• Title/Summary/Keyword: tunnel behavior

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The study on the effect of fracture zone and its orientation on the behavior of shield TBM cable tunnel (단층파쇄대 규모 및 조우 조건에 따른 전력구 쉴드 TBM 터널의 거동 특성 분석)

  • Cho, Won-Sub;Song, Ki-Il;Kim, Kyoung-Yul
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.16 no.4
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    • pp.403-415
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    • 2014
  • Recently, the temperature rise in the summer due to climate change, power usage is increasing rapidly. As a result, power generation facilities have been newly completed and the need for ultra-high-voltage transmission line for power transmission of electricity to the urban area has increased. The mechanized tunnelling method using a shield TBM have an advantage that it can minimize vibrations transmitted to the ground and ground subsidence as compared with the conventional tunnelling method. Despite the popularity of shield TBM for cable tunnel construction, study on the mechanical behavior of cable tunnel driven by shield TBM is insufficient. Thus, in this study, the effect of fractured zone ahead of tunnel face on the mechanical behavior of the shield TBM cable tunnel is investigated. In addition, it is intended to compare the behavior characteristics of the fractured zone with continuous model and applying the interface elements. Tunnelling with shield TBM is simulated using 3D FEM. According to the change of the direction and magnitude of the fractured zone, Sectional forces such as axial force, shear force and bending moment are monitored and vertical displacement at the ground surface is measured. Based on the stability analysis with the results obtained from the numerical analysis, it is possible to predict fractured zone ahead of the shield TBM and ensure the stability of the tunnel structure.

A study on the characteristics of shallow overburden railway tunnel behavior under the existing road (기존도로하부 저토피 통과구간 철도터널 거동특성에 관한 연구)

  • Seo, Yoon-sic;Kim, Yeon-deok;Moon, Gyeong-seon;Kim, Hyeob;Kim, Sang-Hwan
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.19 no.6
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    • pp.1045-1058
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    • 2017
  • This paper is a study on railway tunnel behavior characteristic of shallow overburden under the existing road. In order to understand the behavior characteristics of the ground deformation during tunnel excavation, a horizontal rod extensometers were installed in the passage area of the shallow overburden tunnel under the road, and the measurement and analysis were carried out. To compare the in situ measurement, three dimensional numerical analysis with ground condition and construction step was carried out using MIDAS NX. As a result of the field measurement, large preceding settlement occurred where the poor ground condition with shallow overburden excavation has been conducted. As a result of the numerical analysis, the largest settlement occurred at the shallow overburden point where the ground condition was poor. Therefore, in the shallow overburden section where the soil condition is poor and a sufficient depth can't be secured and the arching effect of the ground around the tunnel can't be expected, careful attention should be paid to the application of stiffness reinforcement measures and to minimize ground loosening.

Comparative analysis of ground settlement and tunnel displacement due to tunnel excavation considering topographic information based on GIS (GIS 기반 지형 정보를 고려한 터널 굴착에 따른 지반침하와 터널 변위 비교 분석)

  • Jae-Eun, Cho;Ye-Rim, Jung;Seong-Min, Song;Ji-Seok, Yun;Sang-Gui, Ha;Han-Kyu, Yoo
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.25 no.1
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    • pp.13-26
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    • 2023
  • Recently, as the development of underground spaces has become active due to rapid urbanization and population density, interest in the ground behavior according to the construction of underground spaces is increasing. In large cities with high population density and many buildings, ground subsidence has a great impact on structures and there may be a risk of collapse, so the analysis of ground behavior due to underground construction is essential. Previous studies have been conducted on the subsidence pattern of the surface and the deformation of the tunnel when constructing the tunnel, but analysis has rarely been conducted by using actual topographic information. Therefore, this study analyzed the difference in ground behavior between the actual topography and the flat topography. As a result, it was confirmed that ground settlement occurs at higher elevations, such as in mountainous topography, and when the numerical analysis is performed considering topographical information, the crown settlement of the tunnel is up to about approx. It showed a difference of 10 mm, and it was found that the sensitivity was less in the case of displacement of tunnel wall compared to the crown settlement and ground settlement. The numerical analysis considering the actual GIS-based topographic information presented in this study can be used to obtain more accurate surface subsidence data to understand the behavior of the upper structure due to tunnel excavation.

Analysis of displacement behavior in fractured fault and groundwater flow under tunnel excavation (터널굴착중 굴착면 단층파쇄대와 지하수 용출 구간에서 단계별 변위 거동 특성 분석)

  • Kim, Nag-Young;Park, Gun-Tae;Baek, Seung-Cheol;Lee, Kang-Hyun;Choi, Jin-Woong;Her, Yol
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.19 no.1
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    • pp.71-82
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    • 2017
  • It is necessary to conduct a detailed geotechnical investigation on the tunnel section in order to secure the tunnel design and construction stability. It is necessary for the importance of geotechnical investigation that needed for the analysis of distribution and size of fractured fault zone and distribution of groundwater in tunnel. However, if it is difficult to perform the ground survey in the tunnel design due to ground condition of the tunnel section and the limited conditions such as civil complaint, the tunnel design is performed using the result of the minimum survey. Therefore, if weathered fault zone exists in the face the reinforcement method is determined in the design process to secure the stability of the tunnel. The most important factor in reinforcing the tunnel excavation surface is to secure the stability of the tunnel by performing quick reinforcement. In particular, if groundwater leaching occurs on the excavation surface, more rapid reinforcement is needed. In this study, fractured fault zone exists on the tunnel excavation surface and displacement occurs due to weathered fracture zone. When the amount of groundwater leaching rapidly increased under the condition of displacement, the behavior of tunnel displacement was analyzed based on tunnel collapse. In the study, reinforcement measures were taken because the first stage displacement did not converge continuously. After the first reinforcement, the displacement was not converged due to increased groundwater leaching and the second stage displacement occurred and chimney collapse occurred.

Groundwater inflow rate estimation considering excavation-induced permeability reduction in the vicinity of a tunnel (터널 굴착으로 인한 터널인접 절리암반 투수계수 감소를 고려한 터널 내 지하수 유입량 산정방법)

  • Moon, Joon-Shik
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.15 no.3
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    • pp.333-344
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    • 2013
  • This paper discussed about the effect of permeability reduction of the jointed rock mass in the vicinity of a tunnel which is one of the reasons making large difference between the estimated ground-water inflow rate and the measured value. Current practice assumes that the jointed rock mass around a tunnel is a homogeneous, isotropic porous medium with constant permeability. However, in actual condition the permeability of a jointed rock mass varies with the change of effective stress condition around a tunnel, and in turn effective stress condition is affected by the ground water flow in the jointed rock mass around the tunnel. In short time after tunnel excavation, large increase of effective tangential stress around a tunnel due to stress concentration and pore-water pressure drop, and consequently large joint closure followed by significant permeability reduction of jointed rock mass in the vicinity of a tunnel takes place. A significant pore-water pressure drop takes place across this ring zone in the vicinity of a tunnel, and the actual pore-water pressure distribution around a tunnel shows large difference from the value estimated by an analytical solution assuming the jointed rock mass around the tunnel as a homogeneous, isotropic medium. This paper presents the analytical solution estimating pore-water pressure distribution and ground-water inflow rate into a tunnel based on the concept of hydro-mechanically coupled behavior of a jointed rock mass and the solution is verified by numerical analysis.

Analysis of Ground Subsidence according to Tunnel Passage in Geological Vulnerable Zone (지질취약구간 터널통과에 따른 지반침하량 분석)

  • Choi, Jung-Youl;Yang, Gyu-Nam;Kim, Tae-Jun;Chung, Jee Seung
    • The Journal of the Convergence on Culture Technology
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    • v.6 no.3
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    • pp.393-399
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    • 2020
  • In this study, the subsidence behavior caused by groundwater ex-flow in a limestone cavity encountered during tunnel excavation was quantified based on numerical analysis and the effect was analyzed. Based on the groundwater level and surface subsidence surveyed at the site, a numerical analysis technique was applied to analyze the characteristics of the subsidence behavior according to the tunnel passage of the geological vulnerabilities. The results of groundwater seepage-coupled analysis were analyzed to reflect the actual ground subsidence behavior. As a result of the study, it was analyzed that the ground subsidence due to the tunnel excavation in the limestone common section(the geological vulnerable zone) was analyzed that the dramatical decrease in groundwater level was the main cause. As a result of numerical analysis, it was analyzed that the long-term cumulative settlement of the asphalt surface after the groundwater ex-flow was 76~118mm due to the reduction of the volume of the soil layer due to the decrease in the groundwater level, and the settlement amount increased as the depth of the soil layer increased.

The numerical study on the ground settlement behavior of box type tunnel enlargement (2차원 수치해석을 통한 초저심도 박스형 터널 편측확폭시 지반침하거동 특성 분석)

  • Cha, Yohan;Cho, Gye-Chun;Hong, Eun-soo
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.18 no.1
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    • pp.83-94
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    • 2016
  • Utility tunnels have been employed in Korea since the 1970s and start to make trouble with structural safety and serviceability. Recently, tunnel enlargement has consequently been proposed due to the impending problems. However there are little study on box type utility tunnels except traffic tunnels. A 2D finite element analysis was conducted to evaluate ground behavior which depends on enlargement size and stiffness by one-side enlargement of the utility tunnel. Settlement scale increased with larger enlargement size and less stiff ground conditions. The observed settlement characteristics due to enlargement are similar to that suggested by Clough & Schmidt (1981). The settlement width is more affected by enlargement size than ground condition.

Displacement Behavior of Tunnel under Bridge Abutment due to Supporting Systems (교량기초 하부에 위치한 터널의 지보방법에 따른 변위거동)

  • Yoo, Nam-Jae;Park, Byung-Soo;Jeong, Gil-Soo;Kim, Seung-Ryul
    • Proceedings of the Korean Geotechical Society Conference
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    • 2005.10a
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    • pp.613-620
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    • 2005
  • This research is experimental paper to prepare the structural safety of the upper bridge for support type on tunnel and the effect of settlement. Unit weight test and uni-axial compression test have been performed to simulate the physical property of foundation on the tunnel. Tunnel model of slip form type for centrifuge model has been developed to performed the tunnel excavation while field stress is activated. And the support type of tunnel such as umbrella arch method and large diameter steel pipe reinforce method has been tested for the centrifuge model. After the analysis of experiment, results show that internal displacement of large diameter steel pipe reinforce method is smaller than that of the umbrella arch method.

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Flow Behavior in a Rectangular Tunnel Opened and Closed at Both Sides Using CFD

  • Lee, Yong-Ho
    • Journal of Advanced Marine Engineering and Technology
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    • v.36 no.3
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    • pp.368-377
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    • 2012
  • Most tunnel simulations have been focused on the thermal field and the critical velocity for suppression of hot back-layering flow in case of fire and on the characteristics of a tunnel fire in terms of the flame propagation and the toxic gas generation. In this paper, a comparative study of the flow characteristics of polluted air with no heat source in a tunnel model opened and closed at both end sides is implemented into a recognized CFD simulation code. The model is used to investigate the flow characteristics depending on the three different Reynolds numbers of 640, 1270 and 2120, which have been chosen by the flow velocities of 0.3, 0.6 and 1.0 m/s through the inlet. The results of this study have shown that the CFD predictive and experimental approaches are available in qualitatively studying the correlation of flow behaviors for a better tunnel design.

Experimental study on the ground subsidence due to the excavation of a shallow tunnel (경사지반에서 얕은터널의 굴착에 따른 지표침하에 대한 실험적 연구)

  • Park, Chan Hyuk;Lee, Sang Duk
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.19 no.5
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    • pp.761-778
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    • 2017
  • The need of the underground space for the infrastructures in urban area is increasing, and especially the demand for shallow tunnels increased drastically. It is very important that the shallow tunnel in the urban area should fulfill not only its own safety conditions but also the safety condition for the adjacent structures and the surrounding sub-structure. Most of the studies on the behavior of shallow tunnels concentrated only on their behaviors due to the local deformation of the tunnel, such as tunnel crown or tunnel sidewall. However, few studies have been performed for the behavior of the shallow tunnel due to the deformation of the entire tunnel. Therefore, in this study the behavior of the surrounding ground and the stability caused by deformation of the whole tunnel were studied. For that purpose, model tests were performed for the various ground surface slopes and the cover depth of the tunnel. The model tunnel (width 300 mm, height 200 mm) could be simulationally deformed in the vertical and horizontal direction. The model ground was built by using carbon rods of three types (4 mm, 6 mm, 8 mm), in various surface slopes and cover depth of the tunnel. The subsidence of ground surface, the load on the tunnel crown and the sidewall, and the transferred load near tunnel were measured. As results, the ground surface subsided above the tunnel, and its amount decreased as the distance from the tunnel increased. The influence of a tunnel ceased in a certain distance from the tunnel. At the inclined ground surface, the wider subsidence has been occurred. The loads on the crown and the sidewall were clearly visible, but there was no effect of the surface slope at a certain depth. The load transfer on the adjacent ground was larger when the cover depth (on the horizontal surface) was lager. The higher the level (on the inclined surface), the wider and smaller it appeared. On the shallow tunnel under inclined surface, the transfer of the ambient load on the tunnel sidewall (low side) was clearly visible.