• Proceedings of the Korean Geotechical Society Conference
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• 1994.09a
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• pp.247-252
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• 1994

우리나라 산사태의 대부분은 사면의 깊이가 얕은 상태에서 발생하며, 지형적 지질적 및 강우조건에 따라 각기 다른 사면 파괴의 형태를 보여주고 있다. 본 논문에서는 IFDM의 기법을 이용하여 강우침투에 의해 발생할 수 있는 불포화지반으로의 침윤전선의 진행, 간극수압의 시간적 발생과정 등을 포함하는 침투해석을 수행하였다. 침투해석으로 얻은 강우침투 결과를 hyperbolic 응력, 변형을 모델에 조합하여 시간별로 응력, 변형해석을 할 수 있는 모델을 제안하였다. 이 모델에 의한 해석예로써 용인군 창리 산사태 지역을 선택하여 기존의 한계평형법과 본 논문에서 제안한 모델의 결과를 비교하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.1
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• pp.1-8
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• 2022

This study proposes a penetration model in soil considering the wake separation and reattachment based on the integrated force law (IFL). Rigid body dynamics, the IFL, and semi-empirical resistance function about soil are utilized to formulate the motion of the hard projectile. The model can predict the trajectory in soil considering the spherical cavity expansion phenomenon under various oblique angles and angles of attack (AOA). The Mohr-Coulomb yield model is utilized as the resistance function of the soil. To confirm the feasibility of the proposed model, a comparative study is conducted with experimental results described in the open literature. From the comparative study, the penetration depth estimated from the proposed model had about 13.4% error compared to that of the experimental results. In general, the finite element method is widely used to predict the trajectory in soil for a projectile. However, it takes considerable time to construct the computational model for the projectile and perform the numerical simulation. The proposed model only needs to the dimension of the projectile and can predict the trajectory of the projectile in a few seconds.

• Journal of the Korea Society for Simulation
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• v.31 no.3
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• pp.11-21
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• 2022

Two methods for analyzing interaction between shaped charge jets and targets are taken in AVEAM-MT (ADD Vulnerability and Effectiveness Assessment Model for Materiel Target), which is a model for vulnerability analysis of materiel targets and being developed by ADD. One is an empirical method improved from the Fireman-Pugh technique for rapid penetration calculation into target components. The other is ADD-TSC(ADD Tandem Shaped Charge), which is a physics-based model extended to be applicable for shaped charge jets from the Walker-Anderson penetration model for higher fidelity analysis. In this paper, the two methods are briefly described, and the empirical technique is compared to the physics-based model in the prediction of residual penetration capacity. The latter is also compared to experimental results found in literature in predicting penetration capacity. These comparisons show that both methods can be used for fast calculations or higher fidelity calculations in vulnerability analysis models like AVEAM-MT which is required to perform a considerable amount of iterative simulation for damage analysis.

• Journal of the Korea Concrete Institute
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• v.15 no.1
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• pp.25-34
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• 2003

The degradation of reinforced concrete (RC) structures due to physical and chemical attacks has been a major issue in construction engineering. Deterioration of RC structures by chloride attack followed by reinforcement corrosion is one of the serious problems. An objective of this study is to develop a form of mathematical model of chloride ingress into concrete. In order to overcome some limits of the previous approaches, a chloride ingress model, consisting of chloride solution intrusion through the capillary pore and chloride ion diffusion through the pore water, was proposed. Moreover, the variability of chloride ion diffusivity due to the degree of hydration of cement, relative humidity in pore, exposure condition, and variation of chloride binding, was considered in the model. In order to verify the proposed model, the results predicted by the proposed model were compared with analysis results of Life-365, a computer program for predicting the service life of reinforced concrete structures exposed to chlorides. In conclusion, the proposed model would be promising to predict the chloride ion profile and to estimate the service life of RC structures.

• Journal of the Korean Geotechnical Society
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• v.21 no.8
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• pp.45-53
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• 2005

Shallow slope failures in residual soil during periods of prolonged infiltration are common over the world. Therefore, this study examines an approximate method to estimate the influence of infiltration on surficial stability of slopes by one-dimensional infiltration model. Modified GAML model based on the Green-Ampt model was extended to predict the infiltration behavior of two-layered slope. Then, the model has been considered to evaluate the likelihood of shallow slope failure which is induced by a particular rainfall event that accounts for the rainfall intensity and duration for various return periods in two-layered soil profile. The results obtained from the approximate method were compared with those obtained from numerical analyses. According to the results, with the use of properly estimated input parameters, the proposed method was found to give good results that agree reasonably well to those of the more rigorous finite element analyses.

• Journal of the Korean GEO-environmental Society
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• v.11 no.5
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• pp.35-43
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• 2010

Partially saturated permeability should be defined by the function of suction (or degree of saturation) and porosity. However, commercial software and most researchers' model often describe as the function of suction. The stability of a soil slope can be affected by both hydraulic and shear strength properties of partially saturated soils. For both studies, we generally use an uncoupled seepage analysis program Seep/W(Geo-Slope, 2007) and a series stress-deformation analysis program Sigma/W, or slope stability analysis program Slope/W. Seep/W is performed for simulations of partially saturated flow problems in non-deformable soil media. However, under real situations, the water flow processes in a deformable soil are influenced by soil skeleton movement and the pore water pressure changed due to seepage will lead to changes in stresses and to deformation of a soil. Many researchers are currently developing their models for solving coupled hydro-mechanical problems to simulate slope stability during a rainstorm. For a proper implementation in the field, the developed model should be still needed in order to achieve appropriate accuracy of the solution for coupled hydro-mechanical problems in soil slope stability. Thus, the paper presents the comparison of slope stability between uncoupled and coupled analyses of seepage and stress deformation problems.

• Journal of the Korea Concrete Institute
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• v.17 no.5 s.89
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• pp.751-760
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• 2005

The chloride penetration model, which considers diffusion and sorption, is proposed. The FEM program developed on the basis of the diffusion and sorption model provides the estimation of chloride concentration variation according to cyclic humidity and temperature. The humidity diffusion analysis is carried out, and the chloride ion diffusion and sorption analysis are conducted on the basis of the pre-estimated humidity data in each element. Each element has different variables at different ages and locations in analysis. At early ages, the difference of relative humidity between inner and outer concretes causes the chloride ion penetration by sorption. As the humidity diffusion reduces the difference of relative humidity between inner md outer concretes with age, the effect of sorption on the chloride ion penetration decreases with age. The cyclic humidity increases the effect of sorption on the chloride ion penetration at early ages, and increases the quantity of chloride ion around steel at later ages. Therefore, the in-situ analysis of chloride ion Penetration for harbor concrete structures must be Performed considering the cyclic humidity conditionandthelongtermsorption.

• Composites Research
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• v.32 no.1
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• pp.56-64
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• 2019

In this paper, a model is developed to simulate carbon/carbon composite fabrication using chemical vapor infiltration, considering density and porosity change in the preform and multi-step hydrocarbons reactions. The model considers the preform as a porous medium whose diffusion and flow properties changes due to the porosity. To verify the theoretical model, two numerical analyses were performed for the case that the flow inside the preform is zero and the case that the flow inside the preform is calculated by fluid mechanics. The numerical results showed good agreement with the experimental data.

• Journal of the Korean Geotechnical Society
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• v.33 no.9
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• pp.5-22
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• 2017

The procedure that combines the result of infiltration analysis into stability analysis based on the limit equilibrium method is widely used to evaluate the impact of rainfall infiltration on slope stability. Accurate prediction of rainfall infiltration is essential to the prediction of landslides caused by rainfall, requires to obtain accurate unsaturated hydraulic properties of the soil. Among the unsaturated hydraulic characteristics of the soil, the importance of the soil-water characteristic curve describing the retained water characteristics of the soil is relatively well known and the measurement by test method to obtain the SWCC is gradually increasing. However, it takes a lot of time and expenses to experimentally measure the unsaturated conductivity characteristics of the soil. Therefore, it is common practice to estimate the hydraulic conductivity function from the SWCC. Although it is widely known that the SWCC has a great influence on rainfall infiltration, studies on the effect of the hydraulic conductivity function estimated from the SWCC on rainfall infiltration are very limited. In this study, we explained how the estimation model of the hydraulic conductivity function affects rainfall infiltration and slope stability analysis. To this end, one-dimensional infiltration analysis and slope stability analysis were conducted by using the data on the SWCC of weathered granite soil widely distributed in Korea. The applicability of each estimation model is discussed through review of the analysis results.

• Journal of the Korean Society for Railway
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• v.14 no.3
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• pp.240-247
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• 2011

Finite element analysis was undertaken to investigate the effect of freezing force of water unexpectedly penetrated into inserts used in railway sleeper on pullout capacity of anchor bolts for fixing base-plate onto concrete sleeper. Based on the in-situ investigation and measurement of geometry of railway sleeper and rail-fastener, the railway sleeper was modeled by 3D solid elements. Nonlinear and fracture properties for the finite element model were assumed according to CEB-FIP 1990 model code. And the pullout maximum load of anchor bolt obtained from the model developed was compared with experimental pullout maximum load presented by KRRI for verification of the model. Using this model, the effect of position of anchor bolt, amount of fastening force applied to the anchor bolt, and compressive strength of concrete on pull-out capacity of anchor bolts installed in railway sleeper was investigated. As a result, it is found that concrete railway sleepers could be damaged by the pressure due to freezing of water penetrated into inserts. And the pullout capacity of anchor bolt close to center of railway is slightly greater than that of the others.