• The Journal of Engineering Geology
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• v.24 no.1
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• pp.1-8
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• 2014

Numerical stability analysis of an unsaturated infinite slope under rainfall-induced infiltration conditions was performed using generalized effective stress to unify both saturated and unsaturated conditions The soil-water characteristic curve (SWCC) of sand with a relative density of 75% was initially measured for both drying and wetting processes. The hydraulic conductivity function (HCF) and suction stress characteristic curve (SSCC) were subsequently estimated. Under the rainfall-induced infiltration conditions, transient seepage analysis of an unsaturated infinite slope was performed using the finite element analysis program, SEEP/W. Based on these results, the stability of an unsaturated infinite slope under rainfall-induced infiltration conditions was examined in relation to suction stress. According to the results, the negative pore-water pressure and water content within the slope soil changed over time due to the infiltration. In addition, the variation of the negative pore-water pressure and water content led to a variation in suction stress and a subsequent change in the slope's factor of safety during the rainfall period.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.71-78
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• 2010

The stability analysis of unsaturated infinite slope under rainfall-induced infiltration condition was performed using the generalized effective stress that unifies both saturated and unsaturated condition recently proposed by Lu and Likos(2004, 2006). The Soil-Water Characteristic Curve (SWCC) of the sand with the relative density of 75% was first measured for both drying and wetting processes. The Hydraulic Conductivity Function (HCF) and Suction Stress Characteristic Curve (SSCC) were subsequently estimated. Also, under the rainfall-induced infiltration condition transient seepage analysis of unsaturated infinite slope was performed using the finite element program, SEEP/W. Based on these results, the stability of unsaturated infinite slope under rainfall-induced infiltration condition was examined considering the suction stress. According to the results, the negative pore water pressure and water content within the soil changed with time due to the infiltration. Also, the variation of those caused the variation of suction stress and then the factor of safety of slope changed consequently during the rainfall period.

• Journal of the Korean Geotechnical Society
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• v.30 no.10
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• pp.5-18
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• 2014

Many regions around the world are vulnerable to rainfall-induced slope failures. A variety of methods have been proposed for revealing the mechanism of slope failure initiation. Current analysis methods, however, do not consider the effects of non-homogeneous soil profiles and variable hydraulic responses on rainfall-induced slope failures. In this study, probabilistic stability analyses were conducted for weathered residual soil slopes with different soil thickness overlying impermeable bedrock to study the rainfall-induced failure mechanisms depending on the soil thickness. A series of seepage and stability analyses of an infinite slope based on one-dimensional random fields were performed to consider the effects of uncertainty due to the spatial heterogeneity of hydraulic conductivity on the failure of unsaturated slopes due to rainfall infiltration. The results showed that a probabilistic framework can be used to efficiently consider various failure patterns caused by spatial variability of hydraulic conductivity in rainfall infiltration assessment for a infinite slope.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.475-480
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• 2003

Traditionally, the statistical methods analyze the relationship between landslide occurrence and related factors(soil depth, soil strength, slope angle, vegetation, etc.) in GIS technique. However, those methods have no mechanical meaning. Therefore, the deterministic model is suggested in this research. The method analyzes the mechanical equilibrium of a potential slide block and then calculates a slope safety factor. Since this method is able to consider the balance of forces applied to the slope and is a more reasonable method for an individual site. In this research, the spatial data is obtained, managed and analyzed using GIS technique. The infinite slope model is used to evaluate factor of safety and analyze the slope stability.

• Proceedings of the KSEG Conference
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• 2003.04a
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• pp.153-158
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• 2003

Traditionally, the statistical methods has been used to analyze the relationship between landslide occurrence and related factors(soil depth, soil strength, slope angle, vegetation, etc.) in GIS technique. However, the method have no mechanical meaning. Therefore, the mechanical model is suggested in this research. The method analyzes the mechanical equilibrium of a potential slide block and then calculates a slope safety factor. Since this method is able to consider the balance of forces applied to the slope and is a more reasonable method for an individual site. In this research, the spatial data is obtained, managed and analyzed using GIS technique, and the infinite slope model is used to evaluate factor of safety and analyze the slope stability.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.496-503
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• 2016

To analyze an infinite slope that is reinforced with stabilizing piles, the forces on the stabilizing pile were estimated by the theory of plastic deformation and the theory of plastic flow and the effects of diverse factors on the factor of safety of an infinite slope were investigated. According to the results of the analyses, the factor of the safety of the slope reinforced with stabilized piles were increased tremendously and the factor of safety decreased as the center to center distance of the stabilizing pile increased. The effect of the existence of seepage of the infinite slope with stabilizing piles on the factor of safety appears to be insignificant. Considering the formulated factor of safety of an infinite slope with stabilizing piles, the width and length of the element of the infinite slope and force on the stabilizing pile influence the factor of safety of the infinite slope with a stabilizing pile including the soil strength parameter, inclination of the slope and depth of the slope, which are important for calculating the factor of safety of a non-reinforced infinite slope. The factor of safety of an infinite slope with stabilizing piles derived from the theory of plastic deformation were increased significantly with the internal friction angle of the soil, and the minimum and the maximum factor of safety under the conditions considered in this study were 13.7 and 65.6, respectively. As the diameter of the stabilizing pile increased, the forces on the stabilizing pile also increased but the factor of safety of the infinite slope with stabilizing piles decreased due to the effects of the width and the length of the element of the infinite slope. The factor of safety of the infinite slope with stabilizing piles derived from plastic flow were much larger than that of the non-reinforced infinite slope and the factor safety of the infinite slope with a stabilizing pile increased with increasing product of the flow velocity and plastic viscosity ( ) and the factor of safety of the infinite slope with stabilizing piles decreased with increasing center to center distance of the pile.

• Journal of the Korean Geotechnical Society
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• v.34 no.4
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• pp.5-11
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• 2018

In conventional analytical solutions for rainfall-induced soil slope stability, the Green-Ampt (1911) equation for estimating the saturation depth and the Skempton & DeLory (1957) equation for calculating the infinite slope shallow failure were compared with the numerical analysis to confirm the error. In the simple evaluation of the reason of soil slope instability due to rainfall using the conventional equations, there are many errors and, overestimation or underestimation of the calculation results. In this study, the equation consisting of the results obtained from infiltration analysis on unsaturated soil slope is proposed by applying the average range of the strength parameters of the granite weathered soils, and its reliability is verified by comparing with the numerical analysis results. The developed equation can be used easily in various fields for the estimation of slope safety factor by checking the rainfall duration and saturation depth.

• Structural Engineering and Mechanics
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• v.40 no.6
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• pp.829-845
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• 2011

This paper evaluates the effects of topographical and geotechnical irregularities on the dynamic response of the 2-D soil-structure systems under ground motion by coupling finite and infinite elements. A numerical procedure is employed, and a parametric study is carried out for single-faced slope topographies. It is concluded that topographic conditions may have important effects on the ground motion along the slope. The geotechnical properties of the soil will also have significantly amplified effects on the whole system motion, which cannot be neglected for design purposes. So, dynamic response of a soil-structure systems are primarily affected by surface shapes and geotechnical properties of the soil. Location of the structure is another parameter affecting the whole system response.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.722-729
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• 2004

The horizontal movement of sloping ground due to flow liquefaction has caused many pile foundations to fail, especially those in ports and harbor structures. In this study, a virtual case is assumed in which flow liquefaction is induced by earthquake loads in a fully saturated infinite sand slope with a single pile installation. Under the assumption that the movement of liquefied ground is viscous fluid flow, the influence of ground movement due to flow liquefaction on the pile behavior was analyzed. Since the liquefied soil is assumed as a viscous fluid, its viscosity must be evaluated, and the viscosity was estimated by the dropping ball method ,md the pulling bar method. Finally, the influence of the flow of liquefied soil on a single pile installed in an infinite slope was analyzed by a numerical method.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.764-771
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• 2010

The stability analysis method of an unsaturated slope considering the suction stress was performed on the infinite sand slope. During drying and wetting processes, the Soil-Water Characteristics Curve (SWCC) of the sand with the relative density of 75% was measured using the automated SWCC apparatus. Also, the Suction Stress Characteristics Curve (SSCC) was estimated. Based on these results, the stability analysis of an unsaturated infinite slope was carried out considering the slope angle, the weathering zone and the relative change in friction angle as a soil depth. According to the result of slope stability analysis, the safety factors of slope were less than 1 when the slope angles were more than $50^{\circ}$. The safety factors of slope tend to increase with increasing the depth from the ground surface. Especially, the safety factors have a tendency to increase and decrease above near the ground water level due to the suction stress. The maximum safety factor of slope in this analysis was occurred at the Air Entry Value (AEV) of drying process. The influence range of suction stress above the ground water level can be found out and can be defined as the funicular zone which means the metric suction range from the air entry point to the point of residual volumetric water content.