• Journal of the Korean GEO-environmental Society
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• v.5 no.3
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• pp.41-50
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• 2004

The study of seepage behavior is very important to slope stability of road landfill for heavy rainfall season. This study is done to propose more stable of road landfill based on analysis of seepage behavior and slope stability for some cases of road landfill. The selected sections of collapsed road landfill are most general case of road landfill, a case is landfill on the ground area and another case is on the slope area. The results of this study is summarized as follows. It is founded that the road landfill on the ground area is increased saturation region due to rainfall infiltration, and the seepage behavior of road landfill is solved by theory of unsaturated flow. The road landfill is more unstable due to rainfall infiltration at the slope surface, especially during heavy rainfall. The case of road landfill on the slope area is analyzed in consideration of slope surface infiltration, and it is founded that the slope instability is increased because of rainfall infiltration. The drain layer located on the original ground which made by more permeable materials could be good action of slope stability in the case of road landfill on the slope area.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2001.04a
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• pp.149-152
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• 2001

장기적인 강수량 및 지하수위 관측과 강수, 지표수 및 지하수에 대하여 동위원소모니터 링을 수행함으로써, 여수지역 소규모 수계에서의 지표수와 지하수 상관관계 및 지하수의 함 양특성을 고찰하였다. 지표수 및 지하수의 동위원소조성은 강우량과 강우의 동위원소조성에 직접적으로 영향을 받고 있음을 보여준다. 또한 강우량이 약 20mm이하일 경우는 강우가 지하수수 침투되지 못함을 나타낸다. 지하수의 동위원소조성은 각 강우사건에 의해 변화된 후, 다시 지하수 저류체의 조정으로 변화되는 양상을 확인하였다. 이는 모니터링된 강우 초기에 는 강우가 상층으로부터 지하수 체계로 유입되고 있음을 보여준다. 혼합방정식을 이용하면 갈수기 이후 첫 번째 강우의 지하수에 침투비율은 16.5%로 산출된다. 지하수의 함양특성에 대하여 기존 방법과 결부시켜, 보완된 동위원소방법을 적용한다면, 지하수 함양율을 보다 정량적으로 평가할 수 있을 것으로 판단된다.

• Journal of the Korean Geotechnical Society
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• v.21 no.6
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• pp.137-146
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• 2005

299 railroad slopes were investigated and the failure characteristics and reinforcement patterns were analyzed. Stability analyses on the 14 cut-off soil slopes were carried out. Surficial failures were predicted by infinite slope analyses assuming the temporarily perched ground water table at soil surface during rainfall period. Limit equilibrium analyses were also carried out and the influences of rainfall infiltration on the slope stabilities were taken Into account by seepage analyses using finite element method and by assuming ground water tables to be located adjacent to soil surface. The adequacy of those analyses was evaluated by comparing the slope failure characteristics between analysis results and the past failure records. From the comparison results, it was deduced that the limit equilibrium analyses were not appropriate to estimate the shallow failure that occurred at most of the railroad cut-off soil slopes. For the better estimation of the surficial failure, not only the increase of pore-water pressure (reduction of matric suction), but also the influence of water flows over slope surface which erode soil mass, should be evaluated and considered.

• Journal of the Korean GEO-environmental Society
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• v.8 no.2
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• pp.11-18
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• 2007

Slope failure triggered by rainfall produces severe effects on the serviceability and stability of railway, Therefore, slope stability problem is one of the major concerns on the operation of railway. In this study, the rainfall conditions triggering slopes failure adjacent to railroads are investigated and the numerical analysis approach in consideration of infiltration and limit equilibrium method based upon multiple slip surfaces are proposed. The rainfall conditions triggering slope failure are as follow: cumulative rainfall is in the range of 150~500 mm, and duration is from 3 to 24 hours. Base upon the rainfall conditions, infiltration analysis and limit equilibrium method for infinite slope condition are carried out. The depth of infinite slope is assumed as 2 m and the multiple slip surfaces modeled with 16.7 cm interval from the bottom slip surface located at the 2 m depth. The assumed bottom slip surface is the location at which factor of safety is converging. The proposed approach shows more reasonable results than the results from the general codes assuming water table at slope surface. In addition, three dimensional plot of cumulative rainfall, rainfall duration, and factor of safety shows that slope stability analysis in consideration of rainfalll must account for cumulative rainfall (rainfall duration).

• Journal of the Korean Geotechnical Society
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• v.29 no.12
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• pp.77-85
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• 2013

Unsaturated slopes experience infiltration during rainfall and become unstable when saturated. On the viewpoint of unsaturated effective stress, as matric suction decreases, both effective stress and shear strength decrease, which declines slope stability consequently. This study is focused on describing effective stress based on suction stress. The actual slope failures are simulated to calculate factors of safety in the field of finite element stress. In the residual soils of Hadong and Pohang, unsaturated properties are evaluated by laboratory tests. For unsaturated slopes, analyses of infiltration, stress and stability were performed to simulate actual failures. Based on unsaturated effective stress principle, the stability of actual slopes could be evaluated successfully. It is verified for the effective stress concept to be applicable to the engineering practice on slope design which considers infiltration by rainfall.

• Journal of the Korean Geotechnical Society
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• v.22 no.7
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• pp.55-64
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• 2006

Shallow failures of slopes in weathered soils are caused by infiltration caused by prolonged rainfall. These failures are mainly triggered by the deepening of the wetting band accompanied by a decrease in suction induced by the water infiltration. In this paper, hysteresis on soil-water characteristic curve (SWCC) of granite and gneiss weathered soils is investigated using transient flow analysis respectively. Each case was subjected to artificial rainfall intensities and time duration depending on the laboratory-based drying and wetting processes. The results show that the unsaturated seepage on weathered slopes are very much affected by the initial suction of soils and unsaturated permeability of the soils. In addition, a granite weathered soil has a lower air-entry value, residual matric suction, and wetting front suction and less hysteresis loop than a gneiss weathered soil.

• The Journal of Engineering Geology
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• v.28 no.4
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• pp.687-699
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• 2018

Understanding rain infiltration into the ground is an important feature of landslide risk evaluation. In this study, a landslide risk index for the study area is suggested, wherein the result of the landslide risk evaluation, based on the factor of safety (FS), is used. The landslide risk index is a landslide risk prediction index that utilizes the saturated depth ratio of the ground. Based on the landslide risk result for the study area, it was found that the FS was first to decrease. However, it gradually became convergent over the 50-year rainfall intensity study period, a result that is similar to the relationship between the saturated depth ratio and soil thickness. Moreover, saturated depth was also found to be deeper on gentle slopes than steep slopes. As such, the landslide risk index, based on the Inhu-ri study result, is thus suggested. Additionally, the suggested landslide risk index was compared and analyzed against the rainfall intensity of previous landslide experience. Results thus revealed that almost all landslides that occurred were over 0.7, which is the second grade, based on the landslide risk index.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3C
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• pp.113-120
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• 2012

An actual slope failure was analyzed in residual soils at Jinju. Due to rainfall infiltration, the safety factor decreases in the unsaturated layers, since the effective stress and shear strength decrease. In this study, the effective stress is based on suction stress using soil water retention curve. Unsaturated properties were evaluated on soil water retention curve, hydraulic conductivity and shear strength with samples from the site. After infiltration analysis of unsaturated flow under the actual rainfall, the distribution of pore water pressure could be calculated in the slope layers. In the stress field of finite elements, an elastic analysis calculated total stress distribution in the layers and also shear stresses on the slip surface using elastic model. On the slip surface, suction stress and effective stress evaluated the shear strength. As a result, the factor of safety was calculated due to rainfall, which could simulate the actual slope failure. In particular, it was found that the suction stress increases and both the effective stress and the shear strength decrease simultaneously on the slip surface.

• 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.

• 지반과기술
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• v.8 no.1
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• pp.54-57
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• 2011