• Title, Summary, Keyword: excavation

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Urban Excavation and Observational Method (도심지 지하굴착 및 정보화 시공)

  • Kim, Hak-Moon
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.3-14
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    • 2005
  • Reliable predictions of the movement of earth retaining structures and the ground adjacent to braced walls in urban excavation are often difficult due to many variable factors. The ground settlement and the damage of adjacent structures in urban excavation has been an important issue. Therefore, the stability of the adjacent structures must be secured with the excavation support and research on the protection of adjacent structure is necessary. This study showed an urban excavation case and introduce observation method for case of damage behavior in urban excavation.

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Sequential Analysis of Adjacent Ground Behaviors Caused by Deep Excavations (굴착 공정별 주변지반 거동 분석)

  • Seo Min-Woo;Seok Jeong-Woo;Yang Ku-Seung;Kim Myoung-Mo
    • Journal of the Korean Geotechnical Society
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    • v.22 no.2
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    • pp.19-28
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    • 2006
  • Long-term field observations were performed in three excavation sites in order to investigate the displacement behavior of adjacent ground during overall excavation procedure, where the depths of deep excavations were 15 m$\∼$29 m. In this study, ground settlements and lateral displacements of braced wall measured during installation of retaining wall and removal of bracing were specially focused to evaluate the behavior quantitatively according to three-stage-divided procedure, i.e. pre-excavation, main excavation, and removal of bracing. Through field measurements on three excavation sites, lateral displacements induced during removal of bracing are approximate to 40$\%$ of the amount found during main excavation stage and additional adjacent ground deformation during post-excavation procedure ranges from 18$\%$ to 33$\%$ of that found during main excavation stage, based on the settlement volume. In conclusion, it was quantitatively identified in this study that the deformations of adjacent ground during pre- and post-excavation stage were not negligible.

A Study on the Rapid Construction Method for Ground Excavation (지반굴착을 위한 급속시공 방안 연구)

  • Sim, Jae-Uk;Son, Sung-Gon;An, Hyung-Jun;Kim, In-Ho
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.1251-1258
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    • 2008
  • The purpose of this research is to introduce the new temporary earth retaining wall system using landslide stabilizing piles. This system is a self-supported retaining wall(SSR) without installing supports such as tiebacks, struts and rakers. The SSR is a kind of gravity structures consisting of twin parallel lines of piles driven below dredge level, tied together at head of soldier piles and landslide stabilizing piles by beams. There are three types of excavation wall structures: standard method for medium retained heights(<8.0m), internal excavation method and slope excavation method for deep-excavation applications(>8.0m). In the present study, the measured data from seven different sites which the SSR was used for excavation were collected and analyzed to investigate the characteristic behavior lateral wall movements associated with urban excavations in Korea.

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2D numerical investigation of twin tunnels-Influence of excavation phase shift

  • Djelloul, Chafia;Karech, Toufik;Demagh, Rafik;Limam, Oualid;Martinez, Juan
    • Geomechanics and Engineering
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    • v.16 no.3
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    • pp.295-308
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    • 2018
  • The excavation of twin tunnels is a process that destabilizes the ground. The stability of the tunnel lining, the control of ground displacements around the tunnel resulting from each excavation and the interaction between them must be controlled. This paper provides a new approach for replacing the costly 3D analyses with the equivalent 2D analyses that closely reflects the in-situ measurements when excavating twin tunnels. The modeling was performed in two dimensions using the FLAC2D finite difference code. The three-dimensional effect of excavation is taken into account through the deconfinement rate ${\lambda}$ of the soil surrounding the excavation by applying the convergence-confinement method. A comparison between settlements derived by the proposed 2D analysis and the settlements measured in a real project in Algeria shows an acceptable agreement. Also, this paper reports the investigation into the changes in deformations on tunnel linings and surface settlements which may be expected if the twin tunnels of T4 El-Harouche Skikda were constructed with a tunneling machine. Special attention was paid to the influence of the excavation phase shift distance between the two mechanized tunnel faces. It is revealed that the ground movements and the lining deformations during tunnel excavation depend on the distance between the tunnels' axis and the excavation phase shift.

Case Study of Characteristic of Ground Deformation and Strut Axial Force Change in Long Span Deep Excavation(II) (장지간 깊은 굴착에서 지반변형 및 버팀보 축력변화 특성 사례연구(II))

  • Kim, Sung-Wook;Han, Byung-Won
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.248-259
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    • 2010
  • In the case of relatively good ground and construction condition in the deep excavation for the construction of subway, railway, building etc., flexible earth retaining systems are often used in an economical point of view. It is generally known that the mechanism of behavior in the flexible earth retaining system is relatively more complicated than the rigid earth retaining system. Moreover in the case of long span strut supporting system the analysis of strut axial force change becomes more difficult when the differences of ground condition and excavation work progress on both sides of excavation section are added. When deeper excavation than the specification or installation delay of supporting system is done or change of ground condition is faced due to the construction conditions during construction process, lots of axial force can be induced in some struts and that can threaten the safety of construction. This paper introduces one example of long span deep excavation where struts and rock bolts were used as a supporting system with flexible wall structure. The characteristics of ground deformation and strut axial force change, the measured data obtained during construction process, were analysed, the effects of relatively deeper excavation than the specification on one excavation side and rapid drawdown of ground water level on the other excavation side were deeply investigated from the viewpoint of mutual influences between ground deformations of both excavation sides and strut axial force changes. The effort of this article aims to improve and develop the technique of design and construction in the coming projects having similar ground condition and supporting method.

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특정 사례터널 해석 결과 및 평가

  • Lee, Seung-Rae;O, Se-Bung;Baek, Gyu-Ho
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.123-132
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    • 1991
  • The GEOKST program was used to solve the tunnel example problem. The package can solve such geotechnical problem as excavation, embankment, foundations, etc., in which the soil can be modeled by various elastoplastic geomaterial models. The main objective was to consider the effects of excavation depth to the face of the tunnel on the stability of the ground and support system. Depended on the strength of the ground materials, the limit excavation depth without any support system could be established by analyzing three-dimensional excavation problem. In this given example problem, the strengths of the ground materials were enough for the stability of the tunnel without any support system up to fairly deep excavation and the maximum tunnel section displacement was stabilized as the excavation proceed. The asymptotic value was approximately the same as that of the plane strain analysis. Thus, assuming the plain strain condition and simulation the actual excavation procedure, the maximum tunnel section displacement was caculated after final step. The maximum calculated displacement occured at the top section of the tunnel geometry and was about 8mm.

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A Study on the Structural Behavior of Underground Openings Considering the Effect of Excavation (굴착영향을 고려한 지하공동의 구조거동연구)

  • 최규섭;김대홍
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.111-117
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    • 1992
  • In order to design and construct a safe and economic underground structure, it is essential to understand the structural behavior of underground openings considering the effect of the sequential excavation. Therefore, this paper includes the study of initial stress distribution before excavation and stress redistribution due to the sequential excavation. And discussion on numerical simulation techniques for the sequential excavation is also included. Then, the underground structure is analyzed using the finite element and distinct element methods of analysis considering the effect of the sequential excavation. Based on the results of the analysis, the followings are discussed: shape of the openings, effect and timing of structural reinforcements. methods and sequence of excavation.

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Excavation and Building Damage Assessment - Fundamentals (지반굴착과 주변 구조물 손상평가 - 기본개념)

  • 유충식
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.263-270
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    • 2002
  • During deep excavation, changes in the state of stress in the ground mass around the excavation and subsequent ground losses inevitably occur. These changes in the stress and ground losses are reflected on surrounding ground in the form of ground movements, which eventually Impose strains onto nearby structures through translation, rotation, distortion, and possibly damage. A substantial portion of the cost of deep excavations in urban environments is, therefore, devoted to prevent ground movements. Prediction of ground movements and assessment of the risk of damage to adjacent structures has become an essential part of the planning, design, and construction of a deep excavation project in the urban environments. This paper presents excavation-induced ground movement characteristics as well as important issues related to excavation-induced building damage assessment.

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Building Response to Excavation-Induced Ground Movements and Damage Estimation (굴착유발 지반변위에 의한 인접구조물의 거동 및 손상도 예측)

  • Son, Moo-Rak;Cording, E.J.
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.249-256
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    • 2006
  • New infrastructures and buildings are being constructed increasingly in congested urban areas, and excavation-induced ground movements often cause distortion and damage to adjacent buildings. Protection of adjacent structures occupies a major part of the cost, schedule and third-party impacts of urban development. To limit damage or mitigate their effects on nearby structures, it is highly important to understand the whole mechanism from excavation to building damage, and to estimate building damage reliably before excavation and provide appropriate measures. This paper investigates the effects of excavation-induced ground movements on nearby structures, considering soil-structure interactions for ground and structures, and a building damage criterion, which is based on the state of strain, is proposed. The criterion is compared with other existing damage estimation criteria and a procedure is finally provided for estimating building damage due to excavation-induced ground movements.

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The illegal case and Improvement of Excavation (흙막이 굴착공사의 부실 사례 및 개선방향)

  • Choi, Jung-Bum;Shin, Seung-Mock
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.643-650
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    • 2009
  • The necessary consequence by the rapid economic growth in large-scale urban excavation is increasing. If the site is the congested in downtown, the scale of excavation will get the large-scale and the extreme depth. We have achieved a high level technology internationally by the design and construction of underground excavation since 1980's. But the accidents during excavation are frequently occurring. So, this demage instigates the human life loss as well as economical loss. The recent accident is come about the damage for public facilities such as the railroad, subway and etc. in addition to the loss of life and property. For these reasons, the recent accident is being caused the damage of copious social overhead capital. The reasons of collapse during excavation can be classified roughly into the administrative part(sanction, permission), the investigation and design, the construction and management and etc. In this study the close check for the cases of the recent collapse is performed and the improvement course for the prevention of collapse is found.

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