• The Journal of Engineering Geology
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• v.34 no.2
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• pp.193-206
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• 2024

A standard slope stability analysis was undertaken for new railway sections, based on the slope of sedimentary rock layers and filling material (sand), to evaluate the stability of the cut-off slope in the section passing through a zone of sedimentary rock. The stability analysis was undertaken during the dry and rainy seasons, accounting for earthquake occurrence, based on slope design criteria. It was found that if the slope of the sedimentary rock formation was <10°, the effect on the safety rate of the cut-off slope was insignificant. Furthermore, a slope relief of 1:1.0 or more should be applied with slopes of 10~20°, and 1:1.2 or more with >20°. This study provides an important reference for evaluation of slope stability when railway and road construction is undertaken in areas of sedimentary rock.

• Journal of the Society of Disaster Information
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• v.14 no.4
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• pp.421-429
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• 2018

Purpose: This study conducted a slope stability study considering changes in the ground water level due to rain phenomena and the duration of rainfall, that is for the purpose of analyzing the stability of the slope surface of the cut section, seepage numerical analysis is performed by height of slope and rainfall accident, and the characteristics of rainfall was applied reasonably in order to determine the slope change during rain by analyzing rainfall and rainfall pattern due to climate change. Results: As a result of numerical analysis of stability for slope composed of the granite weathered soils according to the characteristics of rainfall(Uniform Rainfall, US Army Corps., Huff's method - 1/4, 4/4), Conclusion: The higher the slope, the smaller the safety factor of the slope, the smaller the elevation of the ground water level as the rainwater seepage does not reach the underground water level. In addition, the ground water level was assessed to be rose significantly in condition of case 3 Huff's method - 1/4, rain pattern with the largest initial rainfall duration, and the safety factor was analyzed to be small.

• Journal of the Korean GEO-environmental Society
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• v.25 no.8
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• pp.5-11
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• 2024

Due to the high proportion of mountainous terrain in Korean territory and the concentration of heavy rainfall during the summer season, concerns arise about the potential decrease in slope stability caused by rainfall. Installing slope drainage facilities mitigates the rise in groundwater levels due to infiltration, thus enhancing slope stability. Horizontal drains, classified as auxiliary facilities among drainage systems, lack established installation standards and related research. Slopes with installed horizontal drains have been confirmed to exhibit higher safety factors compared to those without. Furthermore, the safety factor of mimicking horizontal drains by increasing the permeability coefficient of the surrounding ground was compared with that of the conventional simulation method using the Drain function. As a result of the comparison, it was confirmed that the installation length showed better drainage performance than the installation angle in the drainage performance of the horizontal drainage hole, and it was judged that the installation length was a more important factor.

• Journal of the Korean GEO-environmental Society
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• v.17 no.3
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• pp.27-35
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• 2016

Even if the various data analyzing methods were suggested to examine the measured slope behaviors, it is difficult to find methods or procedures for connecting the analyzed results of slope stability and measured slope data. This research suggests the analyzing methods combing the stability analysis and measured data based on progressive failure of slope. Slope failure analysis by time degradation were calculated by strength parameters composed of strength reduction coefficients, also which were compared to the measured data according to the variations of safety factor and displacement of slopes. The accumulated displacement curve were shown as 3rd degree polynomials by suggested procedures, which was the same as before researches. The reverse displacement velocity curves were shown as linear function for prediction of brittle slope failures, also they were shown as 3rd degree polynomials for ductile slope failures, which were the same as the suggested equation by Fukuzono (1985) and they were very similar behaviors to the in-situ failure cases.

• The Journal of Engineering Geology
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• v.30 no.4
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• pp.485-496
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• 2020

The characteristics of volumetric water content changes in soil slopes were studied here in an effort to identify the signs of heavy rain causing shallow slope failure. Volumetric water contents in cases with and without shallow failure were measured in flume and test-bed experiments. Measurement data from 282 experiments of both types revealed that the volumetric water content gradient in shallow failure events ranged from 0.072 to 0.309. In non-failure cases, the range was 0.01~0.32. Therefore, this one specific value cannot predict shallow slope failure. However, as the volumetric water content gradient increased, there was a clear tendency to shallow failure. By using this trend, criteria for four warning levels are suggested.

• Journal of the Korean Geotechnical Society
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• v.31 no.9
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• pp.5-15
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• 2015

In this study, rainfall-induced slope stability and coupling effect are investigated using hydro-mechanical finite element model. This model is developed by formulating constitutive and coupled balance equations and is verified by comparing the numerical results with field matric suction. The homogeneous soil layer (soil column) and soil slope are modeled by this model, and the results of variation in matric suction, mean effective stress, porosity, displacement, factor of safety are compared with those of staggered analysis. It is found that the vertical and horizontal displacement from coupling analysis considering change in porosity is larger than that of staggered analysis. The displacement and matric suction from coupling analysis by rainfall infiltration can affect slope instability, which shows a progressive failure behavior. The lowest factor of safety is observed under short-term rainfall. This results confirm the fact that coupling analysis is needed to design soil slope under severe rain condition.

• The Journal of Engineering Geology
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• v.28 no.4
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• pp.605-618
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• 2018

Korea follows the slope design criteria during construction. It was enacted by the Ministry of Land, Transport and Maritime Affairs. There are cases where the Soil-nail is designed as a measure to secure slope stability. The arrangement of the soil-nail may be arranged at equal intervals or may be arranged differently depending on the soil failure model. The optimum design of the countermeasure method is determined by securing stability of the slope through optimization of dimensions and shape. However, when uniform nails are placed at low elevations in slopes, the standard safety factor is exceeded, which may hinder economic design. It is preferable to arrange the reinforcement of the nails over the entire slope. When the horizontal spacing of the nails was topology optimized according to the slope height, it was possible to minimize the amount of reinforcement while satisfying the standard safety factor. Since the active load is reduced in the section where the slope height is lowered, the safety factor after reinforcement may be excessively increased. Therefore, the phase optimization method is proposed as an economical optimal design method using the reinforcing shape density. In addition, a relational expression was designed to optimize the horizontal spacing by slope height.

• Journal of the Korean Geotechnical Society
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• v.33 no.4
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• pp.5-15
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• 2017

Three-hinge failure occurs in a jointed rock slope with a joint set parallel with slope and a conjugate joint set. Limit Equilibrium Method (LEM) and Finite Element Method (FEM) which are commonly used for slope design, are not suitable for evaluating stability against three-hinge failure, and this study performed parametric study to analyze the failure mechanism and to find influence factors causing three-hinge failure using UDEC which is a commercial two-dimensional DEM based numerical program. Numerical analyses were performed for various joint structural conditions and joint properties as well as ground water conditions. It was found that pore water pressure is the main factor triggering the three-hinge failure and the mode of failure depends on friction angle of basal joint and bedding joint set. The results obtained from this study can be used for adequate and economic footwall slope reinforcement design and construction.

• Journal of the Korean GEO-environmental Society
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• v.21 no.6
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• pp.13-17
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• 2020

In the era of the fourth industrial revolution, drones are being used in various civil engineering fields. Currently, the construction and maintenance of slopes are generally managed by manpower. This method has a risk of safety accidents, and it is difficult to accurately evaluate the slope because it is difficult to secure the vision. In this paper, the effects of RTK and GCP on the 3D model of the slope were studied by using digital images taken by the drone. GNSS coordinates were measured for nine points to compare the quality of the slope 3D model, three points of which were used as the check points and the remaining points were used as GCPs. When making the 3D model of the slope using high-accuracy geotagging images using RTK, it was found that the error at the check point decreases as the number of GCP increases. Even if GNSS was used, it was found that the error at the check points of the 3D slope model was not significant when the GCPs were applied. However, it was found that even if high-accuracy geotagging images are used using the RTK module, a significant error occur when the 3D slope model is created without applying GCPs. Therefore, it can be stated that GCP must be applied to create the 3D slope model in which information about the height as well as plane information is important.

• The Journal of Engineering Geology
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• v.22 no.1
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• pp.83-94
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• 2012

Slopes are commonly formed both above and below roads located in mountainous terrain and along riversides. The Buk-sil site, a cut slope formed below the road, collapsed in October, 2010. A field investigation determined the causes of failure as improper drainage of valley water from the slope above the road and direct seepage of road-surface water. These factors may have accelerated the collapse via complex interaction between water and sub-surface structures such as bedding. Projection analysis of the site showed the possible involvement of plane, wedge, and toppling failure. Safety factors calculated by Limit Equilibrium Analysis for plane and wedge failure were below the standard for wet conditions. The wetness index, analyzed using topographic factors of the study area, was 9.0-10.5, which is high compared with the values calculated for nearby areas. This finding indicates a high concentration of water flow. We consider that water-flow control on the upper road is crucial for enhancing slope stability at the Buk-sil site.