• Title/Summary/Keyword: buried tunnel

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A Case Study on the AC Corrosion Effects of Gas Pipeline by High Voltage Induction in Submarine Tunnel (해저터널내 고전압 유도에 의한 가스배관의 교류전식 영향 사례 연구)

  • Bae, Jeong-Hyo;Ha, Tae-Hyun;Lee, Hyun-Goo;Kim, Dae-Kyeong
    • Proceedings of the KIEE Conference
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    • 2001.07a
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    • pp.346-348
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    • 2001
  • This paper analyze the interference problems, especially AC corrosion when the gas pipeline is buried with power cable in the same submarine tunnel. This paper present the results of the study about AC corrosion, limitation of safety voltage, modeling of power cables, gas pipeline and grounding systems, analysis of induction voltage according to various circumstance, soil resistivity, length of tunnel. and so on.

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Development of Modified Flexibility Ratio - Racking Ratio Relationship of Box Tunnels Subjected to Earthquake Loading Considering Rocking

  • Duhee Park;Van-Quang Nguyen;Gyuphil Lee;Youngsuk Lee
    • Journal of the Korean GEO-environmental Society
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    • v.24 no.2
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    • pp.13-24
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    • 2023
  • Tunnels may undergo a larger or a smaller response compared with the free-field soil. In the pseudo-static procedure, the response of the tunnel is most often characterized by a curve that relates the racking ratio (R) with the flexibility ratio (F), where R represents the ratio of the tunnel response with respect to the free-field vibration and F is the relative stiffness of the tunnel and the surrounding soil. A set of analytical and empirical curves that do not account for the depth and the aspect ratio of the tunnel are typically used in practice. In this study, a series of dynamic analyses are conducted to develop a set of F-Rm relations for use in a frame analysis method. Rm is defined as an adjusted R where the rocking mode of deformation is removed and only the racking deformation is extracted. The numerical model is validated against centrifuge test recordings. The influence of aspect ratio, buried depth of tunnel on results is investigated. The results show that Rm increases with the increase of the buried depth and the aspect ratio. The widely used F-R relations are highlighted to be different compared with the obtained results in this study. Therefore, the updated F-Rm relations with proposed equations are recommended to be used in practice design. The rocking response decreases with either the decrease of the difference of stiffness between surrounding soil and tunnel or the larger aspect ratio of the tunnel section.

3D numerical investigation of segmental tunnels performance crossing a dip-slip fault

  • Zaheri, Milad;Ranjbarnia, Masoud;Dias, Daniel
    • Geomechanics and Engineering
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    • v.23 no.4
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    • pp.351-364
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    • 2020
  • This paper numerically investigates the effects of a dip-slip fault (a normal or a reverse fault) movement on a segmental tunnel which transversely crosses either of this kind of faults. After calibration of the numerical model with results from literature of centrifuge physical tests, a parametric study is conducted to evaluate the effects of various parameters such as the granular soil properties, the fault dip angle, the segments thickness, and their connections stiffnesses on the tunnel performance. The results are presented and discussed in terms of the ground surface and tunnel displacements along the longitudinal axis for each case of faulting. The gradient of displacements and deformations of the tunnel cross section are also analyzed. It is shown that when the fault dip angle becomes greater, the tunnel and ground surface displacements are smaller, in the case of reverse faulting. For this type of fault offset, increasing the tunnel buried depth causes tunnel displacements as well as ground surface settlements to enhance which should be considered in the design.

The contact loads inversion between surrounding rock and primary support based on dynamic deformation curve of a deep-buried tunnel with flexible primary support in consideration

  • Jian Zhou;Yunliang Cui;Xinan Yang;Mingjie Ma;Luheng Li
    • Geomechanics and Engineering
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    • v.36 no.6
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    • pp.575-587
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    • 2024
  • The contact pressure between the surrounding rock and the support is an important indicator of the surrounding rock pressure. There has been a bottleneck in the prediction of contact loads between surrounding rock and primary support in deep-buried mountain tunnels. The main reason is that a reliable method wasn't existed to quantify the contact loads. This study had been taken into account the flexible support role of the primary support, and the fitting curve of surrounding rock deformation for dynamic tunnel construction was proposed. New formulas for the calculation of contact loads between surrounding rock and primary support were obtained by inversion. Comparative analysis of the calculation results with numerical simulation verified the reliability of the calculation method in this study. It can be seen from the analyses that the contact load between surrounding rock and primary support increases, remains unchanged and decreases during acceleration, uniform velocity and deceleration, respectively, and the deformation of the surrounding rock in the acceleration and deceleration stages cannot completely converted into contact loads. The contact loads between surrounding rock and primary support of medium-strength and weak surrounding rock tunnels are generally within 150 kPa and 1 MPa, respectively. For tunnels with weak surrounding rock, advanced support can be installed to reduce the unique release coefficient λ0 and the value of the constant D, with the purpose of reducing the contact loads between surrounding rock and primary support. Changes in support parameters have a small effect on the contact loads between surrounding rock and primary support, but increase or decrease the safety factor, resulting in a waste of resources or a situation that threatens the safety of the support. The results of this research provide guidance for the prediction of contact loads between surrounding rock and primary support for dynamic tunnel construction.

Stability evaluation for the excavation face of shield tunnel across the Yangtze River by multi-factor analysis

  • Xue, Yiguo;Li, Xin;Qiu, Daohong;Ma, Xinmin;Kong, Fanmeng;Qu, Chuanqi;Zhao, Ying
    • Geomechanics and Engineering
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    • v.19 no.3
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    • pp.283-293
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    • 2019
  • Evaluating the stability of the excavation face of the cross-river shield tunnel with good accuracy is considered as a nonlinear and multivariable complex issue. Understanding the stability evaluation method of the shield tunnel excavation face is vital to operate and control the shield machine during shield tunneling. Considering the instability mechanism of the excavation face of the cross-river shield and the characteristics of this engineering, seven evaluation indexes of the stability of the excavation face were selected, i.e., the over-span ratio, buried depth of the tunnel, groundwater condition, soil permeability, internal friction angle, soil cohesion and advancing speed. The weight of each evaluation index was obtained by using the analytic hierarchy process and the entropy weight method. The evaluation model of the cross-river shield construction excavation face stability is established based on the idea point method. The feasibility of the evaluation model was verified by the engineering application in a cross-river shield tunnel project in China. Results obtained via the evaluation model are in good agreement with the actual construction situation. The proposed evaluation method is demonstrated as a promising and innovative method for the stability evaluation and safety construction of the cross-river shield tunnel engineerings.

Analysis of underground post-tensioned precast concrete box utility tunnel under normal fault displacement

  • Wu, Xiangguo;Nie, Chenhang;Qiu, Faqiang;Zhang, Xuesen;Hong, Li;Lee, Jong-Sub;Kang, Thomas H.K.
    • Computers and Concrete
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    • v.29 no.2
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    • pp.69-79
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    • 2022
  • For long underground box utility tunnels, post-tensioned precast concrete is often used. Between precast tunnel segments, sealed waterproof flexible joints are often specified. Fault displacement can lead to excessive deformation of the joints, which can lead to reduction in waterproofing due to diminished contact pressure between the sealant strip and the tunnel segment. This paper authenticates utilization of a finite element model for a prefabricated tunnel fault-crossing founded on ABAQUS software. In addition, material parameter selection, contact setting and boundary condition are reviewed. Analyzed under normal fault action are: the influence of fault displacement; buried depth; soil friction coefficient, and angle of crossing at the fault plane. In addition, distribution characteristics of the utility tunnel structure for vertical and longitudinal/horizontal relative displacement at segmented interface for the top and bottom slab are analyzed. It is found that the effect of increase in fault displacement on the splice joint deformation is significant, whereas the effects of changes in burial depth, pipe-soil friction coefficient and fault-crossing angle on the overall tunnel and joint deformations were not so significant.

Characterization of the brittleness of hard rock at different temperatures using uniaxial compression tests

  • Chen, Guoqing;Li, Tianbin;Wang, Wei;Guo, Fan;Yin, Hongyu
    • Geomechanics and Engineering
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    • v.13 no.1
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    • pp.63-77
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    • 2017
  • The failure mechanism of a deep hard rock tunnel under high geostress and high geothermalactivity is extremely complex. Uniaxial compression tests of granite at different temperatures were conducted. The complete stress-strain curves, mechanical parameters and macroscopic failure types of the rock were analyzed in detail. The brittleness index, which represents the possibility of a severe brittleness hazard, is proposed in this paperby comparing the peak stress and the expansion stress. The results show that the temperature range from 20 to $60^{\circ}C$ is able to aggravate the brittle failure of hard rock based on the brittleness index. The closure of internal micro cracks by thermal stress can improve the strength of hard rock and the storage capacity of elastic strain energy. The failure mode ofthe samples changes from shear failure to tensile failure as the temperature increases. In conclusion, the brittle failure mechanism of hard rock under the action of thermal coupling is revealed, and the analysis result offers significant guidance for deep buried tunnels at high temperatures and under high geostress.

A RESEARCH ON EFFECTIVE FIRE/DISASTER PROTECTION OF UTILITY TUNNEL IN KOREA

  • Park, Hung-joo;Son, Bong-sei;Jee, Nam-yong
    • Proceedings of the Korea Institute of Fire Science and Engineering Conference
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    • 1997.11a
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    • pp.404-412
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    • 1997
  • The pipes and cables buried below ground, which may have helped to improve city landscape, is becoming direct and indirect causes for various kinds of disaster in Korea. Every advantage from the use of utility tunnel can not be converted in a dollar since there is associated huge contribution to safe urban environment. The Korean government has a certain role to play in helping promote utility tunnels for the past years. Most recently, many utility tunnels have been being checked to find out safety level, especially fire safety level, and main problems and shortcomings are checked out as a result of this survey. Because the fire safety level of existing tunnel is low, possible approaches and solutions are presented according to the analysis of fire safety level. In order for these approaches to be effective, existing tunnel should be supplemented appropriately and extra equipment must be installed according to the solutions. Hopefully, by performing both improvement of existing utility tunnel that provide a fire/disaster proof and introducing new types of tunnel which influence utility management and maintenance, the recent disaster rate in Korea can be diminished up to a desirable rate in a near future.

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A new dynamic construction procedure for deep weak rock tunnels considering pre-reinforcement and flexible primary support

  • Jian Zhou;Mingjie Ma;Luheng Li;Yang Ding;Xinan Yang
    • Geomechanics and Engineering
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    • v.38 no.3
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    • pp.319-334
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    • 2024
  • The current theories on the interaction between surrounding rock and support in deep-buried tunnels do not consider the form of pre-reinforcement support or the flexibility of primary support, leading to a discrepancy between theoretical solutions and practical applications. To address this gap, a comprehensive mechanical model of the tunnel with pre-reinforced rock was established in this study. The equations for internal stress, displacement, and the radius of the plastic zone in the surrounding rock were derived. By understanding the interaction mechanism between flexible support and surrounding rock, the three-dimensional construction analysis solution of the tunnel could be corrected. The validity of the proposed model was verified through numerical simulations. The results indicate that the reduction of pre-deformation significantly influences the final support pressure. The pre-reinforcement support zone primarily inhibits pre-deformation, thereby reducing the support pressure. The support pressure mainly affects the accelerated and uniform movement stage of the surrounding rock. The generation of support pressure is linked to the deformation of the surrounding rock during the accelerated movement stage. Furthermore, the strength of the pre-reinforcement zone of the surrounding rock and the strength of the shotcrete have opposite effects on the support pressure. The parameters of the pre-reinforcement zones and support materials can be optimized to achieve a balance between surrounding rock deformation, support pressure, cost, and safety. Overall, this study provides valuable insights for predicting the deformation of surrounding rock and support pressure during the dynamic construction of deep-buried weak rock tunnels. These findings can guide engineers in improving the construction process, ensuring better safety and cost-effectiveness.

Collapse analysis of shallow tunnel subjected to seepage in layered soils considering joined effects of settlement and dilation

  • Yang, X.L.;Zhang, R.
    • Geomechanics and Engineering
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    • v.13 no.2
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    • pp.217-235
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    • 2017
  • The stability prediction of shallow buried tunnels is one of the most difficult tasks in civil engineering. The aim of this work is to predict the state of collapse in shallow tunnel in layered soils by employing non-associated flow rule and nonlinear failure criterion within the framework of upper bound theorem. Particular emphasis is first given to consider the effects of dilation on the collapse mechanism of shallow tunnel. Furthermore, the seepage forces and surface settlement are considered to analyze the influence of different dilation coefficients on the collapse shape. Two different curve functions which describe two different soil layers are obtained by virtual work equations under the variational principle. The distinct characteristics of falling blocks up and down the water level are discussed in the present work. According to the numerical results, the potential collapse range decreases with the increase of the dilation coefficient. In layered soils, both of the single layer's dilation coefficient and two layers' dilation coefficients increase, the range of the potential collapse block reduces.