• Journal of the Korean Geotechnical Society
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• v.34 no.12
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• pp.83-92
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• 2018

The lapse of time may cause in the slope structure various deterioration phenomenon progresses in the ground of slope, and collapse due to deterioration of strength, resulting in a decrease in the service life. The approach to slope stability due to the ground deterioration is a different concept from the existing limit equilibrium analysis, which is limited to the physical characteristics and geometrical structure of ground. In this study, we conducted a comparative analysis of various literature studies related to the slope failure characteristics and behaviors to presented the optimal formulas for shear strength reduction, such as the exponential function, the logarithmic function and the inverse hyperbolic function. And then a case study was performed on cut slope of Gyeongbu High Speed Rail construction site along the Yangsan fault zone, where the slope failure of shale layer vulnerable to deterioration occurred. As a result, it was confirmed that landslide occurred due to reduction of shear strength by deterioration, as safety factor is approx. 1.0 at the time when the slope failure occurred. Based on the comprehensive case study, as a quantitative approach to the evaluation of slope stability due to deterioration of ground, finally we propose a method for evaluating slope stability with optimal strength reduction curves.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.720-723
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• 2006

This study performed slope stability analysis by changing analysis methods and shear strength with the slope stability analysis program. The conclusions of the study are as follows. 1) The safe factor of clayey soil applied with Bishop's simple method turned out to be similar to or slightly higher than those of other methods, for both dry and saturated conditions. 2) The safe factor of sandy soil applied with GLE method turned out to be slightly higher than those of other methods. But when applied with Bishop's simple method, it appeared to be slightly higher than those of other methods. 3) The safe factor of ordinary soil applied with GLE method showed the highest result. 4) Janbu method showed the lowest safe factor among all the methods for the above three types of soils.

• Journal of the Korean Geotechnical Society
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• v.25 no.2
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• pp.25-35
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• 2009

Slope failures are one of the significant disasters which causes lots of human casualties and huge financial losses every year. Previous researches on the slope failure have indicated that most accidents are closely related to the pore water pressure in the slope due to rainfall during the rainy seasons or stormy weather conditions. It would be therefore appropriate to consider the effect of pore water pressure in the design of slopes. As the existing slopes are generally reinforced by plants and other slope protecting measures, their boundary conditions are highly complicated. In this paper an attempt to develop a new modeling and analysis technique of slopes is proposed by including pore water pressure and adopting the coupled finite element method. Non-reinforced and reinforced slope models are considered. Representative analysis showed that the numerical modeling considering pore water pressure is appropriate in slope stability analysis. Flow behavior in the slopes is identified for various hydraulic boundary conditions. It is also shown that the effect of pore water pressure on slope stability is significant.

• Geomechanics and Engineering
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• v.15 no.4
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• pp.947-955
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• 2018

In this study, we propose a three-dimensional simplified slope stability analysis using a hybrid-type penalty method (HPM). In this method, a solid element obtained by the HPM is applied to a column that divides the slope into a lattice. Therefore, it can obtain a safety factor in the same way as simplified methods on the slip surface. Furthermore, it can obtain results (displacement and strain) that cannot be obtained by conventional limit equilibrium methods such as the Hovland method. The continuity condition of displacement between adjacent columns and between elements for each depth is considered to incorporate a penalty function and the relative displacement. For a slip surface between the bottom surface and the boundary condition to express the slip of slope, we introduce a penalty function based on the Mohr-Coulomb failure criterion. To compute the state of the slip surface, an r-min method is used in the load incremental method. Using the result of the simple three-dimensional slope stability analysis, we obtain a safety factor that is the same as the conventional method. Furthermore, the movement of the slope was calculated quantitatively and qualitatively because the displacement and strain of each element are obtained.

• Geomechanics and Engineering
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• v.31 no.5
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• pp.439-452
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• 2022

A forecast of slope behavior during catastrophic events, such as earthquakes is crucial to recognize the risk of slope failure. This paper endeavors to eliminate the significant supposition of predefined slip surfaces in the slope stability analysis, which questions the relevance of simple conventional methods under seismic conditions. To overcome such limitations, a methodology dependent on the slip line hypothesis, which permits an automatic generation of slip surfaces, is embraced to trace the extreme slope face under static and seismic conditions. The effect of earthquakes is considered using the pseudo-static approach. The current outcomes developed from a parametric study endorse a non-linear slope surface as the extreme profile, which is in accordance with the geomorphological aspect of slopes. The proposed methodology is compared with the finite element limit analysis to ensure credibility. Through the design charts obtained from the current investigation, the stability of slopes can be assessed under seismic conditions. It can be observed that the extreme slope profile demands a flat configuration to endure the condition of the limiting equilibrium at a higher level of seismicity. However, a concurrent enhancement in the shear strength of the slope medium suppresses this tendency by offering greater resistance to the seismic inertial forces induced in the medium. Unlike the traditional linear slopes, the extreme slope profiles mostly exhibit a steeper layout over a significant part of the slope height, thus ensuring a more optimized solution to the slope stability problem. Further, the susceptibility of the Longnan slope failure in the Huining-Wudu seismic belt is predicted using the current plasticity approach, which is found to be in close agreement with a case study reported in the literature. Finally, the concept of equivalent single or multi-tiered planar slopes is explored through an example problem, which exhibits the appropriateness of the proposed non-linear slope geometry under actual field conditions.

• Tunnel and Underground Space
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• v.5 no.4
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• pp.308-317
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• 1995

The stability study on the rock slope where have produced failures in Boryung dam site was evaluated using the streonet analysis techniques. SMR(Slope Mass Rating) approach which is suitable for preliminary assessment of slope stability in rock was also carried out for rating rock mass. The 3-4 major discontinuity sets are distributed and all type of failure(plane, wedge and toppling failure) are presented in this slope face. The dip of slope must be lowered to friction angle(26degree), otherwise the possibility of plane and toppling faiue will always exist in this slope.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.5
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• pp.621-640
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• 2019

Quantitative stability assessment of underground cavities can be presented as a factor of safety based on the Shear Strength Reduction Method (SSRM). Also, SSRM is one of the stability evaluation methods commonly used in slope stability analysis. However, there is a lack of research that considers the relationship between the probability of occurrence of cavities in the ground and the potential failure surface of the slope at the same time. In this study, the effect of small underground cavities on the failure behavior of the slope was analyzed by using SSRM. Considering some of the glaciology studies, there is a case that suggests that there is a cavity effect inside the glacier in the condition that the glacier slides. In this study, the stability evaluation of underground cavities and slope stability analysis, where SSRM is used in geotechnical engineering field, was carried out considering simultaneous conditions. The slope stability analysis according to the shape and position change of underground cavities which are likely to occur in the lower part of a mountain road was analyzed by using SSRM in FLAC3D software and the influence of underground cavities on the slope factor of safety was confirmed. If there are underground cavities near slope potential failure surface, it will affect the calculation of a factor of safety. The results of this study are expected to be basic data on slope stability analysis with small underground cavities.

• Economic and Environmental Geology
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• v.33 no.1
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• pp.77-88
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• 2000

The goal of this study is to assess the spatial distribution of natural slopes and cutting slopes under would-be development. For this goal, a quantitative slope stability analysis method using GIS integrated with a computer program was developed. Through field investigations, the discontinuity parameters were collected such as orientation of discontinuity, persistence, spacing, JRC, JCS, and water depth. The distributions were interpolated from the ordinary kriging method in ARC/INFO GIS after variogram analysis. The layers showing all parameters needed for limit equilibrium analysis were constructed. The final layer using GIS works composed of 162,352 polygons, that is, unit slopes. The rock slope stability analysis program was coded by C++ language. This program can calculate geometrical vectors related to rock block failures using input orientation data and direction and dimension of strength to occur failure. Also, this can calculate shear strength of joints through empirical equations and quantitative factors of safety. This methodology was applied to the study area which is located in Jaecheon city and Danyang-gun of the northeastern Keumsu is about 135$km^2$. As a result, the study area was entirely stable but unstable, that is, factor of safety less than 1.0dominantly at the slopes near Keumsil, Daejangri, Keumsungmyun and Sojugol, Mt. Dongsan, Juksongmyun by the natural slope stability analysis. Assuming the cutting slope showing the same direction immediate, and quantitative analysis of factors of safety for a regional area could be conducted through GIS integrated with a computer program of limit equilibrium.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.838-845
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• 2005

Slope stability analyses have been carried out to investigate surcharge loading effects. Finite Element Analysis (FEA) involves the stress-strain behaviour of soils achieving reasonably accurate and useful results of slope stability analysis. Therefore, in this study, one of well known FEA programs, SIGMA/W, has been used to do slope stability analyses with respect to various upper slope angles and surcharge loadings. Factor of Safety(FS) exponentially decreases and significantly good correlation with the increased slope angle for upper slopes. As the surcharge loading increases from 10 t/m to 90 t/m for nail-reinforced slopes, the FS in fully saturated condition decreases from 42% to 47% and from 17% to 25% for relatively low and high strength of soils, respectively, than in dry condition.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.123-131
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• 2018

This study analyzed the collapse course of a mud stone cut slope during the construction of a express and suggested a countermeasure. Experiments were carried out on bedrock mudstone to investigate the engineering characteristics and the slope stability analysis at the time the design was reviewed. In addition, stability analysis, considering the strength softening characteristics of the slope due to the Swelling-Slaking phenomenon, was also performed. As a result of the Swelling-Slaking test, the slake durability was Low-Medium, and the swell potential was Very Low. A review of the stability analysis performed at the time of the design showed different results from the actual results because LEM analysis had been performed without considering the engineering characteristics of mudstone. As a result of additional stability analysis considering the strength softening characteristics, the slope collapse point and the maximum shear strain point of the stability analysis were the same and the standard safety factor was not satisfied. As a countermeasure, a slope mitigation method was found to be most appropriate. The mitigation slope was calculated by Finite element Analysis. A comparison with BIPS to determine the applicability of a mitigation slope revealed most of the unconsolidated mudstone.