• Title/Summary/Keyword: Geo-centrifuge

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Behavior of Soft Ground Improved with Fully-Partly Penetrated Sand Compaction Piles (관통-미관통 모래다짐말뚝으로 개량된 연약지반의 거동)

  • Jeong, Geunchae;Heo, Yol;Bae, Wooseok
    • Journal of the Korean GEO-environmental Society
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    • v.13 no.9
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    • pp.91-99
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    • 2012
  • This study describes the investigation based on centrifuge model tests for the clay ground improved by sand compaction pile. In order to clarify the failure behavior of composite ground improved by partly and fully penetrated SCPs. And, in order to compare the effect of the penetration ratio and the replacement area ratio, nine of the centrifuge tests were carried out. From the test results, settlement reduce ratio in the fully penetrated SCPs ground is bigger than that in the partly penetrated SCPs ground. It is also evaluated that angle of the failure of composite ground improved by SCP are 26, 25, $34^{\circ}$ for As=10%, 22, $29^{\circ}$ for As=30%. And as a result of rigid loading tests, surface displacement decreases linearly with the partly penetration ratio increased.

Numerical Modeling of Soil Liquefaction at Slope Site (사면에서 발생하는 액상화 수치해석)

  • Park, Sungsik
    • Journal of the Korean GEO-environmental Society
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    • v.7 no.6
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    • pp.133-143
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    • 2006
  • A fully coupled effective stress dynamic analysis procedure for modeling seismic liquefaction on slope is presented. An elasto-plastic formulation is used for the constitutive model UBCSAND in which the yield loci are radial lines of constant stress ratio and the flow rule is non-associated. This is incorporated into the 2D version of Fast Lagrangian Analysis of Continua (FLAC) by modifying the existing Mohr-Coulomb model. This numerical procedure is used to simulate centrifuge test data from the Rensselaer Polytechnic Institute (RPI). UBCSAND is first calibrated to cyclic direct simple shear tests performed on Nevada sand. Both pre- and post-liquefaction behaviour is captured. The centrifuge test is then modeled and the predicted accelerations, excess porewater pressures, and displacements are compared with the measurements. The results are shown to be in general agreement. The procedure is currently being used in the design of liquefaction remediation measures for a number of dam, bridge, tunnel, and pipeline projects in Western Canada.

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Development of Construction Simulation Apparatus on Centrifugal Experiment (원심모형실험을 위한 시공단계모사장비개발)

  • Kim, You-Seok;Kim, Kyoung-O;Lee, Jong-Pil;Park, Jin-Woo
    • Proceedings of the Korean Geotechical Society Conference
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    • 2010.09a
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    • pp.979-990
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    • 2010
  • Although a centrifuge model test is performed with scaled models, it has a lot of advantages compared with usual scale model tests, for the reproduction of stress levels equal to a full scale test is possible. At the beginning of the Daewoo Institute of Construction Technology, a servo-motor-driven single axis actuator was introduced and has been in use with a geo-centrifuge. However, for variety of experiments and construction stage simulation, various apparatuses have been developed, such as a vacuum generator, a lateral actuator for tidal power simulation, a gravel hopper and a sand drainer for filled-up ground, and a water level controller. The apparatuses have been manufactured with enough strength and durability to be operated under specific g levels. This paper presents the properties of the apparatuses and the results of the tests performed with those.

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Stability evaluation of levee to foundation type of drainage construction in Using Geo-centrifuge (원심모형시험기를 활용한 통관기초형식에 대한 제방의 안전성 검토)

  • Im, Eun-Sang;Snin, Dong-Hoon;Kim, Jea-Hong;Cho, Sung-Eun
    • Proceedings of the Korean Geotechical Society Conference
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    • 2010.03a
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    • pp.856-861
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    • 2010
  • In recent days, the safety of the levee has been an issue because the levee has become bigger according to the Four-river Restoration Project and so on. The greater part of the levee damage has occurred in the interface between soils and the structures. Specially, the drainage construction crosses the levee keeps its settlement down in order to secure a grade of drainage. However, when the settlement isn't generated by using foundation such as pile, the levee is more likely to have leakage at the interface because the construction doesn't behave with soils. In our study, therefor, testing of the behavior of the levee having the drainage construction was carried out to clarify the effects of the foundation type of drainage construction.

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Centrifuge Modeling on Lateral Flow of Soft Soils and Displacement of Bridge Abutment on the Composite Ground (복합지반상 교대변위 및 지반 측방유동에 관한 원심모델링)

  • Heo, Yol;Park, Sunghun;Yun, Seokhyun;Kwon, Seonuk
    • Journal of the Korean GEO-environmental Society
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    • v.8 no.5
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    • pp.39-46
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    • 2007
  • In this study, the centrifuge tests were performed to investigate the lateral flow behavior and stability of the ground improved by SCP. The centrifuge tests were fulfilled in the case of the back of abutment filled by EPS (case 1) and soil (case 2), and the potentiometer was installed on the abutment and embankment to measure the vertical and horizontal displacement at the top of abutment. As a result, the vertical displacement measured at the back of abutment was maximum 2.1 m, which was about 12% if compared with the height of embankment. In the case of the back of abutment filled by soil, the vertical and horizontal displacement measured at the top of abutment was 10 cm and 1.1 m, respectively, which exceeded the allowable horizontal displacement. On the other hand, in the case of the back of abutment filled by EPS, the vertical displacement of abutment did nor occur and the horizontal displacement was 1.4 cm. Therefore, the effect of SCP improvement with EPS method adopted to prevent the lateral flow and assure the stability of embankment on the soft ground was far superior.

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Comparison of 1-g and Centrifuge Model Tests for Similitude Laws (상사법칙 검증을 위한 1-g 모형실험과 원심모형실험의 비교 연구)

  • Kim Sung-Ryul;Hwang Jae-Ik;Kim Myoung-Mo;Ko Hon-Yim
    • Journal of the Korean Geotechnical Society
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    • v.22 no.5
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    • pp.59-67
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    • 2006
  • The centrifuge and 1-g shaking table tests were performed simultaneously to compare the dynamic behaviors of loose sands of the same geotechnical properties. The prototype soils were 10 m thick liquefiable loose sands. The geometric scaling factors were 20 for 1-g and 40 for centrifuge tests. The excess pore pressure, surface settlement, and acceleration in the soil were measured at the same locations in the 1-g and centrifuge tests. The total excess pore pressure from development to dissipation was measured. In the centrifuge test, viscous fluid was used as the pore water to eliminate the time scaling difference between dynamic time and dissipation time. In the 1-g tests, the steady state concept was applied to determine the unit weight of the model soil, and two different time scaling factors were applied for the dynamic time and the dissipation time. It is concluded that the 1-g tests can simulate the excess pore pressure of the prototype soil if the permeability of the model soil is small enough to prevent dissipation of excess pore pressure during shaking and the dissipation time scaling factor is properly determined.

Centrifuge Modeling on the Deformation Modes of Dredged Clay Slope (준설 점토사면의 변형양상에 관한 원심모델링)

  • Ahn, Kwangkuk;Kim, Jeongyeol;Zheng, Zhaodian;Lee, Cheokeun
    • Journal of the Korean GEO-environmental Society
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    • v.8 no.2
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    • pp.19-27
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    • 2007
  • In this study, the centrifugal tests were performed with varying the angle of slope such as 1:3, 1:2.5, and 1:2 in order to analyze the deformation and failure type of dredged clay slope for a short term. The displacement mode, displacement vector and the variation of pore pressure with the different slope angle were measured. As a results, even though the displacement in the slope after 4 months were developed in the case of 1:3 for the dredged slope, there are little problems to obtain the stability of dredged slope because the original construction section maintains. Also, in the case of 1:2.5 after 4 months the local slope failure occurred and in the case of 1:2 after 2 months the circle failure starting from the point of the tensile crack occurred. After reviewing the results, the maximum vertical displacement occurred at the crest of slope and maximum horizontal displacement was about double of maximum vertical displacement.

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Analysis for Bearing Capacity of Paper Ash in Industrial Waste as Filling Material (성토재로서 산업폐기물 제지회의 지지력 분석)

  • Lee, Cheo-Keun;Ahn, Kwang-Kuk;Heo, Yol
    • Journal of the Korean GEO-environmental Society
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    • v.2 no.2
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    • pp.13-22
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    • 2001
  • In this study, centrifuge model tests were fulfilled to investigate the characteristics of bearing capacity of paper ash as a filling material. The model tests were done varying the footing width and gravity level. The settlement and vertical soil pressure by loading were measured. The results from the tests were compared with the one from FLAC program using finite difference method and bearing capacity theory. After all, it was shown that the characteristics of load-settlement represented the local shear failure, which the settlement ratio s/B showed inflection point around 25~30%. As g-level and footing width were increasing, the load strength was increasing. The ultimate bearing capacity from the tests was very closed the results from Terzaghi's theory. As the distance from footing center was increasing, the vertical soil pressure was decreasing. If E/B is higher than 7, the stress by loading was almost increasing. The vertical displacement from loading was the largest one around under the footing and was almost occurred when the depth>4cm and E/B is higher than 5.0.

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Evaluation of Stability for Settlement Free Reinforced Earth Retaining Wall by Centrifuge Model Tests (원심모형실험에 의한 침하자유형 보강토 옹벽의 안정성 평가)

  • Ahn, Kwangkuk;Bae, Wooseok
    • Journal of the Korean GEO-environmental Society
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    • v.7 no.6
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    • pp.23-34
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    • 2006
  • In this study, the centrifugal tests were performed to evaluate the behavior of reinforced retaining wall that allows the settlement of reinforcement strip. To analyze the stability of reinforced retaining wall, which drives the settlement of reinforcement strip, the results were compared with the conventional reinforced retaining wall. In the centrifugal tests, the aluminum plate for the face was used and the aluminum foil was used as a reinforcement. The decomposed granite soil was adopted as a backfill. As a result, the settlement free reinforced retaining wall reached to the failure at 80g-level. In contrast, the conventional reinforced retaining wall was collapsed at 69g-level. It means that the settlement free reinforced retaining wall has the stronger stability than the conventional reinforced retaining wall. Also, vertical earth pressure of the settlement free reinforced retaining wall near the base of wall was higher 16% than that of the conventional reinforced retaining wall.

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Numerical Evaluation of Boundary Effects in the Laminar Shear Box System (층 분할된 연성전단상자의 경계효과에 관한 수치해석적 분석)

  • Kim, Jin-Man;Ryu, Jeong-Ho
    • Journal of the Korean Geotechnical Society
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    • v.24 no.8
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    • pp.35-41
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    • 2008
  • Laminar-shear-boxes are widely used to simulate free-field seismic ground response by using a l-g shaking table or geo centrifuge in geotechnical earthquake engineering. This study numerically modeled and compared the ground responses in the free field, rigid box, and laminar shear box by using a 3-D FEM program. It is found from the numerical simulations that the laminar shear box can simulate the free field ground movement more precisely than the rigid box. However, the laminar shear box underestimated the surface acceleration of the free field ground. It also showed low-frequency characteristics probably because the stiffness and inertia effect of surrounding ground are neglected.