• Title/Summary/Keyword: Diaphragm wall

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Centrifugal and Numerical Modelling on the Behavior of Unpropped Diaphragm Wall (Unpropped Diaphragm Wall 거동에 관한 원심 및 수치모델링)

  • Lee, Cheo-Keun;Ahn, Kwang-Kuk;Heo, Yol
    • Journal of the Korean Geotechnical Society
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    • v.17 no.2
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    • pp.123-134
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    • 2001
  • 본 연구에서는 화강풍화토 지반상 unpropped diaphragm wall의 거동을 연구하기 위하여 벽체의 근입깊이와 지하수위 조건을 변화시키면서 원심모형실험을 수행하였다. 원심모형실험시 diaphragm wall은 두께 8mm인 알루미늄합금을 사용하였으며, 지반굴착을 재현하기 위하여 zinc chloride 기법을 이용하였다. 수치해석은 대부분의 지반공학문제에 적용할 수 있는 SAGE CRISP 프로그램을 이용하였다. 수치해석에서 모형지반은 수정 Cam-Clay 모델, diaphragm wall은 탄성모델, 지반과 diaphragm wall 사이의 경계면요소는 슬립모델을 사용하여 2차원 평면변형률 조건으로 해석을 수행하였다. 모형실험 결과 파괴면의 직선적인 형태로 파괴면내의 배면측 지반은 벽체를 향하여 하향의 변위를 일으키면서 벽체의 회전에 의해 파괴되었다. 실험 및 유한요소해석 결과 지반의 최대침하량과 최대침하량이 발생하는 위치는 잘 일치하였으며, 깊이에 따른 벽체변위는 선형적인 관계를 나타내었다. 또한, 최대 휨모멘트와 근입깊이로 정규화한 최대 휨모멘트 발생위치($h_{Mmax}$/d=0.4)는 잘 일치하였다.

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Case Study of Self-Supported Diaphragm Wall Method Using Counterfort Technique (부벽식 기법을 사용한 자립식 지하연속벽 공법의 사례 연구)

  • Jeong, Gyeong-Hwan;Park, Hun-Kook;Shin, Min-Sik;Han, Kyoung-Tae;Ryu, Ji-Young
    • Proceedings of the Korean Geotechical Society Conference
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    • 2006.03a
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    • pp.276-285
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    • 2006
  • Application of anchored or strutted wall system for the earth retention of excavation works in a populated urban area or a poor soil deposit can be limited due to various restrictions. Since the strut becomes longer in a wide excavation site, the stability of an earth retaining wall is decreased, the wall deformation is increased, and the ground settlement is also increased due to an increased buckling or bending deformation of struts. Especially, in a populated urban area, the installation of anchors can be problematic due to the property line of adjacent structures or facilities. Thus, a new concept of earth retaining system like Self-Supported diaphragm Wall can solve several problems expected to occur during excavation in the urban area. In this study, Numerical analyses of counterfort diaphragm wall was introduced and the monitored data from the site was compared with the original results of numerical analyses. Also, in the case of the deep excavation applied the counterfort diaphragm wall, numerical analyses was performed to predict the wall deformation and the reinforcement to reduce the wall deformation was suggested.

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THE THEORETICAL AND SITE BEHAVIOUR OF A BRACED DIAPHRAGM WALL-A COMPARISON

  • Kim, Hak-Moon
    • Proceedings of the Korean Geotechical Society Conference
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    • 1990.10a
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    • pp.111-128
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    • 1990
  • Three numerical analysis carried out for the design of a diaphragm wall were examined by the results of field observation data. Utilizing the wall stiffness, supporting system and construction sequence, the relative merits of those factors on the analysis of diaphragm wall have been investigated and their effects are compared tilth the observed behaviour of the wall. The predicted bending moment and wall displacement by elasto-plastic method agreed well with the observed values. The rigid slab supported system (i.e Top-Down Method) found to be the most effective way of controlling ground movement.

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Centrifugal Modelling on the Displacement Mode of Unpropped Diaphragm Wall with Surcharge (과재하중이 있는 Unpropped Diaphragm Wall의 변위양상에 관한 원심모델링)

  • 허열;이처근;안광국
    • Journal of the Korean Geotechnical Society
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    • v.20 no.8
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    • pp.135-145
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    • 2004
  • In this study, the behavior of unpropped diaphragm walls on decomposed granite soil was investigated through centrifugal and numerical modelling. Centrifuge model tests were performed by changing the interval distance of surcharge. Excavation was simulated during the centrifuge tests by operating a solenoid valve that allowed the zinc chloride solution to drain from the excavation. In these tests, ground deformation, wall displacement and bending moment induced by excavation were measured. FLAC program which can be able to apply far most geotechnical problems was used in the numerical analysis. In numerical simulation, Mohr-Coulomb model fur the ground model, an elastic model for diaphragm wall were used for two dimensional plane strain condition. From the results of model tests, failure surface was straight line type, the ground of retained side inside failure line had downward displacement to the direction of the wall, and finally the failure was made by the rotation of the wall. The angle of failure line was about 67 ∼ 74$^{\circ}$, greater than calculated value. The locations of the maximum ground settlement obtained from model tests and analysis results are in good agreements. The displacement of wall and the change of the embedment depth is likely to have linear relationship.

Singapore Case Study of Self-Supported Diaphragm Wall Method Using Counterfort Technique (부벽식 기법을 사용한 자립식 지하연속벽 공법의 싱가폴사례)

  • Jeong, Gyeong-Hwan;Park, Hun-Kook;Shin, Min-Sik;Han, Kyoung-Tae;Ryu, Ji-Young
    • Proceedings of the Korean Geotechical Society Conference
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    • 2008.10a
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    • pp.605-613
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    • 2008
  • Application of anchored or strutted wall system for the earth retention of excavation works in a populated urban area or a poor soil deposit can be limited due to various restrictions. Since the strut becomes longer in a wide excavation site, the stability of an earth retaining wall is decreased, the wall deformation is increased, and the ground settlement is also increased due to an increased buckling or bending deformation of struts. Especially, in a populated urban area, the installation of anchors can be problematic due to the property line of adjacent structures or facilities. Thus, a new concept of earth retaining system like Self-Supported diaphragm Wall can solve several problems expected to occur during excavation in the urban area. Application of self-supported counterfort diaphragm wall was verified in this paper though comparing the design of self-supported counterfort diaphragm wall with the data monitored during excavation in Singapore.

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A Study on the Behaviour of Diaphragm Wall by the installation of CGS (CGS 시공으로 인한 지중연속벽체 거동에 관한 연구)

  • Kim, Dong-Hee;Hong, Sung-Jin;Min, Ki-Hoon;Lee, Woo-Jin
    • Proceedings of the Korean Geotechical Society Conference
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    • 2008.03a
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    • pp.1206-1215
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    • 2008
  • In this study, the equivalent pressure acting on the face of drilled hole was determined by back analysis. This analysis was continued until the difference between the displacement directly measured during field test construction of CGS and the displacement evaluated by numerical analysis was below 10 percent, and the affect of diaphragm wall adjacent to grout bulb was evaluated by numerical analysis using the equivalent pressure. From the analysis results, it was observed that the increase of the pressure acting on the diaphragm wall was greater at reclaimed sandfill layer than silty clay layer during the installation of CGS. Two methods were adopted to reduce the pressure acting on the diaphragm wall. One is installing of trench between diaphragm wall and grout bulb, the other is pre-installing of CGS before construction of diaphragm wall. From the numerical analysis results, above two methods can be considered as an effective method to reduce the pressure. It was analyzed that the amount of reduction of the pressure and the displacement are 689.8% and 564.6%, respectively, in the case of adopting the trench method, and 463.7% and 214.0%, respectively, in the case of adopting pre-installing of 3 columns CGS.

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Uplift Capacity of a Diaphragm Wall Installed in Ground with High Groundwater Table (높은 지하수위 지반 속에 설치된 지중연속벽의 인발저항력)

  • Hong, Won-Pyo;Chim, Neatha
    • Journal of the Korean Geotechnical Society
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    • v.30 no.9
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    • pp.5-17
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    • 2014
  • A series of model tests were conducted in order to observe the failure surface generated around a diaphragm wall embedded in ground with high groundwater table. Images of the soil deformation around the model wall were captured during the test. The configuration of the failure surface in soil around the model wall could be obtained from analyzing the image of the soil deformation. Based on the configuration of the failure surface observed in the model test, an analytical approach was proposed to predict the uplift capacity of a diaphragm wall installed in ground. The analytical approach considers not only the wall properties such as length, thickness and surface roughness of diaphragm walls but also the soil strength properties such as the internal friction angle and the cohesion of soil. The predicted uplift capacity of a diaphragm wall shows a good agreement with the experimental one measured in the model test.

Earth Pressure Equation Acting on the Cylindrical Diaphragm Wall in a Shaft (원형수직구에 설치된 강성벽체에 작용하는 토압산정방법)

  • Kong, Jin-Young;Shin, Young-Wan;Hwang, Yi-Sung;Chun, Byung-Sik
    • Journal of the Korean Geotechnical Society
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    • v.25 no.1
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    • pp.21-29
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    • 2009
  • On plane strain condition, many researchers have investigated the earth pressure according to the shape of wall, and standardized method has been applied to the design of the retaining wall. But on cylindrical diaphragm wall, at-rest earth pressure has been generally used. Even though this method is on conservative side, it may lead to over-design. In this paper, the application of convergence confinement method to the calculation of the earth pressure acting on the cylindrical diaphragm wall of a shaft was suggested. In addition, a model test was carried out to investigate the distributions of earth pressure. Model test results show that the earth pressures of diaphragm wall are about 1.4 times larger than active earth pressure and about 0.8 times less than at-rest earth pressure.

Characteristics and Applicability of CWS(Continuous Wall System)II Method (CWS(Continuous Wall System)II 공법의 특성 및 적용성)

  • Lim, In-sig;Lee, Jeong-bae;Kim, Jae-dong;Lee, Jai-ho;Woo, Sung-woo
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2008.11a
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    • pp.43-47
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    • 2008
  • CWSII method was developed to overcome the problems of frequent occurrence in the application of existing downward construction methods, especially in the case of using slurry wall instead of SCW or CIP as a retaining wall. By the improvements in connecting steel beams with the wall, CWSII method is able to ensure the settlement of a steel beam and the diaphragm effect of a slab while reducing the degree of difficulty and the term of works and the cost of construction. As the desired results, CWS method can be applied as a practical downward construction method regardless of the type of retaining wall. In this paper, besides the concept and features of CWSII method, it can be seen that the method can provide reliable and economical performances by comparing with existing methods.

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Earth Pressure Acting on the Diaphragm Wall of a Shaft in Cohesionless Soils (사질토지반에 설치된 원형수직구의 강성흙막이벽에 작용하는 토압)

  • Chun, Byung-Sik;Shin, Young-Wan;Kong, Jin-Young;Hwang, Yi-Sung
    • Proceedings of the Korean Geotechical Society Conference
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    • 2008.03a
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    • pp.734-741
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    • 2008
  • At-rest and active earth pressure in plane strain condition have been applied to the design of cylindrical retaining walls. But many researchers have indicated that the earth pressure on the cylindrical retaining walls would be smaller than in plane strain condition due to wall deformation and stress relief. In this paper, the distribution of earth pressure acting on diaphragm wall of a shaft in dry sand was predicted by using the convergence confinement method and model test was performed to verify the estimated values. Test results showed that the earth pressure acting on the diaphragm wall of a shaft was expected to be 1.1~1.5 times larger than active earth pressure of plane strain condition and 0.7~0.9 times less than at-rest earth pressure.

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