected, and the percentage of pupil diameter variable (PPDV) was used as a visual characteristic index. The analysis of the overall change in the PPDV of drivers in the experimental sections demonstrated that the PPDV in tunnel groups differed significantly between the nontunnel sections and single tunnel sections. Subsequently, a related model for the PPDV of drivers and the length of the connecting zone between tunnels was established, its reliability evaluated, and the smooth mutation value obtained on the basis of the mutation theory. Thereafter, a tunnel group definition standard based on the visual effect of drivers was developed. A six-zone approach was devised for the analysis of tunnel groups, and the result revealed that the different zones in the tunnel group have different impact on PPDV of drivers. The results revealed that the different zones of tunnel group have different impact on PPDV of drivers. Furthermore, lighting transition facilities should be set in the exit section of tunnel. The PPDV of drivers was negatively correlated with the length of the connecting zone of tunnel groups, and 100 m is the recommended safety length threshold for the connecting zone of tunnel groups.

CONSTRUCTION OF ATAL TUNNEL

Atal tunnel is the world’s longest highway tunnel at an altitude of about 10,000 feet from the Mean Sea Level (MSL). It was formerly known as the Rohtang tunnel and was renamed after India’s former prime minister Atal Bihari Vajpayee. The length of the tunnel is 9.02 Km. It is also the longest bi-directional, single tube roadway tunnel of India and a project of great strategic importance. It is built with modern technologies and specifications in the Pir Panjal Range of Himalayas. The construction method for this tunnel is based on the philosophy of NATM. During construction of this tunnel, the team faced many challenges, unexpected difficulties like sudden collapse, ingress of water from pores of rocks etc. The team overcame such difficulties by solving the challenges using different methods. This paper will briefly give an overview of the strategic importance of the tunnel, geology of the site, construction technologies implemented, challenges faced during constructions and how the team overcame those.

Impactful Study of F-shaped Tunnel FET

In this proposed work, a novel single gate F-shaped channel tunnel field effect transistor (SG-FC-TFET) is proposed and investigated. The impact of thickness of the source region and lateral tunneling length between the gate oxide and edge of the source region on analog and radio frequency parameters are investigated with appropriate source and drain lateral length through the 2D-TCAD tool. The slender shape of the source enhanced the electric field crowding effect at the corners of the source region which reflect in terms of high ON-current (Ion). The Ion of the proposed device is increased up to 10− 4 A/μm with reduced sub-threshold swing (SS) is 7.3 mV/decade and minimum turn-ON voltage (Von = 0.28 V). The analog/RF parameters of SG-FC-TFET are optimized.

Double tunnel technique reduces technical failure during POEM in cases with severe submucosal fibrosis.

Background and study aims Submucosal fibrosis (SMF) is one of the major reasons for technical failure during per-oral endoscopic myotomy (POEM). In this study, we aimed to evaluate the impact of double tunnel technique (DT-POEM) on the technical success of POEM in cases with severe SMF. Patients and methods Data from patients with achalasia in whom SMF was encountered during POEM from Jan 2013 to Jan 2020 at our center were retrospectively evaluated. The technical success and adverse events (AEs) were analyzed and compared between cases with SMF who underwent POEM via single tunnel versus DT-POEM technique. Results A total of 1,150 patients underwent POEM during the study period. There were 14 technical failures (1.2 %). SMF and severe SMF was found in 104 (9 %) and 21 (1.8 %) patients, respectively. The majority of patients (17, 80.9 %) with severe SMF had type I achalasia. Overall, technical failures occurred in 14 cases (1.2 %) and severe SMF resulted in the majority of the technical failures (10, 71.4 %). DT-POEM was utilized in 11 cases (52.4 %) with severe SMF. The median procedure time with DT-POEM was 150 minutes (85–210). There were no major AEs and DT-POEM was technically successful in all the patients. The technical success of POEM in cases with SMF improved after the adoption of the double tunnel technique (98.4 % vs 68.3 %, P = 0.0001). Conclusions Severe SMF is the most common reason for technical failure during POEM. DT-POEM improves the technical success rates of POEM in patients with severe SMF.

Experimental study on drying kinetics for Zingiber Officinale using solar tunnel dryer with thermal energy storage

This research reports an experimental analysis performed using a forced convection solar tunnel dryer integrated with eco-friendly low-cost sensible heat storage material. The experimental setup consists of a single pass air heater and solar tunnel dryer for drying Zingiber Officinale (Ginger). The dryer unit was tested for a two-kilogram ginger load at 12.9165° N, 79.1325° E in the hot air temperature range of 33–74 °C. Performance of drying process for two novel configurations (with sensible heat storage and north wall reflection) and two modes (active and passive) were analyzed. The raw ginger samples initially had a moisture content of 80–82% (w.b.) and were reduced to 9–10% (w.b.) in two successive days. Sensible heat storage found to increase the average temperature of the dryer by 10 °C during the drying process. The results conclude that active drying mode with and without sensible heat storage has the fastest moisture removal rate than passive drying. Amidst the eleven drying models, the models of Midilli – Kucuk and Wang – Singh had best described the kinetics of the product drying. The overall efficiency of the dryer system and specific energy consumption of the ginger was 45% and 5.56 kW-h, respectively for passive mode. The SEM analysis carried out on different micron pore sizes of dried ginger attained uniform moisture removal with a homogeneous surface and a clear fibrous structure.

Single-Incision, Single Patellar Tunnel For Double-Bundle Medial Patellofemoral Ligament Reconstruction: A Technical Note

The medial patellofemoral ligament (MPFL) is the main medial stabilizer of the patella, while reconstruction of the ligament is a common surgery performed by orthopedic surgeons. Although several surgical methods have been described regarding MPFL reconstruction, the common goals of these surgeries are to imitate the anatomic features of the native MPFL. In the single-incision and single patellar tunnel and double-bundle MPFL reconstruction technique, we will present the anatomical footprint of the MPFL located in the medial aspect of the patella, which is filled with the graft. In this technique, graft fixation is performed in the femoral tunnel using only one bioabsorbable screw without the need for fixation in the patella.

Underground tunnel type PSPP

The article discusses the main scheme and advantages of an underground tunnel-type pumped storage power plant (PSPP). Unlike traditional layouts of such stations, the upper and lower basins are located underground and formed by a single tunnel. A description of the design of the new station type and a method for calculating its main parameters were proposed. The analysis showed the limitations that must be taken into account when choosing the main hydraulic equipment for the tunnel-type underground PSPP. Based on the calculations, the optimal diameters of the tunnels were analyzed and identified to ensure the minimum construction period.

3D FEM Model on the Parameters\u2019 Influence of EPB-TBM on Settlements of Single and Twin Metro Tunnels During Construction

The present research exposes the investigation on three-dimensional modeling of the single and twin metro tunnels for the case of the Tehran metro line. At first, simulation implemented on the comparison of the ground movements in the single and twin tunnels. Then the simulation has been performed on the influence of effective parameters of EPB-TBM on the surface settlements throughout excavation. The overcutting, shield conicity, grouting, and the final lining system modeled and the influence of face supporting pressure, grout injection pressure, as well as the clear distance of the tunnels, has been analyzed. The initial results showed a valid ground settlement behavior. The maximum settlements occurred at the end of the shield tail and it was higher in the single tunnel. The face supporting pressure had more effect on the surface settlement in comparison to the grout injection pressure. By increasing the face pressure in the single tunnel, the place of maximum settlement moved back while the grout pressure is insignificant for decreasing the settlements. Furthermore, the influence of the clear distance in the twin tunnels led to zero after the length of 30 m. Accordingly, for more distances, the tunnels must be examined independently and as two different single tunnels.

Quantitative Evaluation of Hardware Binary Stochastic Neurons

Recently there has been increasing activity to build dedicated Ising Machines to accelerate the solution of combinatorial optimization problems by expressing these problems as a ground-state search of the Ising model. A common theme of such Ising Machines is to tailor the physics of underlying hardware to the mathematics of the Ising model to improve some aspect of performance that is measured in speed to solution, energy consumption per solution or area footprint of the adopted hardware. One such approach to build an Ising spin, or a binary stochastic neuron (BSN), is a compact mixed-signal unit based on a low-barrier nanomagnet based design that uses a single magnetic tunnel junction (MTJ) and three transistors (3T-1MTJ) where the MTJ functions as a stochastic resistor (1SR). Such a compact unit can drastically reduce the area footprint of BSNs while promising massive scalability by leveraging the existing Magnetic RAM (MRAM) technology that has integrated 1T-1MTJ cells in ~Gbit densities. The 3T-1SR design however can be realized using different materials or devices that provide naturally fluctuating resistances. Extending previous work, we evaluate hardware BSNs from this general perspective by classifying necessary and sufficient conditions to design a fast and energy-efficient BSN that can be used in scaled Ising Machine implementations. We connect our device analysis to systems-level metrics by emphasizing hardware-independent figures-of-merit such as flips per second and dissipated energy per random bit that can be used to classify any Ising Machine.

MANAGEMENT OF EMERGENCIES CAUSED BY INFLUENCE OF THE FIRE FOR THE COMBINED VENTILATION SYSTEM IN TWO-WAY TRAFFIC TUNNELS

In this paper have been considered the semi-transverse and transverse scheme of system of ventilation for two-way traffic for single tunnel. In same time have been investigated the expected phases of emergencies caused by influence of fire. For conditions of Rikoti road tunnel have been determined that there is accumulation of deviations from the normal course of natural and anthropogenic processes. Measure for the prevention of hazards in tunnel is proposed the establishing a schedule for dangerous goods, when ventilation becomes important, because for saving lives is the need to remove smoke and toxic materials. To design the ventilation system, it is important to establish its functional capabilities for disaster management, both in the initial stage of the fire, and when it is in full development. As is well known, each emergency is characterized by its own rate of development. Emergency same situation due to the presence of fire is a rapidly developing phenomenon. On the scale of the fire situation is within the object. Consequently, the main results of this work are relevant to the management of the tunnel and the corresponding service of Emergency Management for the implementation of adequate measures to save lives.

Breaking of Coulomb blockade by macrospin-assisted tunneling

A magnet with precessing magnetization pumps a spin current into adjacent leads. As a special case of this spin pumping, a precessing macrospin (magnetization) can assist electrons in tunneling. In small systems, however, the Coulomb blockade effect can block the transport of electrons. Here, we investigate the competition between macrospin-assisted tunneling and the Coulomb blockade for the simplest system where both effects meet; namely, for a single tunnel junction between a normal metal and a metallic ferromagnet with precessing magnetization. By combining Fermi's golden rule with magnetization dynamics and charging effects, we show that the macrospin-assisted tunneling can soften or even break the Coulomb blockade. The details of these effects---softening and breaking of the Coulomb blockade---depend on the macrospin dynamics. This allows us, for example, to measure the macrospin dynamics via a system's current-voltage characteristics. It also allows us to control a spin current electrically. From a general perspective, our results provide a platform for the interplay between spintronics and electronics on the mesoscopic scale. We expect our work to provide a basis for the study of Coulomb blockade in more complicated spintronic systems.

Rail‐bound logistics in tunnelling – Challenging logistics for a 30 km long TBM drive

AbstractDuring the early years of the 19th century, narrow‐gauge railways found their way into mines and tunnel projects. Due to economic reasons, these rail‐bound transport systems were successfully used for the transport of personnel, supplies and muck operations. While the worldwide transport logistics developed and changed continuously over the following century, there was limited demand within the tunnelling industry on innovation and improvement for these robust, durable and simple railways. Moreover, rubber‐tired transport systems were introduced to the market and replaced traditional rail equipment on many tunnelling projects. The MTS tunnel Drive 1, originally planned to be 13 km in length and now extended to 30 km, will become the longest single tunnel drive in the world, demonstrating the flexibility of a rail‐bound system. Since the start of the project, various suppliers and manufacturers for rail‐bound equipment and rail track systems have been involved in the development of innovative drive systems, under‐carriages and rail tracks. This article provides an overview of the design, implementation and lessons learned so far.