• Title/Summary/Keyword: buried tunnel

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The Effects of AC Corrosion on Underground Gas Pipeline Running Parallel with High Power Cables (전력케이블과 가스배관의 병행구간에 대한 교류부식 영향)

  • 배정효;김대경;김기준
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.49 no.10
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    • pp.577-582
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    • 2000
  • 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 interference mechanism(inductive coupling, conductive coupling, resistive coupling), AC corrosion, limitation of safety voltage, modeling of power cables, gas pipeline and grounding systems, analysis of induction voltage and optimal arrangement of power cables.

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Case Studies of Safety Diagnosis by GPR (GPR에 의한 안전진단 사례)

  • 한자경;최광철
    • Proceedings of the Korean Geotechical Society Conference
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    • 1999.12a
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    • pp.169-180
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    • 1999
  • Ground penetrating radar(GPR) uses radio waves to detect buried objects in any non-metallic material. Initially it was used to detect structures in ice. GPR has evolved to include the penetration of soils, rocks and man-made structures. GPR uses a sensitive detector to record weak radio waves reflected from objects embedded in the material under investigation. In this study, the GPR is applied to outside plant telecommunication facilities such as cable tunnels, manholes and underground conduits and model experiments to obtain radar characteristics. The thickness and soundness of tunnel lining can be evaluated, and the location of rebars and steel ribs can also be found effectively. The location of underground conduits as well as manholes can be found and the results of GPR give good coincidence with design drawings. In order to investigate the tunnel lining, the GPR mounted vehicle is developed and it is proved that the vehicle can save time and manpower.

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An improved radius-incremental-approach of stress and displacement for strain-softening surrounding rock considering hydraulic-mechanical coupling

  • Zou, Jin-Feng;Wei, Xing-Xing
    • Geomechanics and Engineering
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    • v.16 no.1
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    • pp.59-69
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    • 2018
  • This study focused on the mechanical and hydraulic characteristics of underwater tunnels based on Mohr-Coulomb (M-C), Hoek-Brown (H-B) and generalized H-B failure criteria. An improved approach for calculating stress, displacement and plastic radius of the circular tunnel considering hydraulic-mechanical coupling was developed. The innovation of this study was that the radius-incremental-approach was reconstructed (i.e., the whole plastic zone is divided into a finite number of concentric annuli by radius), stress and displacement of each annulus were determined in terms of numerical method and Terzaghi's effective stress principle. The validation of the proposed approach was conducted by comparing with the results in Brown and Bray (1982) and Park and Kim (2006). In addition, the Rp-pin curve (plastic radius-internal supporting pressure curve) was obtained using the numerical iterative method, and the plastic radius of the deep-buried tunnel could be obtained by interpolation method in terms of the known value of internal supporting pressure pin. Combining with the theories in Carranza and Fairhurst (2000), the improved technique for assessing the reliability of the tunnel support was proposed.

A 2-D Location Determination Model of Buried Persons in Collapsed Shape using Optimal Wireless Communication Technology (최적 무선통신 기술을 활용한 붕괴지형 매몰자의 2차원 매몰위치 결정 모델)

  • Moon, Hyoun-Seok;Lee, Woo-Sik;Lee, Gun-Woo;Han, Dong-Soo
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.12
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    • pp.8879-8888
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    • 2015
  • When the disaster like earthquake in urban area occur, due to the collapse accidents for subway, tunnel space with buildings or underground area, enormous property and human damage are happened. Specially, since it is difficult to identify survived status of humans within collapsed debris and accurately buried locations of the humans, inputs of considerable time and manpower for rescuing them are required. Besides, secondary damage can be occurred by additional collapses. The aim of this study is to propose a stochastic location positioning method that enables to provide aid information by determining locations of mobile devices for buried persons in 2-D plane using wireless communication technologies. This study selected a detection method for buried persons based on Wi-Fi signal, and identified characteristics of signal strengths by distance unit. Using these methods, a stochastic location detection model in 2-D plane was built. It is expected that this technology will be utilized as a core technology that can protects safety and human life of the public by providing data for rescuing quickly buried persons in cases of national disasters for future.

An application of the tubular roof construction method for Seoul subway tunnel construction (서울지하철 터널의 T.R.c.M. 공법 적용 사례 연구)

  • Jie, Hong-Keun;You, Kwang-Ho;Park, Yeon-Jun
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.6 no.4
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    • pp.345-356
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    • 2004
  • Open-cut method has been widely used to construct underground structures, but it causes several problems such as traffic congestion and public resentment resulting from severe construction noise and ground settlement. In many cases, it is very difficult to build underground structures safely due to the unknown locations of buried facilities such as water pipes, drainage pipes, gas pipes and high-pressure cable conduits etc. Also in open-cut method, moving buried facilities causes additional cost and extension of construction period. Therefore, this paper is to present a case study in which Tubular Roof construction Method (T.R.c.M.), a newly developed construction method for underground structures using slab steel pipes and PC wall trench, is applied for the construction of a subway tunnel in Seoul. As a result, it is found that T.R.c.M. is a construction method by which tunnels can be constructed safely without any effect on the surrounding environment and traffic flow due to the minimized construction vibration and noise.

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Effects of parallel undercrossing shield tunnels on river embankment: Field monitoring and numerical analysis

  • Li'ang Chen;Lingwei Lu;Zhiyang Tang;Shixuan Yi;Qingkai Wang;Zhibo Chen
    • Geomechanics and Engineering
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    • v.35 no.1
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    • pp.29-39
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    • 2023
  • As the intensity of urban underground space development increases, more and more tunnels are planned and constructed, and sometimes it is inevitable to encounter situations where tunnels have to underpass the river embankments. Most previous studies involved tunnels passing river embankments perpendicularly or with large intersection angle. In this study, a project case where two EPB shield tunnels with 8.82 m diameter run parallelly underneath a river embankment was reported. The parallel length is 380 m and tunnel were mainly buried in the moderate / slightly weathered clastic rock layer. The field monitoring result was presented and discussed. Three-dimensional back-analysis were then carried out to gain a better understanding the interaction mechanisms between shield tunnel and embankment and further to predict the ultimate settlement of embankment due to twin-tunnel excavation. Parametrical studies considering effect of tunnel face pressure, tail grouting pressure and volume loss were also conducted. The measured embankment settlement after the single tunnel excavation was 4.53 mm ~ 7.43 mm. Neither new crack on the pavement or cavity under the roadbed was observed. It is found that the more degree of weathering of the rock around the tunnel, the greater the embankment settlement and wider the settlement trough. Besides, the latter tunnel excavation might cause larger deformation than the former tunnel excavation if the mobilized plastic zone overlapped. With given geometry and stratigraphic condition in this study, the safety or serviceability of the river embankment would hardly be affected since the ultimate settlement of the embankment after the twin-tunnel excavation is within the allowable limit. Reasonable tunnel face pressure and tail grouting pressure can to some extent suppress the settlement of the embankment. The recommended tunnel face pressure and tail grouting pressure are 300 kPa and 550 kPa in this study, respectively. However, the volume loss plays the crucial role in the tunnel-embankment interaction. Controlling and compensating the tunneling induced volume loss is the most effective measure for river embankment protection. Additionally, reinforcing the embankment with cement mixing pile in advance is an alternative option in case the predicted settlement exceeds allowable limit.

Study on collapse mechanism and treatment measures of portal slope of a high-speed railway tunnel

  • Guoping Hu;Yingzhi Xia;Lianggen Zhong;Xiaoxue Ruan;Hui Li
    • Geomechanics and Engineering
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    • v.32 no.1
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    • pp.111-123
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    • 2023
  • The slope of an open cut tunnel is located above the exit of the Leijia tunnel on the Changgan high-speed railway. During the excavation of the open cut tunnel foundation pit, the slope slipped twice, a large landslide of 92500 m3 formed. The landslide body and unstable slope body not only caused the foundation pit of the open cut tunnel to be buried and the anchor piles to be damaged but also directly threatened the operational safety of the later high-speed railway. Therefore, to study the stability change in the slope of the open cut tunnel under heavy rain and excavation conditions, a 3D numerical calculation model of the slope is carried out by Midas GTS software, the deformation mechanism is analyzed, anti-sliding measures are proposed, and the effectiveness of the anti-sliding measures is analyzed according to the field monitoring results. The results show that when rainfall occurs, rainwater collects in the open cut tunnel area, resulting in a transient saturation zone on the slope on the right side of the open cut tunnel, which reduces the shear strength of the slope soil; the excavation at the slope toe reduces the anti-sliding capacity of the slope toe. Under the combined action of excavation and rainfall, when the soil above the top of the anchor pile is excavated, two potential sliding surfaces are bounded by the top of the excavation area, and the shear outlet is located at the top of the anchor pile. After the excavation of the open cut tunnel, the potential sliding surface is mainly concentrated at the lower part of the downhill area, and the shear outlet moves down to the bottom of the open cut tunnel. Based on the deformation characteristics and the failure mechanism of the landslides, comprehensive control measures, including interim emergency mitigation measures and long-term mitigation measures, are proposed. The field monitoring results further verify the accuracy of the anti-sliding mechanism analysis and the effectiveness of anti-sliding measures.

Quantitative Risk Assessment for Gas-explosion at Buried Common Utility Tunnel (지하 매설 공동구 내부 가스 폭발에 대한 위험성 평가)

  • Jang, Yuri;Jung, Seungho
    • Journal of the Korean Institute of Gas
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    • v.20 no.5
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    • pp.89-95
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    • 2016
  • Keeping the gas pipelines in the common utility tunnel is useful because it has a lower risk of corrosion than conventional burial, and can prevent from excavating construction. But, explosions in common utility tunnels can cause greater damage from the blast overpressure compared to outdoor explosions, due to nature of the confined environment. Despite this fact, however, research on common utility tunnels has been limited to fire hazard and little has been studied on the dangers of explosions. This study developed scenarios of methane gas explosion caused by gas leak from gas piping within the common utility tunnel followed by unknown ignition; the study then calculated the extent of the impact of the explosion on the facilities above, and suggested the needs for designing additional safety measures. Two scenarios were selected per operating condition of safety devices and the consequence analysis was carried out with FLACS, one of the CFD tools for explosion simulation. The overpressures for all scenarios are substantial enough to completely destroy most of the buildings. In addition, we have provided additional measures to secure safety especially reducing incident frequency.

Evaluation of geological conditions and clogging of tunneling using machine learning

  • Bai, Xue-Dong;Cheng, Wen-Chieh;Ong, Dominic E.L.;Li, Ge
    • Geomechanics and Engineering
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    • v.25 no.1
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    • pp.59-73
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    • 2021
  • There frequently exists inadequacy regarding the number of boreholes installed along tunnel alignment. While geophysical imaging techniques are available for pre-tunnelling geological characterization, they aim to detect specific object (e.g., water body and karst cave). There remains great motivation for the industry to develop a real-time identification technology relating complex geological conditions with the existing tunnelling parameters. This study explores the potential for the use of machine learning-based data driven approaches to identify the change in geology during tunnel excavation. Further, the feasibility for machine learning-based anomaly detection approaches to detect the development of clayey clogging is also assessed. The results of an application of the machine learning-based approaches to Xi'an Metro line 4 are presented in this paper where two tunnels buried in the water-rich sandy soils at depths of 12-14 m are excavated using a 6.288 m diameter EPB shield machine. A reasonable agreement with the measurements verifies their applicability towards widening the application horizon of machine learning-based approaches.

The Thermal conductivity analysis and performance evaluation on the pavement applying geothermal snow melting system (지열 융설시스템을 적용한 포장체의 열전도분석 및 구조안전성 검토)

  • Lee, Seung-Ha;Park, Jeong-Sik;Lee, Seok-Jin;Kim, Bong-Chan
    • Journal of the Korean Society for Geothermal and Hydrothermal Energy
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    • v.6 no.1
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    • pp.17-22
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    • 2010
  • A sliding accident on the road have a high percentage by road freezing, especially, it is often appeared at bridges and tunnel of freezing areas. Thus, the stability of road operations is enhanced by preventing a partial freezing phenomenon. According to the geothermal snow melting system analysis, a pattern of thermal conductivity is found out about pavement materials of concrete and asphalt when it is buried. For the feasibility study on geothermal snow melting system, analysis of the ground melting point when operating system, life evaluation of pavements and safety evaluation of pipes are performed.