• Spatial Information Research
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• v.17 no.3
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• pp.381-387
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• 2009

This study investigates the use of geomorphic analysis results obtained from high-resolution LiDAR-derived DEM. The results of analysis, slope angle and eigenvalue ratio (ER) were derived from the DEM for 3 landslide and 1 non-landslide occurrence area. Results of this study highlighted the importance of geomorphic analysis in characterizing landslide feature as well as the various contents in their future occurrence and activity. The relationship between the results of geomorphic analysis and landslides are well expressed in this paper.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05c
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• pp.589-594
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• 1996

도서지역에서의 해수침입에 의한 해수-담수 경계면의 예측은 담수의 이용측면에서 뿐만 아니라 방사성폐기물 영구처분장과 같은 시설을 지하동굴을 이용하여 건설할 경우 설계개념의 설정 및 처분시설의 성능평가 측면에서도 중요한 사항이다. 해수침입의 예측에 널리 사용되어 온 Ghyben-Herzberg 근사식을 자연수위면의 경사가 급한 도서 지하매짙에 적용할 경우 야기되는 문제점을 지적하고, 보다 신뢰성이 향상된 방법인 염분 이동식에 근거한 수치해를 이용하여 해수-담수 경계면을 예측하였다. 경사도가 다른 두 가지 가상 처분시스템에 대한 정상상태에서의 해수침입 해석 결과, Ghyben-Herzberg 근사식은 담수지역에서의 수직 수두구배가 작은 경우에만 적용되며 국내에서 방사성폐기물 처분부지로 고려하였던 굴업도와 같은 작은 도서의 지하매질에서의 해수-담수 경계면 예측시 오류를 범할 수 있으므로 단순 적용은 피해야 할 것으로 판단되었다.

• Solar Energy
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• v.13 no.1
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• pp.1-10
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• 1993

The purpose of this research is to investigate the characteristics of heat transfer in the downward axisymmetric free water jet system impinged on a flat oblique plate which has the uniform heat flux. Experimental conditions considered were Reynolds number, distance between nozzle and Bat plate, inclination angle of heater surface and nozzle exit velocity. Local Nusselt number was subjected to the influence of Re number, Pr number, oblique angle of heating surface and local position of flat plate. In the wall region of downward surface, The secondary peak point of heat transfer appeared at the local point of X/D=-8 from the stagnation point. The stagnation heat transfer rate of this experimental study augments 2.4 times than that of laminar theorical solution. The stagnation nusselt number is function of Reynolds number, nozzle-plate spacing Prandtl number and oblique angle of impinging plate.

• Journal of the Korean Geophysical Society
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• v.2 no.1
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• pp.57-64
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• 1999

To effectively identify near-surface faults with vertical slips from seismic refraction data, the GRM interpretation technique is tested and investigated in terms of various parameters through computer modeling. A characteristic change in shape of the velocity-analysis function near faults is noticed, and a new strategy of `Slope Variation Indicator (SVI)' is developed and tested in this study. The SVI is defined as a first horizontal derivative of the difference of velocity analysis functions for a large XY value and a small one, respectively. As the dip of refractor decreases and as the difference in XY value increases, the peak value of SVI increases and its duration decreases. Consequently, the SVI indicates accurately the location of buried fault in the test models. The SVI is believed to be an efficient tool in seismic refraction method to investigate location and distribution of shallowly buried faults.

• Tunnel and Underground Space
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• v.17 no.2 s.67
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• pp.119-127
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• 2007

Based on the critical plane approach, a methodology far predicting the anisotropic strength ot transversely isotropic rock is Proposed. It is assumed that the rock failure is governed by Hoek-Brown failure criterion. In order to establish an anisotropic failure function, Mohr envelope equivalent to the original Hoek-Brown criterion is used and the strength parameters m, s are expressed as scalar functions of orientation. The conjugate gradient method, which is one of the robust optimization techniques, is applied to the failure function for searching the orientation giving the maximum value of the anisotropic function. While most of the existing anisotropic strength models can be applied only when the stress condition is the same as that of conventional triaxial compression test, the proposed model can be applied to the general 3-dimensional stress conditions. Through the simulation of triaxial compression tests for transversely isotropic rock sample, the validity of the proposed method is investigated by comparing the predicted triaxial strengths and inclinations of failure plane.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.296-296
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• 2008

국내 절토비탈면은 이상 기후 및 건설공사의 증대로 인해 증가하고 있는 추세이며 장마철 및 태풍으로 인해 비탈면의 붕괴로 많은 인명 및 재산피해가 발생되고 있는 실정이다. 국내에서 사용되고 있는 기존의 비탈면의 설계기준은 암반의 불연속면에 대한 조사를 실시하고는 있지만 주로 암반의 굴착난이도를 토층, 리핑암, 발파암으로 구분하여 각각의 비탈면 절취경사를 결정하여 사용하는 방법을 사용하였으며 이러한 기준은 단순히 암석의 강도를 기준으로 설정되어 있으므로 암석의 공학적 특성 즉, 암반내 불연속면 방향성, 연속성, 충진물질, 마찰각, 풍화속도 등의 영향으로 공용후 비탈면 구배의 재조정 및 보강이 빈번하다. 국내외 절토비탈면의 설계기준은 각 기관별로 산재되어 있었으며 비탈면에 대한 설계 및 시공 등에 관한 기준은 도로와 철도 설계기준에 일부 반영되어 있을 뿐 항만, 댐, 택지조성 등 기타 시설 설계기준에는 비탈면에 대한 기준이 마련되어 있지 않아 표준적인 비탈면 설계기준 및 유지관리지침이 등이 필요하였다. 이러한 문제점을 보완하기 위해 2004년부터 2006까지 한국시설안전공단, 한국도로공사, 대한주택공사가 협동으로 연구한 건설공사 비탈면 설계 시공 및 유지관리에 관한 연구의 결과로 2006년도에 "건설공사 비탈면 설계기준"이 수립되었다. 이 설계기준은 건설공사에서의 기존 상이한 기준들을 정리하고 동일화하는 작업을 수행하였으며 지반의 조사에서부터 대책공까지를 막나하여 정리하였다. 그러나 최근에 급격한 기후변화로 인한 비탈면붕괴 빈번함에 따라 과거 적용되어 왔던 이들 기준을 적용하는 경우, 특히 상부 토층 및 풍화암 구간에서 많은 설계안전율을 만족하지 못해 많은 보강을 수반해야 하는 문제가 발생되고 있어 그 원인에 대한 분석을 수행하고자 하였다. 2006년도 정리된 기준은 과거에 적용하여 온 유기시의 안전율 조건을 Fs > 1.1~1.2을 적용하였던 것을 Fs > 1.2로 통일하였으며 지하수위 조건은 지표면에 위치하도록 하였다. 지하수위 조건은 풍화암 및 토층의 경우, 과거 지표면에 -3m를 적용한 시기가 있었으나 지표면에 지하수위를 적용하는 것이 일반적인 해석방법이다. 이러한 결과의 원인을 검토해 보면 다음과 같다. 첫째, 풍화암 및 토층에 적용되어 온 지반강도 정수가 과거 적용한 값보다 최근에는 작아지는 경향을 보이고 있다. 둘째, 지하수위 적용문제로 현재 지표면에 지하수위를 두어 안전율을 감소시키는 문제로 이는 최근 들어 많은 연구기관에서 강우시 간극수압의 증가에 대한 연구가 활발하게 진행되고 있다. 그러나 침투수 해석은 현행 기준에도 강우의 침투를 고려한 해석을 실시하는 경우 FS > 1.3 적용하는 것으로 되어 있으나 대부분의 해석에서는 적용이 되지 못하고 있는 실정이다. 셋째, 안전율이 과거에 주로 적용된 Fs > 1.1에서 Fs > 1.2로 상향 조정되어 우기시의 설계안전율 만족시키지 못하는 문제이다. 그러므로 이러한 문제점을 개선하기 위한 검토가 필요하며 장기적으로 이에 대한 합리적인 기준을 개정하는 작업이 추후에 수행되어야 할 것으로 판단된다.

• The Journal of Engineering Geology
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• v.12 no.2
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• pp.137-150
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• 2002

Recently, plane failure mode occurred frequently along the bedding plane having low angle dip about 20 degree when cutting slopes were constructed in sedimentary rock region of the Gyeongsang Basin. Landslide of the Whangryeong Mountain which was occurred at Busan Metropolitan City in 1999 belongs to the category mentioned above. Reconstruction for cutting slope of the Whangryeong Mountain has finished in 2000 and final grade of reconstructed cutting slope is 1:2.0. To analyze slope failure mode for landslide of the Whangryeong Mountain, various analyses were performed such as in-situ investigation and test, drilling, laboratory test, aerial photograph interpretation, X-ray diffraction analysis, and slope stability analysis using Stereographic Projection and Limit Equilibrium methods. As the result, it is identified that tension cracks had been developed one year before the landslide took place. The tension crack semis to be formed by merging several joint sets. It appears that failure blocks broke down along the sliding planes of different layers. Risk of plane failure is conformed as a result of stability analysis using Stereographic Projection and Limit Equilibrium methods in case that greenish gray tuffaceous shales, regared as sliding planes, are weathered. From now on, a detailed investigation is needed for the thin layers which is sensitive to weathering, and stability analysis for this layer is performed at cut slope construction site having similar geological condition.

• Proceedings of the KSRS Conference
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• 2006.03a
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• pp.101-104
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• 2006

In the Korean seas, Sea Surface Temperature (SST) and Thermal Fronts (TF) were analyzed temporally and spatially during 8 years from 1993 to 2000 using NOAA/AVHRR MCSST. As the result of EOF method applying SST, the variance of the 1st mode was 97.6%. It is suitable to explain SST conditions in the whole Korean seas. Time coefficients were shown annual variations and spatial distributions were shown the closer to the continent the higher SST variations like as annual amplitudes. The 2nd mode presented higher time coefficients of 1993, 94, and 95 than those of other years. Although the influence is a little, that can explain ElNINO effect to the Korean seas. TF were detected by Sobel Edge Detection Method using gradient of SST. Consequently, TF were divided into 4 fronts; the Subpola. Front (SPF) dividing into the north and south part of the East sea, the Kuroshio Front (KF) in the East China Sea (ESC), the South Sea Coastal Front (SSCF) in the South sea, and the Tidal Front in the West sea. TF located in steep slope of submarine topography. The distributions of 1st mode in SST were bounded in the same place, and these results should be considered to influence of seasonal variations. To discover temporal and spatial variations of TF,SST gradient values were analyzed by EOF. The time coefficients fo the 1st mode (variance : 64.55%) showed distinctive annual variations and SPF, KF, and SSCF was significantly appeared in March. the spatial distributions of the 2nd mode showed contrast distribution, as SPF and SSCF had strong '-' value, where KF had strong '+' value. The time of '+' and '-' value was May and October, respectively. Time coefficients of the 3rd mode had 2 peaks per year and showed definite seasonal variations. SPF represented striking '+' value which time was March and October That was result reflected time of the 1st and 2nd mode. We can suggest specific temporal and spatial variations of TF using EOF.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.397-402
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• 2005

In the Korean seas, Sea Surface Temperature (SST) and Thermal Fronts (TF) were analyzed temporally and spatially during 8 years from 1993 to 2000 using NOAA/AVHRR MCSST As the result of EOF method applying SST, the variance of the 1st mode was 97.6%. It is suitable to explain SST conditions in the whole Korean seas. Time coefficients were shown annual variations and spatial distributions were shown the closer to the continent the higher SST variations like as annual amplitudes. The 2nd mode presented higher time coefficients of 1993, 94, and 95 than those of other years. Although the influence is a little, that tan explain EININO effort to the Korean seas. TF were detected by Sobel Edge Detection Method using gradient of SST. Consequently, TF were divided into 4 fronts; the Subpolar Front (SPF) dividing into the north and south part of the East sea , the Kuroshio Front (KF) in the East China Sea (ESC), the South Sea Coastal Front (SSCF) in the South sea, and the Tidal Front in the West sea. TF located in steep slope of submarine topography. The distributions of 1st mode in SST were bounded in the same place, and these results should be considered to influence of seasonal variations. To discover temporal and spatial variations of TF, SST gradient values were analyzed by EOF. The time coefficients fo the 1st mode (variance : 64.55%) showed distinctive annual variations and SPF, KF, and SSCF was significantly appeared in March. the spatial distributions of the 2nd mode showed contrast distribution, as SPF and SSCF had strong'-'value, where KF had strong'+'value. The time of'+'and'-'value was May and October, respectively. Time coefficients of the 3rd mode had 2 peaks per year and showed definite seasonal variations. SPF represented striking'+'value which time was March and October. That was result reflected time of the 1st and 2nd mode. We can suggest specific temporal and spatial variations of TF using EOF.

• Journal of Wetlands Research
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• v.17 no.1
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• pp.26-37
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• 2015

Halophyte distribution pattern and area in the Suncheon-bay and Beolgyo estuary coastal wetlands were analyzed using KOMPSAT-2 landsat images were taken in 2008 and 2009, and field investigations were fulfilled for confirming the precise boundaries of individual halophyte areas. The salt-marsh vegetation in those areas can be classified mainly into two dominant communities: Suaeda japonica-dominant and Phragmites communis-dominant communities. In order to identify sedimentary characteristics, tidal-flat surface leveling and sedimentary facies analysis had been conducted. The sedimentary facies of marsh area are mostly silty clayey and clay facies with a little seasonal change and its slope is very gentle (0.0007~0.002 in gradient). Phragmites communis and Suaeda japonica communities were distributed in the mud-flat zone between 0.7 m and 1.8 m higher than MSL (mean sea level): zone of 1.1~1.8 m in the former and zone of 0.7~1.3 m in the latter. In the Suncheon-bay estuarine wetland, on the basis of 2009 distribution, Phragmites communis-dominant and Suaeda japonica-dominant communities are about $0.79km^2$ and $0.22km^2$ in distribution area, respectively. On the other hand, Bulgyo estuarine marsh shows that the distribution areas of Phragmites communis-dominant and Suaeda japonica-dominant communities are about $0.31km^2$ and 0.031km2 in distribution area, respectively. Individual 105 and 60 dominant community areas and their distribution patterns can be well defined and indicated in the Suncheon-bay and Bulgyo estuarine marshes, respectively. The distribution pattern and area of hylophyte communities analyzed in this study based on 2008/2009 satellite images would be valuable as a base of future monitoring of salt-marsh related studies in the study area which is the most important salt-marsh research site in Korea.