Journal articles on the topic 'CIRCULAR TUNNELS'
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1
Pham, Van Vi, Ngoc Anh Do, and Daniel Dias. "Sub-Rectangular Tunnel Behavior under Seismic Loading." Applied Sciences 11, no. 21 (October 23, 2021): 9909. http://dx.doi.org/10.3390/app11219909.
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Circular and rectangular tunnel shapes are usually chosen when excavating at shallow depths in urban areas. However, special-shaped tunnels such as sub-rectangular tunnels have recently been used to overcome some drawbacks of circular and rectangular tunnels in terms of low space utilization efficiency and stress concentration, respectively. In the literature, experimental studies as well as analytical and numerical models have been developed for the seismic analysis and vulnerability assessment of circular and rectangular tunnels since the early 1990s. However, knowledge gaps regarding the behavior of sub-rectangular tunnels under seismic loading remain and still need to be bridged. The present paper focuses on introducing a numerical analysis of sub-rectangular tunnels under seismic loading. The numerical model of sub-rectangular tunnels is developed based on the numerical analyses of circular tunnels validated by comparing well-known, analytical solutions. This paper aims to highlight the differences between the behavior of sub-rectangular tunnels compared with circular tunnels when subjected to seismic loadings. Special attention is paid to the soil–lining interface conditions. The influence of parameters, such as soil deformations, maximum horizontal acceleration, and lining thickness, on sub-rectangular tunnel behavior under seismic loading is also investigated. The results indicate a significant behavior difference between sub-rectangular and circular tunnels. The absolute extreme incremental bending moments for a circular tunnel (no-slip condition) are smaller than that for the corresponding full-slip condition. The absolute extreme incremental bending moments of sub-rectangular tunnels (no-slip condition) are, however, greater than the corresponding full-slip conditions.
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Yan, Li, and Jun Sheng Yang. "Displacements around Two Closely Adjacent Circular Openings." Applied Mechanics and Materials 170-173 (May 2012): 1397–401. http://dx.doi.org/10.4028/www.scientific.net/amm.170-173.1397.
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Deformations of the tunnels may results in settlements of the ground surface. Based on the characters of deformation of twin closely adjacent tunnels excavated, a basic deformation mechanism of two parallel tunnels constructed close together was present, which is not uniform but oval-shaped ground deformation pattern and represent the ground loss occurred during construction of the tunnels. An improved convergence model of the tunnel boundary for twin closely adjacent tunnels and the related expressions are proposed. Using a computer package FLAC2D, the certain given deformations as the boundary condition were applied to the boundaries of two tunnels, and the surface settlements caused by the excavation of two tunnels were obtained. It is found that the results match well with the measured field results.
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Pham, Vi Van, Anh Ngoc Do, Hung Trong Vo, Daniel Dias ., Thanh Chi Nguyen, and Do Xuan Hoi. "Effect of soil Young’s modulus on Sub-rectangular tunnels behavior under quasi-static loadings." Journal of Mining and Earth Sciences 63, no. 3a (July 31, 2022): 10–21. http://dx.doi.org/10.46326/jmes.2022.63(3a).02.
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Tunnels are an important component of the transportation and utility system of cities. They are being constructed at an increasing rate to facilitate the need for space expansion in densely populated urban areas and mega-cities. The circular and rectangular tunnels cannot completely meet the requirements of underground space exploitation regarding the cross-section. Sub-rectangular tunnels are recently used to overcome some drawbacks of circular and rectangular tunnels in terms of low utilization space ratio and stress concentration, respectively. However, the behavior of the sub-rectangular tunnels under seismic loading is still limited. This need to be regarded and improved. This paper focuses on conducting a numerical analysis to study the behavior of the sub-rectangular tunnels under seismic loadings. Here seismic loadings in this study are represented by quasi-static loadings. Based on the numerical model of the circular tunnel that was validated by comparison with analytical solutions, the numerical model of the sub-rectangular tunnel is created. This paper is devoted to highlight the differences between the behavior of the sub-rectangular tunnels compared with the circular ones subjected to quasi-static loadings. The soil-lining interaction, i.e., full slip and no-slip conditions are particularly considered. The influence of soil’s Young’s modulus on the sub-rectangular tunnel behavior under quasi-static loading is also investigated. The results indicated that soil’s Young’s modulus significantly affects static, incremental, and total internal forces in the tunnel lining under quasi-static loadings. Special attention is a significant difference in total internal forces in the sub-rectangular tunnel lining in comparison with the circular tunnel ones and the stability of the lining tunnel for both the full slip and no-slip conditions when subjected to quasi-static loadings.
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Duan, Yawei, Mi Zhao, Jingqi Huang, Huifang Li, and Xiuli Du. "Analytical Solution for Circular Tunnel under Obliquely Incident P Waves considering Different Contact Conditions." Shock and Vibration 2021 (December 22, 2021): 1–23. http://dx.doi.org/10.1155/2021/1946184.
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An analytical solution for the seismic-induced thrust and moment of the circular tunnel in half-space under obliquely incident P waves is developed in this study, which is the superposition of the solution for deep tunnels under incident and reflected P waves and the reflected SV waves. To consider tangential contact stiffness at the ground-tunnel interface, a spring-type stiffness coefficient is introduced into the force-displacement relationship. Moreover, the tunnel lining is treated as the thick-wall cylinder, providing more precise forecasts than beam or shell models used in previous analytical solution, especially for tunnels with thick lining. The reliability of the proposed analytical solution is assessed by comparing with the dynamic numerical results. Based on the proposed analytical solution, parametrical studies are conducted to investigate the effect of some critical factors on the tunnel’s seismic response, including the incident angles, the tangential contact stiffness at the ground-tunnel interface, and the relative stiffness between the ground and the tunnel. The results demonstrate that the proposed analytical solution performs well and can be adopted to predict the internal forces of circular tunnels under obliquely incident P waves in seismic design.
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Xu, Hua, Tianbin Li, Jingsong Xu, and Yingjun Wang. "Dynamic Response of Underground Circular Lining Tunnels Subjected to Incident P Waves." Mathematical Problems in Engineering 2014 (2014): 1–11. http://dx.doi.org/10.1155/2014/297424.
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Dynamic stress concentration in tunnels and underground structures during earthquakes often leads to serious structural damage. A series solution of wave equation for dynamic response of underground circular lining tunnels subjected to incident plane P waves is presented by Fourier-Bessel series expansion method in this paper. The deformation and stress fields of the whole medium of surrounding rock and tunnel were obtained by solving the equations of seismic wave propagation in an elastic half space. Based on the assumption of a large circular arc, a series of solutions for dynamic stress were deduced by using a wave function expansion approach for a circular lining tunnel in an elastic half space rock medium subjected to incident plane P waves. Then, the dynamic response of the circular lining tunnel was obtained by solving a series of algebraic equations after imposing its boundary conditions for displacement and stress of the circular lining tunnel. The effects of different factors on circular lining rock tunnels, including incident frequency, incident angle, buried depth, rock conditions, and lining stiffness, were derived and several application examples are presented. The results may provide a good reference for studies on the dynamic response and aseismic design of tunnels and underground structures.
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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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Cilingir, Ulas, and S. P. Gopal Madabhushi. "Effect of depth on seismic response of circular tunnels." Canadian Geotechnical Journal 48, no. 1 (January 2011): 117–27. http://dx.doi.org/10.1139/t10-047.
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Tunnels in seismically active areas are vulnerable to adverse effects of earthquake loading. Recent seismic events have shown that there is a need to validate current design methods to better understand the deformation mechanisms associated with the dynamic behaviour of tunnels. The research described in this paper consists of physical and numerical modelling of circular tunnels with dynamic centrifuge experiments and complementary finite element simulations. The aim is to develop an understanding of the effects of tunnel depth on the seismic behaviour of tunnels. Tunnels with different depth-to-diameter ratios were tested in dry, loose silica sand. Accelerations around the tunnel and earth pressures on the lining were measured. A high-speed digital camera was used to record soil and lining deformations. Particle image velocimetry analyses were carried out on the recorded images to measure the deformations. Complementary dynamic finite element simulations were also conducted with a code capable of managing contact simulations at the soil–lining interface. Measurement of centrifuge experiments and finite element analyses show that the tunnel shifts from a static equilibrium to a dynamic equilibrium state as soon as the earthquake starts. The nature of the dynamic equilibrium, however, is difficult to predict using conventional analysis methods.
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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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Leong, Jik Chang, C. L. Chang, Y. C. Chen, and L. W. Chen. "Smoke Propagation in an Inclined Semi-Circular Long Tunnel." Advanced Materials Research 446-449 (January 2012): 2143–48. http://dx.doi.org/10.4028/www.scientific.net/amr.446-449.2143.
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This work used FDS to simulate tunnel fires occur in a semi-circular longitudinally ventilated tunnel. By varying the parameters such as the tunnel gradient, the fire size, and the ventilation velocity, their influence on the backlayering effect and downstream propagation rate can be recognized. Under weak ventilation, the backlayering effect either advances or vanishes depending on the slope of the tunnel. Under stronger ventilation, the backlayering effect would break up. The temperature distributions may become less and less dependent on the tunnel gradient when the ventilation velocity is increased. Although the hot gases and smoke in uphill tunnels propagate faster than those in downhill tunnels, their difference reduces with ventilation velocity.
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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.
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Lyu, Cheng, Zhengqiang Zeng, and Yucang Dong. "Limit Analysis of Progressive Asymmetrical Collapse Failure of Tunnels in Inclined Rock Stratum." Symmetry 11, no. 7 (July 11, 2019): 904. http://dx.doi.org/10.3390/sym11070904.
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Tunnels commonly pass through inclined rock stratum, but research on the collapse of the rock surrounding the tunnels in inclined rock strata is currently underdeveloped. The purpose of this study was to predict the progressive asymmetrical collapse failure of deep-buried tunnels in inclined rock strata to decrease the risk of collapse during tunnel construction. We constructed a new two-dimensional progressive asymmetrical collapse failure mechanism for deep-buried tunnels in inclined rock layers to analyze their collapse failure characteristics with the help of the nonlinear Hoek–Brown yield criterion and the limit analysis theorem. The calculation equations of the range and total weight of the asymmetrical collapsing block in rectangular and circular tunnels were obtained via theoretical derivation. The validity of the proposed method in this work was verified by comparison with existing research. To discuss the impact of different parameters on the range and total weight of an asymmetrical collapsing block of the surrounding rock in inclined rock stratum, the range and total weight of the asymmetrical collapsing block of the most common rectangular and circular tunnels under the varied parameters are provided. The results of this study can provide useful support for practical tunnel construction and design.
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Zhou, Yuan, Yuming Zhu, Shumao Wang, Hu Wang, and Zhengxing Wang. "Rotational Failure Mechanism for Face Stability of Circular Shield Tunnels in Frictional Soils." Advances in Civil Engineering 2019 (March 7, 2019): 1–14. http://dx.doi.org/10.1155/2019/7167802.
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Face stability analyses of shield-driven tunnels are often carried out to determine the required support pressure on the tunnel face. Although various three-dimensional mechanisms have been proposed for circular faces of tunnels in frictional and/or cohesive soils to obtain the limit support pressure, the most critical one has not yet been found. Based on a rotational failure mechanism for the frictional soils, this paper modifies the circular cross section as an ellipse to make the generating collapse surface inscribe the entire circular tunnel face. Using the kinematical approach of limit analysis yields an upper bound to the limit support pressure. Through comparisons with the existing results in the literature, the improved mechanism can better estimate the upper bound and is very similar to the observed failures in the experimental tests. The influences of the pore water pressure are also included in the stability analysis of tunnel faces. Calculated upper-bound solutions are presented in a condensed form of charts for convenient use in practice.
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Mohammed Asadullah, Sher Afghan Khan, Parvathy Rajendran, and Ervin Sulaeman. "Design Intent of Future Tunnels." Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 88, no. 2 (November 1, 2021): 50–63. http://dx.doi.org/10.37934/arfmts.88.2.5063.
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The sound barrier for bullet trains remains a challenge due to the piston effect causing compression waves at the entry and exit of the tunnel. The air ahead of the train nose is compressed, and the wave propagates through the tunnel at the speed of sound and exits with the generation of micro pressure waves. It gives rise to a complex wave pattern comprising compression at the train nose & expansion at the train tail leading to the positive pressure around the nose and suction around the tail. This is intended to provide exhaustive input for the proper design of a futuristic tunnel. The cross-sectional shapes of the tunnel, whether square, rectangular, circular, or semi-circular, will experience pressure compression wave generated by high-speed train but will influence the flow pattern and hence the compression wave. This paper presents the pressure load on the walls of long and short tunnels for subsonic compressible and transonic flows. The experimental investigation is carried out only for length parameters to study short and long tunnels. Further, flow visualization is also provided after the formation of the sonic boom. The results of this investigation can be an essential data source for optimum design of high-speed tunnels so as to suppress or break the sound barriers, thus, resulting in a safer high-speed train network.
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Xu, Hua, Tian Bin Li, and Long Qi Li. "Research on Dynamic Response of Underground Circular Lining Tunnel under the Action of P Waves." Applied Mechanics and Materials 99-100 (September 2011): 181–89. http://dx.doi.org/10.4028/www.scientific.net/amm.99-100.181.
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Dynamic stress concentration of tunnels and underground engineers under the action of earthquake waves is a fundamental problem. Selecting circular lining tunnel in semi-infinite space under the action of P waves as prototype, based on the assumption of large circular arc, a set of dynamic stress series solution in semi-infinite space and lining is deduced by wave function expansion method. With specific examples, the influences on shallow-buried depth rock tunnels of different factors which include incident frequency, incident angle, buried depth, rock conditions and lining rigidity are studied. The results show that low-frequency P waves are more dangerous to tunnel lining than high-frequency P waves; When P waves is incident from the bottom of the vertical tunnel or small angle (θα = 0° ~ 30°), the damage of tunnel lining is more seriously; Under the hard rock conditions, when the tunnel buried depth reaches more than 100m, the thickness of overlying rock is not a major factor effecting the dynamic stress and earthquake damages of tunnel structure lining; Under the soft surrounding rock condition, the value of dynamic stress concentration coefficient of lining is still up to 6.5 when the buried depth of tunnels is more than 100m, and what’s more the tunnel lining may still be caused seriously earthquake damage; With the increasing of lining stiffness, the dynamic stress concentration of lining is more uneven, and the value span is greater; so under the premise of meeting bearing capacity and deformation of lining, soft lining is recommended to adapt in the tunnel structure to decrease earthquake damage of tunnels.
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Fan, Hao, Lei Wang, and Shaobo Li. "A New Approach for Analyzing Circular Tunnels in Nonlinear Strain-Softening Rock Masses Considering Seepage Force." Minerals 13, no. 2 (January 17, 2023): 138. http://dx.doi.org/10.3390/min13020138.
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Accurate calculation of the stresses and deformations of tunnels is of great importance for practical engineering applications. In this study, a three-region model for tunnels considering seepage force was established. A new nonlinear strain-softening model is proposed. Then, a unified solution for the stresses and deformations of tunnels is deduced. Through a series of discussions, the effects of seepage force, softening modulus coefficient of cohesion, and initial support resistance on the stress distribution, radii of the post-peak zone, and surface displacement around the tunnel are discussed. Results show that the tangential stresses are always larger than the radial stresses. As the distance from the tunnel center increases, the radial stress continues to increase, while the tangential stress first increases and then decreases. With the increases in seepage force, the radii of the post-peak zone and surface displacement all increase. With the increases in softening modulus coefficient of cohesion, the radii of the post-peak zone increase while the surface displacement decreases. Tunnels with a higher initial support resistance experience lower radii of the post-peak zone and surface displacement.
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Du, Jingna, and Fei Ye. "The Influence of Hydraulic Conditions on the Stability of Dual Circular Tunnels in Unsaturated Soils." Mathematical Problems in Engineering 2021 (May 4, 2021): 1–22. http://dx.doi.org/10.1155/2021/8503490.
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The performance of geotechnical structures in unsaturated soils is affected significantly by the hydraulic conditions. In the present paper, a unified computational upper bound limit analysis method is applied to study the stability of dual circular tunnels located in unsaturated soils. The linings are substituted by an equivalent uniform pressure exerted on the periphery of the tunnel. The main focus is put on the effect of ground water table and surface water infiltration on the required supporting pressure and collapse mechanisms of dual tunnels. The critical center-to-center spacing above which the interaction of the tunnels disappears is also discussed.
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Boštík, Jiří, and Kamila Weiglová. "Modelling of Discontinuous Environment." Key Engineering Materials 525-526 (November 2012): 33–36. http://dx.doi.org/10.4028/www.scientific.net/kem.525-526.33.
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Deformation process and strength of rock environment is significantly influenced by a presence of discontinuity planes. The paper deals with experimental modeling of underground structures in such a rock environment. Parametric analysis presents results from twin circular tunnels simulated in a scale model. The cases with and without zone of dislocations in between the tunnels were observed. Another variable factor studied was the distance between tunnels. The relation between model surface displacement and excavated length of the tunnel, which was monitored during the simulations, was used for mutual comparison of individual cases.
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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.
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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.
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Akhlaghi, Tohid, and Ali Nikkar. "Effect of Vertically Propagating Shear Waves on Seismic Behavior of Circular Tunnels." Scientific World Journal 2014 (2014): 1–10. http://dx.doi.org/10.1155/2014/806092.
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Seismic design loads for tunnels are characterized in terms of the deformations imposed on the structure by surrounding ground. The free-field ground deformations due to a seismic event are estimated, and the tunnel is designed to accommodate these deformations. Vertically propagating shear waves are the predominant form of earthquake loading that causes the ovaling deformations of circular tunnels to develop, resulting in a distortion of the cross sectional shape of the tunnel lining. In this paper, seismic behavior of circular tunnels has been investigated due to propagation of shear waves in the vertical direction using quasi-static analytical approaches as well as numerical methods. Analytical approaches are based on the closed-form solutions which compute the forces in the lining due to equivalent static ovaling deformations, while the numerical method carries out dynamic, nonlinear soil-structure interaction analysis. Based on comparisons made, the accuracy and reliability of the analytical solutions are evaluated and discussed. The results show that the axial forces determined using the analytical approaches are in acceptable agreement with numerical analysis results, while the computed bending moments are less comparable and show significant discrepancies. The differences between the analytical approaches are also investigated and addressed.
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Abo-Seida, Osama M. "Radio communication in circular tunnels." International Journal of Applied Electromagnetics and Mechanics 29, no. 3-4 (May 27, 2009): 157–61. http://dx.doi.org/10.3233/jae-2009-1010.
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Dudley, D. G. "Wireless propagation in circular tunnels." IEEE Transactions on Antennas and Propagation 53, no. 1 (January 2005): 435–41. http://dx.doi.org/10.1109/tap.2004.836407.
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Luo, Yan-ping, Quan Feng, Tao Zhou, Tao Liu, Zheng-yong Xiao, and Sheng Wang. "The Seismic Response of a Lined Tunnel under Plane P-wave in a Slope Site." Journal of Physics: Conference Series 2230, no. 1 (March 1, 2022): 012014. http://dx.doi.org/10.1088/1742-6596/2230/1/012014.
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Abstract The indirect boundary element method (IBEM) is adopted to solve the 2D scattering problem of circular underground lining tunnels near canyons and slopes to the P-wave. The numerical results show that the canyon and slope topography near the underground lining tunnel has an evident influence on the surface displacement. The horizontal displacement amplification reaches nearly two times. The presence of slopes has a shielding effect on the nearby underground tunnels. The stress concentration exists at the top and bottom of the arch of the lining tunnel. The dynamic interaction between the slope and the tunnel should be considered when building a tunnel close to the slope.
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Liu, Hao, Wen Zhang, Zhenglong Wu, Tieying Guo, Dan Luo, Weiping Peng, and Tao Zhang. "Research on Fuzzy Control Algorithm of Self-walking Platform for Maintenance of Circular Tunnel." Journal of Physics: Conference Series 2218, no. 1 (March 1, 2022): 012087. http://dx.doi.org/10.1088/1742-6596/2218/1/012087.
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Abstract Self-walking platform is used to support subway tunnel maintenance and construction. However, the kinematics model and motion control of the subway tunnel self-propelled platform are different from that of the plane, it is a non-holonomic constrained system with serious sliding, strong coupling and highly nonlinear, and the pipeline environment is complex, so it is difficult to accurately model. In order to solve these differences, the kinematic characteristics of wheels in cylindrical workspace are discussed first. The geometric constraints of self-walking platform in circular tunnels are also analyzed. Secondly, considering the complexities of self-walking platform motion model, a control algorithm based on fuzzy logic is proposed. Finally, through MATLAB and ADAMS joint simulation, the scenarios for virtual platform moving in circular tunnels are simulated, which shows the effectiveness of the algorithm.
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Zou, Yan, Li Ping Jing, Hai Feng Sun, and Yong Qiang Li. "Analysis of Seismic Factors to Tunnels in the Earthquake." Applied Mechanics and Materials 166-169 (May 2012): 2182–89. http://dx.doi.org/10.4028/www.scientific.net/amm.166-169.2182.
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Underground structures have mechanical characteristics and seismic responses very different from common structures on the ground in the earthquake due to the constraints of the surrounding soil. Tunnel destruction has occurred many times in domestic and international earthquake. In order to study seismic factors and failure mechanism of tunnels in the earthquake, numerical simulation of the seismic responses of the circular shield tunnel is carried on. Harmonic P-waves and S-waves are entered to make the tunnel vibrate and deform. Viscous-spring artificial boundary condition is applied in the numerical simulation to consider the semi-infinity of soil. The elastic modulus of soil, the frequency of harmonic waves and the depth of the tunnel are regarded as the main factors. The seismic responses such as stress and relative displacement are analyzed in different parameters to get the failure mechanism of circular tunnel.
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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.
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Yang, Xin, and Jiangping Long. "Reliability Prediction of Tunnel Roof with a Nonlinear Failure Criterion." Mathematics 11, no. 4 (February 12, 2023): 937. http://dx.doi.org/10.3390/math11040937.
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Based on the kinematics-based upper bound theorem and reliability theory, the stability of deep tunnel roofs in nonlinear Hoek-Brown media is investigated. The performance functions of rectangular and circular tunnels are proposed according to the roof collapse mode, respectively, with support pressure and pore water pressure being considered. With the proposed performance function of the rectangular tunnels, the first-order reliability method is utilized to perform reliability analysis. The rock strength parameters are regarded as random variables following the normal or lognormal distribution. To assess the validity of the obtained results, reliability indexes for different support pressure values are calculated and compared with solutions using the response surface method and Monte-Carlo simulation. The agreement shows that the first-order reliability method effectively evaluates the reliability index with the proposed performance function. Sensitivity analysis is performed to throw light on the significance of different random variables, and the impact of the variation coefficient on reliability indexes is discussed. For circular tunnels, MCS is utilized to evaluate the roof stability with the proposed performance function. The influences of the support pressure on the reliability index and the corresponding design points are investigated. The parametric study shows that the normal distribution of random variables has more influence on the failure probability than that of the lognormal distribution. However, the difference between the two distributions is small. σt is the major factor that influences the reliability index compared to the B and ru. The supporting pressure for circular tunnels is smaller than that of rectangular tunnels when a target reliability index of 2.5 (failure probability equals 0.62%) is given.
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Terner, Eleanor R. "Mammal use of underpasses to cross Route 606 in Guacimal, Costa Rica." Neotropical Biology and Conservation 18, no. 2 (August 2, 2023): 107–17. http://dx.doi.org/10.3897/neotropical.18.e102809.
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Roads severely affect the health of ecosystems across the globe by fragmenting and diminishing habitats, reducing population connectivity, and increasing animal mortality. Wildlife underpasses allow for increased road permeability–the ability for animals to safely cross the road. Despite growing success in other regions, little is known about underpass usage in Central America. In this study, I monitored two dry circular culverts and two unfenced tunnels with barbed wire partially blocking their entrances on Route 606 in Guacimal, Costa Rica, from 14 November to 6 December 2021 using 15 camera traps to assess which species used them to cross. Twelve species used the culverts and tunnels for a total of 108 individual crossings. The tunnels were used, in descending order, by agouti (Dasyprocta punctata), common opossum (Didelphis marsupialis), dog (Canis familiaris), nine-banded armadillo (Dasyous novemcinctus), cat (Felis catus), Norway rat (Rattus norvegicus), ocelot (Leopardus pardalis), squirrel (Sciurus variegatoides), northern tamandua (Tamandua mexicana), and coati (Nasua narica). The circular tunnel, Tunnel 1, was used more frequently and by a greater diversity of species than observed in the square tunnel, Tunnel 2. The two smaller culverts were used by common opossum (Didelphis marsupialis), cat (Felis catus), rat opossum (Micoureus alstoni), and Watson’s climbing rat (Tylomus watsoni). Culvert 2 was used more frequently; however, Culvert 1 was used by a greater diversity of species. This study highlights wildlife underpasses as a critical strategy for biological conservation in Costa Rica through improved road safety and habitat connectivity.
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Jin-feng, Zou, Zhang Yan-jun, and Dan Han-cheng. "Three-Dimensional Ground Settlement Induced by Metro Tunnel Excavation Considering the Influence of Group Piles." Mathematical Problems in Engineering 2016 (2016): 1–13. http://dx.doi.org/10.1155/2016/4964191.
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Considering the influence of group piles, a prediction model for three-dimensional ground surface settlement induced by circular metro tunnels excavation in incompressible rock masses is proposed based on the stochastic medium theory and the shear displacement method. The surface settlement caused by the metro tunnel opening is divided into two parts. One part is soil mass settlement caused by the metro tunnel opening and calculated by the stochastic medium theory. The other part is the settlement induced by the friction force between the group piles and the soil mass around the metro tunnel cross section and calculated by the shear displacement method. The three-dimensional prediction of the ground surface settlement is obtained by the linear superposition of the two parts. The validation of the proposed prediction approach is proved by comparing with the measured data and the numerical model of the double tunnels under thePuyuanoverpass where metro tunnels undercrossed group piles. The effects of buried depth, radial convergences, center distance of double tunnels, position and size of piles, and group piles are analyzed and discussed. The improved prediction approach can be applied to calculate the three-dimensional ground settlement, especially for the metro tunnels crossing through group piles.
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Singh, DK, SR Karumanchi, A. Mandal, YB Katpatal, and A. Usmani. "Effect of earthquake excitation on circular tunnels: Numerical and experimental study." Measurement and Control 52, no. 7-8 (May 22, 2019): 740–57. http://dx.doi.org/10.1177/0020294019847705.
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This paper studies the behaviour of circular tunnel subjected to dynamic excitation. Tunnels with three different diameters were selected to perform the shake table test at three different covers. The dry sandy soil was used for testing. The mechanical properties like Young’s modulus and shear modulus of sand was calculated from bender element test. The soil–tunnel interface coefficient was calculated from the direct shear test. The soil pressure generated due to dynamic loading were measured by soil pressure transducers. The actual motion of shake table was captured by hand-held vibration analyser. The tunnel was placed parallel and perpendicular to the direction of shaking. The three-dimensional finite-element model was developed for tunnel with both the orientations. The tunnel was assumed to be elastic. Dry sand was assumed to follow non-linear elasto-plastic material using Mohr–Coulomb failure criterion with non-associated flow rule. The results obtained from numerical analysis are compared with experimental results and are expressed in the form of peak dynamic stresses. The time history and fast Fourier transform results of dynamic stresses are also compared. It shows reasonable agreement with both values. Finally, the seismic design guidelines for tunnel are suggested.
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Wilson, Daniel W., Andrew J. Abbo, Scott W. Sloan, and Andrei V. Lyamin. "Undrained Stability of Dual Circular Tunnels." International Journal of Geomechanics 14, no. 1 (February 2014): 69–79. http://dx.doi.org/10.1061/(asce)gm.1943-5622.0000288.
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Vardakos, S., and M. Gutierrez. "Simplified parameter identification for circular tunnels." Tunnelling and Underground Space Technology 21, no. 3-4 (May 2006): 372. http://dx.doi.org/10.1016/j.tust.2005.12.187.
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Fakhriyeh, Hamed, Reza Vahdani, and Mohsen Gerami. "Spectral Velocity of the Ground Surface in Alluvial Soils due to the Presence of Circular Urban Subway Tunnels." Shock and Vibration 2022 (April 25, 2022): 1–16. http://dx.doi.org/10.1155/2022/3861288.
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In this study, the effect of urban subway tunnels with a circular cross section on the spectral velocity of the ground surface in alluvial soils was investigated. By changing the soil characteristics of the tunnel construction site and the geometric characteristics of the tunnel section (such as the radius and thickness of the lining and the depth of its placement), the frequency of the soil-tunnel system was changed. Then, the maximum velocity values were extracted for different parts of the ground surface. By averaging the data for each model, the amount of spectral velocity for different parts of the ground surface was extracted. The results show that the spectral velocity of the ground surface decreases by increasing the tunnel radius by 92% to a maximum of 12.3% in the tunnel center image on the ground’s surface. Also, by increasing the doubling of the depth of the tunnel, the spectral velocity of the ground surface at a distance approximately equal to the radius of the tunnel is reduced to a maximum of 4.42%. The increase in the spectral velocity of the ground surface due to the increase in the depth of the tunnel is a maximum of 12.13% and occurs at a distance approximately equal to the tunnel radius. In a small number of reviewed models, increasing the depth of the tunnel placement increases the spectral velocity of the ground around the tunnel. The effect of increasing the thickness of the tunnel lining on the spectral velocity of the ground surface was also investigated. In tunnels with greater overhead depth, the spectral velocity of the ground surface increases by a maximum of 10.86% with increasing thickness of the tunnel lining and occurs in the image of the center of the tunnel on the ground surface. In tunnels with less overhead depth, the spectral velocity of the ground surface decreases by a maximum of 7.56% with increasing thickness of the tunnel lining and occurs approximately at a distance equal to the diameter of the tunnel from the image of the tunnel center to the ground surface. The study was performed using PLAXIS 2D and Ansys finite element software.
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Oevering, P., and A. J. Pitman. "Characteristics of Attack of Coastal Timbers by Pselactus spadix (Herbst) (Col.: Curc.: Cossoninae) and an Investigation of its Life History." Holzforschung 56, no. 4 (June 27, 2002): 335–59. http://dx.doi.org/10.1515/hf.2002.053.
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Summary Pselactus spadix attack of marine timbers was characterised by circular emergence holes 1.48±0.05 mm in diameter and adult tunnels (1.49±0.34 mm) breaking through the wood surface. Larval tunnels measured 0.407–1.892 mm in diameter, initiated from adult tunnels and increased in diameter away from the adult tunnel terminating in frass free pupal chambers (1.6±0.3 mm × 3.5±0.7 mm). Observations of larval tunnel locations indicated oviposition occurred inside the adult tunnels. P. spadix life history was investigated in Scots pine (Pinus sylvestris) heartwood at 22±2 °C and 99±1% r.h. Mean adult longevity was 11.5±6.5 months, with mean post-mating longevity for males (11.7±2.9 months) significantly longer than for females (6.3±1.1 months). Adults of at least 2–3 months old were found mating in galleries, which, with observations of the larval tunnel pattern, indicated P. spadix can complete its life cycle without emerging from wood. Five larval instars were identified by measurement of 1722 head capsule widths and application of Dyar's law. Mean development time from 2nd instar to adult emergence was 70.5±6.9 weeks and pupation took 14.6±5.8 days. Development from 2nd instar to reproductive adult took between 17–20 months, with life cycle approximating 24 months at 22±2 °C and 99±1%
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Liu, Ning, Yi-Xiong Huang, Wei Cai, and Kun Chen. "Application of Improved Single-Hole Superposition Theory in Nonequal Cross-Section Tunnel Intersection." Advances in Civil Engineering 2020 (December 10, 2020): 1–15. http://dx.doi.org/10.1155/2020/8837480.
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With the excavation towards the intersecting tunnels’ direction, the impact on the surrounding rock stress between the two tunnels will gradually decrease, but how it decreased is not clear. At present, engineers often directly superimpose the stress in the triangular area of the crossing tunnel when calculating the stress in this area (single-hole superposition theory). The theory is also used as the main theory to consider the surrounding rock stress for support which is difficult to explain the situation of nonuniform cross-section centers not in the same plane. The safety level of support is mainly determined by construction experience which is unable to determine how to adjust the support level with the increase in the horizontal distance of intersecting tunnel, causing the insufficient utilization of materials. This paper derives theoretically the stress calculation of the triangular area of circular cross tunnels with different cross sections and analyzes the surrounding rock stress law of the intersecting tunnels triangular area from different cross-section dimensions (the difference in diameter between the two tunnels is twice, 3 times, and 4 times) and different intersection angles. And the results show that, compared with the case of equal tunnel diameters, the stress influence area of the surrounding rock in the triangle area mainly expands to the side of the small section with the increase of the cross-section difference of the intersecting tunnels; the dangerous area of the surrounding rock in the triangle area moves vertically to the small section; the safest condition is the two tunnels with 90° intersecting angle. The theoretical calculation model of this paper is verified by the previous research results.
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Liu, He, Junbo Liu, Peng Zhang, Yahong Zhao, Zhigang Wang, Lixin Jiao, Jingyao Luan, and Zihao Zhu. "FEM-Based Analysis of the Loading Capacity of Defective Cable Tunnel Structures." Buildings 12, no. 9 (September 2, 2022): 1368. http://dx.doi.org/10.3390/buildings12091368.
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With the popularized application of underground cable tunnels in China, various structural defects such as cracking, deforming and material deteriorating also emerge. In cable tunnels that have been poorly maintained for a long time, there is always a coexistence of several kinds of defects, and with the current methods of monitoring, it is difficult to identify the major defect affecting the load-carrying capacity and resolve it. However, the finite element method (FEM) can better solve this problem by analyzing the effect of a single defect parameter separately. In this paper, four different types of cable tunnels, namely the circular, rectangular, arched and trenched sectional tunnels, are modelled and analyzed with FEM. Defect parameters, including crack dimensions and concrete deterioration, are considered as variables, which are controlled and studied respectively. The results of the simulation indicate that the impact of crack propagation on the residual-bearing capacity of cable tunnels is much larger than that of concrete deterioration, especially the deepening of cracks. Works in this paper have the potential to be further referenced for cable-tunnel structure estimation and defect prevention.
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Wang, Mingnian, Xiao Zhang, Jianjun Tong, Wenhao Yi, Zhilong Wang, and Dagang Liu. "A New Semi-Analytical Method for Elasto-Plastic Analysis of a Deep Circular Tunnel Reinforced by Fully Grouted Passive Bolts." Applied Sciences 10, no. 12 (June 26, 2020): 4402. http://dx.doi.org/10.3390/app10124402.
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The use of fully grouted passive bolts as a reinforcement technique has been widely applied to improve the stability of tunnels. To analyze the behaviors of passive bolts and rock mass in a deep circular tunnel, a new semi-analytical solution is presented in this work based on the finite difference method. The rock mass was assumed to experience elastic–brittle–plastic behavior, and the linear Mohr–Coulomb criterion and the nonlinear generalized Hoek–Brown criterion were employed to govern the yielding of the rock mass. The interaction and decoupling between the rock mass and bolts were considered by using the spring–slider model. To simplify the analysis process, a bolted tunnel was divided into a bolted region and an unbolted region, while the contact stress at the bolted–unbolted interface and the rigid displacement of the bolts were obtained using two boundary conditions in combination with the bisection method. Comparisons show that the results obtained using the proposed solution agree well with those from the commercial numerical software and the in situ test. Finally, parametric analyses were performed to examine the effects of various reinforcement parameters on the tunnel’s stability. The proposed solution provided a fast but accurate estimation of the behavior of a reinforced deep circular tunnel for preliminary design purposes.
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Chen, Jia, Xuansheng Cheng, Shangrong Qi, Huan Feng, Liang Ma, and Lijun Gong. "Optimal Sections of Tunnels’ Cross Sections with Different Overburdens." Open Civil Engineering Journal 11, no. 1 (September 21, 2017): 714–25. http://dx.doi.org/10.2174/1874149501711010714.
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Introduction: In order to obtain the optimal section for super-large cross-section loess tunnels with different overburdens, the ANSYS software is applied in this paper. Methods: Based on the calculation nonconvergence criteria and Mohr-Coulomb criteria, the static stability of loess tunnel section is analyzed by the finite element static strength reduction method. According to the safety factors of rock mass surrounding tunnel in the case of critical failure, the safety factors of super-large cross-section loess tunnel is discussed with different section forms (rectangular cross-section, circular cross-section, horseshoe cross-section and curve wall cross-section) and different overburdens under gravity. Results and Conclusion: The results show that the safety factors of circular section and curve wall cross-section are bigger than the safety factors of the horseshoe cross-section and rectangular cross-section. The curve wall cross-section is considered to be the optimal section because of the fact that the force around the vault and the arch bottom is uniform and symmetrical, and the maximum vertical displacement of the lining is small. The horseshoe cross-section should be avoided in the loess tunnel, because the safety factor of horseshoe cross-section is so small, and stress concentration phenomenon is obvious in the case of deep buried tunnel.
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Huang, Zhongkai. "Resilience Evaluation of Shallow Circular Tunnels Subjected to Earthquakes Using Fragility Functions." Applied Sciences 12, no. 9 (May 8, 2022): 4728. http://dx.doi.org/10.3390/app12094728.
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The present work aims to introduce an integrated framework for the resilience evaluation of shallow circular tunnels subjected to earthquakes using fragility and restoration functions. A typical shallow circular tunnel in Shanghai city of China is examined in this work and a corresponding numerical model is established using ABAQUS. Then, a set of ground motions are well chosen to implement large numbers of non-linear numerical analyses so as to determine the lining responses of the tunnel structure with various levels of seismic intensities. According to the above numerical results, fragility functions in terms of the peak ground acceleration (PGA) and peak ground velocity (PGV) at the free-field ground surface are generated, accounting for the main sources of uncertainty, and the direct seismic loss for the examined tunnel is obtained. Moreover, according to the developed fragility functions and the existing empirical tunnel restoration functions, the evolution of the resilience index (Re) with various levels of PGA and PGV for the examined tunnel is derived and quantified. The results indicate that the tunnel resilience will decrease significantly as the earthquake intensity measure (IM), i.e., PGA or PGV herein, increases. The proposed framework is expected to help city managers support adaptations to seismic hazards with the development of preventive or retrofitting measures as part of efforts to provide more resilient metro systems.
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Han, Xingbo, Yongxu Xia, Xing Wang, and Lunlei Chai. "Complex Variable Solutions for Forces and Displacements of Circular Lined Tunnels." Mathematical Problems in Engineering 2018 (September 16, 2018): 1–12. http://dx.doi.org/10.1155/2018/2037845.
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A complex variable method for solving the forces and displacements of circular lined tunnels is presented. Complex potentials for the stresses and displacements are expressed in the term of series expression. The undetermined coefficients of the complex potentials are obtained according to the stress boundary conditions along the lining inner surface and the displacement and surface traction boundary condition along the lining and rock-mass interface. Solutions for the stresses and displacements of the tunnel lining and rock-mass are then established by applying Muskhekishvili’s complex variable method. In addition, forces solutions for linings are presented based on the tangential stress at the two boundaries. Examples are finally established to reveal the applicability and accuracy of the proposed method. The effects of the degrees from the tunnel crown to the invert, coefficient of the lateral earth pressure, and distance from the rock-mass to the interface on the regulations of the lining forces and rock-mass stresses are also thoroughly investigated.
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Zhang, Jinfeng, and Ming Zhao. "Monitoring System for Circular Deformation in Metro Shield Tunnels in Soft Soils." Advances in Civil Engineering 2020 (September 1, 2020): 1–12. http://dx.doi.org/10.1155/2020/8886402.
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For in-service metro shield tunnels in soft soils, large circular deformations are a major concern because they usually lead to various problems, such as water leakage, joint openings, and concrete cracks. However, the monitoring of circular deformation depends mainly on manual surveying, and the automatic monitoring methods developed in recent years generally have low economic applicability and are not widely implemented. In this study, an automatic and cost-effective system was presented to monitor circular deformation in shield tunnels by using only inclinometers. Experiments were conducted to prove the assumption that each segment can be regarded as a rigid body and to investigate the position of the joint rotation center. Then, a method for monitoring circular deformation based on the rigid body and plane section assumptions was proposed. The joint opening angle, maximum joint opening width, horizontal diameter convergence, and bolt strain were calculated from rotation angles of segments which can be monitored directly by inclinometer. A case study was conducted for a section of a metro shield tunnel with an ongoing pit excavation nearby. The rotation of segments was measured using MEMS inclinometers, and the data were transmitted using ZigBee and general packet radio service (GPRS) wireless communication technology. Results show that the proposed system could be implemented to improve transportation safety in relevant situations and similar conditions.
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Razavian Amrei, Seyed Amin, Reza Vahdani, Mohsen Gerami, and Gholamreza Ghodrati Amiri. "Correlation Effects of Near-Field Seismic Components in Circular Metro Tunnels: A Case Study—Tehran Metro Tunnels." Shock and Vibration 2020 (May 30, 2020): 1–13. http://dx.doi.org/10.1155/2020/3016465.
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Seismic evaluation of underground structures such as tunnels requires nonlinear dynamic analysis, due to the complex dynamic behavior of soil and the interaction of soil and structure. Simulation of the seismic response of the structure using nonlinear dynamic analysis is possible only with proper acceleration time history. Considering the vertical component of the earthquake (such as near-fault earthquakes) on the site is an important factor to achieve real structural responses. In the current study, soil-tunnel system has been modeled in ABAQUS software, considering Mohr–Coulomb nonlinear model for soil and concrete damage plasticity model for tunnel lining. In order to investigate the effect of seismic components correlation under different combinations of loads on the acceleration, axial force, and maximum shear force in tunnel lining, nonlinear dynamic analysis has been performed under four near-field earthquakes with different horizontal and vertical component ratios, considering 15 load combinations. The results show that increasing the vertical-horizontal component ratio has an insignificant effect on the maximum horizontal acceleration experienced by the tunnel lining. Also, the results of axial forces and shear forces indicate that increasing the ratio of vertical to horizontal components of the earthquake is the most effective factor on the axial force response.
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Zhang, Xuepeng, Yujing Jiang, Yue Cai, Xin Li, Naser Golsanami, Xiao Wang, Jian Hao, Ningbo Li, Fabo Wu, and Xiaohan Wang. "A Simplified Method for Predicting Tunneling-Induced Ground Movement considering Nonuniform Deformation Boundary." Shock and Vibration 2022 (January 13, 2022): 1–11. http://dx.doi.org/10.1155/2022/6289303.
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Stochastic medium (SM) theory is a practical method in ground settlement prediction, while its nonintegrable double integral form makes the solution process complicated. A simplified analytical solution based on the SM theory is developed to predict the ground movement in tunneling excavation. With the simplified solution, the ground movement for single tunnel and twin tunnels could be predicted based on the gap parameter G and influence angle β. A feasible approach is developed to estimate these two parameters using the maximum ground settlement Smax and tunnel design parameters, including tunnel depth H and diameter R. The proposed approach can be used to predict the ground movement curve for both circular and noncircular cross section tunnels. To validate its accuracy, the results predicted by the simplified procedure are compared with those obtained by the SM theory and measured in situ. The comparisons show that the current results agree well with those obtained by the SM theory and measured in situ. The comparison of five tunnels in literature illustrates that the simplified method can provide a more reasonable prediction for the ground movement induced by tunneling.
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Bao, Tong, Sulei Zhang, Chang Liu, and Qing Xu. "Experimental Study on the Effect of Hydraulic Deterioration of Different Drainage Systems on Lining Water Pressure." Processes 10, no. 10 (September 30, 2022): 1975. http://dx.doi.org/10.3390/pr10101975.
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With the increasing operation time of tunnels, the drainage system cannot fulfil its proper function as a result of the deterioration of traditional waterproof and drainage systems (TWDS), such as the blockage of drainage blind pipes and the failure of drainage boards. Therefore, the lining bears a high water pressure and even causes disasters such as tunnel leakage and lining cracking. An effective solution to mitigate these issues is to adjust the tunnel drainage scheme. In view of this, a composite waterproof and drainage system (CWDS) is proposed in this paper. To verify the effectiveness of the proposed system, a series of model experiments were conducted to study the change law of the seepage field of two drainage systems under different blockage conditions. The study results showed that longitudinal blind pipe blockage caused a more significant increase in water pressure than circular blind pipe blockage. In the case of blind pipe blockage, the water pressure of the TWDS tunnels rise rapidly, while the CWDS tunnels could effectively drain and reduce pressure.
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Guo, Qifeng, Jiliang Pan, Xinghui Wu, Xun Xi, and Meifeng Cai. "A New Unified Solution for Circular Tunnels Based on Generalized SMP Criterion considering the Strain Softening and Dilatancy." Advances in Civil Engineering 2019 (April 2, 2019): 1–10. http://dx.doi.org/10.1155/2019/1684707.
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According to the strain-softening characteristics of rock mass, an ideal elastic strain-softening model is developed, and the surrounding rock of tunnels is subdivided into the plastic broken zone, plastic strain-softening zone, and elastic zone. Based on the generalized spatially mobilized plane criterion, an elastic-plastic analytical solution of a circular tunnel is derived. The effects of intermediate principal stress, strain softening, and dilatancy are considered in the unified solution. The stress, displacement, and plastic zone radius of surrounding rock based on the SMP criterion are compared with those based on the Mohr–Coulomb criterion. Furthermore, the effects of parameters such as the softening modulus, dilatancy angle, and internal friction angle on the deformation and stress of tunnels are discussed. It has been found that the larger the dilatancy angle is, the larger the plastic zone displacement and the radius of the broken zone are. The larger the internal friction angle, the smaller the sizes of the plastic zone, the strain-softening zone, and the broken zone are. The deformation of surrounding rock in the broken zone is more sensitive to the internal friction angle than that in the strain-softening zone. The unified solution based on the SMP criterion provides a well understanding for the elastic-plastic state of tunnels, which can be the guidance for tunnel excavations and support designs.
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Borovkov, V. S., S. A. Pankratov, and N. L. Pankratova. "Maximum capacity of circular free-flow tunnels." Hydrotechnical Construction 23, no. 2 (February 1989): 96–98. http://dx.doi.org/10.1007/bf01427934.
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Li, Lei, and Ke Lei. "Preliminary Design and Cross-Sectional Form Study of Closed-Type Concrete-Filled Steel Tube Support for Traffic Tunnel." Symmetry 12, no. 8 (August 17, 2020): 1368. http://dx.doi.org/10.3390/sym12081368.
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In view of the structural form and common construction methods of traffic tunnels, the bearing performance of the closed-type CFST support designed for traffic tunnels is studied. The closed-type CFST support, which consist of a CFST girder with external shotcrete, is improved from the CFST support used in mine roadways. The reasonable cross-sectional form of closed-type CFST support is analyzed by the FEM. The closed-type CFST support is mainly composed of CFST arches, a shotcrete layer, sleeves, and blind flanges. The post-buckling analysis of the closed-type CFST circular arch members using circular-shaped, rectangular-shaped, triangular-shaped, and trapezoidal-shaped steel tubes is implemented. The result shows that the closed-type CFST support has better performance than the traditional tunnel support. The study also found that for closed-type CFST support, the triangular-shaped steel tube section has the highest bearing capacity, stiffness, and steel utilization rate, which is the preferred cross-sectional form. The bearing capacity of the circular-shaped steel tube section is acceptable. Moreover, the circular-shaped steel tubes are more convenient to obtain and process, so it is also an optional cross-sectional form. The square-shaped and trapezoidal-shaped steel tube sections have neither performance advantages nor economic efficiency, so these two forms are not recommended.
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Bai, Jiashe, Zhongbin Wu, Tongyong Chen, Wenqiang Li, Ping Zhang, and Yu Li. "Influence of Ventilation Duct Parameter Optimization on Pollutant Diffusion in Spiral Tunnels." Sustainability 14, no. 17 (August 24, 2022): 10540. http://dx.doi.org/10.3390/su141710540.
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The spiral tunnel could flexibly design the curvature and slope of the tunnel according to the geological structure, avoiding the adverse effect of complex terrain and topography, and had a strong advantage in engineering applications. Different from ordinary straight linear tunnels, spiral tunnels have a circular trend with obvious curvature and slope, which ensures certain differences between construction ventilation of the two types of tunnels, especially in terms of ventilation air flow field and pollutant diffusion. Relying on the actual spiral tunnel project, this paper studies the diffusion mechanism of ventilation pollutants in spiral tunnel construction. Optimization of the layout of the air duct based on numerical simulation and proposed pulsating ventilation method was performed to improve the ventilation and drainage effect of the tunnel. The time to reach the carbon monoxide concentration after blasting, and the dust concentration during the spraying process, were determined as indicators to measure the ventilation effect during the construction period. The hanging position of the air duct, the distance from the air duct outlet to the palm face, and the air speed were determined as the main factors affecting the ventilation effect. The main factors, the degree of influence and sensitivity of each influencing factor on the index, are studied, and the optimal air duct layout scheme suitable for the site is determined. The scheme can improve the ventilation effect and ventilation quality and provide effective reference for ventilation problems during the construction of other spiral tunnels. Meanwhile, more factors need to be examined to study the impact of pollutants in spiral tunnel construction, and physical models are needed to study the diffusion mechanism of pollutants in a spiral tunnel.
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Han, Xingbo, and Yongxu Xia. "Analytic Solutions of the Forces and Displacements for Multicentre Circular Arc Tunnels." Mathematical Problems in Engineering 2018 (2018): 1–14. http://dx.doi.org/10.1155/2018/8409129.
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A complex variable method for solving the forces and displacements for multicentre circular arc (MCA) tunnels by using analytical solutions is presented. The governing equations for the stresses and displacements are expressed in terms of series expression. Combined with the boundary conditions at lining inner region, lining-surrounding rock-mass interface, and infinity area, the undetermined coefficients of the analytic functions are obtained by solving a linear equation set. Forces solutions for linings are also presented according to the tangential stress at the two boundaries. Conformal mapping function for the MCA tunnel is given from the optimization method. Calculation results show that solutions with high accuracy can be obtained when the number of terms of power series is greater than 30. The effects of the degrees from the tunnel crown to the invert, coefficient of the lateral earth pressure, and distance from the rock-mass to the interface on regulations of the lining forces and rock-mass stresses are also thoroughly investigated.
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Fan, Hao, Lianguo Wang, and Kai Wang. "Stability Analysis of Surrounding Rock in Circular Tunnels Based on Critical Support Pressure." Advances in Civil Engineering 2020 (October 16, 2020): 1–9. http://dx.doi.org/10.1155/2020/8870928.
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Accurate calculation for the critical support pressure of tunnels plays an important role in tunnel stability evaluation and support design. In this study, a mechanical model for circular tunnels is developed. Considering the intermediate principal stress and strain-softening characteristic of rock mass, the critical support pressure when the plastic zone and damage zone begin to occur is determined based on the unified strength criterion and strain-softening model. Through the example study, the critical support pressure under different intermediate principal stress coefficient is solved. Furthermore, the effect of initial field stress, softening coefficient, and maximum damage variable on the critical support pressure are also discussed. The results show that the critical support pressure and radii of plastic and damage zones all decrease with the increase of the intermediate principal stress coefficient. The larger the initial field stress, the larger the critical support pressure. The softening coefficient and maximum damage variable of rock mass has no influence on the critical support pressure when the plastic zone begins to form, but has a significant effect on the critical support pressure when the damage zone begins to form. As softening coefficient increases and maximum damage variable decreases, the critical support pressure when the damage zone which begins to form increases. Data presented in this contribution provide significant theoretical insights into evaluating tunnel stability and support system reliability.