• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.1260-1268
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• 2008

In case of deep excavation analysis, the theory of beam on elasto-plastic geo-material (elasto-plastic theory) can not consider the inclined ground layers appropriately. It is frequently assumed that the soil layers are parallel to the surface. However, the soil layers are generally inclined and even asymmetric. The common modelling of the asymmetric half section of the excavation system using the elasto-plastic theory, can lead differences from the real behaviour of ground, which has critical significance in case of deep excavation in urban area. In this study, an attempt to find appropriate modelling methods was made by carrying out a comparative study between the FEM and the elasto-plastic analyses. It is shown that in case of the upward-inclined soil profile the elasto-plastic theory may underestimate the performance of retaining structures.

• Geomechanics and Engineering
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• 제32권4호
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• pp.397-409
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• 2023

This study examines two traditional approaches (non-linear elastic and elasto-plastic) in association with 2D and 3D FEM analyses of a box-section pile embedded in sand. A particular emphasis is placed on stress singularities concerning both reentrant corners of the pile section and the resulting tension zones. From the experience gained in this study, non-linear elastic soil models are less restrictive when one considers stress singularities and their possible effects on convergence of the solution. At least for monotonic loading, when compared with field tests, non-linear elastic models yield better results than the plasticity ones. On the other hand, although elasto-plastic models are not limited to monotonic loading, they are much more sensitive to stress singularities. For this reason, a spherical elastic region is necessary at the pile tip to ensure convergence. Without this region, one must artificially impose an apparent cohesion to limit the tension stresses within a sand medium.

• 한국환경복원기술학회지
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• 제5권4호
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• pp.19-30
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• 2002

The stability of slope using root-pile like to the reinforcements is affected by the interaction behavior mechanism of soil-reinforcements. Through the studying on the interaction in joint of its, therefore, the control roles can be find out in installed slope. In study, the stress level ratio based on the insert angle of installed reinforcements in soil used to numerical analysis, which was results from the duty direct shear test in Lab. The maximum shear strain variation on the reinforcements was observed at insert angle, which was approximately similar to the calculated angle based on the equation proposed by the Jewell. The elasto-plastic joint model on the contact area of soil-reinforcements was presumed, the reinforced soil assumed non-linear elastic model and the reinforcements supposed elastic model, respectively. The finite element analysis of assumed models was performed. The shear strain variation of non-reinforced state obtained by the FEM analysis including elasto-plastic joint elements were shown the rationality of general limit equilibrium analysis for the slope failure mode on driving zone and resistance zone, which based on the stress level step according to failure ratio. Through the variation of shear strain for the variation of inserting angle of reinforcements, the different mechanism on the bending and the shear resistance of reinforcements was shown fair possibility.

• 대한토목학회논문집
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• 제13권4호
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• pp.199-208
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• 1993

소성지수 등을 이용한 경험식 및 역해석기법을 이용하여 구한 각종 토질정수를 사용하여 탄성해석, 탄소성해석(Cam-clay model) 및 탄점소성해석(Sekuguchi-Ohta model)을 실시하고, 그 결과를 압밀실험 결과와 비교하여, 토질정수의 간접적 산정법 및 구성모델의 적합성에 대하여 고찰하여 다음과 같은 결과를 얻었다. 압밀실험결과에 가장 근접한 해석방법은 역해석결과를 이용한 탄성해석과 역해석에서 구한 투수계수를 이용한 탄소성해석이었으며, 압밀실험에서 구한 투수계수를 이용한 탄소성해석 및 탄점소성해석은 상재하중 $10t/m^2$ 이하에서는 압밀실험결과와 유사한 결과를 나타내었고, 역해석에서 구한 투수계수를 이용한 탄점소성해석이 가장 큰 차이를 나타내었다. 탄점소성해석결과와 압밀실험결과의 차이가 가장 큰 이유는 소성지수가 매우 작은 시료에는 탄점소성모델의 적용이 적합하지 않기 때문인 것으로 판단된다.

• 한국지반공학회논문집
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• 제20권5호
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• pp.5-16
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• 2004

본 연구에서는 토목섬유로 보강된 다짐토의 보강 메카니즘이 제시되며, 이러한 보강 메카니즘은 다짐토의 체적팽창(부의 다일러탄시)을 토목섬유에 의해 구속 억제하는 과정에서 생성되는 효과로 간주된다. 먼저, 실내실험을 위한 구체적인 방법으로서, 토목섬유의 보강효과를 정량적으로 파악하기 위하여 사질토를 다짐하여 공시체를 만들어 그 주위에 토목섬유를 설치한 후 전체적으로 압축전단시험을 실시하였다. 실험에서 초기 다짐도는 각각의 종류에 대하여 다일러탄시의 특성이 다르기 때문에 각각의 공시체에 대하여 변화시켰다. 여기서 전단시험 도중에 다짐토의 다일러탄시 변형을 방지하기 위한 토목섬유에 작용하는 축방향 힘들(axial forces)이 조사되었다. 또한 다짐토의 탄소성 모델과 이러한 모델에 필요한 초기 입력치 값의 결정 방법들이 제시된다. 마지막으로, 탄소성 구성 모델에서 항복 이전의 탄성 영역의 거동을 모사하기 위하여 Hashiguch(1989)가 제안한 subloading surface의 개념을 도입하여, 유한요소(FEM) 해석을 통해 얻어진 결과들을 실내시험의 결과와 비교 분석하였다.

• 한국지반공학회논문집
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• 제20권2호
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• pp.37-46
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• 2004

본 연구에서는 토목섬유로 보강된 다짐토의 메카니즘이 제시되며, 이러한 메카니즘은 다짐토의 체적팽창(다일러턴시)을 토목섬유에 의해 구속 억제하는 과정에서 생성되는 효과로 간주된다. 먼저, 실내실험을 위한 구체적인 방법으로서, 토목섬유의 보강효과를 정량적으로 파악하기 위하여 사질토를 다짐하여 공시체를 만들어 그 주위에 토목섬유를 설치한 후 전체적으로 압축전단시험을 실시하였다. 실험에서 초기 다짐도는 각각의 종류에 대하여 다일러턴시의 특성이 다르기 때문에 각각의 공시체에 대하여 변화시켰다. 여기서 전단시험 도중에 다짐토의 다일러턴시 변형을 방지하기 위한 토목섬유에 작용하는 축방향 힘들(axial farces)이 조사되었다. 또한 다짐토의 탄소성 모델과 이러한 모델에 필요한 초기 입력치 값의 결정 방법들이 제시된다. 마지막으로, 탄소성 구성 모델에서 항복 이전의 탄성영역의 거동을 모사하기 위하여 Hashiguch(1989)가 제안한 subloading surface의 개념을 도입하여, 유한요소(FEM)해석을 통해 얻어진 결과들을 실내시험의 결과와 비교 분석하였다.

• Geomechanics and Engineering
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• 제19권6호
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• pp.513-522
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• 2019

This study presents an elasto-plastic (EP) solution for drained cavity expansion on the basis of unified strength failure criterion and considers the influence of initial stress state. Because of the influence of initial consolidation of soil mass, the initial stress may be anisotropic in the natural soil mass. In addition, the undrained hypothesis is usually used in the calculation of cavity expansion problem, but most of the cases are in the drained situation in practical engineering. Eventually, the published solution and the presented solution are compared to verify the suitability of the study.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 가을 학술발표회 논문집
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• pp.351-356
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• 1999

An elasto-plastic constitutive model was Proposed, in which the behavior at small-to-large strain level can be modeled. From a mathematical approach it was proved that the model includes the previous successful models. The experimental results of a series of resonant column tests, torsional shear tests and triaxial tests were verified and as a result the proposed model could predict small-to-large strain behavior more consistently and accurately than the hyperbolic model and the Ramberg-Osgood model for a weathered granitic soil.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1199-1203
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• 2008

It has been recognized that unsaturated soil behavior plays an importantrole in geomechanics. In the last decade several constitutive models have been proposed and used in the analysis. Many of them, however, are constructed in the frame work of rate independent model such as elasto-plastic one. Although rate dependency is an important characteristics of soil for both saturated and unsaturated soils, very few models have been developed taking account of rate dependency. In the present paper, we have developed an elasto-viscoplastic model considering an effect of suction based on the overstress-type viscoplasticity with soil structure degradation. In the model, we have adopted an averaged pore pressure composed of pore water pressure and air pressure to determine the effective stress.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 봄 학술발표회 논문집
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• pp.395-402
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• 2000

Recently, the deep excavations have been peformed to utilize the under ground space. As the ground excavation is deeper, the damage of the adjacent structure and the ground occurs frequently. The analysis of the retaining structures is necessary to the safety of the excavation works. There are many methods such as elasto-plastic, FEM, and FDM to analyze the displacement of the retaining structure. The elasto-plastic method is generally used in practice. In this thesis, GEBA-1 program by the Nakamura-Nakajawa elasto-plastic method was developed. The program for Windows was used the Visual Basic 6.0, and the Main of the program consists of three subroutines, SUB1, SUB2, and SUB3. The lateral displacement of the wall was analyzed by the developed program GEBA-1, SUNEX, and EXCAD, and compared with the measured displacement by the Inclinometer(at three excavation work sites). The excavation method of each site is braced retaining wall using H-pile. Each excavation depth is 14m, 14m, or 8.2m. The results of the analyses are the followings ① In the multi-layer soil, the lateral displacement by the GEBA-1 and EXCAD which is considering the distribution of the strut load is equal to the measured displacement. Elasto-plasto programs can't consider the change of the ground water in clay. Therefore, the analysis displacement was expected only 20% of the measured wall displacement. ③ At the final excavation step, the maximum lateral displacement of analysis and field occurred 7∼18m at the 85∼92% of the excavation depth. ④ The maximum lateral displacement in clay, as 50mm, occurred on the ground surface.