• Title, Summary, Keyword: 지표면 침하

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Field Measurements of Ground Movements Around Tunnel (현장계측에 의한 터널주변지반의 변위연구)

  • 홍성완;배규진
    • Geotechnical Engineering
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    • v.1 no.2
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    • pp.41-54
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    • 1985
  • Generally, ground settlements and lateral displacements are accompanied by underground excavation associated with open-cut or tunnling. These ground movements cause a harmful influence upon nearby super.structures and sub-structures. Occasionally, the ground movements may pose serious problems as the function of the nearby structures may be disrupted. Therefore, prior to the subway construction in an urban area, it is necessary to identify the causes of ground settlements and estimating the extent St the magnitude of ground movements since any potential damage to the nearby structures such as gas lines, water mains, high buildings and cultural assets must be assessed. The research was performed mainly on ground movements such as surface settlements, lateral displacements, subsurface settlements and crown settlements to predict the maximum settlement and settlement zone, and to identify the causes of ground settlements in NATM sections of Busan subway. As a result, it was found that lateral distribution of settlements could be approximated reasonably by a Gaussian normal probability curve and longitudinal distribution of settlements by a cumulative Gaussian probability curve, and that the early closure of temporary invert was very important to minimize ground settlements.

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Numerical analysis of tunnelling-induced ground movements (터널굴착으로 발생한 지반거동에 대한 수치해석적 분석)

  • Son, Moo-Rak;Yun, Jong-Cheol
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.11 no.3
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    • pp.229-242
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    • 2009
  • Numerical analysis has been performed to estimate maximum settlement, maximum horizontal displacement and total settlement volume at the ground surface due to tunnel excavation varying ground condition, tunnel depth and diameter, and construction condition (volume loss at excavation face). The maximum surface settlement from the numerical analysis has been compared with the maximum settlement at tunnel crown considering ground condition, tunnel depth and diameter, and construction condition, and it has been also compared with the maximum horizontal displacement. In addition, the volume loss ($V_L$) at tunnel excavation face has been compared with the total surface settlement volume ($V_s$) with the variation of ground condition, tunnel depth, and tunnel diameter. The results from the numerical analysis have been compared with field measurements to confirm the applicability and validity of the results and by this comparison it is believed that the numerical results in this study can be utilized practically in analyzing the ground movements due to tunnel excavation.

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Lateral Displacement and Ground Rising Movement with Soil Embankment (성토에 따른 지반의 측방변위와 지표면 융기량)

  • Jeong, Ji-Cheol;Shin, Bang-Woong;Oh, Se-Wook
    • Journal of the Korean Geoenvironmental Society
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    • v.5 no.2
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    • pp.63-69
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    • 2004
  • During and after the construction of embankment on soft ground, consolidation settlements and lateral displacements develop. But generally it's very difficult to predict the magnitude of lateral deformations and the correct distribution of lateral displacements with depth under the toe of embankment because the consolidation and the shear deformations of soft ground occur simultaneously. This study shows that later displacements of ground surface arise by embankment loading act on soft clay hight water contents in laboratory model testing. The results of model test are observed settlement of embankment, amount of maximum rising and displacement of ground surface with loading velocity. The formula were proposed to predict lateral movement by test series.

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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.

Probabilistic Study of Surface Subsidence due to the Collapse of Underground Void during Earthquakes (지진에 따른 지하공동의 붕괴로 인한 지표면 함몰에 대한 확률론적 연구)

  • Kim, Young Soo;Lee, Chin
    • Journal of The Korean Society of Civil Engineers
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    • v.13 no.4
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    • pp.217-226
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    • 1993
  • This study is related to the surface subsidence due to the collapse of a underground void during earthquakes. The amount of the settlement due to the collapse of a underground void will depend on the depth of the void, the initial condition of unit weight of sand, the size and type of foundation, the strength of earthquake, the size of a void, etc. The purpose of the paper is to estimate the amount of the subsidence, analyse the factors affecting the subsidence, and develop a program determining the probability of the damages to structures in terms of absolute and differential settlement and rotational settlement. On the base of the results obtained in this study, when the depth of a void is constant and the width of the void increases, the change of the subsidence factor due to the angle of internal friction and the actual effective factor of the void become smaller than that due to the unit weight of sand deposits. In the same condition, the probabilities of damages due to the absolute and differential settlement increase, and those due to the rotational settlement decrease.

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Comparison of Ground Movements in A Single Ground Layer and Multiple Ground Layers due to Nearby Tunnel Excavation (터널굴착으로 발생한 주변 단일지층 및 복합지층 지반에서의 지반변위에 대한 거동비교)

  • Son, Moorak;Yun, Jongcheol
    • Journal of The Korean Society of Civil Engineers
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    • v.30 no.3C
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    • pp.167-174
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    • 2010
  • In this study, numerical analysis has been performed to compare the ground movements in a single ground layer and multiple ground layers due to nearby tunnel excavation. The numerical analysis has been conducted in the different ground layer conditions considering different construction conditions (volume loss at excavation face), and the results of the maximum surface settlement and horizontal displacement have been compared considering the ground layer and construction conditions. In addition, the maximum surface settlement from the numerical analysis has been compared with the maximum settlement at tunnel crown considering the ground layer and construction conditions, and the maximum surface settlement has been also compared with the maximum horizontal displacement with the ground layer conditions. Besides, the volume loss($V_L$) at tunnel excavation face has been compared with the total surface settlement volume($V_s$) with the variation of ground layer condition. The results from the numerical analysis have been compared with field measurements and by this comparison it is believed that the numerical results in this study can be utilized practically in analyzing the nearby ground behavior in different ground layer and construction conditions due to tunnel excavation.

A development of the ground settlement evaluation chart on tunnel excavation (터널굴착에 따른 지반침하 예측을 위한 침하량 평가도표 개발)

  • Park, Chi Myeon;You, Kwang-Ho;Lee, Ho
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.20 no.6
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    • pp.1105-1123
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    • 2018
  • The main risk factors of tunnel excavation through urban areas are ground settlement and surface sink which caused by ground conditions, excavation method, groundwater condition, excavation length, support method, etc. In the process of ground settlement assessment, the numerical analysis should be conducted considering the displacement and stress due to tunnel excavation. Therefore a technique that can simplify such process and easily evaluate the influence of tunnel excavation is needed. This study focused on the tunnelling-induced ground settlement which is main consideration of underground safety impact assessment. The parametric numerical analyses were performed considering such parameters as ground conditions, tunnel depth, and lateral distance from tunnel center line, etc. A simplified ground settlement evaluation chart was suggested by analyzing tendency of ground subsidence, lateral influence area and character by depth. The applicability of the suggested settlement evaluation chart was verified by comparative numerical analysis of settlement characteristics.

Effects of Reinforced Pseudo-Plastic Backfill on the Behavior of Ground around Cavity Developed due to Sewer Leakage (하수관 누수에 의해 발생되는 공동 주변 지반의 거동에 대한 가소성유동화토의 보강효과)

  • Oh, Dongwook;Kong, Sukmin;Lee, Daeyoung;Yoo, Yongseon;Lee, Yongjoo
    • Journal of the Korean Geoenvironmental Society
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    • v.16 no.12
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    • pp.13-22
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    • 2015
  • Developed ground cavity due to leakage of decrepit old sewer pipe causes ground surface settlement and brittle fracture of pavement. Recently, for 5 years, frequency of occurrence of ground subsidence phenomenon tends to increase rapidly and/or steadily. It is difficult to investigate ground surface settlement and/or subsidence in urban area because most ground surfaces are covered with asphalt or concrete pavement. In this research, therefore, ground surface settlement, influence zone and settlement of sewer pipe were analyzed using finite element method. Not only reinforced effect of pseudo-plastic backfill that is applied to prevent ground surface settlement or subsidence spot, was compared and analyzed using numerical analysis program, but also direct shear test was carried out to determine strength parameters of pseudo-plastic backfill.

The Analysis of Excavation Behavior Considering Small Strain Stiffness (미소변형율 강성을 고려한 지반굴착 해석)

  • Kim, Young-Min
    • Journal of the Korean Geosynthetics Society
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    • v.9 no.2
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    • pp.21-31
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    • 2010
  • This paper describes research on the prediction of the vertical displacement of surface, horizontal displacements and bending moments in two anchored retaining wall for an excavation by a finite element program. It is very important to consider the appropriate constitutive model for the numerical analysis in excavation behavior. It is shown in this paper that the analyses of excavation considering small strain stiffness gives the more reasonable prediction of the vertical displacement of surface. and the parametric study on the small strain stiffness parameters for excavation analysis has been analysed.

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Deformation Analysis of a Shallow NATM Tunnel using Strain Softening Model and Field Measurement (변형률 연화모델과 현장계측을 이용한 저토피 NATM터널의 변형해석)

  • Lee, Jaeho;Kim, Youngsu;Moon, Hongduk;Kim, Daeman;Jin, Guangri
    • Journal of the Korean Geoenvironmental Society
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    • v.8 no.6
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    • pp.29-36
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    • 2007
  • The control and prediction of surface settlement, gradient and ground displacement are the main factors in urban tunnel construction. This paper carried out the estimation and prediction of ground behavior around tunnel due to excavation using computational method and case study in detail for the analysis of deformation behavior in urban NATM tunnel. Computational method was performed by FLAC-2D with strain softening model and elastic plastic model. Field measurements of surface subsidence and ground displacement were adopted to monitor the ground behavior resulting from the tunneling and these values were applied to modify tunnel design parameters on construction.

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