• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.411-418
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• 2009

So far the Limit Equilibrium Method has been widely used by way of 2-D slope stability analysis for the evaluation of land slides and slope failures. However recently the evaluation of 3-D slope stability analysis has been comparatively possible owing to the developments of obtaining the terrain data and geological data and of 3-D slope stability analysis softwares. In Japan the evaluation of the 3-D slope stability analysis has been necessary for the stability analysis of the tunnel mouth. In this study we inspected the economic effects introducing the 3-D slope stability analysis for larger scale landslides and slope failures. In case of 3-D slope stability analysis of landslides we acquired the results that we reduce the cost of the countermeasure work of pile work by 40% comparing the 2-D slope stability analysis. Moreover in case of the stability analysis of slope failures we figured out the results that we reduce the cost of the countermeasure work of anchor works by 20%. Furthermore we proved that 3-D slope stability analysis is effective for the stability analysis of tunnel mouths around the sides of landslides and large scale embankment which we could have not evaluated by conventional 2-D section stability analysis.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.711-719
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• 2006

In this study, a 3D laser scanner is applied to evaluate of the stability of rock slope and to establish a adequate counter-method. From 3D scanning results, three dimensional digital data of rock slope is acquired, and then it is investigated for the engineering properties of discontinuities in rock mass. On the base of the result, we carry out the analysis of slope stability using the methods of the stereographic projection. In particular, the use of a 3D laser scanner is powerful about the slope on which person is difficult to approach because we can obtain the informations of discontinuities from the 3D digital data.

• Geomechanics and Engineering
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• v.34 no.2
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• pp.187-195
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• 2023

Intensive rainfall during the summer season in Korea has triggered numerous devastating landslides outside of downtown in mountainous areas. The 2D slope stability analysis that is generally used for cut slopes and embankments is inadequate to model slope failure in mountainous areas. This paper presents a new 3D slope stability formulation using the global sliding vector in the limit equilibrium method, and it uses an ellipsoidal slip surface for static and quasi-static analyses. The slip surface's flexibility of the ellipsoid shape gives a lower FS than the spherical failure shape in the Fellenius, Bishop, and Janbu's simplified methods. The increasing sub-columns of each column tend to increase the FS and converge to a steady value. The symmetrical geometric conditions of the convex turning corners do not indicate symmetrical failure of the surface in 3D analysis. Pseudo-static analysis shows that the horizontal seismic force decreases the FS and increases the mass volume at the critical failure state. The stability index takes the FS and corresponding sliding mass into consideration to assess the potential risk of slope failure in complex mountainous terrain. It is a valuable parameter for selecting a vulnerable area and evaluating the overall risk of slope failure.

• Geomechanics and Engineering
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• v.10 no.1
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• pp.59-76
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• 2016

The non-linear Hoek-Brown failure criterion has been widely accepted and applied to evaluate the stability of rock slopes under plane-strain conditions. This paper presents a kinematic approach of limit analysis to assessing the static and seismic stability of three-dimensional (3D) rock slopes using the generalized Hoek-Brown failure criterion. A tangential technique is employed to obtain the equivalent Mohr-Coulomb strength parameters of rock material from the generalized Hoek-Brown criterion. The least upper bounds to the stability number are obtained in an optimization procedure and presented in the form of graphs and tables for a wide range of parameters. The calculated results demonstrate the influences of 3D geometrical constraint, non-linear strength parameters and seismic acceleration on the stability number and equivalent strength parameters. The presented upper-bound solutions can be used for preliminary assessment on the 3D rock slope stability in design and assessing other solutions from the developing methods in the stability analysis of 3D rock slopes.

• Geomechanics and Engineering
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• v.31 no.4
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• pp.375-384
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• 2022

The variation of the undrained shear strength (c_u) is an important consideration for assessing slope stability in engineering practice. Previous studies focused on the three-dimensional (3D) stability of slopes in normally consolidated clays generally assume the undrained shear strength increases linearly with depth but does not vary in the horizontal direction. To assess the 3D stability of slopes with spatially varying undrained shear strength, the kinematic approach of limit analysis was adopted to obtain the upper bound solution to the stability number based on a modified failure mechanism. Three types failure mechanism: the toe failure, face failure and below-toe failure were considered. A serious of charts was then presented to illustrate the effect of key parameters on the slope stability and failure geometry. It was found that the stability and failure geometry of slopes are significantly influenced by the gradient of c_u in the depth direction. The influence of c_u profile inclination on the slope stability was found to be pronounced when the increasing gradient of c_u in the depth direction is large. Slopes with larger width-to-height ratio B/H are more sensitive to the variation of c_u profile inclination.

• Geomechanics and Engineering
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• v.32 no.6
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• pp.639-652
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• 2023

Stepped earth slopes incorporated with anti-slide piles are widely utilized in landslide disaster preventions. Explicit consideration of the three-dimensional (3D) effect in the slope design warrants producing more realistic solutions. A 3D limit analysis of the stability of pile stabilized stepped slopes is performed in light of the kinematic limit analysis theorem. The influences of seismic excitation and surcharge load are both considered from a kinematic perspective. The upper bound solution to the factor of safety is optimized and compared with published solutions, demonstrating the capability and applicability of the proposed method. Comparative studies are performed with respect to the roles of 3D effect, pile location, pile spacing, seismic and surcharge loads in the safety assessments of stepped slopes. The results demonstrate that the stability of pile reinforced stepped slopes differ with that of single stage slopes dramatically. The optimum pile location lies in the upper portion of the slope around L_x/L = 0.9, but may also lies in the shoulder of the bench. The pile reinforcement reaches 10% universally for a looser pile spacing D_c/d_p = 5.0, and approaches 70% when the pile spacing reaches D_c/d_p = 2.0.

• The Journal of Engineering Geology
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• v.27 no.3
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• pp.267-274
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• 2017

Behavior of rock mass depend on the mechanical properties of intact rock and geometrical property of discontinuity distributed in rock mass. In case of rock slope, particularly, location of slope failure surface and behavior after failure are changed due to discontinuities. In this study, two 3D slope stability analysis methods were developed for two different failure types which are circular failure and planar failure, considering that failure type of rock slope is dependent on scale of discontinuity which was then applied to real rock slope to review the applicability. In case of circular failure, stable condition was maintained in natural dry condition, which however became unstable when the moisture content of the surface was increased by rainfall. In case of planar failure, rock slope become more unstable comparing to dry condition which is attributable to decrease in friction angle of discontinuity surface due to rainfall. Viewing analysis result above, analysis method proved to have well incorporated the phenomenon occurred on real slope from the analysis result, demonstrating its applicability to reviewing the slope stability as well as to maintaining the slope.

• Geomechanics and Engineering
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• v.31 no.1
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• pp.71-86
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• 2022

In Taiwan, an efficient approach for enhancing the stability of colluvium slopes is the drilled shaft method. For slopes with drilled shafts, the soil arching effect is one of the primary factors influencing slope stability and intertwines to the failure mechanism of the pile-soil system. In this study, the contribution of soil arching effect to slope stability is evaluated using the FEM software (Plaxis 3D) with the built-in strength reduction technique. The result indicates the depth of the failure surface is influenced by the S/D ratio (the distance to the diameter of piles), which can reflect the contribution of the soil arching effect to soil stability. When α (rock inclination angles)=β (slope angles) is considered and the S/D ratio=4, the failure surface of the slope is not significantly influenced by the piles. Overall, the soil arching effect is more significant on α=β, especially for the steep slopes. Additionally, the soil arching effect has been included in the proposed stability charts. The proposed charts were validated through two case studies, including that of the well-known Woo-Wan-Chai field in Taiwan. The differences in safety factor (FoS) values between the referenced literature and this study was approximately 4.9%.

• The Journal of Engineering Geology
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• v.14 no.4 s.41
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• pp.451-460
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• 2004

The strength of sliding plane is usually assigned on the whole sliding plane with same value in 2D limit equilibrium slope stability method. However, the potential sliding plane is divided into two or three parts which have different sliding resistances. According to the calculation results of 3D slope stability analyses using 4 types of slope cutting models, marginal sliding resistance could affect the safety of slope significantly. In this calculation two kinds of the sliding plane strengths were applied differently to the parts of bottom and margin of the model slope. The effect of marginal resistance was calculated quantitatively. In case of lower sliding resistance of the bottom, the safety factor becomes low in a margin cutting model. However, in case of higher sliding resistance of the bottom, the safety factor decreased slightly in a lower part cutting model and increased in a upper margin cutting model.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.4
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• pp.387-400
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• 2013

In this study, the slope stability analysis and the landslide hazard assessment in tunnel portal slope were carried out. First, we selected highly vulnerable areas to slope failure using the slope stability analysis and analyzed the slope failure scale. According to analyses results, high vulnerable area to slope failure is located at 485~495 m above sea level. The slope is stable in a dry condition, while it becomes unstable in rainfall condition. The analysis results of slope failure scale show that the depth of slope failure is maximum 2.1 m and the length of slope failure is 18.6 m toward the dip direction of slope. Second, we developed a 3-D simulation program to analyze characteristics of runout behavior of debris flow. The developed program was applied to highly vulnerable areas to slope failure. The result of 3-D simulation shows that debris flow moves toward the central part of the valley with the movement direction of landslide from the upper part to the lower part of the slope. 3-D simulation shows that debris flow moves down to the bottom of mountain slope with a speed of 7.74 m/s and may make damage to the tunnel portal directly after 10 seconds from slope failure.