• Title/Summary/Keyword: lining model

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IE-SASW Method for Nondestructive Testing of Geotechnical Concrete Structure : II. Experimental Studies (콘크리트 지반구조물의 비파괴검사를 위한 충격반향-표면파 병행기법 : II. 실험적 연구)

  • 김동수;서원석;이광명
    • Journal of the Korean Geotechnical Society
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    • v.18 no.4
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    • pp.271-283
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    • 2002
  • P-wave velocity of concrete is a crucial parameter in determining the thickness of concrete lining, the location of cracks or other defects in Impact-Echo(IE) method. This study introduces an IE-SASW method that may determine the P-wave velocity on a surface of each testing area using the Spectral Analysis of Surface Wave (SASW) method. In numerical studies(Part I), it was verified that P-wave velocities could be obtained from SASW. In this paper(Part II), experimental studies were made in slab type concrete model specimens in which voids and waterproof sheet were included at the known locations. Accordingly, the feasibility of the proposed method was evaluated. The IE-SASW method was also performed in the precast model tunnel on ground and open-cut tunnel in ground. SASW tests were performed to determine the P-wave velocity of the concrete and then IE tests were carried at regularly spaced points along the testing lines to determine the thickness of structures. The nondestructive testing method which combined SASW and IE tests showed the great potential in the field applications.

Numerical Modeling on the Prediction of Groundwater Recovery in the Youngchun Area, Kyungbook Province (경상북도 영천지역의 지하수위 회복 예측 수치 모델링)

  • 이병대;추창오;이봉주;조병욱;함세영;임현철
    • Economic and Environmental Geology
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    • v.36 no.6
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    • pp.431-440
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    • 2003
  • A modeling was performed to predict the groundwater recovery in the vicinity of the waterway tunnel area using a groundwater flow model MODFLOW. The model was calibrated to reproduce measured groundwater levels and observed flow rates into the tunnel prior to lining, and then used for flow simulation under transient condition. Model predictions under steady-state condition revealed that if tunnel conductance had been reduced by 25% to 90%, groundwater levels would recover between 8% and 72.4% of their initial levels and flow into the tunnel will decrease between 5.5% and 82.7%. In case of 75% tunnel condutance ruduction in transient simulation. most of wells were predicted to recover within 20 years or so. The complete recovery for the wells with the groundwater level over 70 m was found to be impossible. For the 90% tunnel conductance reduction, all wells were found to be recovered within 15 years.

Numerical analysis of segmental tunnel linings - Use of the beam-spring and solid-interface methods

  • Rashiddel, Alireza;Hajihassani, Mohsen;Kharghani, Mehdi;Valizadeh, Hadi;Rahmannejad, Reza;Dias, Daniel
    • Geomechanics and Engineering
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    • v.29 no.4
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    • pp.471-486
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    • 2022
  • The effect of segmental joints is one of main importance for the segmental lining design when tunnels are excavated by a mechanized process. In this paper, segmental tunnel linings are analyzed by two numerical methods, namely the Beam-Spring Method (BSM) and the Solid-Interface Method (SIM). For this purpose, the Tehran Subway Line 6 Tunnel is considered to be the reference case. Comprehensive 2D numerical simulations are performed considering the soil's calibrated plastic hardening model (PH). Also, an advanced 3D numerical model was used to obtain the stress relaxation value. The SIM numerical model is conducted to calculate the average rotational stiffness of the longitudinal joints considering the joints bending moment distribution and joints openings. Then, based on the BSM, a sensitivity analysis was performed to investigate the influence of the ground rigidity, depth to diameter ratios, slippage between the segment and ground, segment thickness, number of segments and pattern of joints. The findings indicate that when the longitudinal joints are flexible, the soil-segment interaction effect is significant. The joint rotational stiffness effect becomes remarkable with increasing the segment thickness, segment number, and tunnel depth. The pattern of longitudinal joints, in addition to the joint stiffness ratio and number of segments, also depends on the placement of longitudinal joints of the key segment in the tunnel crown (similar to patterns B and B').

Prediction of Long-term Behavior of Tunnel in the Presence of Geological Anomalies (지질이상대가 존재하는 구간에서의 터널의 장기거동 예측)

  • Hoki Ban;Heesu Kim;Jungkuk Kim;Donggyou Kim
    • Journal of the Korean GEO-environmental Society
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    • v.24 no.8
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    • pp.13-20
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    • 2023
  • Tunnelling through the geological anomalies has widely known to have many difficulties such as bottom heave, crack of lining, squeezing and so on. To stabilize the tunnel during the construction or after construction, various reinforcing methods have been introduced and applied such as micropiling at the bottom of tunnel to prevent the bottom heave. In this study, long-term behavior of tunnel in the presence of geological anomalies was predicted using numerical analyses. To this end, material properties for swelling rock model capable of representing the rock swelling behavior was obtained using matching process with measured data to validate the adopted model. After the model validation, simulations were performed to predict the long-term behavior of tunnel in the geological anomalies.

The Behaviours of Existing Tunnels in response to Multiple side-by-side Tunnel Construction in Soft Ground (연약지반 다수의 터널 병렬시공 시 기존터널의 거동)

  • Ahn, Sung Kwon
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.12 no.6
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    • pp.193-204
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    • 2008
  • This paper describes laboratory experiments modelling multiple tunnel construction in soft ground. A series of small-scale model tests have been conducted at approximately 1/50 scale in order to investigate the behaviours of existing tunnels in response to the construction of new tunnels in close proximity. The model tunnels were constructed in a consolidated Speswhite Kaolin clay using a tunnelling device involving an auger type cutter within a shield. Strain gauges and LVDTs were used for instrumenting the existing tunnels. The findings obtained from the analyses of these tests were compared to the field measurements involving the reconstruction of the Northern Line London Underground Ltd. tunnels at Old street, United Kingdom. The results were also compared to the ground movement measurements obtained from a separate set of tests undertaken using the same apparatus and experimental procedures.

A simplified combined analytical method for evaluating the effect of deep surface excavations on the shield metro tunnels

  • Liu, Bo;Yu, Zhiwei;Han, Yanhui;Wang, Zhiliu;Yang, Shuo;Liu, Heng
    • Geomechanics and Engineering
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    • v.23 no.5
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    • pp.405-418
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    • 2020
  • Deep excavation may have impact on the adjacent tunnels. It is obvious that the excavation will adversely affect and even damage the existing tunnels if the induced deformation exceeds the capacity of tunnel structures. It hence creates a high necessity to predict tunnel displacement induced by nearby excavation to ensure the safety of tunnel. In this paper, a simplified method to evaluate the heave of the underlying tunnel induced by adjacent excavation is presented and verified by field measurement results. In the proposed model, the tunnel is represented by a series of short beams connected by tensile springs, compressional springs and shear springs, so that the rotational effect and shearing effect of the joints between lining rings can be captured. The proposed method is compared with the previous modelling methods (e.g., Euler-Bernoulli beam, a series of short beams connected only by shear springs) based on a field measured longitudinal deformation of subway tunnels. Results of these case studies show a reasonable agreement between the predictions and observations.

Multi-sensor data fusion based assessment on shield tunnel safety

  • Huang, Hongwei;Xie, Xin;Zhang, Dongming;Liu, Zhongqiang;Lacasse, Suzanne
    • Smart Structures and Systems
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    • v.24 no.6
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    • pp.693-707
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    • 2019
  • This paper proposes an integrated safety assessment method that can take multiple sources data into consideration based on a data fusion approach. Data cleaning using the Kalman filter method (KF) was conducted first for monitoring data from each sensor. The inclination data from the four tilt sensors of the same monitoring section have been associated to synchronize in time. Secondly, the finite element method (FEM) model was established to physically correlate the external forces with various structural responses of the shield tunnel, including the measured inclination. Response surface method (RSM) was adopted to express the relationship between external forces and the structural responses. Then, the external forces were updated based on the in situ monitoring data from tilt sensors using the extended Kalman filter method (EKF). Finally, mechanics parameters of the tunnel lining were estimated based on the updated data to make an integrated safety assessment. An application example of the proposed method was presented for an urban tunnel during a nearby deep excavation with multiple source monitoring plans. The change of tunnel convergence, bolt stress and segment internal forces can also be calculated based on the real time deformation monitoring of the shield tunnel. The proposed method was verified by predicting the data using the other three sensors in the same section. The correlation among different monitoring data has been discussed before the conclusion was drawn.

Mechanical Mechanism of Main Tunnels and Cross Passage Construction - A 3D Numerical Investigation

  • Yoo, Chungsik;Shuaishuai, Cui;Ke, Wu;Qianjn, Zhang;Zheng, Zhang;Jiahui, Zhao
    • Journal of the Korean Geosynthetics Society
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    • v.18 no.1
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    • pp.11-23
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    • 2019
  • This paper presents the results of a three-dimensional numerical investigation into the mechanical mechanism of main tunnels and cross passage construction. Aimed at the complex space structure composed of two main tunnels and cross passage, 3D numerical model of the structure and surrounding rock was built to analyze the influence. Comparative analysis of different buried depths were carried out. The results of the study indicate that the stress concentration was occurred in the intersecting linings, especially in the opening side lining, which leads to an unfavorable form of force that is pulled up by the upper and lower sections in the intersecting linings due to the construction of the cross passage. The excavation of the cross passage also destroys the stability of the original soil layer and causes settlement of the surface and main tunnels. Practical implications of the findings are discussed.

Analysis of Environmental Load by Work Classification for NATM Tunnels (NATM터널의 공종별 환경부하 특성 분석)

  • Lee, Ju-hyun;Shim, Jin Ah;Kim, Kyong Ju
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.36 no.2
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    • pp.307-315
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    • 2016
  • Many countries are trying to reduce a greenhouse gas to step up their fight against climate change. There are many studies related to building only for reducing a greenhouse gas in construction area but studies related to reducing a comprehensive environmental load including various pollutants that affects the global environment are lacking. This study aims to analyse the characteristics of environmental load by work type for tunnel projects. Analysis showed that seven work types, including lining concrete, shotcrete, tunnel portal and open-cut tunnel work, etc., are representative works generated environmental load. These seven works represent 89.22 percent of total environmental load. In addition, comparison results of environmental load per tunnel's length by work type showed that a major factor of environmental load is caused by a tunnel portal and open-cut tunnel work with relatively short length (excavation length). And lining concrete and shotcrete work are larger than any other environmental load with tunnel's total length. It is expected that the result of this study will be used to make a estimation model for environmental load using approximate quantity survey of representative work types in the early stage of tunnel design. And it will be play a considerable role in establishing of environment management plan for sustainable infrastructure construction.

A Study of a Heat Flux Mapping Procedure to Overcome the Limitation of Heat Flux Gauges in Fire Tests (화재실험시 열유속 센서 사용의 단점을 보완한 Heat Flux Mapping Procedure에 관한 연구)

  • Choi, Keum-Ran
    • Journal of the Korean Society of Safety
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    • v.20 no.4 s.72
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    • pp.171-179
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    • 2005
  • It is essential to understand the role of wall lining materials when they are exposed to a fire from an ignition source. Full-scale test methods permit an assessment of the performance of a wall lining material. Fire growth models have been developed due to the costly expense associated with full-scale testing. The models require heat flux maps from the ignition burner flame as input data. Work to date was impeded by a lack of detailed spatial characterization of the heat flux maps due to the use of limited instrumentation. To increase the power of fire modeling, accurate and detailed heat flux maps from the ignition burner are essential. High level spatial resolution for surface temperature can be provided from an infrared camera. The objective of this study was to develop a heat flux mapping procedure for a room test burner flame to a wall configuration with surface temperature information taken from an infrared camera. A prototype experiment was performed using the ISO 9705 test burner to demonstrate the developed heat flux mapping procedure. The results of the experiment allow the heat flux and spatial resolutions of the method to be determined and compared to the methods currently available.