• Title/Summary/Keyword: Tunnel behavior

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A Study on the Behavior of a Closely-spaced Tunnel by Using Particle Flow Code (입자 유동 해석(PFC)을 통한 근접터널의 거동에 관한 연구)

  • Suh, Byung-Wook;Jo, Seon-Ah;Jung, Seon-Ah;Lee, Seok-Won
    • Proceedings of the Korean Geotechical Society Conference
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    • 2008.03a
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    • pp.159-169
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    • 2008
  • In general, it is considered that a pillar between closely-spaced tunnel is sensitive for stress concentration. Stability of a pillar is key factor for excavation of closely-spaced tunnel. In this paper, the study is focused on tracing the behaviors, displacement and plotting damages around tunnels that is modelled with Particle Flow Code, $PFC^{2D}$. Parametric study was performed with changing distance between center of tunnels and coefficient of earth pressure(K). Scaled-model tests were also carried out to validate a numerical analysis model. It was found that $PFC^{2D}$ could show dynamic visualized result in quite good agreement with the experimental test.

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The Pre-Evaluation of Stability during Tunnel Excavation using Unconfined Compression Strength of Intact Rock or Rock Mass and Crown Settlement Data (터널천단변위와 암석 또는 암반의 일축압축강도를 이용한 시공 중인 터널의 예비 안정성 평가)

  • Park, Young Hwa;Moon, Hong Duk;Ha, Man Bok
    • International Journal of Highway Engineering
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    • v.17 no.6
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    • pp.27-32
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    • 2015
  • PURPOSES : It is difficult to estimate tunnel stability because of lack of timely information during tunnel excavation. Tunnel deformability refers to the capacity of rock to strain under applied loads or unloads during tunnel excavation. This study was conducted to analyze a methods of pre-evaluation of stability during tunnel construction using the critical strain concept, which is applied to the results of tunnel settlement data and unconfined compression strength of intact rock or rock mass at the tunnel construction site. METHODS : Based on the critical strain concept, the pre-evaluation of stability of a tunnel was performed in the Daegu region, at a tunnel through andesite and granite rock. The critical strain concept is a method of predicting tunnel behavior from tunnel crown settlement data using the critical strain chart that is obtained from the relationship between strain and the unconfined compression strength of intact rock in a laboratory. RESULTS : In a pre-evaluation of stability of a tunnel, only actually measured crown settlement data is plotted on the lower position of the critical strain chart, to be compared with the total displacement of crown settlement, including precedent settlement and displacement data from before the settlement measurement. However, both cases show almost the same tunnel behavior. In an evaluation using rock mass instead of intact rock, the data for the rock mass strength is plotted on the lower portion of the critical strain chart, as a way to compare to the data for intact rock strength. CONCLUSIONS : From the results of the pre-evaluation of stability of the tunnel using the critical strain chart, we reaffirmed that it is possible to promptly evaluate the stability of a tunnel under construction. Moreover, this research shows that a safety evaluation using the actual instrumented crown settlement data with the unconfined compression strength of intact rock, rather than with the unconfined compression strength of a rock mass in the tunnel working face, is more conservative.

Behavior of double lining due to long-term hydraulic deterioration of drainage system

  • Shin, Jong-Ho;Lee, In-Keun;Joo, Eun-Jung
    • Structural Engineering and Mechanics
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    • v.52 no.6
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    • pp.1257-1271
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    • 2014
  • The hydraulic deterioration of the drainage system in tunnel linings is one of the main factors governing long-term lining-ground interactions during the lifetime of tunnels. Thus, in the design procedure of a tunnel below the groundwater table, the possible detrimental effects associated with the hydraulic deterioration should be addressed. Hydraulic deterioration in double-lined tunnels can occur because of reasons such as clogging of the drainage layer and drain-pipe blockings. In this study, the coupled mechanical and hydraulic interactions between linings due to drain-pipe blockings are investigated using the finite-element method. A double-lined structural model incorporating hydraulic behavior is developed to represent the coupled structural and hydraulic behavior between the linings and drainage system. It is found that hydraulic deterioration hinders flow into the tunnel, causing asymmetric development of pore-water pressure and consequent detrimental effects to the secondary lining.

The Effect of Cut-slope on Structural Behavior of Cut-and-Cover Tunnel (굴착경사가 개착식터널의 구조적거동에 미치는 영향에 관한 연구)

  • 유건선
    • Journal of the Korean Geotechnical Society
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    • v.17 no.6
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    • pp.245-255
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    • 2001
  • Existing cut-and-cover tunnels are designed regardless of cut-slope under the assumption that the overburden weight of backfill soil acts on tunnel arch and the earth pressure at rest acts on tunnel walls. However, actual earth pressures acting on the tunnel lining depend on open-cut size composed of cut-slope and cut-width, and thus the tunnel lining shows a different structural behavior. This study investigated the effect of cut-slope on structural behavior of the cut-and-cover tunnel lining as follows; Firstly, a comprehensive numerical analysis method using FLAC2D code was used and verified by field measurements of tunnel profile. Secondly, based on the verified numerical analysis technique, earth pressure acting on the lining, and displacement and sectional force developed on the lining were estimated with various shapes of cut-slopes$30^{\circ}\;, 456{\circ},\; 60^{\circ},\; and\;75^{\circ}%). Numerical analysis results indicate that the steeper cut-slope shows the more displacement and moment of the tunnel lining.

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A Study on the Concrete Lining Behavior due to Tunnel Deterioration (터널 열화로 인한 콘크리트 라이닝의 거동에 관한 연구)

  • Han, Young-Chul;Jeong, Sang-Seom
    • Journal of the Korean Geotechnical Society
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    • v.30 no.4
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    • pp.21-34
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    • 2014
  • This paper studies the time-dependent behaviors of tunnel and surrounding ground due to tunnel deterioration. In the first part, the literature on deterioration characteristics of tunnels was reviewed. In the second part, a numerical analysis was performed to investigate the behavior of concrete lining on the typical section of Korean high-speed rail tunnel (weathered rock) after determination of input variables related to deterioration impact. The result shows that the settlement at the crown of tunnel and surface ground increased up to 7.0% and 30.2% of the total settlements during construction stage, respectively, and the internal convergence reduction of 9.0 mm for concrete linings was generated within 30 years after completion of tunnel construction. Also the loosening height increased up to 2.55 times of tunnel height within 50 years, which is higher than that of Terzaghi's recommendation on ultimate state. Due to this process of extending zones, it is found that additional loads were applied to concrete lining with the axial stress about 3.20~3.66 MPa, which accelerates tunnel deterioration. Finally the quantitative design approach to evaluate time-dependent behavior of lining and surrounding ground due to tunnel deterioration was proposed.

The Development of Tunnel Behavior Prediction System Using Artificial Neural Network (인공신경망을 이용한 터널 거동 예측 시스템 개발)

  • 이종구;문홍득;백영식
    • Journal of the Korean Geotechnical Society
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    • v.19 no.2
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    • pp.267-278
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    • 2003
  • Artificial neural networks are efficient computing techniques that are widely used to solve complex problems in many fields. In this study, in order to predict tunnel-induced ground movements, Tunnel Behavior Prediction System (TBPS) was developed by using these artificial neural networks model, based on a Held instrumentation database (i.e. crown settlement, convergence, axial force of rock bolt, compressive and shear stress of shotcrete, stress of concrete lining etc.) obtained from 193 location data of 31 different tunnel sites where works are completed. The study and test of the network were performed by Back Propagation Algorithm which is known as a systematic technique for studying the multi-layer artificial neural network. The tunnel behaviors predicted by TBPS were compared with monitored data in the tunnel sites and numerical analysis results. This study showed that the values obtained from TBPS were within allowable limits. It is concluded that this system can effectively estimate the tunnel ground movements and can also be used f3r tunneling feasibility study, and basic and detailed design and construction of tunnel.

A Study on the Behavior of an Existing Tunnel and the Safety Implications on its Facilities from a New Tunnel Blasting (신설 터널 발파 시 기존 터널 거동 및 시설물 안전에 관한 연구)

  • Kim, Sung Hoon;Cho, Woncheol
    • Journal of Korean Society of societal Security
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    • v.3 no.2
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    • pp.57-64
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    • 2010
  • In this study, the behavior and safety of an existing tunnel and its facilities are investigated when a new tunnel adjacent to the existing tunnel is blasted. The design of the new tunnel puts priority on stability of the tunnel itself over the safety of the facilities which are installed within the existing tunnel such as jet fans. And thus, a detailed consideration on securing the safety of the existing facilities has been insufficient. An analysis on the types of traffic accidents in the last ten years shows that most incidents were due to the driver's improper response in emergency situations and unexpected obstacles. In consideration of this analysis, the safety of the facilities in the existing tunnel was secured by minimizing the charging amount for each hangfire and changing the excavation method of evacuation communication shelters to the large center hole cut blasting method to reduce blasting vibration. For a more quantitative analysis, measurement devices were installed inside the existing tunnel, at houses adjacent to the new tunnel, near jet fans in the existing tunnel. This enabled real time measurement of displacements of the existing tunnel, adjacent houses, and jet fans without interrupting traffic flow. Therefore, the improvements of charging amount for each hangfire, the blasting method, and the measurement method are suggested in this paper to secure the safety of the facilities in the existing tunnel when a new tunnel, located on a large city and adjacent to an existing tunnel, is designed.

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ANALYSIS OF STEADY FIRE-DRIVEN FLUID FLOW FOR RAILWAY TUNNEL BY DIFFERENT VELOCITY CONDITIONS AT THE END OF TUNNEL (종단부 유속조건 변화에 따른 철도터널 내 정상상태 화재유동해석)

  • Lee, D.C.;Lee, D.H.;Jung, W.S.;Park, S.H.
    • 한국전산유체공학회:학술대회논문집
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    • 2010.05a
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    • pp.208-213
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    • 2010
  • In this study CFD(Computational Fluid Dynamics) analysis of the steady fire-driven fuid flow for the performance test of ventilation at railway tunnel between Heuksok and Nodeul Station from Seoul Metro 9 is performed. There were fans with exhaust and intake modes and each was installed at the middle and both ends of the tunnel. For this test, the pool fire source of methyl alcohol with 1.5MW and smoke generators were installed between the middle of tunnel and Heuksok Station. In this test, the smoke behavior from natural convection was observed for 10 minutes from the ignition of pool fire and then fans with intake-modes at both sides of Heuksok effect of fan-on with intake mode located in the opposite side of the tunnel nearby Heuksok Station on fire-driven fluid flow is studied on when the boundary conditions of fan-on at the tunnel between Heuksok and Nodeul Station are the same as test. FLUENT, a commercial CFD code, is used for this analysis.

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Assessment of time-dependent behaviour of rocks on concrete lining in a large cross-section tunnel

  • Mirzaeiabdolyousefi, Majid;Nikkhah, Majid;Zare, Shokrollah
    • Geomechanics and Engineering
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    • v.29 no.1
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    • pp.41-51
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    • 2022
  • Tunneling in rocks having the time-dependent behavior, causes some difficulties like tunnel convergence and, as a result, pressure on concrete lining; and so instability on this structure. In this paper the time-dependent behaviour of squeezing phenomenon in a large cross section tunnel was investigated as a case study: Alborz tunnel. Then, time-dependent behaviour of Alborz tunnel was evaluated using FLAC2D based on the finite difference numerical method. A Burger-creep viscoelastic model was used in numerical analysis. Using numerical analysis, the long-time effect of squeezing on lining stability was simulated.This study is done for primary lining (for 2 years) and permanent lining (for 100 years), under squeezing situations. The response of lining is discussed base on Thrust Force-Bending Moment and Thrust Force-Shear Force diagrams analysing. The results determined the importance of consideration of time-dependent behaviour of tunnel that structural forces in concrete lining will grow in consider with time pass and after 70 years can cause instability in creepy rock masses section of tunnel. To show the importance of time-dependent behavior consideration of rocks, elastic and Mohr-Coulomb models are evaluated at the end.

Behavior of double deck tunnel due to feature change and variation of ground water table (다목적 복층터널의 기능전환과 지하수위 변화에 따른 거동분석)

  • Park, No-Hyeon;Kim, Ho-Jong;Shin, Jong-Ho
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.18 no.6
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    • pp.581-591
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    • 2016
  • Several attempts to construct multi-purpose tunnel for both road and waterway have been made. The multi-purpose tunnel is mainly used as a road tunnel, however it is transferred to waterway to control flood during rainy season. The planning of the multi-purpose tunnel is recognized as cost-effective way of infrastructure construction. In case of the multi-purpose tunnel constructed beneath groundwater table, seasonal fluctuation of groundwater table and repeated flow in the tunnel may cause long-term deterioration of the tunnel system. In this study, the behavior of multi-purpose tunnel in view of groundwater table or flow in the tunnel is investigated using model test and numerical modeling method. The results have shown that rising of groundwater table caused buoyant force to the tunnel and the fluctuation of rainwater in the tunnel generated loosening of surrounding ground. It is recommended to evaluate the effect of the long-term water pressure variation in the design of a multi-purpose tunnel.