• Proceedings of the Korean Nuclear Society Conference
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• 1998.05b
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• pp.356-362
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• 1998

가동중인 터빈로터의 계속운전/보수/교체여부 등을 판단하기 위해 해외에서는 결정론적 방법외에 확률론적 파괴역학 해석방법을 이용하여 잔여수명을 평가하고 있다. 한편 국내에서는 현재까지 결정론적 방법을 주로 활용하고 있으며, 향후 확률론적 평가방법의 도입이 예상된다. 이러한 배경에서 본 논문에서는 터빈로터의 수명평가에 확률론적 파괴역학 해석기법을 이용하기 위한 기초연구로 터빈로터를 대상으로 응력해석, 결정론적 파괴해석 및 확률론적 파괴해석을 수행하였다.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.365-372
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• 2000

현장상황에 대한 불충분한 자료와 파괴 메커니즘에 대한 불완전한 이해로 인해 발생하는 가변성(variability)과 불확실성(uncertainty)은 암반사면공학뿐만 아니라 지반공학에서 흔히 접하게 되는 문제점이다. 특히 암반사면공학에서는 이러한 가변성과 불확실성이 불연속면의 방향 및 기하학적 특성, 그리고 실내실험 결과의 분산으로 나타난다. 그러나 안전율(factor of safety)의 개념을 기초로 하는 전통적인 결정론적 해석방법(deterministic analysis)은 이러한 분산을 고려하지 않은 채 단일 대표 값만을 이용하여 구조물의 안정성을 판단하여 왔다. 확률론적 해석방법(probabilistic analysis)은 이러한 가변성과 불확실성을 효과적으로 정량화하여 해석에 이용할 수 있는 방법 중의 하나로 제안되었다. 이러한 해석방법은 불연속면의 기하학적 특성과 강도 특성을 확률변수(random variable)로 취급하여 신뢰성이론(reliability theory)과 확률이론(probability theory)을 근거로 분석하였으며 이를 기초로 하여 Monte Carlo Simulation과 같은 해석법을 이용, 구조물의 붕괴가능성을 확률로 표현하였다. 확률론적 해석 방법은 기존의 안전율을 대체하여 구조물의 안정성을 붕괴확률(probability of failure)로 제안하였으며 이 붕괴확률은 안전율의 확률분포함수 (probability density function)에서 안전율이 1보다 작을 가능성을 확률로 나타낸 수치이다. 본 논문에서는 확률론적 해석방법을 이용하여 불연속면 특성들의 확률특성을 고찰하였으며 이를 기초로 하여 암반사면의 안정성 해석에 응용했다.

• Journal of the Korean Geotechnical Society
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• v.23 no.4
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• pp.125-132
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• 2007

The oedometer, radial CRS and Rowe cell tests, composite discharge capacity tests and smear effect tests are carried out to estimate the parameters for the reliability-based design of vertical drain method. Also the sensitivity analysis, the probabilistic and deterministic solutions of radial consolidation theory are presented. The result of probabilistic analysis was compared to that of deterministic analysis using the tested and estimated parameters. The results indicated that the drain spacing in the deterministic method is larger than that in the probabilistic method because the former does not consider the uncertainties in the geotechnical property. The divergence of two methods is dependent on the probability of achieving target degree of consolidation by a given time and the coefficient of variation (COV) of the coefficient of horizontal consolidation ($c_h$).

• Economic and Environmental Geology
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• v.52 no.3
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• pp.231-241
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• 2019

Kinematic analysis determines the stability of rock slope by analyzing the relationship between the slope face orientation and the discontinuity orientation. In this study, terrestrial LiDAR was used to obtain a large amount of discontinuity orientation data and then, the probabilistic characteristics of the orientation data obtained using terrestrial LiDAR were analyzed. Subsequently, the probabilistic kinematic analysis was carried out using the discontinuity orientations generated randomly from Fisher function in Monte Carlo simulation. In addition, the probabilistic kinematic analysis was also performed using the actual orientation data obtained from the terrestrial LiDAR to compare their results. Consequently, the results of both probabilistic analyses showed similar results. Therefore, if sufficient orientation data are provided by other means such as terrestrial LiDAR, the probabilistic analysis will show reasonable results using the actual field data without randomly generating orientation data. In addition, the deterministic kinematic analysis was also carried out using representative orientation of discontinuity sets. The analysis result of the probabilistic analysis showed similar results with the deterministic analysis because the dispersion of the discontinuity orientations in a joint set is not large.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05a
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• pp.751-756
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• 1998

고리 1호기 원전 수명 연장을 위한 가압열충격(Pressurized Thermal Shock : PTS) 해석은 확률론적 안전성 평가 방법에 따라 수행된다. 본 연구는 가압열충격 상세 해석 연구의 일환으로 가압열충격 해석을 위한 계통해석시 사용되는 최적 평가(Best Estimate) 방법과 기존의 PCT(Peak Cladding Temperature) 관점의 해석에 사용되는 결정론적 안전성 평가 방법간의 해석 방법론 차이에 의한 열수력 거동의 상이점을 평가하기 위함이다. 이를 위해 1998년 설치 예정인 고리 1호기 교체 증기발생기(Replacement Steam Generator ; RSG) 안전성 분석 보고서$^{[1]}$ 의 주증기관 파단사고 해석 결과와 동일한 파단 크기 및 운전 출력에 대해 최적 평가 방법론에 따라 해석된 본 연구의 해석 결과를 비교, 평가하였다. 해석 결과 전출력 소형 주증기관 파단 사고에서는 터빈 유량 모델링 및 반응도 계수, 고온 영출력 대형 파단 사고에서는 가압기 모델, 반응도 계수 및 정지여유도가 해석 방법론에 따른 열수력 거동의 차이에 영향이 큰 것으로 평가되었다

• Journal of the Korean Geotechnical Society
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• v.18 no.2
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• pp.97-105
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• 2002

Random properties of discontinuities were attributed to the limitation of test methods and lack of obtained data. Therefore, the uncertainties are pervasive and inevitable in rock slope engineering as well as other geotechnical engineering fields. The probabilistic analysis has been proposed to deal properly with the uncertainty. However, previous probabilistic approaches do not take account of the condition of kinematic instability but consider only kinetic instability. In this study, in order to overcome the limitation of the previous studies, the geometric characteristics as well as the shear strength characteristics in discontinuities are taken account into the probabilistic analysis. Then, the new approach to evaluate the probability of failure is suggested. The results of the deterministic analysis which was carried out to compare with the result of the probabilistic analysis, are somewhat different from those of the probabilistic approach. This is because the selected and used data in the deterministic approach do not take account of the random properties of discontinuities.

• Economic and Environmental Geology
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• v.33 no.4
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• pp.295-307
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• 2000

Probabilistic analysis is a powerful method to quantify variability and uncertainty common in engineering geology fields. In rock slope engineering, the uncertainty and variation may be in the form of scatter in orientations and geometries of discontinuities, and also test results. However, in the deterministic analysis, the factor of safety which is used to ensure stability of rock slopes, is based on the fixed representative values for each parameter without a consideration of the scattering in data. For comparison, in the probabilistic analysis, these discontinuity parameters are considered as random variables, and therefore, the reliability and probability theories are utilized to evaluate the possibility of slope failure. Therefore, in the probabilistic analysis, the factor of safety is considered as a random variable and replaced by the probability of failure to measure the level of slope stability. In this study, the stochastic properties of discontinuity parameters are evaluated and the stability of rock slope is analyzed based on the random properties of discontinuity parameters. Then, the results between the deterministic analysis and the probabilistic analysis are compared and the differences between the two analysis methods are explained.

• Journal of the Korean Geotechnical Society
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• v.18 no.5
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• pp.271-280
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• 2002

A probabilistic approach to identify the effects of uncertainties of soil strength parameters on searching a critical slip surface with the lowest reliability is introduced. In general construction field, it is impossible for the engineer to always gather a variety of statistical information of soil strength parameters for which lots of laboratory and in-situ soil testing are required and to use it with enough statistical knowledge. Thus, in order that the engineer may easily understand the probabilistic concept for the slope stability analysis, this study proposes a combined procedure to incorporate the engineering probabilistic tools into the existing deterministic slope stability analysis methods. Using UTEXAS 3, a slope stability analysis computer program developed by U.S. Army Corps of Engineers (U.S. COE), this study provides the results of this probabilistic slope stability analysis in terms of probability of failure or reliability index. This probabilistic method f3r slope stability analysis appears to yield more comprehensive results of slope reliability than does existing deterministic methods with safety factors alone.

• The Journal of Engineering Geology
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• v.20 no.4
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• pp.437-447
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• 2010

A probabilistic analysis of slope stability is an appropriate solution in dealing with uncertainty in problems related to engineering geology. In this study, a Monte Carlo simulation was performed to evaluate the performance function that is Barton's equation. A large number of randomly generated values were obtained for random variables, and the performance function was calculated repeatedly using randomly generated values. A previous study provided information of slope geometry and the random characteristics of random variables such as JRC and JCS. The present approach was adopted to analyze two failed slopes. The probabilities of failure were evaluated for each slope, and sensitivity analysis was performed to assess the influence of each random variable on the probability of failure. The analysis results were then compared with the results of a deterministic analysis, indicating that the probabilistic analysis yielded reliable results.

• Journal of the Korean Geotechnical Society
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• v.18 no.6
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• pp.117-127
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• 2002

A deterministic approach of slope stability, which is generally corresponding to the model of a simple non-linear function for slopes, is problematic in that it does not account the versatile characteristics of ground layers in an effective way. To resolve this problem, this study proposes a new way of analyzing slope stability, so-called “genetic algorithm method, ” so as to reflect some particular conditions pertaining to the grounds under concern. Similarities and differences in slope stability that may exist between homogeneous and multiple ground layers are examined in a competitive manner, Overall, though similarities deemed a little bit salient, the algorithm method turned out to be very applicable to estimating the validity of slope stability. Furthermore, an additional effort to consider long-standing sequential and dynamic changes in both the amount of rainfall and the underground water level is made in order to improve the results.