• Journal of the Korean Geotechnical Society
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• v.15 no.4
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• pp.19-42
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• 1999

In urban area, there are several major factors to be considered in tunnel design and construction. The first is to predict the magnitude and distribution of ground movements for particular ground conditions and construction procedures. The second is to assess the potential damage to nearby structures in response to the predicted ground movements. The third is to select the measures to be taken if a potential damage is foreseen. This study is concerned primarily with the first and second stages of the problem. Particularly, this paper is focused on the second stage to assess the potential damage to the nearby building with any type of geometries and locations above ground surface. In order to solve this problem, we introduced damage parameters(angular distortion, deflection ratio, maximum building settlements, maximum differential settlements, horizontal strain, etc.), and extended these parameters into 3-dimensional safety assessment. Also, to assess the safety of any walls existing in the building, we developed a 3-dimensional analysis program, and various parametric studies for the nearby building with any type of geometries and locations were presented. In addition to these parametric studies, we compared the results of the proposed techniques with some abroad case records for particular tunnels and adjacent buildings.

• Journal of the Korean Geosynthetics Society
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• v.21 no.1
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• pp.49-56
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• 2022

In this study, finite element numerical analysis was performed considering various influence factors(cavity shape and size, pavement thickness and size of traffic load) in order to analyze the impact factors in the underground of the road where the cavity occurred and to evaluate the stability of the ground. In order to verify the reliability of the numerical analysis method applied in this study and the results it was compared and analyzed with the results of previous studies and field measurements. The correlation between the influence factors was analyzed through the distribution of vertical displacement obtained from the numerical analysis results, the distribution of surface settlement and surface settlement, the distribution of the stress ratio, and the distribution of the safety factor. As a result, it was confirmed that as the size of the cavity and traffic load increased and the thickness of the pavement decreased, the vertical displacement and surface settlement at the top of the cavity increased. Also, the shape of the cavity was square, the stability of the ground was significantly reduced compared to the case of a circular cavity. Through these results, it was possible to confirm the overall stability of the lower ground of the road where the cavity was generated.

• Journal of the Korean Geotechnical Society
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• v.37 no.5
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• pp.19-31
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• 2021

Groundwater level (GWL) causes the stress state within soil and affects the bearing capacity and the settlement of foundation. In this study, the analyses of influencing factors on GWL fluctuation were performed. From the results, river stage and moving average of precipitation were main influence components for urban near large river and rural areas, respectively. In addition, the prediction performance of GWL using artificial neural network (ANN) was conducted with respect to the influence components. As a result, the effect of main component was significant on the prediction performance of GWL.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2002.10a
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• pp.31-42
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• 2002

최근 지하철 터널은 사용자 편의성, 도심지 접근성 및 원활한 교통처리 등을 고려하여 지반조건이 불리한 상황에서도 터널로 계획되는 경우가 많아지고 있다 따라서 시공중의 터널안정성확보, 굴착에 따른 인접구조물의 침하영향, 발파진동영향 등을 종합적으로 고려한 지보패턴 및 보조·보강공법의 결정이 매우 중요하나 정량적인 판단기준의 부재로 인하여 주로 경험적인 설계에 의존하는 경우가 많다. 본 연구에서는 도심지 지하철 터널의 복합적인 거동특성을 고려하기 위하여 여러 가지 예상위험요소의 정량화 방안을 제안하고, 다변량 통계분석기법을 활용하여 여러 가지 위험 요소들의 특성을 함축적으로 나타내는 소수의 총합적인 지표(안정성인자, 환경성인자)로 대표화 할 수 있음을 검증하였다. 안정성 인자 및 환경성 인자를 이용한 서울시 지하철 00공구 설계사례를 통해 정량화지표(Multiple Index)의 터널설계에의 적용성을 평가하고 이의 설계시 활용방안을 제안하고자 하였다.

• Journal of the Korean Geotechnical Society
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• v.33 no.1
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• pp.31-38
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• 2017

Skin friction of prebored and precast pile may be one of the most critical factors affecting the bearing capacity and settlement. Special attention was given to the interface behavior of pile-cement milk-surrounding soil when the load is acting on the prebored and precast pile. The cases of single pile were analyzed through a three-dimensional finite element approach and pile loading tests. A series of numerical analyses of the interface of pile-cement milk-soil was conducted with the proposed t-z curve and field measurements. It is shown that the use of cement milk around the pile increases the skin friction and reduces the pile settlement. It is also known that the suggested t-z curve between the cement milk and the soil, enhances the accuracy of the numerical analysis results.

• Journal of the Korean GEO-environmental Society
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• v.7 no.3
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• pp.69-76
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• 2006

In this study, an experimental study in sand ground that was prepared by raining method was performed for modeling the bearing capacity behavior of strip footing above a cavity. The critical range of bearing capacity of the strip footing affected by underground cavity was investigated by comparing results between experiment and theory. The size of the critical region depends on several factors such as footing shape, soil property, cavity size and cavity shape. The ultimate bearing capacity was more influenced by the depth of the underground cavity than the eccentricity of the underground. In addition, an underground cavity influences on not only the decrease of the bearing capacity, but also the differential settlement of a strip footing.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.129-132
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• 2007

고분자 전해질 연료전지의 성능에 영향을 주는 많은 인자들 중에서도 촉매층의 조성과 구조의 최적화는 성능변화에 큰 요인으로 작용 된다. 촉매층내 반응 활성점인 삼상계면을 형성시키기 위해 함침하는 Nafion binder를 anode와 cathode의 두 전극에 이온당량(Equivalent weight, EW)이 동일하게 함침시켜 그 성능을 확인하였다. 그 결과를 토대로 anode와 cathode에 이온당량을 각기 다르게 하여 각각의 전극마다 이온당량이 미치는 영향에 대해서도 살펴보았다. Anode와 cathode의 이온당량을 동일하게 EW1100, EW1000, EW900으로 변화 시켜주었을 경우 이온당량의 물성치가 상대적으로 향상된 EW900의 단위 전지 성능이 가장 우수하였으며, 이온당량이 EW900이었을 때 최적의 Nafion binder 함침량은 EW1100의 Nafion binder 함침량과 동일하였다. Anode와 cathode에 함침하는 Nafion binder의 이온당량을 각각 EW1100과 EW900, EW900과 EW1100으로 MEA를 제조하여 전극에 따라 이용당량이 미치는 영향을 살펴보았다.

• Journal of the Korean Geotechnical Society
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• v.33 no.7
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• pp.43-53
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• 2017

Road subsidence, frequently occurring in urban areas, is caused by collapsing of surface layer due to underground cavities followed by a loss of soils. To better understand this phenomenon, the mechanism of cavity formation should be identified firstly. Two kinds of possible subsidence mechanisms were established through previous case studies and the numerical analyses based on Distinct Element Method were conducted for each of these mechanisms. It was confirmed that particle loss and surface settlement can develop differently depending on slit size, void ratio, and particle shape among the various factors influencing the road subsidence. The result demonstrated that the effects of varying cavity diameter and depth could be quantified as a damage chart.

• Journal of the Korean GEO-environmental Society
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• v.20 no.2
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• pp.49-58
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• 2019

A study on the analysis of underground ground condition using 3D-GPR exploration was carried out in this paper. The test bed was constructed similar to the field, and the detection analysis was carried out for each depth of cavity and underground burial. Through this, we were able to know the permittivity of the ground by inversion, and we could confirm the depth of detection for the joint by accurate calculation. We confirmed the signal waveforms in the cavity under the road through 3D-GPR exploration, analyzed more quantitatively in subjective and empirical analysis. The subsidence and depth of the subsurface settlement can be observed through 3D-GPR survey, and ground condition change after the ground reinforcement can be confirmed through the exploration section.

• Journal of the Korean Geotechnical Society
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• v.23 no.9
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• pp.17-28
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• 2007

Urban tunnels are usually important in terms of prediction and control of surface settlement, gradient and ground displacement. This paper has studied the application of strain softening analysis to predict deformation behavior of an urban NATM tunnel. The applied strain softening model considered the reduction of shear stiffness and strength parameter after yielding with strain softening effects of a given material. Measurements of surface subsidence and ground displacement were adopted to monitor the ground behavior resulting from the tunneling and to modify tunnel design. The numerical analysis results produced a strain distribution, deformational mechanism and surface settlement profile, which are in good agreement with the results of case study. The approach of strain softening modeling is expected to be a good prediction method on the ground displacement associated with NATM tunneling at shallow depth and soft ground.