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1
Dhake, Shubham. "Tunneling in Various Shapes Using Numerical Analysis." International Journal for Research in Applied Science and Engineering Technology 9, no. VII (July 31, 2021): 3483–92. http://dx.doi.org/10.22214/ijraset.2021.37108.
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Tunnelling has gained popularity in the recent times due to lack of space and the rapidly increasing population. Thus, going underground is the only option to provide the infrastructure facilities which will meet the need of increasing population. The shape and dimensions of the tunnel cross section usually depends on certain parameters like purpose for which the tunnel is provided, drainage & maintenance requirements, requirement of escape route, etc. Geology plays an important role in deciding the shape of the tunnel. The ground behaves in a complex manner, when a tunnel is excavated in it as new stresses are developed. Based on the ground types, the shape is selected in such a way that the stresses developed in the ground should distribute properly around the tunnel periphery and should not cause convergence of the tunnel boundary. Also, requirement of support system should not be too heavy, as it will increase the cost. Apart from the above parameters, the availability of the equipment & the construction method also decides the shape of the tunnel. There are various shapes of tunnels like D-shape, Circular, Elliptical, Egg-shape, Box type, Horseshoe & Modified Horseshoe shape. In the present course of work three shapes of tunnels viz. Horseshoe Shape, Modified Horseshoe Shape & D-Shape tunnels are considered. By hypothetical assumption the geology and overburden are taken into account for the tunnels and the tunnels are simulated for roof collapse and shear failure case by using RS2 FEM based software.
2
Cutler, Paul M. "Modelling the evolution of subglacial tunnels due to varying water input." Journal of Glaciology 44, no. 148 (1998): 485–97. http://dx.doi.org/10.3189/s002214300000201x.
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AbstractThe time evolution of a subglacial tunnel cross-section is examined usine a two-dimensional finite-element ice-flow model coupled to an idealized drainage system. Simulations are driven by physically based calculations of surface water-input variations at Slorgiaciaren, Sweden. Highlights of the model are its ability to handle unsteady conditions and irregular tunnel shapes. Agreement between modelled water pressure and borehole water levels is good. The following conclusions are reached: (i) Tunnels adapt to fluctuating inflow on time-scales of days. Storms, during which effective pressure ranges from 0 to 0.9 MPa, cause significant adjustments but daily fluctuations due solely to melt-water inflow are minor, (ii) Open-channel flow may become commonplace late in the ablation season, (iii) Initial tunnel shape influences subsequent tunnel evolution and seasonal water-pressure variation. Over the course of a summer, tunnels retain some of their initial shape, though in all experiments the width-to-height ratio increased with time, (iv) Tunnel contraction forms broad low tunnels. However, (v) given two tunnels of equal initial area, the higher narrower one expands more rapidly. Thus, more semi-circular tunnels may capture How from broader neighbours early in the summer.
3
Cutler, Paul M. "Modelling the evolution of subglacial tunnels due to varying water input." Journal of Glaciology 44, no. 148 (1998): 485–97. http://dx.doi.org/10.1017/s002214300000201x.
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AbstractThe time evolution of a subglacial tunnel cross-section is examined usine a two-dimensional finite-element ice-flow model coupled to an idealized drainage system. Simulations are driven by physically based calculations of surface water-input variations at Slorgiaciaren, Sweden. Highlights of the model are its ability to handle unsteady conditions and irregular tunnel shapes. Agreement between modelled water pressure and borehole water levels is good. The following conclusions are reached: (i) Tunnels adapt to fluctuating inflow on time-scales of days. Storms, during which effective pressure ranges from 0 to 0.9 MPa, cause significant adjustments but daily fluctuations due solely to melt-water inflow are minor, (ii) Open-channel flow may become commonplace late in the ablation season, (iii) Initial tunnel shape influences subsequent tunnel evolution and seasonal water-pressure variation. Over the course of a summer, tunnels retain some of their initial shape, though in all experiments the width-to-height ratio increased with time, (iv) Tunnel contraction forms broad low tunnels. However, (v) given two tunnels of equal initial area, the higher narrower one expands more rapidly. Thus, more semi-circular tunnels may capture How from broader neighbours early in the summer.
4
Dang, Van Kien, Ngoc Anh Do, Tai Tien Nguyen, Anh Duy Huynh Nguyen, and Van Vi Pham. "An overview of research on metro tunnel lining in the sub-rectangular shape." Journal of Mining and Earth Sciences 62, no. 4 (August 31, 2021): 68–78. http://dx.doi.org/10.46326/jmes.2021.62(4).08.
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Circular tunnels are the most popular shapes used in urban underground transportation systems when mechanized tunneling is used for tunnel excavation. However, circular tunnels have a small space utilization ratio. With the material development, non - circular tunnels such as sub - rectangular, U - shaped lining, etc. are now common, and their cross - section helps to improve the underground space utilization. However, there have been not many studies on the structure and the calculation method of the metro tunnels with the above cross - sections. The paper uses the analytical synthesis method to find out the advantages and disadvantages, the application conditions of the sub - rectangular shape, as well as the development direction for the complete calculation methods for this cross - section in Vietnamese conditions.
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Lin, Da Ming, Yan Jun Shang, Guo He Li, and Yuan Chun Sun. "Numerical Analysis of Damage for Y-Shape Tunnel." Advanced Materials Research 368-373 (October 2011): 2517–20. http://dx.doi.org/10.4028/www.scientific.net/amr.368-373.2517.
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There are many effective researches about tunnel at home and abroad, because the complexity of design and construction for Y-shape tunnel, in public there is no research about it yet, with the background of nanliang-tunnel which merge two single-beam into a two-lane tunnel as Y-shape. This paper obtains the rock mass mechanics parameters on the basis of nonlinear Hoek-Brown criterion first, and has a numerical simulation according the tunnel construction with FLAC-3D. we arrange many monitor sections in this model and discuss the law of deformation and failure in different section, at last have a comprehensive analysis of displacement, stress, plastic zone of different sites which caused by tunnel construction and discover that: with the distance of two single tunnels decreased, the interaction caused by the merging increase together with the compressive stress, tensile stress. The displacements of surrounding rock increase corresponding, the amplitude of variation is up to 44.8%, After the two-lane tunnel is 15m long, the stress and displacements redistribution of surrounding rock become stable.
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Zhang, Chengping, and Kaihang Han. "Collapsed Shape of Shallow Unlined Tunnels Based on Functional Catastrophe Theory." Mathematical Problems in Engineering 2015 (2015): 1–13. http://dx.doi.org/10.1155/2015/681257.
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This paper investigates the collapse mechanisms and possible collapsing block shapes of shallow unlined tunnels under conditions of plane strain. The analysis is performed following the framework from a branch of catastrophe theory, functional catastrophe theory. First, the basic principles of functional catastrophe theory are introduced. Then, an analytical solution for the shape curve of the collapsing block of a shallow unlined tunnel is derived using functional catastrophe theory based on the nonlinear Hoek-Brown failure criterion. The effects of the rock mass parameters of the proposed method on the shape and weight of the collapsing block are examined. Moreover, a critical cover depth expression to classify deep and shallow tunnels is proposed. The analytical results are consistent with those obtained by numerical simulation using the particle flow code, demonstrating the validity of the proposed analytical method. The obtained formulas can be used to predict the height and width of the collapsing block of a shallow unlined tunnel and to provide a direct estimate of the overburden on the tunnel lining. The obtained formulas can be easily used by tunnel engineers and researchers due to their simplicity.
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Jearsiripongkul, Thira, Suraparb Keawsawasvong, Chanachai Thongchom, and Chayut Ngamkhanong. "Prediction of the Stability of Various Tunnel Shapes Based on Hoek–Brown Failure Criterion Using Artificial Neural Network (ANN)." Sustainability 14, no. 8 (April 11, 2022): 4533. http://dx.doi.org/10.3390/su14084533.
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In this paper, artificial neural network (ANN) models are presented in order to enable a prompt assessment of the stability factor of tunnels in rock masses based on the Hoek–Brown (HB) failure criterion. Importantly, the safety assessment is one of the serious concerns for constructing tunnels and requires a reliable and accurate stability analysis. However, it is challenging for engineers to construct finite element limit analysis (FELA) algorithms with the HB failure criterion for tunnel stability solutions in rock masses. For the first time, a machine-learning-aided prediction of tunnel stability based on the HB failure criterion is proposed in this paper. Three different shapes of tunnels, i.e., heading tunnel, dual square tunnels, and dual circular tunnels, are considered. The inputs include four dimensionless parameters for the heading tunnel including the cover-depth ratio, the normalized uniaxial compressive strength, the geological strength index (GSI), and the mi parameter. Moreover, dual square and circular tunnels include one more additional parameter namely the distance ratio. The results present the best ANN models for each tunnel shape, providing very reliable solutions for predicting the tunnel stability based on the HB failure criterion.
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Mandal, Jagriti, ManmohanDass Goel, and AjayKumar Agarwal. "Effect of Horizontal Curve on the Response of Road Tunnels under Internal Explosion." Proceedings of the 12th Structural Engineering Convention, SEC 2022: Themes 1-2 1, no. 1 (December 19, 2022): 1293–97. http://dx.doi.org/10.38208/acp.v1.653.
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Internal explosion in a tunnel is a complex loading phenomenon where the tunnel lining is subjected to not only direct impact of explosion but also loading due to multiple reflection of blast waves which could be of magnitude higher than that of incident blast wave. This kind of loading is complex in nature and difficult to predict using simple analysis tools. Further, it poses a serious threat to its structural integrity. Studies have been conducted in the past to understand the behaviour of tunnel under internal explosion. However, they have been focused on straight tunnels ignoring the convex and concave shapes introduced due to horizontal and vertical curves. Shape of the target surface has significant effect on the characteristics of blast wave. This study investigates the effect of horizontal curves on the damage behaviour of tunnel lining due to internal explosion. A series of numerical simulation are performed on box-shaped tunnel with varying curvature radius and the results are compared with that of straight tunnel adopting Multi-Material Arbitrary Lagrangian-Eulerian (MM-ALE) method using LS-DYNA®. Explosive and air are modeled using ALE formulation, whereas, tunnel and soil are modeled using Lagrangian formulation. Further, Jones-Wilkins-Lee equation of state is used to model the explosion. Damage to the tunnel lining is measured in terms of peak particle velocity (PPV) and von-Mises stress. It is observed that walls of curved tunnels undergo more PPV compared with straight tunnel wherein concave wall show the highest PPV. Propagation of blast wave along the tunnel length is significantly affected due to the introduction of curvature resulting in change in reflection patterns. This further leads to variation in stress contours on tunnel lining with higher concentration of stress in curved tunnels than in straight tunnel.
9
Wang, Shi Min, Chuan He, Si Jin Liu, and Lei Lei Lan. "Study on the Construction Mechanic Behaviors of Different Cross-Section Shape Connected Aisle in the Shield Tunnel with High Hydraulic Pressure." Advanced Materials Research 243-249 (May 2011): 3472–75. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.3472.
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With the construction of large quantities of shield tunnels, based on the consideration of the performance, disaster prevention, relief and tunnel drainage requirement, it becomes more and more important to set the connected aisle in the shield tunnel section. The shape of the connected aisle cross-section has an obvious effect on the deformation and stress of the connected aisle. In order to draw reasonable connected aisle type for the subway construction under high hydraulic conditions, the comparative analysis of stress state of the circular and horseshoe-shaped connected aisle section is applied based on the construction of the connected aisle in the shield tunnel across the Yangtze River in Wuhan subway. It is recommended that the horseshoe-shaped cross-section should be applied to connected aisle construction in the shield tunnel in Wuhan subway.
10
Khan, Babar, Syed Muhammad Jamil, Jung Joo Kim, Turab H. Jafri, and Jonguk Kim. "Rock Mass Behavior under Tunnel Widening in Asymmetric and Symmetric Modes Considering Different Shapes and Parametric Conditions." Geosciences 9, no. 12 (December 16, 2019): 518. http://dx.doi.org/10.3390/geosciences9120518.
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To accommodate traffic volume on roads due to ever-increasing population growth, the widening of highways and motorways is in high demand. Nevertheless, the widening of tunnels on these road networks is quite complex due to the presence of numerous rock types, in situ stress, and different widening modes. To overcome these complexities, eight different tunnel shapes were simulated under varying support conditions for asymmetric and symmetric widening. It was found that the tunnels with a round shape, such as horseshoe and semicircular with flatbed, are more effective for asymmetric widening, whereas the provision of a rounded invert in these shapes can reverse the widening option to symmetric. Furthermore, an insignificant effect of the difference in asymmetric and symmetric widening of regular tunnel shapes, such as box, rectangular, and semi-elliptical, was found. A full factorial design statistical analysis confirmed the decrease in tunnel deformation by using various tunnel support systems and showed a significant deformation difference according to monitoring locations at the tunnel periphery. The deformation difference in the case of both tunnel widening modes was also analyzed according to different design parameters. This study provides a comprehensive understanding of rock mass behavior when the widening of any underground opening is carried out.
11
Gonzalez, F. J., P. K. Kaiser, and M. S. Diederichs. "Energy Release Resulting from Sudden Excavation Shape Changes during Two-sided Strainbursts." IOP Conference Series: Earth and Environmental Science 1124, no. 1 (January 1, 2023): 012082. http://dx.doi.org/10.1088/1755-1315/1124/1/012082.
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Abstract When tunnels in underground hard rock mines experience strainbursts, the effective shape of the tunnel suddenly changes as part of the rock fails, notches form and the broken rock bulks inside the strainburst volume. For circular tunnels, this dynamic rupture and bulking process causes a shape change with associated displacements and velocities in the surrounding elastic rockmass and at the excavation walls. This process can be approximated for circular tunnel bursting in elastic rock by a shape change from circular to elliptical and Maugi’s solution [1] can be adapted to estimate related displacements and average ground velocities. If these velocities are imposed on a volume of rock or shotcrete with a given mass, the mass can be ejected, and the corresponding kinetic energy can be estimated. When combined with the sudden bulking of the fractured rock, displacements and velocities are magnified between the elliptical shape and the pre-burst (circular) shape of the tunnel. This study focuses on the effect of the combined excavation response with elastic and bulking deformations to assess frequently observed excavation damage processes involving ‘shotcrete rain’ and heave of floor slabs caused by these shape changes. An analytical solution is presented for circular tunnels to estimate the elastic and bulking displacements, the resulting velocities, and energy demands.
12
Xu, Jian Lin, Yuan Gui Mei, Fan Yang, and Xin Liu. "Numerical Simulation of Effect of Nose Shape on Tunnel Entry/Exit Wave Induced by a High-Speed Train Passing through a Tunnel." Applied Mechanics and Materials 97-98 (September 2011): 712–15. http://dx.doi.org/10.4028/www.scientific.net/amm.97-98.712.
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The air flow around the high-speed train passing through a tunnel is three dimensional, compressible and unsteady in nature. This paper carried out the numerical simulation of it and evaluated the effect of nose shapes of high-speed trains on tunnel entry/exit waves radiated directly from tunnel entrance or exit. The elliptical, parabolic and conical nose shapes were analyzed. A commercial CFD code STAR-CD based on the finite volume method was used applying the SIMPLE algorithm and a moving grid technology. The comparison study shows that though the patterns of tunnel entry waves or exit waves induced by high-speed trains with above three nose shapes are similar, the amplitudes of them are different. The wave amplitude of elliptical shape is the highest, and that of conical shape is the lowest, which implies that with the nose shape be more streamlined and slender, it might be more likely to reduce the amplitudes of tunnel entry/exit waves.
13
Hao, Xianjie, Shaohua Wang, Duoxiang Jin, Bo Ren, Xiangyang Zhang, Kailong Qiu, and Yingjie Fan. "Instability Process of Crack Propagation and Tunnel Failure Affected by Cross-Sectional Geometry of an Underground Tunnel." Advances in Civil Engineering 2019 (May 2, 2019): 1–17. http://dx.doi.org/10.1155/2019/3439543.
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The process of crack propagation and tunnel failure is affected by the cross-sectional geometry of an underground tunnel. In order to quantify the effect of section shape on the process of crack propagation in deep tunnels under high ground stress conditions, a total of four physical models with two cross-sectional shapes and twelve stress levels were designed and several large-scale physical model tests were conducted. The results indicated that, when the vertical stress is 4.94 MPa, the length and depth of the cracks generated in the rock surrounding the horseshoe tunnel are about eight times that around a circular tunnel. The position where the circumferential displacement of the horseshoe tunnel begins to be stable is about two, to two and a half, times that around a circular tunnel. After the deep chamber was excavated, continuous spalling was found to occur at the foot of the horseshoe tunnel and microcracks in the surrounding rock were initially generated from the foot of the side wall and then developed upwards to form a conjugate sliding shape to the foot of the arch roof, where the cracks finally coalesced. Discontinuous spalling occurred at the midheight of the side wall of the circular tunnel after excavation, and microcracks in the surrounding rock were initially generated from the midheight of the side wall and then extended concentrically to greater depth in the rock mass surrounding the tunnel. Tensile failure mainly occurred on the surface of the side wall: shear failure mainly appeared in the surrounding rock.
14
Pham, Nhan Thi, and Fuzhou Qi. "Application of the numerical method to analyze the effect of cross-sectional type in stabilizing the coal mine tunnel." Journal of Mining and Earth Sciences 63, no. 2 (April 30, 2022): 62–70. http://dx.doi.org/10.46326/jmes.2022.63(2).06.
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For the coal mine tunnel, each type of cross-section of the tunnel will cause different laws of mechanical change in the rock mass around the tunnel. This difference is expressed through quantities such as displacement, stress, the damage zones within rock mass, etc.. It is completely unreasonable to adopt an independent mechanical parameter to evaluate the selection of the most optimal shape for the tunnel. To simulate the tunnel excavation process with different types of cross-section shapes in the same geological conditions, the software FLAC3D was employed. The data extracted from numerical simulation including displacement, stress field, plastic deformation area, the thickness of plastic deformation zone at the top, side, and bottom of the tunnel are evaluated. The type of section shape with the highest score will be evaluated as the most optimal one. The present case study shows that the type of cross-sectional shape of the straight wall with curved arch and deviated trapezoid got the highest scores of 36 points and 30 points, respectively. Therefore, the type of cross-sectional shape of the straight wall with curved arch and deviated trapezoid should be used. This shape choice will be the most optimal, and beneficial to the stability of the tunnel both during excavation and production progress.
15
Cheng, Xiaodong, Tianqiu Hong, Zhitang Lu, and Xiaochun Cheng. "Characterization of Underlying Twin Shield Tunnels Due to Foundation-Excavation Unloading in Soft Soils: An Experimental and Numerical Study." Applied Sciences 11, no. 22 (November 19, 2021): 10938. http://dx.doi.org/10.3390/app112210938.
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Excavation near or above existing shield tunnels often results in adverse impacts on tunnel stability. To ensure the serviceability of existing tunnels, this paper presents experimental and numerical studies with reference to a foundation pit case history excavated above twin-tube shield tunnels in soft soils. The experimental tests were firstly applied to study the deformation characteristics and structural response of the shield tunnels. Thereafter, an extensive numerical investigation was performed to determine the influence of some factors such as cover-to-excavation depth ratio, length-to-depth ratio, and unloading ratio on tunnel displacement behaviors. It was demonstrated that the tunnel heaves as the excavation proceeds, and heaves and horizontal displacements reach their maximum values when the excavation is finished. The earth pressure around the tunnels is symmetrically distributed in a gourd shape, with a larger reduction at the tunnel crown and invert and a smaller reduction at tunnel side walls. Additionally, the earth pressure at the tunnel crown and invert changes more significantly than that at other parts. The tunnel moment increment is significantly affected by the tunnel excavation depth. The axial force at or near the side walls of the tunnel is the most sensitive to the unloading effect induced by the excavation activity.
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Zhang, Zixin, Xiaogeng Gao, and Shuaifeng Wang. "Role of Particle Shape on Ground Responses to a Circular Tunnel Excavation in Sandy Soil: Consequences from DEM Simulations." Materials 15, no. 20 (October 12, 2022): 7088. http://dx.doi.org/10.3390/ma15207088.
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Due to the sensitivity of sandy soil’s mechanical behavior to the particle shape, it is thus of importance for interpreting the effect of particle shape on the ground response induced by tunnel excavation in sandy formations. We conducted a series of 2D DEM (discrete element method) simulations on a common circular tunnel excavation in sandy soil with variable-shaped particles, which are characterized as two descriptors, i.e., aspect ratio (AR) and convexity (C). The macroscopic responses and the microscopic characteristics of the sandy ground are elaborated in detail. The simulation results show obvious asymmetrical features of the excavated ground, which results from the ground heterogeneity caused by the irregular particle shape. In addition, we investigate the roles of AR and C on the ground response and find that reducing AR or increasing C will enlarge the ground settlement, i.e., the sandy ground deformation is more sensitive to the particles with more irregular shapes. However, elongated particles are beneficial for the generation of soil arching with stronger bearing capacity and thus reduce the soil pressure on the tunnel lining. Our findings have important implications for the safety assessment of the tunnel excavation, as well as other underground structure construction in sandy formations.
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Liu, Shuhong, Jinlu Fan, Chenhao Wu, and Yongquan Zhu. "Elastic Stress and Plastic Zone Distributions around a Deeply Buried Tunnel under the Nonhydrostatic Pressure." Geofluids 2022 (July 4, 2022): 1–10. http://dx.doi.org/10.1155/2022/2363291.
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The elastic stress and the plastic zone are the important mechanical parameters to determine the tunnel support design. Based on Muskhelishvili’s complex variable function, the analytical solution for the elastic stress around a deeply buried noncircular tunnel under the nonhydrostatic pressure is firstly derived. The shape and size of the plastic zone of the surrounding rock mass are then determined by substituting the elastic stresses into the Drucker-Prager yield criterion. Finally, taking a horseshoe-shaped tunnel as an example, the analytical solutions of elastic stress distribution and plastic zone shape around the tunnel under different lateral pressure coefficients are in good agreement with ANSYS numerical solutions. The calculation results show that if the vertical in situ stress exceeds the critical value, with increasing lateral pressure coefficient, the hoop stress at the roof and floor of the tunnel increases significantly and the shape and size of the plastic zone change obviously.
18
Dang, Vinh, and Jessica S. Purcell. "Cusp shape and tunnel number." Proceedings of the American Mathematical Society 147, no. 3 (December 7, 2018): 1351–66. http://dx.doi.org/10.1090/proc/14336.
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Inoue, Fumihiro, Soonsu Kwon, Satoru Nakamura, and Yoshitaka Yanagihara. "Shape Adaptation of the Inspection Guide Frame in Tunnels to Avoid Obstacles Detected by a Laser Range Finder." Journal of Robotics and Mechatronics 31, no. 6 (December 20, 2019): 752–61. http://dx.doi.org/10.20965/jrm.2019.p0752.
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To advance the automated inspection and maintenance of the inner wall of tunnels, an advanced inspection system aimed at regulating traffic was developed. In this inspection system, a guide frame was installed along the tunnel ceiling wall that is above the protection frame built over the road and resembles a gantry crane. The inspection device was fitted with an inspection guide frame (IGF), which stabilized its movement and improved its accuracy. However, as this protection frame moves along the tunnel, the guide frame should have the capacity to avoid convex obstacles such as the duct fan, the lamp and road traffic signs within the tunnel. Therefore, the entire inspection guide frame is made of variable geometry truss (VGT), which makes it possible to suitably alter the shape of the guide frame whenever necessary and pass it through the tunnel. To enable the guide frame adapt to any shape, the inverse analysis method and mathematical interpolation method were applied. The orientation of each frame was reversely analyzed according to the shape of the obstacle measured using the laser range finder (LRF), and the frame’s actuator was controlled simultaneously. We investigated the construction of a system that can perform a series of tasks such as searching for obstacles and positioning, frame shape simulation, frame shape change, inspection of the device and movement. By applying spline interpolation, we managed to practically determine the shape of the guide frame that would avoid obstacles.
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Xue, Yunchuan, Guodong Sun, and Xiaoguang Jin. "Simulation analysis of seismic dynamic response of small interval tunnel in deep backfill area based on model test." Vibroengineering PROCEDIA 42 (May 16, 2022): 45–51. http://dx.doi.org/10.21595/vp.2022.22620.
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In order to reveal the seismic dynamic response law of small interval tunnel in soil rock backfill area, relying on the subway section tunnel project, a three-dimensional finite element model is established on the basis of model test to analyze the seismic dynamic response of tunnel lining structure and foundation pile. The results show that: 1) under the action of earthquake, the greater the peak acceleration of seismic wave , the stronger the stratum nonlinearity; 2) under the action of Kobe wave and Wolong wave, the bending moment of the left and right spandrels of the tunnel is the largest in the X direction, showing an “X” shape distribution as a whole; In the Y direction, the bending moment at the arch foot of tunnel lining is the largest, and the overall distribution shape is an inverted “V”; 3) under the action of Kobe wave and Wolong wave, the tensile stress and shear stress of the lining of the left and right tunnels are the largest at the left and right arch feet, showing an “X” shape distribution as a whole; 4) under the action of different peak Kobe wave and Wolong wave, the horizontal displacement of tunnel-pile structure gradually increases with the increase of height, and reaches the maximum at the top of lining arch.
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Fu, Yanbin, Kaihang Han, Dong Su, Xiaochao Pang, Xiaohua Bao, Beibei Hou, Hao Wu, and Junsheng Wen. "A Prediction Model for the Potential Plastic Zone Induced by Tunnel Excavation Adjacent to a Pile Foundation in a Gravity Field." Symmetry 11, no. 10 (October 16, 2019): 1306. http://dx.doi.org/10.3390/sym11101306.
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The construction of metro tunnels in urban areas often encounters existing underground structures, such as the pile foundations of adjacent existing buildings. Under the mutual effects and impacts of pile foundation load and tunnel excavation, the soil around tunnel and pile foundations can experience stress redistribution or even yield prior to support installation, which could adversely affect and even damage the adjacent pile foundations. This paper proposes an effective prediction model consisted of axisymmetric tunnel and pile foundation to investigate the shape and range of potential plastic zones induced by tunnel excavation adjacent to pile foundations. Then the results obtained from the proposed method are compared with the existing approaches and numerical simulations, which shows that the shape of the potential plastic zone develops towards a butterfly shape in a gravity field, similar to those from numerical simulations. Finally, a parametric analysis is performed to investigate the influences of different parameters, such as soil parameters, axisymmetric boundary conditions, and pile parameters on the boundaries of the potential plastic zone. This proposed prediction model might provide a certain basis for making protective measures for existing pile foundations influenced by tunnel excavation, and provide a quick estimate of the boundaries of the potential plastic zone induced by tunnel excavation adjacent to pile foundations in a gravity field, thus resulting in time and cost savings.
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Shin, Jinwon, Seungki Pang, and Dong-Keon Kim. "Effects of Entrance Shape and Blast Pocket on Internal Overpressure Mitigation for Protective Tunnels Exposed to External Detonation on the Ground." Applied Sciences 13, no. 3 (January 30, 2023): 1759. http://dx.doi.org/10.3390/app13031759.
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This study presents a numerical analysis to reduce the overpressure inside protective tunnels for external detonations. A three-dimensional computational fluid dynamics model of a tunnel subjected to detonation for a hemispherical charge with a charge weight of 555 kg and a standoff distance of 7.6 m was established, based on a mesh sensitivity study to obtain an optimal element size, stability analysis of overpressure, and validation study to evaluate the accuracy of the numerical results based on Unified Facilities Criteria (UFC) 3-340-02. A parametric analysis was performed using the validated numerical model to investigate the effects of the entrance shape and blast pockets on the reduction in the maximum overpressure. The maximum overpressures were effectively reduced as the slope angle of the tunnel entrance decreased and the length of the blast pocket divided by the tunnel width decreased. An optimized shape of the tunnel was proposed based on the numerical results, where the peak overpressures were reduced by a maximum of 64.5%. This study aims to protect facilities, personnel, and equipment and further reduce construction costs by lowering the overpressure rating of blast valves in protective tunnels.
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Xie, Hong Tao. "Numerical Analysis on Influence of Cross Section Shape on Earthquake Resistant Capability of Shallow-Buried Tunnel." Applied Mechanics and Materials 405-408 (September 2013): 1292–96. http://dx.doi.org/10.4028/www.scientific.net/amm.405-408.1292.
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Taking portal segment in some shallow-buried tunnel in seismic region with strong motion as objects of study, the finite element analysis method was used to compare and assess the seismic behavior of the tunnel with different cross section shape. The results show that the linings displacement response of the tunnel with different cross section shape differs very minor under seismic load. Meanwhile there exists obvious difference in the lining internal forces of the tunnel with different cross section shape. Among all the tunnel with different section shape, the mechanics situation of the tunnel with triple arched sections is the best. While the section of the tunnel is closer to circular in shape, the mechanics situation of the lining can be effectively improved under seismic load.
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Cao, Lixue, Wentai Cui, Zhe Qin, Rui Xu, Tongtong Wang, and Yanbing Liu. "Analysis of Arch Forming Factors of Shallow Buried Hard Rock Tunnel under Overlying Load." Buildings 13, no. 9 (August 30, 2023): 2210. http://dx.doi.org/10.3390/buildings13092210.
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To investigate the arching effect of shallow buried hard rock tunnels under overlying load, the engineering scenario of a subway station on Qingdao Metro Line 6 is utilized. A large-scale tunnel loading model test is conducted, in conjunction with finite element numerical simulations, to analyze the impact of various overburden ratios on strata arching. The results show that: when the tunnel excavation span is certain, with an increase in the overlying rock mass, the stress diffusion process of the surrounding rock can be better accomplished to form the arch effect. This means that the thickness of the overburden of the tunnel determines whether or not the surrounding rock appears to have a stratified arch effect. When the tunnel overlying rock thickness is certain, the span of the tunnel determines the shape of the formation into an arch, that is, the curvature of the arch. The joint surface is an important factor in tunnel stability. When the overlying load increases to a certain value, the rock mass at the joint plane slips relatively, leading to the displacement phenomenon of the surrounding rock, which then affects the formation and shape of the formation arch.
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Wang, Ya-Qiong, Wei-Kang Kong, and Zhi-Feng Wang. "Effect of Expanding a Rectangular Tunnel on Adjacent Structures." Advances in Civil Engineering 2018 (November 6, 2018): 1–13. http://dx.doi.org/10.1155/2018/1729041.
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The expansion of urban underpass has become the mainstream of development to cope with urban congestion, and the effect on adjacent existing structures during enlarging construction is also an important issue in the construction process. In order to better understand the influence of tunneling on adjacent structures, the pedestrian underpass expanding project above-crossing Xi’an Metro Line 1 was investigated. The aim was to analyze the deformation curves characteristics of adjacent structures by field observation of ground settlement, heave of existing tunnels, and settlement of piles. The results show that the ground settlement curve in the vertical direction of the underpass is similar to the shape of V, and the maximum settlement appearing in the center line of underpass is 18.7 mm. Due to the effect of existing tunnels on the ground deformation, the settlement curve in the parallel direction of the underpass is similar to the shape of M. Above-crossing tunneling would cause the existing tunnels to heave, and the heave mainly occurs in the range of −6 m to 12 m between the pedestrian tunnel face and the center line of each tunnel. The heave curve is similar to the shape of inverted U. The settlement of piles is linear with its axial stress and significantly affected by its location. The settlement curve of piles is similar to the shape of S in two dimensions. On the basis of deformation curves, this paper presents some equations to describe the shape of V, M, inverted U, and S, respectively, by the inverted Gaussian distribution curve, superimposed Gaussian distribution curve, Gaussian distribution curve, and arctangent function.
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Seghateh Mojtahedi, Alireza, and Ali Nabizadeh. "A numerical approach to evaluating the asymmetric ground settlement response to twin-tunnel asynchronous excavation." Soils and Rocks 45, no. 2 (March 2, 2022): 1–10. http://dx.doi.org/10.28927/sr.2022.071021.
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Due to the importance of surface and subsurface settlements to prevent damages to building foundations and sensitive structures in the urban cities, in this study, the ABAQUS finite element software has used to conduct a series of numerical modeling analysis on ground surface settlement caused from the asynchronous excavation of twin-tunnel. The effects of tunnel diameter, center-to-center tunnel spacing, and tunnel depth are discussed in detail and the shape of the surface settlement curves is also plotted. The numerical modeling has been verified by the results of three sequential twin-tunneling centrifuge tests conducted by the City University of London with 94.22%, 98.71% and 99.56% accuracy, respectively. Based on the results of this study, reducing the tunnel diameter decreases the amount of the maximum ground surface settlements and reducing the depth of tunnels and the distance between twin-tunnel to less than 2D (D is the diameter of the tunnels) increase the maximum surface settlements. Installation of 30 cm of tunnel lining can decrease the maximum ground surface settlement up to almost 79%.
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Shen, Guoshun, Yuanhao Lou, Jianguo Wu, Xiaoguang Jin, and Yunchuan Xue. "Simulation analysis on seismic dynamic response of pile supported tunnels in deep backfill area of soil-rock mixture." Vibroengineering PROCEDIA 46 (November 18, 2022): 33–40. http://dx.doi.org/10.21595/vp.2022.22712.
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To reveal the seismic dynamic response of the pile-supported tunnel group in the soil-rock mixture deep backfill region, a three-dimensional finite element model was established based on the engineering conditions of the subway section and three tunnels with close access lines. Subsequently, the seismic dynamic response of the tunnel lining structure was studied. The results show that: Under the action of seismic, the soil-rock mixture stratum presents nonlinear characteristics with shear failure and plastic deformation. In addition, the acceleration and earth pressure of the soil-rock mixture stratum is in a “saturated” state; The seismic dynamic response of the three tunnels influences each other. The bending moments in the X and Y directions of the tunnel lining cross-section are distributed in “X” and inverted “V” shapes, respectively. Meanwhile, the tensile stress and shear stress are distributed in an “X” shape; Under the action of seismic, the main failure form of tunnel lining is tension shear failure, and the most vulnerable position is the left and right arch foot, followed by the left and right arch shoulder; The bending moment of the pile body changes nonlinearly in the height direction. The most significant bending moment value appears at the top 1/5 of the pile length and the junction of different strata. Furthermore, the most significant horizontal displacement of the lining structure occurs at the tunnel vault.
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Mao, Yu Feng, Hao Li, and Yan Lan He. "Key Techniques of Fast Photographic Geological Logging in Exploration Tunnel." Applied Mechanics and Materials 701-702 (December 2014): 316–24. http://dx.doi.org/10.4028/www.scientific.net/amm.701-702.316.
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Because of the special geometric shape and narrow space of exploration tunnel, field geological logging in exploration tunnels has always been staying at manual drafting stage with low efficiency and low level of informatization. This paper studies the existing issues of photographic geological logging in exploration tunnel, including the control method, image acquisition method, geometric correction of original images and the generation of display images, etc. This paper realizes fast acquisition and processing of the image data of geological logging, meeting the accuracy requirement of photographic geological logging in exploration tunnels, filling the vacancy of photographic geological logging technologies in exploration tunnels, improving the efficiency, level of automation and informatization of geological logging in exploration tunnels.
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Roper, Jack. "Shape of the Future." Aerospace Testing International 2020, no. 3 (September 2020): 18–26. http://dx.doi.org/10.12968/s1478-2774(22)50339-7.
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Han, Xian Min, Ming Lei Sun, and Yong Quan Zhu. "Study on Section Shape and Support Parameters of Guanjiao Tunnel under Carbonaceous Slate Stratum of the 2nd Line between Xining and Golmud." Advanced Materials Research 261-263 (May 2011): 1699–704. http://dx.doi.org/10.4028/www.scientific.net/amr.261-263.1699.
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Guanjiao tunnel being reconstructed is the key engineering in the 2nd line between Xingning and Golmud. It is 32.645km long. Carbonaceous slate stratum thereinto is nearly 300m long. The rock mass was suffered tectonic movement and crushed, and its physical and mechanical properties are poor. So large deformation will occur while tunnelling under high horizontal tectonic stress. Numerical simulation along with field experiments were utilized to study the mechnical effect of tunnel section shape. Two kinds of section shapes were considered, that are horseshoe-shaped section and large curvature wall, quasi-circle-shape section. Results show that quasi-circle-shape section could effectively lessen the deformation of tunnel and minish stress concentration of support. Field experiments of different support forms were also conducted. Support forms include Grid steel frame (4×ф22mm)with 0.5m span, I 20a steel frame with 0.67m span and I 20a steel frame with 0.5m span. Pressure of surrounding rock, axial force of anchor, stress of steel frame and shotcrete under different support form were measured and analysed. Because composite lining was adopted in the tunnel, the contact pressure shared by secondary lining and stress of molded concrete under different primary support stiffness were also analysed. Results showed stress of support are rational under support form of I20a. Deformation of tunnel measured in situ under different support forms showed that support form of I20a could control deformation of surrounding rock. Synthetically considering the above and economic benefit, support form of I 20a steel frame with 0.67m span was deemed to be optimal in carbonaceous slate stratum. That could offer engineering experience to tunneling in soft rock under high tectonic stress.
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Zhang, Qiongfang, Kang Cheng, Yadong Lou, Tangdai Xia, Panpan Guo, and Xiaolu Gan. "Analytical Method to Interpret Displacement in Elastic Anisotropic Soil due to a Tunnel Cavity with an Arbitrary Cross Section." Advances in Civil Engineering 2021 (July 1, 2021): 1–14. http://dx.doi.org/10.1155/2021/9921059.
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Based on complex variable theory and conformal mapping method, the paper presents full plane elastic solutions around an unlined tunnel with arbitrary cross section in anisotropic soil. The solutions describe soil elastic solutions for assuming that the displacement vectors along the tunnel boundary are directed towards the center of the tunnel. Tunnels with different cross sections are used to illustrate the method and its correctness. An elliptical unlined tunnel case is discussed in detail in the paper. Using the image method, an approximate solution for predicting surface displacement and subsurface horizontal displacement around an unlined tunnel in anisotropic soil can be obtained. The results show anisotropic stiffness properties n n = E h / E v and m m = G v h / E v have a great effect on the displacement distribution patterns around an elliptical tunnel with certain shape.
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Endou, Ken, Takafumi Ikenoya, and Ryo Kurazume. "Development of 3D Scanning System Using Automatic Guiding Total Station." Journal of Robotics and Mechatronics 24, no. 6 (December 20, 2012): 992–99. http://dx.doi.org/10.20965/jrm.2012.p0992.
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Techniques for creating 3D shape model are expected to be applied to as-built management for structures under construction. However, common techniques currently widely used, still have lacks in usability and accuracy, hence still haven’t reached the stage of actual use in the field. Due to the above circumstance, the authors have developed a 3D tunnel shape scanning system that uses a moving platform and auto tracking total station. The system provides improved usability and accuracy. Using the developed system, we have carried out a verification experiment in a mock tunnel, and we confirmed the possibility of real-time evaluation and the system’s measuring accuracy under actual conditions. We also carried out measurements on three actual tunnel sites. We confirmed that it is fully capable of measurements not only in favorable environments but also in harsh environments, such as in tunnels that are under construction.
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Lv, Xin, Shuzhi Wang, Yu Qiu, and Xiangxin Liu. "Study on the Influence of Tectonic Stress on Stability of Horseshoe-Shaped Tunnels." Advances in Materials Science and Engineering 2021 (July 30, 2021): 1–10. http://dx.doi.org/10.1155/2021/5566142.
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While the tunnel is in the high tectonic stress environment and surrounding rock of tunnel has the characteristics of soft texture and stronger expansion, the preference of tunnel shape is horseshoe. An elastic-plastic model is analyzed by complex function theory in accordance with the deformation characteristics of a horseshoe-shaped tunnel in an engineering site. The numerical model of the tunnel is built by FLAC3D, and the influence of the magnitude and direction of structural stress on the horseshoe-shaped tunnel is studied in detail. Finally, the security support of the tunnel is discussed. Results show that the stress concentration phenomenon is easily focused on the left, right, and bottom sides of the tunnel; these places should therefore be the focus of attention of tunnel stability analysis. The magnitude and direction of tectonic stress greatly affect the stability of the horseshoe-shaped tunnel. Similarly, the magnitude of tectonic stress can significantly affect the deformation state of the tunnel. The direction of tectonic stress mainly reflects the orientation of the tunnel. In addition, the orientation of the tunnel should be arranged along the maximum direction of principal stress.
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Neral, Mithun, Dan Winger, Joseph Imbriglia, and Ronit Wollstein. "Hand Shape and Carpal Tunnel Syndrome." Current Rheumatology Reviews 12, no. 3 (October 20, 2016): 239–43. http://dx.doi.org/10.2174/1573399812666160805160846.
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Nawel, Bousbia, Messast Salah, and Houssou Noura. "A simplified 3D model for existing tunnel response to piles construction." Selected Scientific Papers - Journal of Civil Engineering 16, no. 2 (December 1, 2021): 87–103. http://dx.doi.org/10.2478/sspjce-2021-0018.
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Abstract The construction and loading of deep foundations (piles) of high-rise buildings causes a considerable effect in terms of stresses and deformation and requires assessing their impact on the response of adjacent tunnels to deformations, particularly for pile foundations, which are often constructed in locations very close to existing tunnels. The execution process for piles structures generates displacements, stresses, and forces, which are transferred through the piles’ soil surrounding a nearby existing tunnel. The research presented in this paper has led to a significantly improved understanding of pile-tunnel interaction problem. It is crucial for the analysis of the impact of the pile construction on an existing tunnel. The treated topic appears in a setting of an urban environment, where we construct numerous profound foundations, sometimes in contact or adjacent to a. In this paper, the response of the existing tunnel under constructed pile process is studied. Numerical modeling was carried out using Plaxis3D software in which the Mohr-Coulomb Model (MC) has been used for modeling, while the piles/ tunnels are modeled as a linear elastic material. Furthermore, a parametric study is conducted, and its cases are investigated. The displacements and the stresses generated on the tunnel lining decreases with the increase in relative distance between pile and tunnel (spacing), the location/length of the pile from the tunnel, the pile diameter, the number of piles. We have also identified two geometrical parameters of the tunnel: shape section and thickness lining which play a prominent role in the interaction between an existing tunnel and a new pile to excavate.
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Li, Dongli, and Echuan Yan. "An Improved GPR Method Based on BP and RPCA for Tunnel Lining Defects Detection and Its Application in Qiyue Mountain Tunnel, China." Applied Sciences 11, no. 21 (November 1, 2021): 10234. http://dx.doi.org/10.3390/app112110234.
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Tunnel lining defects are one of the most common problems that tunnels experience during operation, and they can pose severe safety risks. The most popular nondestructive testing method for detecting tunnel lining defects is ground penetrating radar (GPR), one of the basic geophysical applications. However, detection responses might differ significantly from the real shape of tunnel lining defects, making it challenging to identify and interpret. When data quality is poor, interpretation and identification become more challenging, resulting in a high cost of tunnel repairs. The improved back projection (BP) imaging and robust principal component analysis (RPCA) are used in this work to offer a GPR data processing method. Even in the event of poor data quality, our method could recover GPR responses, allowing the shapes and locations of tunnel lining flaws to be clearly depicted. With BP imaging, this approach recovers the tunnel defects’ responses to better forms and positions, and with RPCA, it further isolates the target imaging from clutters. Several synthetic data demonstrate that the approach presented in this work may successfully repair and extract the positions and forms of lining defects, making them easier to identify and comprehend. Furthermore, our technique was used to GPR data gathered from the Qiyue Mountain Tunnel in China, yielding more accurate findings than the traditional method, which was validated by the actual scenario to illustrate the efficiency of our method on real data.
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Zheng, Xueyu, Luchen Zhang, Shiqiang Wu, and Kai Song. "Study on the Shape of the Aerator of High-Head Discharge Tunnel with Mild Bottom Slope." Water 13, no. 15 (August 2, 2021): 2128. http://dx.doi.org/10.3390/w13152128.
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Due to the high flow velocity and easy cavitation of high-head drainage tunnels, it is usually necessary to set up aeration facilities. In particular, when the bottom slope of the tunnel is mild, the aeration facilities often have problems such as difficulty with air intake, short cavity, and serious water accumulation, which aggravate the risk of cavitation damage. In this paper, based on the Rumei hydropower station and the Gushui hydropower station, a method combining theoretical analysis and model testing is used to solve the connection problem between the aeration facility and the 3% mild bottom slope of a tunnel body, and the aeration facility shape of “lifting ridge + flat (mild) slope + steep slope” is put forward. The research shows that the steep slope section can smoothly connect the water flow over the cantilever, reduce the jet impact angle, prevent the water from backtracking, and produce a long and stable cavity in the flat (mild) slope section. The aeration concentration along the bottom of the tunnel is higher than 3% at 140 m over the top of the dam. The aeration effect of this type is better, and it can provide effective long-distance protection for a drainage tunnel with high head and a mild bottom slope.
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Dharmireddy, Ajay Kumar, Dr Sreenivasa Rao Ijjada, and Dr I. Hema Latha. "Performance Analysis of Various Fin Patterns of Hybrid Tunnel FET." International Journal of Electrical and Electronics Research 10, no. 4 (December 30, 2022): 806–10. http://dx.doi.org/10.37391/ijeer.100407.
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High speed and low power dissipation devices are expected from future generation technology of Nano-electronic devices. Tunnel field effect transistor (TFET) technology is unique to the prominent devices in low power applications. To minimize leakage currents, the tunnel switching technology of TFETs is superior to conventional MOS FETs. The gate coverage area of different fin shape hybrid tunnel field-effect transistors is more impacted on electric characteristics of drive current, leakage current and subthreshold slope. In this paper design various fin patterns of hybrid TFET devices and shows on better performance as compared with other fin shape hybrid tunnel FET. The TCAD simulation tool is used to determine the characteristics of different fin shape tunnel FET.
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Mabey, D. G., and F. W. Steinle. "Computer studies of hybrid slotted working sections with minimum steady interference at subsonic speeds." Aeronautical Journal 89, no. 884 (April 1985): 135–48. http://dx.doi.org/10.1017/s0001924000014664.
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SummaryCurrently there is renewed interest in the evaluation and reduction of steady wind tunnel wall interference, especially for large models.Evaluation of previous predictions for perforated and slotted tunnels suggests that a hybrid slotted tunnel, ie a slotted tunnel with closed slats and perforated slots) should offer minimum corrections for upwash, flow curvature and solid blockage. This suggestion is confirmed by the present computer studies of a range of rectangular hybrid slotted tunnels.The computer studies are for tunnel working section height to breadth ratios of 0·835 and 0·600 over the Mach number range from 0 to 0·85. Wings swept at 28° and 50°, with ratios of model span to tunnel breadth varying from 0 to 0·7, are considered. An idealised fuselage shape is used to predict solid and wake blockage corrections for the wall configurations selected on the basis of minimum upwash and curvature interference.
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Zhang, Long, Jian Jun Yang, and Jun Zhang. "Investigation of OpenCV Image Processing Technique Applied in Wind Tunnel Ice-Shape Measurement." Applied Mechanics and Materials 220-223 (November 2012): 1350–55. http://dx.doi.org/10.4028/www.scientific.net/amm.220-223.1350.
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Model ice-shape measurement is an essential part in the icing test in wind tunnel. The principle investigation of camera calibration and image processing technology based on OpenCV library which apply to ice-shape measurement in wind tunnel is presented in this paper. A kind of software with perfect function and good reproducibility was successfully developed. Ice-shape measurement test was conducted in wind tunnel and the application of OpenCV library in image post-processing was proved to be practical. This program can also be effectively used in aero-optics research, model attitude measurement and model deformation measurement in wind tunnel.
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Chen, Zhi Gang. "Dynamic Response of Shallow Buried Tunnel Subjected to SH Wave." Advanced Materials Research 163-167 (December 2010): 4265–68. http://dx.doi.org/10.4028/www.scientific.net/amr.163-167.4265.
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The dynamic stress concentration on quadratic and U-shaped cavities in half space, which are similar to the cross-section of the tunnels, is solved in this paper impacted by SH-wave. The analytical solution for the cavity in elastic half space is gained by the complex function method. In the complex plane, the scattering wave which satisfies the zero-stress condition at the horizontal surface can be constructed, the problem can be inverted into a set of algebraic equations to solve coefficients of the constructed scattering wave by least square method. For the earthquake-resistance researches, the numerical examples of the dynamic stress concentration around the quadratic and U-shaped cavities impacted by SH-wave are given. The influences of the dynamic stress concentration by the incident wave number and angle, the depth and shape of the cavity are discussed. It is showed that the interaction among the wave, the surface and the shallow buried tunnels should be cared in half space. In this situation, the dynamic stress concentration around the tunnel is greater obvious than the whole space.
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Huang, Bo, and Rui Jun Liu. "The Study of Numerical Analysis about the Stability of Tunnels with Typical Planes of Fracture." Applied Mechanics and Materials 353-356 (August 2013): 1507–10. http://dx.doi.org/10.4028/www.scientific.net/amm.353-356.1507.
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The optimum shape of the tunnel is usually decided by many factors. Not only should it ensure the stability of surrounding rock and the advantageous of masonry's stress, but also it need to meet the using requirements of the cavern, the convenience of the construction, the least excavated volume and the best economic results. Seeking the optimal shapes of the carven which is under the specific condition has always been paid great attention by engineers. With the help of ADINA finite element analysis software, this paper imitates related data in elastic theory about the excavation of tunnels with the typical planes of fracture which are under the same geology condition. After that, it contrasts the actual computing results with the theoretical analysis, and then studies planes of fracture's optimal excavated shapes of the tunnels.
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Sekularac, Milan, Novica Jankovic, and Petar Vukoslavcevic. "Ventilation performance and pollutant flow in a unidirectional-traffic road tunnel." Thermal Science 21, suppl. 3 (2017): 783–94. http://dx.doi.org/10.2298/tsci160321117s.
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To develop a reliable method for modeling fire case scenarios within the road tunnels and observing the effects of the skewed velocity, experimental and numerical approach is used. Experimental results obtained from a laboratory tunnel model installation, are used to define geometry and boundary conditions. The result for the overall ventilation performance is compared to the available cases, for empty tunnel and stationary bi-directional vehicle traffic. For a unidirectional traffic road tunnel, in traffic loaded conditions, with a ventilation system based on axial ducted fans, the numerical simulation is used to determine the flow and temperature fields, the ventilation efficiency (efficiency of momentum transfer), and to assess the shape of the velocity distribution. The effect that a skewed velocity distribution can have on the resulting thermal and pollutant fields (CO2), smoke backlayering and stratification, is evaluated using numerical simulations, for the model-scale tunnel fire conditions. The effect of two possible limiting shapes of the velocity distribution, dependent only on the location of the fire with respect to the nearest upstream operating fans, is analyzed. The numerical results for a fire are scenario are a starting point in assessing the feasibility of a laboratory model fire-scenario experiment, what is planned as the next step in this research.
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Luo, Yanbin, Jianxun Chen, Zhou Shi, Shaoqiang Zhang, Weiwei Liu, Yao Li, and Lijun Chen. "Performance of Super-Large-Span Tunnel Portal Excavated by Upper Bench CD Method Based on Field Monitoring and Numerical Modeling." Advances in Civil Engineering 2020 (August 13, 2020): 1–15. http://dx.doi.org/10.1155/2020/8824618.
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The number of super-large-span tunnels is increasing in both new construction and reconstruction projects in China recently. In super-large-span tunneling engineering, the deformation properties and mechanical behaviors of tunnel portal structure are more complex than those of common tunnel due to the flatter shape and larger construction span. The mechanical behaviors of rock mass change in response to different sequential excavation methods and supporting parameters. The upper bench CD method has been gradually applied in the construction of super-large-span tunnels in China. In this paper, the design parameters for the supporting structure of super-large-span tunnel were studied by the field monitoring and numerical modeling in a case study of Laohushan tunnel. It was found that the crown settlement was larger than the clearance convergence, and the stress of arch was greater than that of the side wall in tunnel portal section. The invert structure was flat with small curvature. Therefore, the shotcrete was mainly subjected to tensile stress. The use of H200 × 200 steel rib with spacing of 60 cm and C25 shotcrete with thickness of 30 cm is recommended. The results of this paper provide basis for the development of design specifications and construction standards for super-large-span tunnels and provide reference for similar projects in the future.
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Wang, Zhiwei, and Weibin Ma. "Classification of the loosening zones and estimation of the loosening pressures of tunnels in layered jointed rock strata." Science Progress 105, no. 2 (April 2022): 003685042210988. http://dx.doi.org/10.1177/00368504221098886.
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Due to the complexity of tunnels, accurate prediction of their loosening pressures in layered jointed rock strata is a very difficult engineering task. To recognize loosening patterns and estimate loosening pressures, numerical tests were employed in areas where tunnels were excavated in layered jointed rock strata. A total of 12 influential factors, including joints, tunnel depth, and strata, were considered in each of the numerical models. Three loosening patterns were found in the numerical testing: a ringent trumpet-shaped boundary, an arch-shaped boundary, and a closing-trend trumpet-shaped loosening zone. Empirical expressions for the loosening zone boundaries were further established and, in the form of the 12 influential factors, considered in the simulation. Given the boundary function, the loosening pressures were further deduced, which were categorized according to loosening pattern, i.e., ringent trumpet shape or arch shape, and the excavation condition of whether or not the embedded depth was deeper than the soft layer. Two case studies were used to test this method. The newly-proposed method was found to perform better than existing methods, with loosening pressure values that were slightly larger than, but very close to, actual measured field data.
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Awadelseid, Khalid Musa Fadlelmula. "Morphological Study of the Posterior Tibial Nerve in Tarsal Tunnel of the Human Foot." International Journal of Human Anatomy 2, no. 3 (June 26, 2020): 1–9. http://dx.doi.org/10.14302/issn.2577-2279.ijha-20-3445.
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The passage of the posterior tibial nerve in the tarsal tunnel has a great clinical significance, thus detailed anatomical knowledge is mandatory for safe clinical intervention. This study was to identify the morphological appearance of the tibial nerve and its bifurcation. Sixty lower limbs of formalin embalmed cadavers were randomly selected. Data were collected through the application of standard dissection method of the tarsal tunnel of lower limbs (30 rights and 30 left) of formalin embalmed cadavers. The posterior tibial nerve and its branches were exposed from the distal end of the leg toward plantar surface beyond its bifurcation by resecting the skin and flexor retinaculum. The study triggered several findings: The posterior tibial nerve is flattened shaped in 21 specimens 70% and has a rounded shape in 9 specimens 30%in the right foot. In the left foot it is flattened in 17 specimens 56.7% and rounded shape in 13 specimens 43.3%. Posterior tibial nerve bifurcates into medial and lateral planter nerves inside tarsal tunnel in 20 specimens 66.7% in the right foot and in 21 specimens 70% in the left foot. This study concludes that posterior tibial nerve commonly has flattened shape and divided into medial and lateral planter nerves inside tarsal tunnel.
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Ghadimi, Behnam, Mojtaba Dehghan Manshadi, and Mehrdad Bazazzadeh. "Investigation of Transient Shock Wave in Supersonic Wind Tunnel." Applied Mechanics and Materials 232 (November 2012): 228–33. http://dx.doi.org/10.4028/www.scientific.net/amm.232.228.
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Wind tunnels are the experimental apparatuses which provide an airstream flowing under controlled conditions so that interesting items in aerospace engineering such as pressure and velocity can be tested. In this work, Shock wave passes through the intermittent blow-down wind tunnel at Mach=2,3,4 has been investigated. The shape of the nozzle contour for a given Mach number was determined using the method of characteristics. For this purpose MATLAB code was developed and this code was verified with Osher’s and AUSM methods, FORTRAN code and FLUENT software was used for these two methods, respectively. Dimensions of different parts of wind tunnel are determined and minimum pressure ratio for the starting condition has been founded using FLUENT software. Good agreement was considered compared with the data from eleven tunnels over their range of Mach number.
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Ahn, Jin Hwan, Ji Hoon Bae, Yong Seuk Lee, Kuiwon Choi, Tae Soo Bae, and Joon Ho Wang. "An Anatomical and Biomechanical Comparison of Anteromedial and Anterolateral Approaches for Tibial Tunnel of Posterior Cruciate Ligament Reconstruction: Evaluation of the Widening Effect of the Anterolateral Approach." American Journal of Sports Medicine 37, no. 9 (May 26, 2009): 1777–83. http://dx.doi.org/10.1177/0363546509332508.
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Background An anterolateral approach to the tibial tunnel of posterior cruciate ligament reconstruction is used to reduce the sharpness of the graft-tunnel angle, the so-called killer turn effect. However, with the anterolateral approach, the tunnel might be widened into an ovoid shape because of the small angle between the tunnel and the anterolateral cortex. Hypothesis The fixation strength of the posterior cruciate ligament graft in the tibial tunnel will be weaker in the anterolateral approach compared with the anteromedial approach. Study Design Controlled laboratory study. Methods Twenty paired cadaveric tibias were used. Tibial tunnels were made using following approaches: an anteromedial approach for 10 tibias and an anterolateral approach for 10 tibias. The anterior cortex-tunnel angle and the diameter of the tunnel entrance were measured by 2-dimensional computed tomographic scans. After fixation of the Achilles tendon allograft with a biodegradable screw, the maximal strength of the graft at failure was measured using a materials testing machine. Results The mean cortex-tunnel angle was 47.5° ± 9.3° in the anteromedial approach group and 28.3° ± 7.4° in the anterolateral approach group. The mean long diameter of the tunnels in the anteromedial approach group was 10.6 ± 1.0 mm and in the anterolateral approach group it was 14.0 ± 1.5 mm. These two parameters showed statistically significant differences between the 2 groups (P < .01). The mean maximum load at failure for the anteromedial approach group was 385.4 ± 139.7 N, and for the anterolateral approach group it was 225.1 ± 144.1 N. This difference was statistically significant (P = .021). Conclusion The anterolateral approach resulted in a tunnel with a wider entrance, a more acute cortex-tunnel angle, and a lower maximal load at failure compared with tunnels created using the anteromedial approach. Clinical Relevance The use of additional fixation methods, such as post ties or ligament washers and screws, should be considered when using an anterolateral approach for tibial tunnel of posterior cruciate ligament reconstruction.
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Konstantas, Ioannis, Janne Paajanen, Juha Salmelainen, and Jukka Yli-Kuivila. "Blominmäki wastewater treatment plant’s sewage tunnels: Challenging connection of a vertical shaft to the existing operating offshore tunnel." IOP Conference Series: Earth and Environmental Science 1124, no. 1 (January 1, 2023): 012127. http://dx.doi.org/10.1088/1755-1315/1124/1/012127.
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Abstract The sewage tunnels of the Blominmäki Wastewater Treatment Plant (WWTP) consist of approximately 20 kilometers of inlet and discharge tunnels, access tunnels and shafts. The most challenging and technically critical part of this project was the connection of the operating offshore tunnel of the old treatment plant with the Blominmäki discharge route, through a vertical shaft. Lack of information regarding the exact location, the shape and the geological conditions of the existing tunnel called for an accurate excavation design to avoid a potential tunnel collapse and rock blocking or massive waterflow during breakthrough. An additional complexity related to the continuous operation of the tunnel in question, as both non-stop flow of treated wastewater and cooling water of the nearby heat and powerplant, had a huge impact to the ways that all work phases were carried out. All parts involved, including the clients, the contractor and a variety of consultants cooperated in order that one of the most demanding shaft excavations in Finland be carried out successfully. This paper aims to present an overview of the related challenges, along with the detailed design, risk assessment and respective mitigation measures, information about problem solving and lessons learned during the execution.
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Li, Wen Bo, Wen Pei Wang, Lian Jin Tao, and Yin Tao Zhang. "Surface Settlement Law Induced by Shield Tunnel Excavation Using Modified Gap Model." Applied Mechanics and Materials 170-173 (May 2012): 1515–19. http://dx.doi.org/10.4028/www.scientific.net/amm.170-173.1515.
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GAP model will be modified and programmed by FISH language, which can be used in FLAC2D programs. The modified GAP model is used to study the variation of surface settlement shape with depth, the variation of the maximum settlement value with depth, and the variation of settlement gradient with depth. The results show that: the settlement shape is narrow and deep with the conditions of shallow buried depth of tunnel; on the contrary, the settlement shape is wide and shallow; When the tunnel depth is less than the critical value, the tunnel depth and the maximum surface settlement is approximately linear; when the tunnel depth is greater than the critical value, the curve of maximum surface settlement value with depth becomes flat and with the increase of the tunnel, the surface settlement gradient gradually decreases and eventually tends to zero. It is more reasonable to assess the influence of tunnel excavation near adjacent buildings, using the maximum surface settlement and the settlement gradient as a control standard.