• The Journal of Engineering Geology
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• v.23 no.2
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• pp.149-160
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• 2013

Volcanic activity commonly creates a highly complicated volcanic complex due to the admixture of lava flow and sedimentation of volcanic ash. The Song-Gok site is composed of volcanic rocks that collapsed at the lower part of the slope, in combination with several discontinuities in and around a fault. The results of projection analysis indicated the possibility of plane, wedge, and toppling failure in the failure section. The results of discontinuity modeling using the Distinct Element Method (DEM) revealed a total displacement of 207 mm and a joint shear displacement of 114 mm. The yield surface zone was verified at the fault plane of the failure section. In geotechnical terms, volcanic rock slopes are characteristically vulnerable to failure because of differential weathering among the various rock types, the effect of groundwater based on the permeability of the rocks, and the presence of systematic joints generated by the cooling and contraction of lava. When considering the stability of a volcanic rock slope, it is necessary to consider data such as the geological features of the rock, as obtained through detailed geological survey, and variations in discontinuities and rock blocks.

• Journal of Korean Society of Forest Science
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• v.111 no.1
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• pp.115-124
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• 2022

This study was conducted to obtain basic data that could help prevent damage caused by slow-moving landslides (land-creep). Specifically, the geological, topographic, and physical characteristics of land-creep were analyzed in Jiphyeon-myeon, Jinju-si. The first and second analyzed land-creeps occurred in 1982 and 2019, respectively. The area damaged in the second land-creep was about 11.5-fold larger than that damaged in the first land-creep. The dominant constituent rock in the land-creep area was sedimentary rock, which seems to be weakly resistant to weathering. The areas that collapsed due to land-creep were related to the presence of separated rocks between the bedding plane in the estimated activity surface over the slope direction and the vertically developed joint surface. Thus, surface water and soil debris were introduced through the gaps of separated rocks. Additionally, the areas collapsed due to the combination of the bedding plane and joint surface shale and sandstone showed an onion structure of weathered outcrop from the edge to inner part caused by weathering from ground water. Consequently, core stones were formed. The study area was a typical area of land-creep in a mountain caused by ground water. Land-creep was classified into convex areas of colluvial land-creep. The landslide-risk rating in the study area was classified into three and five classes. The flow of ground water moved to the northeast and coincided with the direction of the collapse. Soil bulk density in the collapsed area was lower than that in ridge area, which was rarely affected by land-creep. Thus, soil bulk density was affected by the soil disturbance in the collapsed area.

• The Journal of Engineering Geology
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• v.12 no.4
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• pp.367-378
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• 2002

Recently, the number of tunnels on national roads has been increased due to the trend that construction of the large-scaled cut slopes is limited because of the environmental issues. Therefore, the slope failures of tunnel portal have often occurred. The tunnel portal in use has limitations on selection of the countermeasure and construction against slope failure. In the cases of Suanbo hot springs 1 and 2 tunnel portals, seedding was chosen and constructed as the countermeasureof slope failure when the tunnel was first built but collapsed in April, 2002. In this study, the failure sites were examined accurately through the site investigation and an efficient countermeasure according to stability analysis is presented. It is shown that it is very efficient to use resloping for Suanbo hot springs 1 tunnel and concrete buttress, rock anchor to reinforcement countermeasure, and attached rockfall prevention net by dividing the site into 3 sections for Suanbo hot springs 2 tunnel.

• Journal of Korean Society of Forest Science
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• v.88 no.2
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• pp.240-248
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• 1999

On the basis of data obtained from five forest roads collapsed due to a heavy rainfall of 1995 in Chunchon, Kangwon-do, this study was carried out to evaluate and predict the fill slope failure of forest roads with four factors of forest road structure and those of location condition by using Quantification theory(II). The results were summarized as follows ; In the structure factors of forest road, the fill slope failure was mainly occurred in longitudinal gradients less than $2^{\circ}$ or more than $4^{\circ}$, distance of surface-flow longer than 80m, fill slope length greater than 6m, and fill slope gradients steeper than $35^{\circ}$. In the factors of location condition, the failure was mainly occurred in ridge portion of road position, weathered rock and soft rock of constituent material, slope gradients in the range from $35^{\circ}$ to $45^{\circ}$, and concave and convex of longitudinal slope forms. The priority order for factors influencing on fill slope failure was ranked by fill slope length, constituent material, road position, and so on. And the rate of correct discrimination by analysis of fill slope failure was estimated at the high prediction of 86.5%.

• The Journal of Engineering Geology
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• v.11 no.3
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• pp.303-313
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• 2001

A cut-slope near Guam-Ri Hwado-Eup Namyangju-Si Kyunggi-Do collapsed during a heavy rainfall over 400mm at 28th of August 2000. The cut-slope collapse reportedly developed mainly by block sliding along a set of discontinuities, although slope angle of the cut-slope was 40$^{\circ}$(1:1.2) that agrees with the road construction criteria. This study aims to analyze differences and correlations among several data-collecting methods limited to discontinuity analysis related with cut-slope collapse. This study started with analysing discontinuity surface characteristics, geology of the country rock and orientations of the discontinuities directly related with the collapse. Analysis of aerial photos around the study area provided regional lineament data, and discontinuity plane description and measurements were collected from core logging and Borehole Image Processing System (BIPS). Spearmans correlation ranking coefficient method was used to get correlation of discontinuity planes according to analysis methods. The result suggests that the correlation coefficient is ${\gamma}_s$ = 0.91 Plus, stability analysis of discontinuity plane orientation data using equal-area stereonet revealed that the study area is unstable to planar failure. This study suggests that the cut-slope angles currently applied should be shallower and that significant attention is required to orientation distribution of discontinuities existed in cut-slopes studies.

• Journal of Korean Society of Forest Science
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• v.107 no.4
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• pp.393-401
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• 2018

The aim of this study was to analyze the characteristics of ground subsidence and land-creeping in four mining areas in Korea. Land creeping were occurred by large-scale sinkholes and tensile cracks in the mining areas. This ares showed the shape as large-scale landslides by the collapsed stone debris pushed in the direction of gravity. The rock type in the No. 4 survey area was sandstone and shale, whereas that of other three areas was limestone. The limestone was generally vulnerable to land creeping. The ground subsidence and land creeping in four mining areas were located near the ridge of the mountain. The land creeping by ground subsidence in the mining areas showed complex shapes due to the cavity of underground tunnel and the colluvial debris by gravity in the mountain area, whereas the land creeping in Korea are in the shape of landslide. The average slope of the mining area was ranged from $30.4^{\circ}$ to $33.7^{\circ}$. The values were higher ($1.5^{\circ}{\sim}4.8^{\circ}$) than the average slopes for landslide areas.