• The Journal of Engineering Geology
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• v.34 no.1
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• pp.13-24
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• 2024

The purpose of this study is to identify the geology, geologic structure, hydrogeology and geomorphic characteristics of the Nari Basin and establish the controls on the discharge of water 20,000~40,000 m³/day from the Choosan Yongchulso, Ulleung Island, South Korea. Pumice and lapilli tuffs showing well-developed stratification are the predominant rock types surrounding the spring. The spring shows a structure whereby discharge occurs along a lens-like erosion cave formed by differential erosion of strata comprising tuff or pumice tuff. The Choosan Yongchulso is located at the point where the planation surface of the Nari Basin' ends and steep slopes begin. The basin is bounded on all sides by these steep slopes, except in the north, where the Choosan Yongchulso is located. Given these geomorphic characteristics, the Choosan Yongchulso is regarded as the ultimate outlet of the basin catchment area.

• Korean Journal of Soil Science and Fertilizer
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• v.33 no.3
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• pp.139-144
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• 2000

This study was conducted to obtain the basic information to increase the practical use of soil survey data through the subdividing of valley shapes with soil sequences due to different parent rocks, and to study the relationship between the valley shapes and parent rock. The various rocks such as sedimentary(gray shale and sand stone) and igneous rocks(granite, granite gneiss and andesite porphyry) which are the major parent rocks in Yeongnam area were investigated. The characteristics of valleys formed and the kinds of soils derived from different rocks were analysed by using aerial photographs and topographical maps scaled 1:5,000. The rill density in igneous rock area was as high as 40. But the rill bifurcation ratio of first order stream was higher in the sedimentary than the igneous rocks except granite area. The mean slope of valleys in igneous areas was about 8%, which was higher than that of the sedimentary areas. The variability of valley width in the complexly metamorphosed rock, such as granite gneiss, and andesite porphyry, was greater than in sedimentary and in granite rocks. Based on the variability of valley widths and valley slopes, it was possible to classify the valleys into two types. The "Uterus-shaped valleys" had wide variability of valley width and were located in the areas of granite gneiss and andesite porphry rocks. while the "Roots-shaped valleys" had narrow variability of valley width and were located in the sedimentary areas. "Uterus-shaped valleys" were typified by having land forms of mountain foot slopes and alluvial fans, and the soil drainage sequences also had complexities. So that, we concluded that the variability of valley width and valley slopes was associated with kinds of parent rocks and metamorphism which influences soil sequence and characteristics.

• Journal of the Korean Geotechnical Society
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• v.15 no.6
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• pp.263-272
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• 1999

Slice method is commonly used in solving slope stability problems since it is easy to use and its computation time is rather short. But depending upon the assumptions on the inter-slice forces, different methods are available. Quite often the difference between methods are so big that it is very difficult to make engineering decisions. This paper describes a method to calculate the factor of safety of a slope using FLAC, a finite difference based program. A FISH routine is developed to calculate the factor of safety, and verified by comparing with Chen's limit equilibrium solution. An example problem was selected from Fredlund and Krhan's paper, and results were compared for different soil and water conditions. The difference was less than 0.01 when the soil is homogeneous, and less than 5 % when a weak layer is embedded. Since most geotechnical application programs are capable of considering complicated ground conditions as well as the effect of ground supports, numerical methods are believed to be very useful in making engineering decisions. The developed routine can be applied to the calculation of the factor of safety of jointed rock slopes or weathered rock slopes where the use of slice method is limited.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.6 no.2
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• pp.103-113
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• 2001

This study presents Quaternary sedimentation pattern around Dok-Island volcanoes (Dok Island and Dok Seamount), based on analysis of high-resolution (chirp) echo characters. Echo facies If, showing sharp, continuous bottom echo without subbottom reflectors, is recorded mainly from the flat tops of the volcanoes. This facies indicates sands and gravels (re) deposited by shallow marine processes. Echo facies IIA in the basin floor and basal slopes of the volcanoes and Oki Bank is characterized by semi-prolonged bottom and several parallel subbottom echoes. This facies reflects hemipelagic settling with intermittent influences of turbidity currents in the slope areas. Echo facies IIC is recorded from acoustically-transparent debrite masses on the basal slopes of the volcanoes and Oki Bank. Echo facies IIIA is characterized by irregular hyperbolic echoes in the slope areas of the volcanoes. It suggests hard rock basement or irregular volcanic edifices. Echo facies IIIC shows regularly-overlapping hyperbolic bottom echoes. It is interpreted to represent rock-fall deposits (talus) accumulated in the mid-slope area. Echo characters and topography suggest that the tops of Dok-Island volcanoes were flattened and lowered by shallow-marine erosional processes. The eroded sediments were transported to and deposited in the base of slope and basin plain mainly by debris flows and turbidity currents along submarine canyons and valleys.

• The Journal of Engineering Geology
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• v.20 no.3
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• pp.243-255
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• 2010

The slope design of an open-pit mine must consider economical efficiency and stability. Thus, the overall slope angle is the principal factor because of limited support or reinforcement options available in such a setting. In this study, slope displacement, as monitored by a GPS system, was analyzed for a coal mine at Pasir, Indonesia. Predictions of failure time by inverse velocity analysis showed good agreement with field observations. Therefore, the failure time of an unstable slope can be roughly estimated prior to failure. A GIS model that combines fuzzy theory and the analytical hierarchy process (AHP) was developed to assess slope instability in open-pit coal mines. This model simultaneously considers seven factors that influence the instability of open-pit slopes (i.e., overall slope gradient, slope height, surface flows, excavation plan, tension cracks, faults, and water body). Application of the proposed method to an open-pit coal mine revealed an enhanced prediction accuracy of failure time and failure site compared with existing methods.

• Tunnel and Underground Space
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• v.18 no.1
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• pp.20-32
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• 2008

The study shows a method called a square-inventory method, which is a better and faster method than scanline survey and window method for an analysis of slope stability. The study area is located in the Changri area, Boeun-Gun, Chungbuk, and consists of many formations of the Okcheon Supergroup. Various types of failure are observed from the phyllite including the rocks in the study area. The physical properties of meta-sedimentary rocks are that minerals of the rocks are composed of microcrystalline quartz and sericite, which are arranged parallel to bedding (or schistosity) and crenulation cleavage. Therefore, such properties affect geotechnical ones of the rock. The slope stability are analyzed by selecting 3 areas, each of which are divided into 2 or 3 slopes of $1m{\times}1m$ area that represent each of 3 investigation sites. The possibility of wedge and toppling failure is very high in all 3 areas by using square-inventory method. Although possibility of plane failure is weak in the investigation site 2, the plane failures are frequently found from the slope of site 2. The bedding (or schistosity) plane and cleavage, another types of discontinuity coexist in meta-sedimentary rocks uulike igneous rocks, and therefore are important factors to be considered together with joint structures in th ε analysis of slope stability.

• Journal of Forest and Environmental Science
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• v.17 no.1
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• pp.104-115
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• 2001

This study was carried out to to execute the slope stabilization scheme of soil and weathered rock slope with forest road generating slope failure due to heavy rainfall. The timber piled stabilization by Shin's formulae for landslide-restraint pile as elastically supported elastic columns under distributed loads was applied on the unstable fill slope. The results obtained were summarized as follows: The timber piled stabilization was applied for unstable slopes such as the soil slope and weathered rock slope of metamorphic rock regions. The results indicated that pile interval of 0.5~1.0m was appropriate in the case of high hillslope gradients and 0.7~2.0m in the case of low hillslope gradients of soil slope, and Pile interval of 0.5~1.3m in the case of high hillslope gradients and 0.7~2.0m in the case of low hillslope gradients of weathered rock slope. Recommended pile length was around 4m for pile 1, 2 and 3, and nearly 3m for pile 4 and 5.

• Economic and Environmental Geology
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• v.47 no.2
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• pp.121-131
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• 2014

The stability of rock slope is mainly controlled by the orientation and shear strength of discontinuties in rock mass. Therefore, in kinematic analysis, the orientation of the combination of discontinuities and slope face is examined to determine if certain modes of failure can be occurred. In previous kinematic analysis, a representative orientation of the slope face and mean orientation of discontinuity set were used as input parameters. However, since the orientations of slope face varies according to locations of measurement, the representative slope face orientation could cause misunderstanding for kinematic instability. In addition, since the orientations of each discontinuity are scattered in the same discontinuity set, there is the possibility that uncertainties are involved in the procedure of kinematic analysis. Therefore, in this study, the detailed digital topographic map was used to obtain the orientation of slope face. In addition, the probabilistic analysis approach was utilized to deal properly with the uncertainties in discontinuity orientation. The proposed approach was applied to steep slopes in mountain road located in Baehuryeong, Chunncheon city, Gangwon-Do. The analysis results obtained from the deterministic and probabilistic analysis were compared to check the feasibility of proposed the analysis.

• The Journal of Engineering Geology
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• v.16 no.3 s.49
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• pp.245-254
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• 2006

Using a natural gradient tracer test, the characteristics of hydrodynamic dispersion according to each depth of a fractured rock were studied, and the effective porosity and longitudinal dispersivity of the fractured rock were estimated. The difference of vertical hydrodynamic dispersion was identified by concentration breakthrough curves linear regression analyses of bromide concentrations according to depths versus time, and hydraulic fracture characteristics at two intervals of the monitoring well. Higher concentration and faster arrival time at GL- 18 m depth (RQD 13%, average joint spacing 2 cm, TCR 100%) than at GL- 25 m depth (RQD 41%, average joint spacing 7 cm, TCR 100%) resulted from shorter distance and more fractures. Tracer was transported through the 1 st fractures until the arrival of its peak concentration and through the 2nd fractures or matrix diffusion after the arrival of its peak concentration. The increase/decrease slopes of bromide concentration versus time were 3.46/-1.57 at GL-18 m depth and 3.l9/-0.47 at GL- 25 m depth of the monitoring well. So the faster bromide transport was confirmed at GL- 18 m depth with more fractures. The concentration increment of bromide was fitted by a Gaussian function and the concentration decrement of bromide was fitted by an exponential function. Effective porosity and longitudinal dispersivity estimated by CATTI code were 10.50% and 0.85 m, respectively.

• Journal of Korean Society of Forest Science
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• v.104 no.4
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• pp.588-597
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• 2015

This study was carried out to identify the reasons of the landslide by land creeping in South Korea in order to provide basic information for establishing the management plan for prevention. Total 29 sites of landslide areas caused by land creeping were observed in South Korea. Among them, the soil-composition of most frequent landslide areas occurred by land creeping was colluvium landslide as 75.9% (22 sites), followed by clay soil landslide as 10.3% (3 sites), bedrock landslide as 6.9% (2 sites), and weathered rock landslide as 6.9% (2 sites). According to the types of parental rocks, the investigated landslide areas were divided into 3 types: 1) metamorphic rocks including schist, phylite, migmatitic gneiss, quartz schist, pophyroblastic gneiss, leucocratic granite, mica schst, banded gneiss and granitic gneiss, 2) sedimentary rocks including limestone, sandstone or shale and mudstone, 3) igneous rocks such as granite, andesite, rhyolite and masanite. As a result, it was noticed that the landslides occurred mostly at the metamorphic rocks areas (13 sites; 44.8%), followed by sedimentary rock areas (12 sites; 41.4%), and igneous rock areas (4 sites; 13.8%). Looking at the direct causes of the landslide, the anthropological activities (71%) such as cut slopes for quarrying, construction of country house, plant, and road, farming of mountain top, and reservoir construction were the biggest causes of the landslides, followed by the land creeping landslides (22%) caused by geological or naturally occurred (22%), and cliff erosions (7%) by caving of rivers and valleys.