• Advances in nano research
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• 제13권2호
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• pp.135-146
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• 2022

The accurate assessment of the performance of nonuniform systems requires a thorough understanding of stability analysis. As a result, the theoretical modeling of the influence of various variables on the performance of small-scale nonuniform structures with conventional and non-conventional geometries is presented in this paper. According to the fundamental computer simulation based on mathematical and mechanical principles, the stability of the nonuniform structures is examined. Thus, a numerical procedure is used to simulate the stability and instability characteristics of the nonuniform small-scale structures via computer aid. Theoretic simulation methods provide a great deal of the design and production of small-scale structures at a low cost compared to experimental simulations. Thus, this paper provides a good presentation of the stability analysis of the nonuniform nanoscale structures with high accuracy without actual experimental.

• 대한원격탐사학회지
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• 제23권5호
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• pp.335-346
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• 2007

This study is aiming at improving the Environmental Conservation Value Assessment Map(ECVAM) of National Land in Korea. The ECVAM items are composed of legal and environmental/ecological assessments. A popular method applied to ECVAM is an overlay environmental/ecological assessment items. The purpose of this study is to offer complementary items of the ECVAM by examining assessment items. In this study we assessed the ECVAM by five methods. Method 1 is Grade 1 areas of each administrative district; Method 2 is comparing overlapped areas of each assessment items Grade 1, 2 and permission of each assessment items duplication; Method 3 is Grade 1, 2 areas by only singular assessment items; Method 4 is Grade 1 areas only of Method 2; and Method 5 is Grade 2 areas only of Method 2. Method 1 showed Seoul and other metropolitan cities revealed a large proportion of Grade I regions by the legal assessment items. Gang won-Do, showed a large proportion of Grade I regions by the environmental/ecological assessment item. Method 2 showed 93.4% of diameter Grade II(standard for stability); forest diameter item accounted for 99.9% by Method 3, Method 4 showed 95.7% of forest diameter, and forest density accounted for 66.4% by Method 5. This study contributes to reduce the complexity in the process of manufacturing ECVAM of National Land, and to raise the flexibility in the process of managing and updating this map.

• 한국터널지하공간학회 논문집
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• 제4권2호
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• pp.123-133
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• 2002

광산지역을 통과하는 터널 건설 공사에서, 기존 광산 갱도는 터널의 굴착 시공 뿐만 아니라 장기적 유지관리에 걸쳐 터널 안정성에 영향을 미칠 수 있다. 본 연구에서는 기존 광산지역을 통과하는 도로 터널의 시공사례에 대한 현장 조사 및 FLAC을 이용한 수치해석을 통하여, 터널에 대한 기존 갱도의 존재 패턴 및 암반조건에 따른 터널의 안정성을 분석하였다. 그리고 기존 갱도를 포함하는 인접 영역에 대한 그라우팅 보강 방안을 제시하고 터널 안정성을 확보할 수 있는 보강 효과를 수치해석적으로 검증하였다. 이상에서, 광산지역내 도로 터널 건설에 있어서 인접한 기존 갱도 존재와 관련한 터널 안정성 평가는 기존 갱도 규모, 터널과의 거리, 암반상태, 지하수 조건 등에 따라 그 영향 정도가 다르게 나타나므로 이러한 요소들을 복합적으로 고려하여 이루어져야 할 것이다.

• 터널과지하공간
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• 제23권2호
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• pp.99-109
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• 2013

노천광산사면은 일반적으로 경제성 문제로 지보대책을 고려하지 않고 설계된다. 그러나 최종 잔벽사면은 장기적인 안정성이 필요하므로 경우에 따라서는 안정성을 높일 수 있는 적절한 대책이 필요하다. 본 연구를 위해 S 석회석 광산의 지질 및 불연속면 조사, 암반평가, 강도시험 등 현장조사를 수행하였다. 그리고 최종 잔벽사면에 대해 평사투영, SMR, 수치해석을 통한 안정성 평가를 실시하고, 최종 잔벽사면의 처리방안을 제안하였다. 해석결과, 사면 전체규모에서 파괴는 예상되지 않지만, 벤치규모의 사면파괴는 발생할 가능성이 있다. 최종 잔벽사면은 프리스플리팅 발파로 정리하고, 중간 소단에 폭이 넓은 berm을 설치하거나 국부적으로 지하수 유출이 있는 곳에는 수평배수공 등을 시공하여 벤치사면의 안정성을 높일 수 있을 것이다.

• 한국지반공학회논문집
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• 제22권11호
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• pp.101-111
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• 2006

사면안정해석은 많은 불확실한 요인을 내포하는 지반공학적 문제이다. 이러한 불확실성 중 일부는 해석 수행과정에 필요한 지반 물성의 변동성과관련이 있다 본 연구에서는 확률론적 사면안정 해석기법을 개발하기 위하여 절편법의 일종인 Spencer의 방법을 바탕으로 한 결정론적 해석방법을 지반정수의 불확실성과 공간적 변동성을 고려할 수 있도록 확장하였다. 제안된 방법은 Hasofer-Lind의 신뢰지수를 구하는 일차신뢰도법과 Monte-Carlo Simulation을 바탕으로 한다. 지반정수의 변화에 따른 파괴확률의 변화를 구하기 위해 단일지층과 2층 지반의 사면에 대한 확률론적 사면안정 해석을 수행하였다. 예제의 결과는 사면안정해석에 대한 지반의 불확실성을 고려할 수 있는 관점을 제시하며 확률론적 해석결과에 미치는 지반정수의 공간적 변동성의 영향을 보여준다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.456-459
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• 2007

This study was performed for improving the Environmental Conservation Value Assessment Map (ECVAM) of National Land in Korea. The ECVAM items are composed of legal assessment and environmental/ecological assessment. An assessment method applied to ECVAM is basically an overlay method for environmental/ecological assessment items. The purpose of this study is to offer complement items of the ECVAM by examining assessment items. For this, our study was preceded as follows; In this study we assessed the ECVAM by 4 kinds of method. Method I is Comparing overlapping areas of each assessment items Grade 1, 2 and Permission of each assessment items'duplication, Method 2 is Grade 1, 2 areas by only singular assessment items, Method 3 is Only Grade 1 areas of Method 2 and Method 4 is Only Grade 2 areas of Method 2. As results, Method1 showed 93.4% of diameter Grade II(standard for stability), forest diameter item was accounted for 99.9% by Method 2, Method 3 showed 95.7% of forest diameter and forest density was accounted for 66.4% by Method 4. From now on, this study will contribute to reduce the complexity in the process of manufacturing ECVAM of National Land, and to raise the pliability in the process of managing and updating this map.

• KIEE International Transactions on Power Engineering
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• 제5A권3호
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• pp.244-251
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• 2005

Power transfer capability has been recently highlighted as a key issue in many utilities. It is determined by the thermal stability, dynamic stability and voltage stability limits of generation and transmission systems. In particular, voltage stability affects power transfer capability to a great extent in many power systems. This paper presents a tool for determining total transfer capability from a static voltage stability viewpoint using IPLAN, which is a high level language used with the PSS/E program. The tool was developed so as to analyze static voltage stability and to determine the total transfer capability between different areas from a static voltage stability viewpoint by tracing stationary behaviors of power systems. A unified power flow controller (UPFC) is applied for enhancing total transfer capability between different areas from the viewpoint of static voltage stability. Evaluation of the total transfer capability of a practical KEPCO power system is performed from the point of view of static voltage stability, and the effect of enhancing the total transfer capability by UPFC is analyzed.

• Geomechanics and Engineering
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• 제18권5호
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• pp.493-502
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• 2019

Internal stability is an important safety issue for levees, embankments, and other earthen structures. Since a large part of the world's population lives near oceans, lakes and rivers, floods resulting from breaching of dams can lead to devastating disasters with tremendous loss of life and property, especially in densely populated areas. There are some main factors that affect the internal stability of dams, levees and other earthen structures, such as the erodibility of the soil, the water velocity inside the soil mass and the geometry of the earthen structure, etc. Thus, the mechanism of internal erosion and stability of soils is very complicated and it is vital to investigate the assessment methods of internal stability of soils in embankment dams and their foundations. This paper presents an improved support vector machine (SVM) model to predict the internal stability of soils. The grid search algorithm (GSA) is employed to find the optimal parameters of SVM firstly, and then the cross - validation (CV) method is employed to estimate the classification accuracy of the GSA-SVM model. Two examples of internal stability of soils are presented to validate the predictive capability of the proposed GSA-SVM model. In addition to verify the effectiveness of the proposed GSA-SVM model, the predictions from the proposed GSA-SVM model were compared with those from the traditional back propagation neural network (BPNN) model. The results showed that the proposed GSA-SVM model is a feasible and efficient tool for assessing the internal stability of soils with high accuracy.

• Geomechanics and Engineering
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• 제31권4호
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• pp.375-384
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• 2022

The variation of the undrained shear strength (c_u) is an important consideration for assessing slope stability in engineering practice. Previous studies focused on the three-dimensional (3D) stability of slopes in normally consolidated clays generally assume the undrained shear strength increases linearly with depth but does not vary in the horizontal direction. To assess the 3D stability of slopes with spatially varying undrained shear strength, the kinematic approach of limit analysis was adopted to obtain the upper bound solution to the stability number based on a modified failure mechanism. Three types failure mechanism: the toe failure, face failure and below-toe failure were considered. A serious of charts was then presented to illustrate the effect of key parameters on the slope stability and failure geometry. It was found that the stability and failure geometry of slopes are significantly influenced by the gradient of c_u in the depth direction. The influence of c_u profile inclination on the slope stability was found to be pronounced when the increasing gradient of c_u in the depth direction is large. Slopes with larger width-to-height ratio B/H are more sensitive to the variation of c_u profile inclination.

• 한국환경복원기술학회지
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• 제11권3호
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• pp.74-86
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• 2008

To assessment the disturbances of the Namgang caused by dam construction, upstream area was selected for the reference reach and downstream area was selected for the comparison reach. And these reaches were surveyed and analyzed according to the assessment criteria of the river disturbances.The artificial factors of river disturbances were classified as river improvement works, dam construction and aggregate dredging. The indexes were physical factors as like epifaunal (bottom), embeddedness, velocity/depth regime, sediment deposition, channel flow status, channel alteration, frequency of riffles, bank stability, vegetative protection, riparian zone etc.The assessment results showed 46% of the assessment criteria which was serious status in dam downstream area and 89.5% of it which was excellent status in dam upstream.Finally, the results showed that physical river environment in downstream area was disturbed by the discharge control and the interception of sediment discharge by dam, consequently this disturbance give rise to impact of ecosystem in river.