• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.1
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• pp.147-157
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• 2005

In this study, consolidation analysis methods reflecting various ground condition and changing coefficient of consolidation with consolidation process are presented. Research activities include development of numerical program consists of two parts considering vertical drainage only and both drainage condition with vertical and radial direction. Also, interface equation of adjacent two layers and function for changing coefficient of consolidation are added to developed program. This paper presents the results from a detailed consolidation analyses, which explores consolidation process with time in varying layered system and changing coefficient of consolidation

• Journal of the Korean Geotechnical Society
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• v.16 no.6
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• pp.43-50
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• 2000

충북단양군 영춘면 휴석동 지역에 위치한 위험사면은 1972년 456mm의 집중강우에 의해 사면붕괴가 발생하여 가옥 2채붕괴 등의 피해를 유발시켰으며, 지속적인 지반침하가 진행되고 있다. 남한강 하류에 접하고 있는 상기의 위험사면은 산사태에 의한 토사의 이동시 남한강을 덮치게 되어 그 유로의 변화를 일으켜 영춘면의 지역의 침수피해의 대규모의 재해를 일으킬 수 있는 위험성이 내재되어 있다. 본 연구는 상기 위험사면에 대한 지반조사, 지하수 특성 조사 등을 통해 붕적토 사면의 안정해석을 수행하여 최적의 조강 대책안을 제시하고 이에 따른 재해 예방을 도모하고자 한다. 보강대책을 붕적토 사면의 거동특성과 위험사면의 지형적 특성 등을 고려하여 집수정, 수평배수공, 앵커공 및 보강토 옹벽의 복합공법에 의해 위험사면의 안정성을 확보하는 방안을 제안하였다.

• Journal of the Korean Geotechnical Society
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• v.16 no.6
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• pp.105-115
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• 2000

본 연구는 현실에 부합하는 연약지반의 압밀거동을 예측하기 위한 연구로서, 일단 3차원 배수 조건하에서 지반의 자중 및 압축성과 투수성의 비선형적 성질이 고려된 비선형 압밀모델을 구성하였다. 또한 연직 배수재의 시공과정에서 발생할수 있는 지반의 교란현상 및 다양한 이질층의 구성, 점증적인 하중재하 조건, 연직배수재의 부분관입 조건에 대한 고려가 가능하도록 비선형 압밀모델을 수정, 보완하였다. 이상의 연구결과를 바탕으로 유한차분방법에 의한 수치해석을 실시하였고 최종적으로 각종 희귀분석과정을 도입한 3차원 비선형 압밀해석 프로그램을 개발하였다. Ska-Edeby의 시험시공 사례를 통한 개발 프로그램의 검증을 실시하였는데, 시험시공 사례의 경우, 현장에서 측정한 깊이별 침하량 및 간극수압 결과를 개발 프로그램에 의한 예측결과와 비교, 분석하였다. 또한 개발 프로그램을 이용하여 다층지반 해석과 관련된 기존 해석방법의 문제점 및 지반의 교란효과와 연직배수재의 부분관입조건, 점증적인 하중재하 조건등이 지반의 압밀거동에 미치는 영향에 대해 살펴보았다.

• Journal of the Korean GEO-environmental Society
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• v.8 no.2
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• pp.29-39
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• 2007

In this study, the centrifugal tests were fulfilled to analyze the displacement characteristics caused by the embankment construction on soft ground. Embankment of height, undrained shear strength and with or without geotextile were selected to evaluate the displacement characteristics of soft ground by embankment. As a result, the replacement section without geotextile showed the parabola shape. The replacement section with geotextile showed the trapezoidal shape which represents the uniform settlements. The replacement angle is increasing nearly lineally with increasing the height of embankment and G-level. The position, where the maximum horizontal displacement occurred, was between $0.24H_0$ and $0.35H_0$ and was at $0.3H_0$ on the average. In the case of with and without geotextile, the relationship between the maximum settlement of ground(S) and maximum horizontal displacement(${\delta}_m$) was ${\delta}_m$ = 0.60S, ${\delta}_m$ = 0.54S, respectively.

• Journal of the Korean Geotechnical Society
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• v.20 no.5
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• pp.17-25
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• 2004

The flat dilatometer test (DMT) is a geotechnical tool to estimate in-situ properties of various types of ground materials. The undrained shear strength is known to be the most reliable and useful parameter obtained by DMT. However, the existing relationships which were established for other local deposits depend on the regional geotechnical characteristics. In addition, the flat dilatometer test results have been interpreted using three intermediate indices - material index $(I_D)$, horizontal stress index $(K_D)$, and dilatometer modulus (E$_{D}$) and the undrained shear strength has been estimated merely using the horizontal stress index $(K_D)$. In this paper, the applicability of the flat dilatometer to Korean soft clay deposit has been investigated. Then an artificial neural network was developed to evaluate the undrained shear strength by DMT and the ANN, based on the $p_0, p_1, p_2, {\sigma '}_v$ and porewater pressure. The ANN which adopts the back-propagation algorithm was trained based on the DMT data obtained from Korean soft clay. To investigate the feasibility of ANN model, the prediction results obtained from data which were not used to train the ANN and those obtained from existing relationships were compared.

• Journal of the Korean GEO-environmental Society
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• v.13 no.3
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• pp.29-37
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• 2012

This study is to find out the characteristics of the behavior of Geosyntehtic Reinforced Retaining Earth Wall(GRREW) through the laboratory experiment with the reduced-scale model, and to verify the effect of reinforcement by materials of GRREW. The loading tests after combining nonwoven geosynthetic, re-bar mesh nets and drainage blocks respectively among the components of the GRREW were performed in three cases of their slopes. In the cases of the behavior analysis including all of the components of the GRREW, the maximum horizontal displacement was generated 8.4mm at the location of 0.57H in the slope of 1:0.3; 3.8mm at the location of 0.57H in the slope of 1:0.6; 3.6mm at the location of 0.86H in the slope of 1:1.0. On average, the horizontal displacements of the GRREW were reduced by 83.8% against those of the original slopes. Lastly, seepage analysis and slope stability analysis were performed by modelling section of field, to confirm the effect of installation of drainage block in GRREW. We can confirm to compare increasing the slope safe factor and decreasing ground water in accordance with drainage blocks.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.1
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• pp.183-194
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• 2004

It's essential process to study non-linear material function related to characteristics of compressibility and permeability when we predict the consolidation behavior of soft clay ground. In this study, laboratory tests were conducted to find out the material function using marine clay. Standard oedometer test and Rowe cell test were performed with conditions, which were classified into vertical drainage only, radial drainage only and vertical-radial drainage case. Modified oedometer test equipment was developed to find out the material function and special extrusion device was originated to minimize the sample disturbance effect. Reliability of the results in modified oedometer test could be confirmed by comparing with the Rowe cell's one. Effective stress - void ratio - permeability relations were analyzed using all testing results. As a result, void ratio with effective stress level could be expressed by the power function and permeability with void ratio could be expressed by exponential function. In soft clay with high initial water content and low shear strength, non-linear characteristics related to compressibility and permeability varied with wide range by the effective stress levels. It's important to note that non-linearity of the material function should be considered at prediction of the consolidation behavior.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.89-92
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• 2006

In the present study, the flow field of a mesh type suppressor with varying holes at the central portion is studied to investigate drain flow characteristics in a cylindrical tank. Further, an attempt is made to understand the changes in the flow field brought about by the suppressors of different kinds in a circular tank which ultimately prevents vortex formation. For this purpose, flow visualization studies using PIV (Particle Image Velocimetry) to determine the flow patterns in a cylindrical tank with circular cross section without suppressor and with suppressor are carried out after imparting rotation to the liquid in the tank. Results are obtained when there is no draining and with draining. The flow field is visualized both in horizontal and vertical planes.

• Geotechnical Engineering
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• v.1 no.1
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• pp.73-84
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• 1985

This Paper aims at investigating the distribution of stresses and the displacement of soft foundation layer subject to embankment load by the finite elements method (FEM). The stresses include the volumetric stress, the Pore water Pressure, the vertical stress. The horizontal stress and the shear stress. The Christian-Boehmer's method was selected as technique for FEM and the general elasticity model and modified Cam-clay model as the governing equations under Plain-strain condition depending on drained and undrained conditions. The results obtained are as follows: 1. The volumetric stress is almost consistent with the pore water pressure. This means that the total stress is the same value with the pore water pressure under the undrined condition 2. The vertical stress appears in the same value regardless of the drained or undrained condition and the model of the constitutive equations. 3. The horizontal stress has almost same value with the drain condition model. 4. depending on the constitutive model. The shear stress is affected by both the drain condition and the constitute model. The resulted value by the modified Cam-clay model has the largest. 5. The direction of the displacement vector turns outward near the tip of load during the increasing load. 6. The magnitude of displacement due to the modified Cam.clay model is as twice large as that due to elastic model.

• Journal of the Korean Geotechnical Society
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• v.17 no.3
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• pp.41-50
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• 2001

본 연구는 모래사면의 언덕근처에 설치된 짧은 말뚝의 수평하중의 영향에 관한 것이다. 3차원 탄소성 유한요소법해석과 실내 모형실험의 결과를 비교하였다. 경사 30$^{\circ}$의 사면에 시공된 짧은 말뚝의 특성을 파악하기 위해, 사면언덕에서 모형말뚝까지의 거리를 3종류로 상이하게 하여, 모형실험을 실시하였다. 사용된 모래의 지반특성은 배수조건하의 삼축압축실험으로 결정하였다. 동시에 3차원 탄소성 유한요소법에 의한 수치해석결과와 모형실험결과를 비교하였다. 본 유한요소법의 해석에 있어서 모래지반을 탄성완전소성모델(Elastic-perfectly plastic model)로 가정하여, 파괴기준으로 Mohr-Coulomb 식과 소성 포텐셜에 대해서는 Drucker-Prager 식을 적용한 MC-DP 모델로 하였다. 이러한 MC-DP 모델의 구성식은 유한요소법에서 있어 계산치의 수렴에 유익하다. 3차원 탄소성 유한요소법에 의한 수치해석이 사질토 사면의 언덕 부근에 설치된 단하의 수평거동에 대한 파악에 유효하다는 것을 확인하였다.