• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.269-276
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• 1999

The program ESRAS Ver 0.5 that can assess the risk of slopes by means of fuzzy inference is developed in this paper. The results of assessment involve the degree of stability of slopes, the possible travel distance of the soil mass being failed, and anticipated loss of life and properties. With this program, vulnerable slopes can be managed most effectively and the fuzzy inference is used to express quantitatively the judgement of an expert and the uncertainty of slope stability. The fuzzy rule base is composed of an evaluation list for slope stability together with the experience of an expert. This program has been examined for 88 slopes which have been failed or shown a possibility of failure. With this examination, the standards to assess the stability of slopes can be presented and it is proven that this is particularly useful in determining the priority of investment for remedial works of slopes.

• Journal of The Geomorphological Association of Korea
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• v.23 no.3
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• pp.67-78
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• 2016

Soil carbon(C) is an essential property for characterizing soil quality. Understanding spatial patterns of soil C is particularly limited for mountain areas. This study aims to predict the spatial pattern of soil C using terrain analysis in a steep mountainous area. Specifically, model performances and prediction uncertainties were investigated based on the number of resampling repetitions. Further, important predictors for soil C were also identified. Finally, the spatial distribution of uncertainty was analyzed. A total of 91 soil samples were collected via conditioned latin hypercube sampling and a digital soil C map was developed using support vector regression which is one of the powerful machine learning methods. Results showed that there were no distinct differences of model performances depending on the number of repetitions except for 10-fold cross validation. For soil C, elevation and surface curvature were selected as important predictors by recursive feature elimination. Soil C showed higher values in higher elevation and concave slopes. The spatial pattern of soil C might possibly reflect lateral movement of water and materials along the surface configuration of the study area. The higher values of uncertainty in higher elevation and concave slopes might be related to geomorphological characteristics of the research area and the sampling design. This study is believed to provide a better understanding of the relationship between geomorphology and soil C in the mountainous ecosystem.

• Journal of the Korean Geotechnical Society
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• v.33 no.4
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• pp.25-34
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• 2017

The soil-water characteristics is the most important state parameter for understanding changes in suction and water contents of unsaturated soil slopes. In the field, the hysteretic behaviors of drying and wetting soil-water characteristic curve are real and the adoption of path-dependent suction-water content is needed to predict the hydro-mechanical analysis of unsaturated soils. In this study, in-situ monitored hydraulic behavior of various soil slopes are compared with the data from numerical analysis with the laboratory soil water characteristic curve. Then, the verifications are performed based on the field monitored data respectively. Therefore, the use of path-dependent soil-water characteristic curves could be more rational for design and analysis of unsaturated soil slopes under rainfall conditions.

• Journal of the Korean GEO-environmental Society
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• v.8 no.4
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• pp.67-74
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• 2007

Many studies for slope stability studies have indicated that the infiltration of rainwater into a slope decrease the slope stability. In order to minimize damage caused by slope failure, most design codes suggest that the slope stability be analyzed by saturated condition during rainy season. However it would be excessively conservative condition that every soil slope is saturated in rainy season irrespective of rainfall intensity, soil type and slope geometry. In addition, because most soil slopes are in an unsaturated state, it is necessary to consider the unsaturated characteristics of slope. This paper suggests a prediction method of saturation time for the weathered granite soil slopes due to rainfalls. The finite element analysis of transient water flow through unsaturated slope was used to investigate effects of soil-water characteristics, permeability at saturation, slope geometry, and rainfall intensity. From the result of these analyses, the prediction charts considering soil-water characteristics, permeability at saturation, and slope height were proposed in this study. It is possible to the time required to be saturated slope after rainfall.

• Geomechanics and Engineering
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• v.23 no.1
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• pp.15-30
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• 2020

The probabilistic bearing capacity of a strip footing placed on the edge of a purely cohesive reinforced soil slope is computed by combining lower bound finite element limit analysis technique with random field method and Monte Carlo simulation technique. To simulate actual field condition, anisotropic random field model of undrained soil shear strength is generated by using the Cholesky-Decomposition method. With the inclusion of a single layer of reinforcement, dimensionless bearing capacity factor, N always increases in both deterministic and probabilistic analysis. As the coefficient of variation of the undrained soil shear strength increases, the mean N value in both unreinforced and reinforced slopes reduces for particular values of correlation length in horizontal and vertical directions. For smaller correlation lengths, the mean N value of unreinforced and reinforced slopes is always lower than the deterministic solutions. However, with the increment in the correlation lengths, this difference reduces and at a higher correlation length, both the deterministic and probabilistic mean values become almost equal. Providing reinforcement under footing subjected to eccentric load is found to be an efficient solution. However, both the deterministic and probabilistic bearing capacity for unreinforced and reinforced slopes reduces with the consideration of loading eccentricity.

• Geomechanics and Engineering
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• v.1 no.1
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• pp.35-52
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• 2009

A significantly thick zone of steep slopes is commonly encountered above groundwater table and the soils within this zone are unsaturated with negative pore-water pressures (i.e., matric suction). Matric suction contributes significantly to the shear strength of soil and to the factor of safety of unsaturated slopes. However, infiltration during rainfall increases the pore-water pressure in soil resulting in a decrease in the matric suction and the shear strength of the soil. As a result, rainfall infiltration may eventually trigger a slope failure. Therefore, understanding of shear strength characteristics of saturated and unsaturated soils under shearing-infiltration (SI) conditions have direct implications in assessment of slope stability under rainfall conditions. This paper presents results from a series of consolidated drained (CD) and shearing-infiltration (SI) tests. Results show that the failure envelope obtained from the shearing-infiltration tests is independent of the infiltration rate. Failure envelopes obtained from CD and SI tests appear to be similar. For practical purposes the shear strength parameters from the CD tests can be used in stability analyses of slopes under rainfall conditions. The SI tests might be performed to obtain more conservative shear strength parameters and to study the pore-water pressure changes during infiltration.

• Journal of the Society of Disaster Information
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• v.3 no.2
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• pp.23-35
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• 2007

Recently, for places with poor vegetating environment, such as slopes made of weathered soil or rocks, erosion tranquilizers, coverings and composite fertilizers have been mixed with seeds and sprinkled onto soil. Also, these plant revegetations have been mixed with nets and used to strengthen cohesion. However, this technique often obstructed plant growth and caused pollution because of not decomposing nets. This study has tested influence on plant revegetation B for slope of weathered soil and rocks and decomposition of naturally decomposing polyester filament yarn. In result, it was showed that plant revegetation B does not harm environment in case of applying it to soil slope and enhance protection capacity of slopes as time goes by. Also, naturally decomposing polyester filament yam was analyzed its physical properties with the passage of time and was known that naturally decomposing polyester filament yarn transformed into a structure easy to decompose by hardening. Thus it is considered that the revegetation method used this study was very effective method for plant establishment and stability of slope.

• Geomechanics and Engineering
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• v.13 no.3
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• pp.517-533
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• 2017

In this paper, with a graphical approach, a series of stability charts for homogeneous slopes with benches are presented based on the upper bound limit analysis theory and strength reduction technique. The objective function of the slope safety factor $F_s$ is optimized by the nonlinear sequential quadratic programming, and a substantial number of examples are illustrated to use the stability charts for homogeneous slopes with benches driven by only the action of the soil weight. These charts can be applied to quick and accurate estimations of the stability status of homogeneous slopes with benches. Moreover, the failure modes and the formula for safety factor Fs of homogeneous slopes with benches are provided to illustrate the stability analysis of slopes with benches, which is validated by samples.

• Journal of Climate Change Research
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• v.9 no.3
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• pp.293-302
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• 2018

This study was carried out to provide basic information on efficient preservation and management of an Abies koreana forest through analyzing the ecological characteristics by slope in Seseok, Mt. Jirisan. Soil moisture content at southern and northern slopes was 29.9% and 21.7%, respectively, and there was no significant difference among soil properties between southern and northern slopes. The importance value of A. koreana in the southern and northern slopes was high for tree and subtree layers, respectively. It is noteworthy that many seedling and saplings of A. koreana were present on the southern slope. The species diversity was 0.413 for the tree layer, 0.632 for the subtree layer, and 0.609 for the shrub layer on the southern slope and 0.396 for the tree layer, 0.783 for the subtree layer, and 1.215 for the shrub layer on the northern slope. Evenness and dominance ranged from 0.371 to 0.609 and 0.629 to 0.391 on the southern slope and from 0.380 to 0.968 and 0.620 to 0.032 on the northern slope, respectively. The mortality of A. koreana was 9.6% on the southern slope and 24.4% on the northern slope, a distinct difference between the slopes. The mortality type at two slopes was the highest proportion of standing dead. Annual mean tree ring growth of A. koreana on the southern slope (1.76 mm/yr) was higher than that on the northern slope (1.64 mm/yr).

• Journal of the Korean Society of Environmental Restoration Technology
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• v.2 no.4
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• pp.64-73
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• 1999

This study was conducted to find out the effects of hydroseeding material and seed mixture on the revegetation of rock cut-slopes by PEC4 (Polymer-Ecology-Control) Hydroseeding Measures. PEC4 hydroseeding material was applied to four cut-slopes using hydroseeding measures from April to August, 1999, and the field survey was carried out by monthly. PEC4 material consisted of bark compost and organic soil amendments. This material has high content of organic matter and high level of water holding capacity. PEC4 hydroseeding material shows low level of soil hardness, so it gives to good condition for seed germinating and plant growing in early stage. PEC4 material attached at rock cut-slopes by two types of adhesive agent was not eroded by rainfall. The plant coverage and number of plant species were affected by mixing ratio of seeds and seeding timing. From the viewpoint of plant establishment, the optimal hydroseeding timing of mixed seeds for plant growth seems to be in May. Most of the plant seeds were germinated well and they covered rock cut-slopes so quickly and effectively. Plant importance value of Silene armeria and Platycodon grandiflorum. were higher than any other seeded-native species in the competition between native species and exotic species, so they have enough possibility to be used for slope revegetation works. Thus it leads to conclusion that the revegetation method used in this experiment was a very effective method for plant establishment on rock cut-slopes.