• 한국지반공학회논문집
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• 제22권1호
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• pp.25-34
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• 2006

본 연구에서는 비교적 높은 초기 유효응력을 가진 지반구조물의 액상화연구에 사용된 동적 원심모형실힘결과를 이용하여 유효응력모델검증에 관한 연구를 수행하였다. 원심모형 지반은 최대 유효응력 380kPa를 가진 충분히 포화된 느슨한 Nevada 모래 지반으로 구성되었으며, 수치해석에서는 1차원의 기둥형태로 가정하였다. 수치해석에 이용한 두 종류의 원심모형실험에서는 상당한 깊이(37m 및 22m)까지도 액상화가 발생하였으나, 깊이에 따른 액상화발생 경향은 경험적 액상화 평가방법과 상반된 결과를 보였다. 즉, 원심모형실험에서 계측된 과잉간극수압을 기준으로 해석하였을 때, 액상화는 모형지반의 윗부분에서 먼저 발생한 후 점차적으로 아랫부분으로 이동함을 알았다. 이와 같은 실험결과는 수치해석에서 비교적 잘 예측된 것으로 판단되었다 원심모형 지반의 초기 포화도와 원심력 증가에 따른 지반의 상대밀도 증가가 액상화모형실험의 수치해석에서 중요한 역할을 함을 알 수 있었다.

• 한국지반공학회논문집
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• 제22권11호
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• pp.151-158
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• 2006

균일한 모래지반을 이용한 원심모형실험에서는 지표면근처에서 액상화가 발생한 후에 점차적으로 깊은 곳으로 전파되는 경향을 보였다. 이와 같은 현상은 실내실험에서 상재하중효과를 고려했을 때 관찰되는 액상화현상과 상반되는 것처럼 보인다. 그러나, 응력증가에 따른 모형지반의 상대밀도증가가 구속압증가에 따른 액상화저항감소를 상쇄시킨다. 이와 같은 응력증가에 따른 상대밀도증가는 실제 원심모형실험에서 발생하고 있으나, 모형지반성형법에서는 고려되고 있지 않다. 따라서, 본 논문에서는 원심모형실험에서 발생할 수 있는 상대밀도증가를 고려한 새로운 원심모형지반성형법을 제안하였다. 새로운 모형지반성형법은 액상화에 관한 $K_0$ 효과를 연구하는데 사용될 수 있으며, 본 연구에서는 수치해석방법을 이용하여 그 실용성을 증명하였다.

• Geomechanics and Engineering
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• 제16권5호
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• pp.513-525
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• 2018

Slope stability of sensitive clayey soils is particularly important when subjected to strength loss and deformation. Except for progressive failure, for most sensitive and insensitive slopes, it is important to review the feasibility of conventional analysis methods based on peak strength since peak strength governs slope stability before yielding. In this study, as a part of efforts to understand the behavior of sensitive clay slopes, a total of 12 centrifuge tests were performed for artificially sensitive and insensitive clay slopes using San Francisco Bay Mud (PI = 50) and Yolo Loam (PI = 10). In terms of slope stability, the results were analyzed using the updated instability factor ($N_I$). $N_I$ using equivalent unit weight to cause a failure is in reasonable agreement shown in the Taylor's chart ($N_I$ ~ 5.5). In terms of dynamic deformation, it is shown that two-way sliding is a more accurate approach than conventional one-way sliding. Two-way sliding may relate to diffused shear surfaces. The outcome of this study is contributable to analyzing stability and deformation of steep sensitive clay slopes.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.744-751
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• 2006

In case of the Soil Nail System applied to a slope, effects of vibrations from blasting, earthquake and creep of long term behaviors cause reductions of adhesion between grout and soil-nail. There are some reports of nail's pull-out failure by those reasons. In this paper it is suggested that the Cone Nailing System is enable to diminish effects of vibrations and creep. In this study on Cone Nailing System, the cones are installed to each nail by 2m. By such installing cones, the adhesion between nail and grout will increase and the long term creep behavior will decrease. In this study, the centrifuge test is performed to understand the behaviors of the Cone Nail System. For the centrifuge test, the soil tank is 52cm in width, 17cm in length and 35cm in height. In comparison with general soil nail, the centrifuge test of general soil nail(without cone) is performed equally. Additionally, the interface between cone nail and soil through the pull-out test is applied to FLAC 2D version 3.3. and the evaluation of application for the Cone Nail System in slope is performed.

• 한국지반공학회논문집
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• 제28권2호
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• pp.23-31
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• 2012

본 연구에서는 사질토 지반에 설치한 원형수직터널에서 아칭효과를 고려한 토압의 거동 특성을 분석하기 위해 실제의 응력상태를 재현할 수 있는 원심모형실험(centrifuge model test)을 수행하였다. 이를 위해 직경 6.0m, 높이 15.0m의 원형수직터널을 대상으로 축소모형 실험체를 제작하였으며, 중력장 75G를 가속하여 2회 반복실험을 수행하였다. 더불어, 지반굴착에 따른 토압의 거동특성과 크기를 분석하기 위하여 모형 수직터널 벽체를 2단으로 분리하여 굴착효과를 모사하였으며, 그 결과를 선행연구에서 제안한 이론토압식과 비교하였다. 실험결과, 원형수직터널에 작용하는 토압은 기존의 2차원(Ko) 토압에 비해 약 70% 가까이 전토압이 저감되는 효과가 관찰되었으며, 이는 3차원 아칭효과에 의해 토압이 경감된 것으로 판단된다.

• Geomechanics and Engineering
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• 제27권5호
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• pp.447-463
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• 2021

Caisson-type structures are widely used as quay walls in coastal areas. In Korea, for a long time, many caisson-type quay walls have been constructed with a low front water depth. These facilities can no longer meet the requirements of current development. This study developed a new technology for deepening existing caisson-type quay walls using grouting and rubble mound excavation to economically reuse them. With this technology, quay walls could be renovated by injecting grout into the rubble mound beneath the front toe of the caisson to secure its structure. Subsequently, a portion of the rubble mound was excavated to increase the front water depth. This paper reports the results of an investigation of the seismic behavior of a renovated quay wall in comparison to that of an existing quay wall using centrifuge tests and numerical simulations. Two centrifuge model tests at a scale of 1/120 were conducted on the quay walls before and after renovation. During the experiments, the displacements, accelerations, and earth pressures were measured under five consecutive earthquake input motions with increasing magnitudes. In addition, systematic numerical analyses of the centrifuge model tests were also conducted with the PLAXIS 2D finite element (FE) program using a nonlinear elastoplastic constitutive model. The displacements of the caisson, response accelerations, deformed shape of the quay wall, and earth pressures were investigated in detail based on a comparison of the numerical and experimental results. The results demonstrated that the motion of the caisson changed after renovation, and its displacement decreased significantly. The comparison between the FE models and centrifuge test results showed good agreement. This indicated that renovation was technically feasible, and it could be considered to study further by testbed before applying in practice.

• 산업기술연구
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• 제24권B호
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• pp.107-116
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• 2004

This thesis is results of experimental works on the behavior of the cut-and-cover tunnel. Centrifuge model tests were performed to simulate the behavior of the cut-and-cover tunnels having cross sections of national road and subway tunnels. Model experiments were carried out with changing the cut slope and the slope of filling ground surface. Displacements of tunnel lining resulted from artificially accelerated gravitational force up to 40g of covered material used in model tests, were measured during centrifuge model tests. In model tests, Jumunjin Standard Sand with the relative density of 80 % and the zinc plates were used for the covered material and the flexible tunnel lining, respectively. Basic soil property tests were performed to obtain it's the property of Jumumjin Standard Sand. Shear strength parameters of Jumunjin Standard Sand were obtained by performing the triaxial compression tests. Direct shear tests were also carried out to find the mechanical properties of the interface between the lining and the covered material. Compared results model tests estimation with respect to displacements of the lining.

• 산업기술연구
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• 제23권A호
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• pp.119-130
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• 2003

This thesis is results of experimental works on the behavior of the cut-and-cover tunnel. Centrifuge model tests were performed to simulate the behavior of the cut-and-cover tunnels having cross sections of national road and subway tunnels. Model experiments were carried out with changing the cut slope and the slope of filling ground surface. Displacements of tunnel lining resulted from artificially accelerated gravitational force up to 40g of covered material used in model tests, were measured during centrifuge model tests. In model tests, Jumunjin Standard Sand with the relative density of 80 % and the zinc plates were used for the covered material and the flexible tunnel lining, respectively. Basic soil property tests were performed to obtain it's the property of Jumumjin Standard Sand Shear strength parameters of Jumunjin Standard Sand were obtained by performing the triaxial compression tests. Direct shear tests were also carried out to find the mechanical properties of the interface between the lining and the covered material. Compared results model tests estimation with respect to displacements of the lining.

• 한국지진공학회논문집
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• 제26권3호
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• pp.117-125
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• 2022

In this study, centrifuge model tests were performed to evaluate the seismic response of multi-DOF structures with shallow foundations. Also, elastic time history analysis on the fixed-base model was performed and compared with the experimental results. As a result of the centrifuge model test, earthquake amplification at the fundamental vibration frequency of the soil (= 2.44 Hz) affected the third vibration mode frequency (= 2.50 Hz) of the long-period structure and the first vibration mode (= 2.27 Hz) of the short-period structure. The shallow foundation lengthened the periods of the structures by 14-20% compared to the fixed base condition. The response spectrum of acceleration measured at the shallow foundation was smaller than that of free-field motion due to the foundation damping effect. The ultimate moment capacity of the soil-foundation system limited the dynamic responses of the multi-DOF structures. Therefore, the considerations on period lengthening, foundation damping, and ultimate moment capacity of the soil-foundation system might improve the seismic design of the multi-DOF building structures.

• 한국지반공학회논문집
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• 제25권7호
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• pp.23-33
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• 2009

본 연구에서는 말뚝지지 전면기초의 거동을 원심모형시험과 수치해석기법을 이용하여 연구하였다. 단말뚝, 기초판, 군말뚝 및 말뚝지지 전면기초의 극한지지력 비교를 통하여 말뚝지지 전면기초의 지지력을 평가하였고, 말뚝과 기초판에 전달되는 하중 분담율을 분석하여 말뚝지지 전면기초의 극한지지력을 산정할 수 있는 경험적 상관계수를 획득하였다. 또한, 원심모형시험과 동일말뚝조건을 대상으로 수치 시뮬레이션을 수행하여 원심모형시험 결과를 검증하고 말뚝지지 전면기초의 지지력을 위한 상관계수를 평가하였다.