• The Journal of Engineering Geology
• /
• v.10 no.1
• /
• pp.1-12
• /
• 2000

Heaving of road and subsidence of slope took place at the Wiri region of the local highway 999 in Gyeongsangbukdo, Korea after heavy rain in the next year of construction. Although the state government had performed remedial treatments by reducing the angle and the height of the slope, deformation had never stopped. Therefore, we have preformed the analysis of deformation and stabilityof the slope. Study area consists of the Cretaceous shale, siltstone and sandstone and two faults are found. The major deformation occurred by sliding of rock mass along faults after heavy rain because not only thepore pressure at the fault plane and the unit weight of sliding mass increased, but did the shearstrength of saturated fault clay become very low. The decrease in shear strength of saturated fault clayis the major factor among the reasons for deformation. Numerical simulations using limit equilibriummodel, finite difference model and finite element model were performed for eight cross sections.Although safety factors are above 1.7 during the dry season, they become below 1.0 when groundwaterlevel raises to surface. The maximum displacement is about 15-3Ocm. However, safety factors increasedto above 2.4 and the maximum displacement is below 2.08cm after remedial treatment, Indicating thatthe slope becomes stable.

• Journal of the Korean GEO-environmental Society
• /
• v.8 no.2
• /
• pp.19-27
• /
• 2007

In this study, the centrifugal tests were performed with varying the angle of slope such as 1:3, 1:2.5, and 1:2 in order to analyze the deformation and failure type of dredged clay slope for a short term. The displacement mode, displacement vector and the variation of pore pressure with the different slope angle were measured. As a results, even though the displacement in the slope after 4 months were developed in the case of 1:3 for the dredged slope, there are little problems to obtain the stability of dredged slope because the original construction section maintains. Also, in the case of 1:2.5 after 4 months the local slope failure occurred and in the case of 1:2 after 2 months the circle failure starting from the point of the tensile crack occurred. After reviewing the results, the maximum vertical displacement occurred at the crest of slope and maximum horizontal displacement was about double of maximum vertical displacement.

• Geomechanics and Engineering
• /
• v.32 no.1
• /
• pp.111-123
• /
• 2023

The slope of an open cut tunnel is located above the exit of the Leijia tunnel on the Changgan high-speed railway. During the excavation of the open cut tunnel foundation pit, the slope slipped twice, a large landslide of 92500 m³ formed. The landslide body and unstable slope body not only caused the foundation pit of the open cut tunnel to be buried and the anchor piles to be damaged but also directly threatened the operational safety of the later high-speed railway. Therefore, to study the stability change in the slope of the open cut tunnel under heavy rain and excavation conditions, a 3D numerical calculation model of the slope is carried out by Midas GTS software, the deformation mechanism is analyzed, anti-sliding measures are proposed, and the effectiveness of the anti-sliding measures is analyzed according to the field monitoring results. The results show that when rainfall occurs, rainwater collects in the open cut tunnel area, resulting in a transient saturation zone on the slope on the right side of the open cut tunnel, which reduces the shear strength of the slope soil; the excavation at the slope toe reduces the anti-sliding capacity of the slope toe. Under the combined action of excavation and rainfall, when the soil above the top of the anchor pile is excavated, two potential sliding surfaces are bounded by the top of the excavation area, and the shear outlet is located at the top of the anchor pile. After the excavation of the open cut tunnel, the potential sliding surface is mainly concentrated at the lower part of the downhill area, and the shear outlet moves down to the bottom of the open cut tunnel. Based on the deformation characteristics and the failure mechanism of the landslides, comprehensive control measures, including interim emergency mitigation measures and long-term mitigation measures, are proposed. The field monitoring results further verify the accuracy of the anti-sliding mechanism analysis and the effectiveness of anti-sliding measures.

• Journal of Industrial Technology
• /
• v.33 no.A
• /
• pp.73-80
• /
• 2013

This paper is results of numerical analysis on the behavior of colluvium slope with combinations of soil nails and earth anchors during excavation. In order to maintain the stability of the colluvium cut, being composed of gravel and boulder and thus local in stability being expected during slope cut, temporary reinforcing method of soil nailing with shotcrete might be used. Subsequent method of cast-in-place facing with earth anchors can be used to maintain cut slope stable permanently. For the cut slope where these methods had been applied, the numerical techniques were applied to their behaviors and investigate the stability of the slope. Limit equilibrium methods were used to confirm to maintain the slope stability during and after excavation and application of those reinforcing methods. Another numerical technique of FEM was also used to find the stress and strain as well as deformation distribution in reinforcing materials and slope ground during excavation.

• Journal of the Korean Geotechnical Society
• /
• v.35 no.5
• /
• pp.21-30
• /
• 2019

While the study of the shallow tunnel has been mainly on the longitudinal load transfer and horizontal surface conditions, the study of the ground behavior of shallow tunnel under the slope is not sufficient. Therefore, in this study on the ground behavior around a tunnel due to the sidewall deformation of shallow tunnel under the slope that is excavated in longitudinal direction, a scale-down model test has been performed. The model tunnel has the dimension of 320 mm wide, 210 mm high and 55 mm long with enough material strength in aluminum and the model ground has the uniform ground conditions by 3 types of carbon rods. The model test has been performed with the variables of slopes and the cover depths by controlling the tunnel sidewall deformation, and the change of sidewall-load, load transfer, ground subsidence was monitored and analyzed. According to the increase of the slope, the maximum ground subsidence increased by 20~39% compared to the horizontal surface. The load ratio increased by maximum 20% in the tunnel crown and decreased in sidewall according to the surface slope. The load transfer shows maximum 128% of increase at the cover depth of 1.0D, while at the 1.5D cover depth it shows non-critical difference from horizontal surface. The slope has major effects on load transfer at the cover depth of 1.0D.

• Geomechanics and Engineering
• /
• v.35 no.5
• /
• pp.539-554
• /
• 2023

This article is dedicated to the pursuit of establishing a robust empirical relationship that allows for the estimation of in-situ modulus of deformations (E_m and G_m) within sedimentary rock slope masses through the utilization of Q_slope values. To achieve this significant objective, an expansive and thorough methodology is employed, encompassing a comprehensive field survey, meticulous sample collection, and rigorous laboratory testing. The study sources a total of 26 specimens from five distinct locations within the South Pars (known as Assalouyeh) region, ensuring a representative dataset for robust correlations. The results of this extensive analysis reveal compelling empirical connections between E_m, geomechanical characteristics of the rock mass, and the calculated Q_slope values. Specifically, these relationships are expressed as follows: E_m = 2.859 Q_slope + 4.628 (R² = 0.554), and G_m = 1.856 Q_slope + 3.008 (R² = 0.524). Moreover, the study unravels intriguing insights into the interplay between in-situ deformation moduli and the widely utilized Rock Mass Rating (RMR) computations, leading to the formulation of equations that facilitate predictions: RMR = 18.12 E_m0.460 (R² = 0.798) and RMR = 22.09 G_m0.460 (R² = 0.766). Beyond these correlations, the study delves into the intricate relationship between RMR and Rock Quality Designation (RQD) with Qslope values. The findings elucidate the following relationships: RMR = 34.05e^0.33Qslope (R² = 0.712) and RQD = 31.42e^0.549Qslope (R² = 0.902). Furthermore, leveraging the insights garnered from this comprehensive analysis, the study offers an empirically derived support system tailored to the distinct characteristics of discontinuous rock slopes, grounded firmly within the framework of the Q_slope methodology. This holistic approach contributes significantly to advancing the understanding of sedimentary rock slope stability and provides valuable tools for informed engineering decisions.

• Journal of the Korean GEO-environmental Society
• /
• v.11 no.5
• /
• pp.35-43
• /
• 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.

• Journal of the Korean Geotechnical Society
• /
• v.32 no.1
• /
• pp.19-33
• /
• 2016

Stability analysis based on the limit equilibrium method combined with the result of infiltration analysis is commonly used to evaluate the effect of rainfall infiltration on the slope stability. Soil is a three-phase mixture composed of solid particle, water and air. Therefore, a fully coupled mixture theories of stress-deformation behavior and the flow of water and air should be used to accurately analyze the process of rainfall infiltration through soil slope. The purpose of this study is to study the effect of interaction of air and water flow on the mechanical stability of slope. In this study, stability analyses based on the coupled hydro-mechanical model of three-phases were conducted for slope of weathered granite soil widespread in Korea. During the process of hydro-mechanical analysis strength reduction technique was applied to evaluate the effect of rainfall infiltration on the slope stability. The results showed an increase of air pressure during infiltration because rain water continuously displaced the air in the unsaturated zone. Such water-air interaction in the pore space of soil affects the stress-deformation behavior of slope. Therefore, the results from the three-phase model showed different behavior from the solid-water model that ignores the transport effect of air in the pores.

• Geomechanics and Engineering
• /
• v.19 no.2
• /
• pp.167-178
• /
• 2019

Open-pit (OP) and underground (UG) mining are usually used to exploit shallow and deep ore deposits, respectively. When mine deposit starts from shallow subsurface and extends to a great depth, sequential use of OP and UG mining is an efficient and economical way to maintain mining productivity. However, a transition from OP to UG mining could induce significant rock movements that cause the slope instability of the open pit. Based on Yanqianshan Iron Mine, which was in the transition from OP to UG mining, a large-scale two-dimensional (2D) model test was built according to the similar theory. Thereafter, the UG mining was carried out to mimic the process of transition from OP to UG mining to disclose the triggered rock movement as well as to assess the associated slope instability. By jointly using three-dimensional (3D) laser scanning, distributed fiber optics, and digital photogrammetry measurement, the deformations, movements and strains of the rock slope during mining were monitored. The obtained data showed that the transition from OP to UG mining led to significant slope movements and deformations that can trigger catastrophic slope failure. The progressive movement of the slope could be divided into three stages: onset of micro-fracture, propagation of tensile cracks, and the overturning and/or sliding of slopes. The failure mode depended on the orientation of structural joints of the rock mass as well as the formation of tension cracks. This study also proved that these non-contact monitoring technologies were valid methods to acquire the interior strain and external deformation with high precision.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2010.09a
• /
• pp.743-748
• /
• 2010

The stability forecasting of rock slope is more difficult than soil slope because catching the sign of failure in monitoring is not easy and deformation of the rock is small in failure process. But in the rock slope, there is small deformation like crack propagation in rock itself and it accumulates gradually in failure process. If it is possible to detect the small change in the rock slope, we can know the failure time exactly. Because the individual signal is gathered in the acoustic emission monitoring, it is possible to monitoring the slope if many sound signal is accumulated. Detection test of acoustic emission was performed. Uniaxial, two types of bending test, and two plane shear test were done with various cement paste sample. Wave propagation velocity of uniaxial test sample was increased with curing time. Wave Analysis give us the result that there is a AE sign signal before the failure, the AE count is suddenly increased. And frequency level 125kHz before failure is changed to level 200-250kHz after failure. In two plane shear test we can catch the AE signal and can know the failure type from wave shape. Monitoring test site is tunnel slope in Hongcheon but special signal is not collected.