• 한국구조물진단유지관리공학회 논문집
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• 제10권3호
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• pp.165-175
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• 2006

사면거동 및 파괴를 분석하기 위하여, 일반적으로 암반사면에는 Polynomial model, 토사사면에는 Growth model을 별도로 적용하여 사용하여 왔다. 이 기법은 사면의 파괴예측보다 사면의 누적변위를 묘사하기 위한 그래프 형태 위주이다. 따라서 본 연구에서는 사면의 거동보다는 파괴 예측에 초점을 맞추어 일반적으로 사용되는 두 모델을 병합하여 파괴예측을 위한 Asymptote(점근선)과 누적변위량도 같이 묘사할 수 있는 3차 방정식 모델 (3-degree polynomial model)로 단일화 할 것을 제안하여 현장 계측 data를 분석하였다. 국도 절취 사면부인 단양군 고수재 사면과 영덕군 축산면에 위치한 영덕 사면에 본 해석 모델을 적용하였다. 고수재는 토사사면으로 Growth model에 다른 거동을 나타내었고, 영덕사면은 Polynomial model에 따른 거동을 나타내었다. 분석결과, Polynomial model 과 Growth model로 구분된 해석 모델 형태를 $y=ax^3+bx^2+cx+d$ 의 형태를 가지는 3차 방정식을 사용하면, 하나의 모델로 사면의 거동 및 파괴를 해석할 수 있으며, 그 거동 해석 및 파괴 예측능력이 더 우수하다는 것이 증명되었다. Polynomial model의 경우, 방정식의 차수를 증가시켜도, 그래프의 $R^2$값과 형태가 유사함을 알 수 있었다.

• Journal of the Korean Statistical Society
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• 제24권2호
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• pp.519-536
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• 1995

In the design of experiments for response surface analysis, sometimes it is of interest to estimate the difference of responses at two points. If differences at points close together are involved, the design that reliably estimates the slope of response surface is important. This idea was conceptualized by slope rotatability by Hader & Park (1978) and Park (1987). Until now, second order polynomial models were only studied for slope ratatability. In this paper, we will propose the necessary and sufficient conditions for slope rotatability over all directions for the thired order polynomial models in two, three and four independent variables. Also practical slope rotatable designs over all directions for two independent variables are suggested.

• Geomechanics and Engineering
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• 제31권1호
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• pp.15-30
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• 2022

Slope stability during the excavation of twin road tunnels is considered crucial in terms of safety. In this research, physical model testing and numerical analysis were used to investigate the characteristics of the settlement (uz) and vertical stresses (σz) along the two tunnel sections. First, two model tests for a (fill-rock) slope were conducted to study the settlement and stresses in presence and absence of slope support (plate support system). The law and value of the result were then validated by using a numerical model (FEM) based on the physical model. In addition, a finite element model with a slope supported by piles (equivalent to the plate) was used for comparison purposes. In the physical model, several rows of plates have been added to demonstrate the capacity of these plates to sustain the slope by comparing excavating twin tunnels in supported and unsupported slope, the results show that this support was effective in the upper part of the slope, while in the middle and lower part the support was limited. Additionally, the plates appear to induce less settlement in several areas of the slope with differing settlement and stress distribution as compared to piles. Furthermore, as a results of the previous mentioned investigation, there are many factors influence the stress and settlement distribution, such as the slope's cover depth, movement during excavation, buried structures such as the tunnel lining, plates or piles, and the interaction between all of these components.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2012년도 학술발표회
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• pp.34-34
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• 2012

Heavy storms rainfall has caused many landslides and slope failures especially in the mountainous area of the world. Landslides and slope failures are common geologic hazards and posed serious threats and globally cause billions in monetary losses and thousands of casualies each year so that studies on slope stability and its failure mechanism under rainfall are being increasing attention of these days. Rainfall-induced slope failures are generally caused by the rise in ground water level, and increase in pore water pressures and seepage forces during periods of intense rainfall. The effective stress in the soil will be decreased due to the increased pore pressure, which thus reduces the soil shear strength, eventually resulting in slope failure. During the rainfall, a wetting front goes downward into the slope, resulting in a gradual increase of the water content and a decrease of the negative pore-water pressure. This negative pore-water pressure is referred to as matric suction when referenced to the pore air pressure that contributes to the stability of unsaturated soil slopes. Therefore, the importance is the study of saturated unsaturated soil behaviors in evaluation of slope stability under heavy rainfall condition. In an actual field, a series of failures may occur in a slope due to a rainfall event. So, this study attempts to develop a numerical model to investigate this failure mechanism. A two-dimensional seepage flow model coupled with a one-dimensional surface flow and erosion/deposition model is used for seepage analysis. It is necessary to identify either there is surface runoff produced or not in a soil slope during a rainfall event, while analyzing the seepage and stability of such slopes. Runoff produced by rainfall may result erosion/deposition process on the surface of the slope. The depth of runoff has vital role in the seepage process within the soil domain so that surface flow and erosion/deposition model computes the surface water head of the runoff produced by the rainfall, and erosion/deposition on the surface of the model slope. Pore water pressure and moisture content data obtained by the seepage flow model are then used to analyze the stability of the slope. Spencer method of slope stability analysis is incorporated into dynamic programming to locate the critical slip surface of a general slope.

• Structural Engineering and Mechanics
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• 제89권3호
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• pp.253-263
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• 2024

Slope stability is generally paid more attention to in slope protection works, especially for slope containing weak layers. Two indexes of safety factor and failure model are selected to perform slope stability. Moreover, the finite element limit analysis method comprehensively combines the advantage of the limit analysis method and the finite element method obtaining the upper and lower bounds of the safety factor and the failure mode under the slope stability limit state. In this study, taking a waste dump containing a weak layer as an engineering background, the finite element limit analysis method is adopted to explore the potential failure mode. Meanwhile, the sensitivity analysis of slope stability is performed on geometrical and geotechnical parameters of the waste dump. The results show that the failure mode of the waste dump slope is two wedges if the weak layer is located on the ground surface (Model A), while the slope can be observed as three wedges failure if the weak layer is below the ground surface (Model B). In addition, both failure modes are highly sensitive to the friction angle of the weak layer and the shear strength of waste disposal, and moderately sensitive to the heap height, the dip angle and cohesion of the weak layer, while the toe cutting has limited effect on the slope stability. Moreover, the sensitivity to the excavation of the ground depends on the location of the weak layer and failure mode.

• 토지주택연구
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• 제9권2호
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• pp.51-57
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• 2018

The causes of landslides are dependant on rainfall events and the soil characteristics of a slope. For the conventional slope stability, the slope stability analysis has been carried out assuming the saturated soil theory. But, in order to clearly explain a proper soil slope condition by rainfall, the research should be performed using the unsaturated soil mechanism suitable for a soil slope in the field. In the study, by using two major categories of soils in Korea, such as granite and gneiss weathered soils, landslide model test and finite element method have been compared with the difference of seepage and soil stability analysis. The hydraulic conductivity of gneiss weathered soil is slower than that of granite weathered soil, and the gneiss weathered soil contains much finer soils than the granite weathered soil. It was confirmed that the instability of the slope was progressing slowly due to the slow rate of volumetric water content of the surface layer.

• 한국농공학회논문집
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• 제52권4호
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• pp.1-10
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• 2010

In this study, two estimation equations for preparing stream data for distributed storm runoff model were developed by analyzing the nonlinear relation between upstream flow-length and stream width, and between upstream flow-length and stream bed-slope. The equations for stream cell were tested in Chungjudam watershed (6,661 $km^2$) using KIMSTORM. Six storm events occurring between 2003 and 2008 were selected for the model calibration and verification before the test of equations. The average values of the Nash-Sutcliffe model efficiency (ME), the volume conservation index (VCI), the relative error of peak runoff rate (EQp), and the difference of time to peak runoff (DTp) were 0.929, 1.035, 0.037, and -0.406 hr for the calibrated four storm events and 0.956, 0.939, 0.055, and 0.729 hr for the two verified storm events respectively. The estimation equations were tested to the storm events, and compared the flood hydrograph. The test result showed that the estimation equation of stream width reduced the peak runoff and delaying the time to peak runoff, and the estimation equation of stream bed-slope showed the opposite results.

• 지질공학
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• 제14권4호
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• pp.451-460
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• 2004

사면안정해석에 일반적으로 이용되는 2차원 한계평형해석에서는 활동면의 강도를 활동면 전체에 동일하게 설정한다. 그러나 사면의 활동면에서 저면부와 가장자리부의 강도는 다른 경우가 대부분이다. 4가지 절취모델을 이용한 3차원 사면안정해석의 결과에 따르면 활동면내에서 가장자리부의 저항력이 사면의 안정성에 크게 영향을 미치는 것으로 나타났다. 3차원 사면안정해석에서 활동면 강도를 저면부와 가장자리부로 구분하여 설정함으로써 지금까지 고려하지 못했던 사면 가장자리부의 전단강도가 사면안정에 미치는 영향을 정량적으로 파악할 수 있었다. 활동 저면부의 저항력이 낮은 경우에는 사면의 측부 절토에 의하여 안전율이 크게 저하되며, 저항력이 높은 경우에는 말단부 절토에 의하여 안전율이 저하되고 두부 절토에 의하여 안전율이 향상된다.

• 한국지반공학회논문집
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• 제19권5호
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• pp.99-107
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• 2003

포장 시스템 내에서의 습기흐름과 열흐름은 상호간에 복합적인 작용을 하는 과정들로 인식되어 왔다. 습기의 흐름과 열흐름에 기인한 포장내에서의 습기와 온도의 분포는 계절적으로 변화할 뿐만 아니라 수직 그리고 수평적으로도 변화한다. 이 논문은 불포화토에서의 이차원 복합적인 습기와 열흐름에 대해서 유한요소법을 사용한 분석모델을 제시한다. 모델을 검증하기 위해 모델에 의한 분석결과는 Canada Alberta에 소재한 GEO-SLOPE사에 의해 개발된 소프트웨어인 GEO-SLOPE에 의해 분석된 결과와 비교하였다. 그리고 모델에서 사용된 입력데이터가 모델분석에 미치는 영향을 알아보기 위해 ASTM 방법에 의한 민감도 분석을 수행하였다.

• Geomechanics and Engineering
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• 제34권4호
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• pp.341-380
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• 2023

This study evaluates the seismic fragilities in fill slopes in South Korea through parametric finite element analyses that have been barely investigated thus far. We consider three slope geometries for a slope of height 10 m and three slope angles, and two soil types, namely frictional and frictionless, associated with two soil states, loose and dense for frictional soils and soft and stiff for frictionless soils. The input ground motions accounting for four site conditions in South Korea are obtained from one-dimensional site response analyses. By comparing the numerical modeling of slopes using PLAXIS^2D against the previous studies, we compiled suites of the maximum permanent slope displacement (D_max) against two ground motion parameters, namely, peak ground acceleration (PGA) and Arias Intensity (I_A). A probabilistic seismic demand model is adopted to compute the probabilities of exceeding three limit states (minor, moderate, and extensive). We propose multiple seismic fragility curves as functions of a single ground motion parameter and numerous seismic fragility surfaces as functions of two ground motion parameters. The results show that soil type, slope angle, and input ground motion influence these probabilities, and are expected to help regional authorities and engineers assess the seismic fragility of fill slopes in the road systems in South Korea.