• Journal of the Korean Geotechnical Society
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• v.33 no.6
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• pp.5-16
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• 2017

Rocking behavior of shallow foundation during the earthquake can reduce the seismic load of the superstructure. The dynamic centrifuge tests were performed to investigate the availability of using rocking behavior for the weathered soil condition. The centrifuge test model was composed of the weathered soil, shallow foundation and single degree of freedom structure. And the accelerations of soil, foundation and structure, and the foundation settlement were measured during the earthquake. From the test result, the seismic load of the structure for the strong earthquake input was reduced by the rocking behavior with foundation uplift and the maximum foundation settlement was less than 0.5% of the foundation width. This shows the potential that the rocking foundation concept can be used in the economical seismic design of foundation for the weathered soil in the future with additional research and verification.

• Journal of the Korean Geotechnical Society
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• v.22 no.12
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• pp.89-98
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• 2006

In this paper the behavior of saturated sand deposits where liquefaction occurred before is studied for successive earthquakes. The relationship between past pore pressure generation and reliquefaction resistance is examined by using cyclic direct simple shear tests. If the soil sample in direct simple shear produced nearly 90% of excess pore pressure during first time loading, its liquefaction resistance increased during following cyclic loading after consolidation. However, a fully liquefied soil during first time loading has a densely packed condition but shows less liquefaction resistance for the following cyclic loading. UBCSAND model that can account for pore pressure change and stiffness loss of soil during shaking is used to analyze the centrifuge test simulating reliquefaction. The pore pressure rise during first time cyclic loading controls liquefaction resistance. The measurements from reliquefaction centrifuge test are compared with numerical predictions. By considering frequent earthquakes having occurred at the Southern Korea near Japan, such effective stress approach is necessary for reliquefaction study.

• Journal of Industrial Technology
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• v.21 no.B
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• pp.205-212
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• 2001

This paper is experimental and numerical research about the sliding behavior of cantilever retaining walls resisting surcharge loads. In experimental research, centrifuge model tests at the lg and 40 g-level were performed by changing the location of model footing and its width. Bearing capacity of model footing and characteristics of load-settlement and load-lateral displacement of retaining wall were investigated. Test results of bearing capacity were compared with modified jarquio method, based on the limit equilibrium method with elasticity theory. For the numerical analysis, the commericially available program of FLAC was used by implementing the hyperbolic constitutive relationships to compare with test result about load-settlement and load-displacement of retaining wall, bearing capacity of strip footing.

• Journal of the Korean Society of Safety
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• v.23 no.3
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• pp.12-16
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• 2008

For industrial centrifuges, the state of their welding areas, even with a naked-eye observation, offers potential safety problems such as inconsistent bead formation. STS304, which is used mainly in centrifuges, is made of metal alloys with chrome and nickel as the main ingredients, offering excellent corrosion resistance, thermal resistance, and high strength, and thus allowing it to be used for diverse purposes. This paper conducted tensile and fatigue tests of STS304 to improve the safety of centrifuges. In the findings, for the static behavior of the STS304 material, welded specimens increased their yield and tensile strength compared with the base test specimens, but decreased their elongation ratio. Also, the data dispersion phenomenon of welded specimens remarkably increased.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2000.05a
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• pp.141-144
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• 2000

The slope stability of waste landfill has been a problem in domestic and foreign countries. Waste landfills are being constructed in a reclaimed land or mountainous area. But most of these places are consisted of steep slope and hence it is necessary to use the geosynthetic liners in there. The large size direct shear test(30cm x 30cm) equipment was used to determine the interface friction angles between CCLs and soil & geomembranes. The centrifuge model tests were performed to investigate the slope stability with considering various geosynthetic liners conditions and degree of slope. The results of centrifuge model test indicate that the degree of saturation of GCL, roughness of geomembrane, and slope of landfill have greatly influenced on the slope stability of solid waste landfill.

• Journal of the Korean Geotechnical Society
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• v.17 no.5
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• pp.5-16
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• 2001

소일네일링 구조물의 설계 및 안정해석에 관한 지금까지의 연구는 대부분 굴착 배면지반의 자중만을 고려하여 연구 개발된 굴착사면에 인접하여 하중이 재하되는 경우, 그의 거동에 관한 연구는 미비한 실정이다. 따라서 본 연구에서는 원심모형시험기를 사용하여 하중재하시 소일네일링 구조물의 거동과 파괴 메카니즘에 관한 매개변수적 실험을 실시하였다. 매개변수적 실험에서는 네일의 길이 및 간격, 네일의 설치각, 하중재하위치 등을 다양하게 변화시키면서 1g 상태에서 축소모형실험을 실시하는 한편, 30g 및 50g까지 중력수준을 증가시킨 상태에서 상재하중실험을 실시하였다. 실험으로부터 얻어진 결과를 바탕으로 하중-침하 특성, 매개변수의 변화에 따른 영향, 중력수준의 증가에 따른 영향, 파괴메카니즘 등을 비교 분석하였다.

• Journal of the Korean Geotechnical Society
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• v.16 no.6
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• pp.153-160
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• 2000

본 연구는 과제하중의 재하폭과 재하위치를 매개변수로 변화시켜 옹벽의 뒤채움재 상부 지표면에서 제한폭의 과재하중작용시 그의 활동거동에 관한 실험적, 수치적 해석적 연구이다. 중력 수준을 1g, 20g,40g로 변화시켜 수행한 원심모형실험을 통해 구한 기초의 극한지지력 및 하중-침하특성, 하중-옹벽수평변위특성에 관하여 조사연구 하였다. 또한, 옹벽의 활동으로 인한 지반파괴의 영향을 받기 시작하는기초의 재하위치를 추정하기 위하여 종래의 얕은 기초의 극한지지력 실험을 수행하여 이들 결과와 함께 비교하였다. 한편, 모형실험결과와 기존의 이론식을 수정보완한 해석 결과와 비교분석하였다.

• Geotechnical Engineering
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• v.7 no.4
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• pp.35-48
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• 1991

Based on centrifuge model tests, the failure mechanism of reinforced earth retaining wall under strip load was investigated in this paper. Tests were performed by changing the materials of reinforcing strips, strip lengths, and strip arrangements. The strips were strain-gauged to measure the tensions in strips. The results were analyzed and compared with various design methosds in use to verify their feasibility. Consequently, a centrifuge model test was an effective method of investigating the behavior of reinforced earth retaining wall. The 2 : 1 stress diffusion method showed comparable results with tests in estimating the capacity of the reinforced earth wall under strip load. The superposition of tensions due to selfweight of the backfill and strip load was valid to estimate total tensions mobilized in strips. Using the elasticity theory to estimate the maximum tension mobilized in strips due to surcharge, while solutions of Boussinesq and Westergaard underestimated less tensions than the measured valises, Frohlich solution showed the comparable results with tests.

• 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.

• Geomechanics and Engineering
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• v.24 no.4
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• pp.389-397
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• 2021

Pile foundation is a typical form of bridge foundation and viaduct, and large-diameter rock-socketed piles are typically adopted in bridges with long span or high piers. To investigate the effect of a mountain slope with a deep overburden layer on the bearing characteristics of large-diameter rock-socketed piles, four centrifuge model tests of single piles on different slopes (0°, 15°, 30° and 45°) were carried out to investigate the effect of slope on the bearing characteristics of piles. In addition, three pile group tests with different slope (0°, 30° and 45°) were also performed to explore the effect of slope on the bearing characteristics of the pile group. The results of the single pile tests indicate that the slope with a deep overburden layer not only accelerates the drag force of the pile with the increasing slope, but also causes the bending moment to move down owing to the increase in the unsymmetrical pressure around the pile. As the slope increases from 0° to 45°, the drag force of the pile is significantly enlarged and the axial force of the pile reduces to beyond 12%. The position of the maximum bending moment of the pile shifts downward, while the magnitude becomes larger. Meanwhile, the slope results in the reduction in the shaft resistance of the pile, and the maximum value at the front side of the pile is 3.98% less than at its rear side at a 45° slope. The load-sharing ratio of the tip resistance of the pile is increased from 5.49% to 12.02%. The results of the pile group tests show that the increase in the slope enhances the uneven distribution of the pile top reaction and yields a larger bending moment and different settlements on the pile cap, which might cause safety issues to bridge structures.