• Geomechanics and Engineering
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• v.14 no.1
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• pp.19-27
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• 2018

It follows from the basic principles of mechanics of deformable solids relating to the strength, stability and propagation of elastic waves that the Earth's inner core cannot exist in the form of a spherical structure in the assumed thermobaric conditions and calculation values of physico-mechanical parameters. Pressure level reaches a value that is significantly greater than the theoretical limit of medium strength in the model approximations at the surface of the sphere of the inner core. On the other hand, equilibrium state of the sphere is unstable on the geometric forming at much lower loads under the influence of the "dead" surface loads. In case of the action of "follower" loads, the assumed pressure value on the surface of the sphere is comparable with the value of the critical load of "internal" instability. In these cases, due to the instability of the equilibrium state, propagation of homogeneous deformations becomes uneven in the sphere. Moreover, the elastic waves with actual velocity cannot propagate in such conditions in solid medium. Violation of these fundamental conditions of mechanics required in determining the physical and mechanical properties of the medium should be taken into account in the integrated interpretations of seismic and laboratory (experimental) data. In this case, application of the linear theory of elasticity and elastic waves does not ensure the reliability of results on the structure and composition of the Earth's core despite compliance with the required integral conditions on the mass, moment of inertia and natural oscillations of the Earth.

• Journal of the Korean Geosynthetics Society
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• v.15 no.4
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• pp.25-32
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• 2016

The two-dimensional (2D) analysis is widely used in geotechnical engineering for slope stability analysis assuming a plane-strain condition. It is implicitly assumed that the slip surface is infinitely wide, and thus three-dimensional (3D) end effects are negligible because of the infinite width of the slide mass. The majority of work on this subject suggests that the 2D factor of safety is conservative (i.e. lower than the 'true' 3D factor of safety). Recently, the 3D finite element method (FEM) became more attractive due to the progress of computational tools including the computer hardware and software. This paper presents the numerical analyses on rotational mode and translational mode slopes using the 2D and 3D FEM as well as 2D limit equilibrium methods (LEM). The results of the parametric study on the slope stability due to mesh size, dilatency angle, boundary conditions, stress history and model dimensions change are analysed. The analysis showed that the factor of safety in 3D analysis is always higher than that in the 2D analysis and the discrepancy of the slope width in W direction on the factor of safety is ignored if the roller type of W direction conditions is applied.

• Journal of the Korean Geosynthetics Society
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• v.9 no.3
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• pp.87-93
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• 2010

The change of water level in reservoirs is an important factor causing failure of bank slopes, i.e. landslide. The water level of Three Gorges reservoir in China fluctuate between 145 m and 175 m, as a matter of flood control. During its normal operational state, the rate of water level fluctuation is supposed to range from 0.67 m/d to 3.0 m/d. Majiagou slope is located on the left bank of Zhaxi River, 2.1 km up from the outlet. Zhaxi River is a tributary of the Yangtze River within the Three Gorges area, of which the water level changes with the reservoir. At the back of Majiagou slope, a 20 m long and 3~10 cm wide fissure developed just after the reservoir water level rose from 95 m to 135 m in 2003. This big fissure was a full suggestion of potential failure of this slope. In this study, the pore water pressure files obtained from seepage analysis were used to evaluate the change in factor of safety (FS) with reservoir water level. Slope stability analyses then were carried out, with fully specified slip surface and limit equilibrium method. In the limit equilibrium analysis, the contribution of negative pore water pressure to shear strength was considered by the use of Fredlund's shear strength equation for unsaturated soils. On the base of the analyses, the change of FS with reservoir water level was interpreted in detail. It was found that FS against bank slopes decreases with the rise of the reservoir water level and increases with the drawdown of the reservoir water level. The most dangerous state was when the reservoir water level stays at the highest for a long time.

• 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.25 no.3
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• pp.264-274
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• 2015

In this study, the applicability of geotextile mesh soil nails on slopes was evaluated by numerical analysis to reduce environmental problems which a general soil nailing might produce and to improve its economical efficiency and construction convenience. To this end, in situ pull-out tests were conducted for both general soil nail and geotextile mesh soil nail and their pull-out characteristics were analyzed. Also, finite difference method was used to verify the suitability of numerical simulation. Parameters for nail and ground conditions were selected and sensitivity analysis was performed for the evaluation of slope stability. In addition, analysis was performed by limit equilibrium method which is widely used for slope stability analysis in practice. As a result, if the nail diameter was same, there is no big difference between geotextile mesh soil nails and general soil nails in terms of slope stability. Therefore it can be expected that geotextile mesh soil nails could be effective for slope reinforcement since they could keep a slope as stable as general soil nails and give better economical efficiency and construction convenience than general soil nails.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.670-675
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• 2006

The purpose of this study is the infiltration characteristics of soil cut-slope by the repetition & concentration rainfall. The maximum rainfall concentrate from June until September which is a rainy season in our country Stability analysis of soil cut-slopes has been conducted by limit equilibrium method on Seep/w and finite element method on Slope/w.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.735-738
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• 2005

The purpose of this study is the infiltration characteristics of soil cut-slope by rainfall. Stability analysis of soil cut-slopes has been conducted by limit equilibrium method on Seep/w and finite element method on Slope/w. Result is same as following. First. the hour when seepage line and groundwater in contact is proportionate from rainfall rate condition and upper natural slope gradient condition which is identical. Second, when seepage line and groundwater is contact, seepage line moves gradually at soil cut-slope surface. Finally, seepage line is formed similarly with soil cut-slope gradient. Third, when rainfall is ended, from the recording upper natural slope where the hour will pass it is stabilized

• Korean Journal of Agricultural Science
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• v.35 no.2
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• pp.213-223
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• 2008

The instability of rock slopes caused by heavy rainfall and soil mass sliding needs the preventable and reinforcing method. The most important factor for the stability is the shear strength available in the planar part of the failure surface, which shows that a progressive failure takes place and a reinforcing of rock slope using FRP grout is effectively available. In this study, a grouting bolting interval predictions by limit equilibrium analysis and Matlab mathematical computer codes in several cases is presented for FRP reinforced rock slope. The proposed mathematical computer code can be easily applied for seeking properly FRP grout intervals prior to design and execute a reinforcement of a rock slope in practice.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2000.09a
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• pp.183-193
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• 2000

A series of studies such as geological logging data analysis, detailed geological survey, rock mass evaluation, in-situ and laboratory tests, rock strength and mechanical properties of the rock were concerned. The stability of the slope were carried out inorder to design the pit slope and individual benches using the stereographic projection analysis and numerical methods in Roto Pit of Pasir coal fetid. The bedding plane was one of the major discontinuities in the Roto Pit and the dip of which is about $60^{\circ}$in the northern part and $83^{\circ}$in the southern part. The dip of bedding becomes steeper from north to south. The plane and toppling failures are presented in many slopes. In laboratory test the average uniaxial compressive strength of mudstone was 9 MPa and that of weak sandstone was 10 MPa. In-situ test showed that the rocks of Roto north mining area are mostly weak enough to be classified in grade from R2(weak) to R3(medium strong weak) and the coal is classified in grades from R1(Very weak) to R2(Weak). The detailed stability analysis were carried out on 4 areas of Roto north(east, west, south and north), and 2 areas of Roto south(east and west). In this paper, the minimum factor of safety was set to 1.2 which is a general criterion for open pit mines. Using the stereographic projection analysis and the limit equilibrium method, slope angles were calculated as 30~$36^{\circ}$for a factor of safety greater than 1.2. Then these results were re-evaluated by numerical analysis using FLAC. The final slope angles were determined by rational described abode. A final slope of 34 degrees can guarantee the stability for the eastern part of the Roto north area, 33 degrees for the western part, 35 degrees for the northern part and 35 degrees for the southern part. For the Roto south area, 36 degrees was suggested for both sides of the pit. Once the pit slope is designed based on the stability analysis and the safety measures. the stability of 니ope should be checked periodically during the mining operations. Because the slope face will be exposed long time to the rain fall, a study such aspreventive measures against weathering and erosion is highly recommended to be implemented.

• Tunnel and Underground Space
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• v.10 no.3
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• pp.430-440
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• 2000

A series of studies such as geological logging data analysis, detailed geological survey, rock mass evaluation, in-situ and laboratory tests, rock strength and mechanical properties of the rock were concerned. The stability of the slope were carried out inorder to design the pit slope and individual benches using the stereographic projection analysis and numerical methods in Roto Pit of Pasir coal field. The bedding plane was one of the major discontinuities in the Roto Pit and the dip of which is about 60$^{\circ}$ in the northern part and 83$^{\circ}$ in the southern part. The dip of bedding becomes steeper from north to south. The plane and toppling failures are presented in many slopes. In laboratory test the average uniaxial compressive strength of mudstone was 9MPa and that of weak sandstone was 10MPa. In-situ test showed that the rocks of Roto north mining area are mostly weak enough to be classified in grade from R2(weak) to R3(medium strong weak) and the coal is classified in grades from R1(Very weak) to R2(Weak). The detailed stability analysis were carried out on 4 areas of Roto north (east, west, south and north), and 2 areas of Roto south(east and west). In this paper, the minimum factor of safety was set to 1.2 which is a general criterion for open pit mines. Using the stereographic projection analysis and the limit equilibrium method, slope angles were calculated as 30∼36$^{\circ}$ for a factor of safety greater than 1.2. Then these results were re-evaluated by numerical analysis using FLAC. The final slope angles were determined by rational described above. A final slope of 34 degrees can guarantee the stability for the eastern part of the Roto north area, 33 degrees for the western part, 35 degrees for the northern part and 35 degrees for the southern part. For the Roto south area, 36 degrees was suggested for both sides of the pit. Once the pit slope is designed based on the stability analysis and the safety measures, the stability of slope should be checked periodically during the mining operations. Because the slope face will be exposed long time to the rain fall, a study such aspreventive measures against weathering and erosion is highly recommended to be implemented.