• 한국환경과학회지
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• 제12권12호
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• pp.1245-1254
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• 2003

A numerical simulation for 11 February 1996 has been done to grasp main mechanisms of the occurrence of strong downslope winds near Gangnung area. The simulation performed by using ARPS (Advanced Regional Prediction System) showed that enhanced surface winds were not related with a reflection of vertically propagating gravity waves. Froude numbers were about 1.0, 0.4 and 0.6 for the atmosphere above Daekwanryoung and above a place located 220km upstream, and above another place located 230km downstream from the Taebak mountains, respectively. This suggested that as a subcritical flow ascended the upslope side of the Taebak mountains, Froude numbers would tend to increase according to the increase in wind speed, and near the crest the flow would become supercritical and continue to accelerate as it went down the downslope side until it was adapted back to the ambient subcritical conditions in a turbulent hydraulic jump. Simulated Froude numbers corroborated the hydraulic jump nature of the strong downslope wind. In addition, the inversion was found near the mountain top height upstream of the mountains, and it was favorable for the occurrence of strong downslope winds.

• 대기
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• 제25권4호
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• pp.591-600
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• 2015

We have analyzed wind and eddy covariance data collected within roughness sublayer over sloping terrain. The study site is located on non-flat terrain with slopes in both south-north and east-west directions. The surface elevation change is smaller than the height of roughness element such as building and tree. This study examines the directional wind shear for data collected at three levels in the lowest 10 m in the roughness sublayer. The wind direction shear is caused by drag of roughness element and terrain-induced motions at this site. Small directional shear occurs when wind speed at 10 m is strong and wind direction at 10 m is southerly which is the same direction as upslope flow near surface at this site during daytime. Correlation between vertical shear of lateral momentum and lateral momentum flux is smaller over steeply sloped surface compared to mildly sloped surface and lateral momentum flux is not down-gradient over steeply sloped surface. Quadrant analysis shows that the relative contribution of four quadrants to momentum flux depends on both surface slope and wind direction shear.

• Geomechanics and Engineering
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• 제30권6호
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• pp.579-586
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• 2022

Pile-supported structures are installed on saturated sloping grounds, where the ground stiffness may decrease due to liquefaction during earthquakes. Thus, it is important to consider saturated sloping ground and pile interactions. In this study, we conduct a centrifuge test of a pile-supported structure, and analyze the p-y_p loops, p-y_p loops provide the correlation between the lateral pile deflection (y_p) and lateral soil resistance (p). In the dry sand model (UV67), the p-y_p loops stiffness increased as ground depth increased, and the p-y_p loops stiffness was larger by approximately three times when the pile moved to the upslope direction, compared with when it moved to the downslope direction. In contrast, no significant difference was observed in the stiffness with the ground depth and pile moving direction in the saturated sand model (SV69). Furthermore, we identify the unstable zone based on the result of the lateral soil resistance (p). In the case of the SV69 model, the maximum depth of the unstable zone is five times larger than that of the dry sand model, and it was found that the saturated sand model was affected significantly by kinematic forces due to slope failure.

• 한국지반신소재학회논문집
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• 제18권4호
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• pp.225-242
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• 2019

2016년 9월 12일 발생한 경주지진의 영향으로 석굴암 진입도로 구간 내 대형낙석이 발생되었다. 낙석의 발생 원인 규명과 진입도로 전체 구간의 비탈면 위험성을 확인하고, 적정한 대책방안을 마련하기 위한 정밀조사가 실시되었다. 석굴암 진입도로 주변의 지형 및 지질 특성 확인, 현황도 작성을 통한 특성 파악 등을 바탕으로 구간별 위험도를 위험, 주의, 안정으로 분류하였다. 또한 음영기복도를 활용하여 경사도, 방위도, 상부사면기여면적, 습윤지수 등을 도출함으로써, 지진 발생으로 인한 위험 구간과 지형적 요인의 특성에 대하여 고찰하였고, 이를 통해 대형낙석 발생 구간이 취약 구간이었음을 확인할 수 있었다. 본 연구를 통해 석굴암 진입도로 전반에 대한 비탈면 안정 상태를 평가하여, 붕괴 위험정도에 따라 위험구간과 주의구간으로 분류함으로써, 석굴암 진입도로 주변의 산사태 관리를 위한 기반을 마련하였다.

• Geomechanics and Engineering
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• 제3권1호
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• pp.1-16
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• 2011

Piles passing through sloping liquefiable deposits are prone to lateral loading if these deposits liquefy and flow during earthquakes. These lateral loads caused by the relative soil-pile movement will induce bending in the piles and may result in failure of the piles or excessive pile-head displacement. Whilst the weak nature of the flowing liquefied soil would suggest that only small loads would be exerted on the piles, it is known from case histories that piles do fail owing to the influence of laterally spreading soils. It will be shown, based on dynamic centrifuge test data, that dilatant behaviour of soil close to the pile is the major cause of these considerable transient lateral loads which are transferred to the pile. This paper reports the results of geotechnical centrifuge tests in which models of gently sloping liquefiable sand with pile foundations passing through them were subjected to earthquake excitation. The soil close to the pile was instrumented with pore-pressure transducers and contact stress cells in order to monitor the interaction between soil and pile and to track the soil stress state both upslope and downslope of the pile. The presence of instrumentation measuring pore-pressure and lateral stress close to the pile in the research described in this paper gives the opportunity to better study the soil stress state close to the pile and to compare the loads measured as being applied to the piles by the laterally spreading soils with those suggested by the JRA design code. This test data shows that lateral stresses much greater than one might expect from calculations based on the residual strength of liquefied soil may be applied to piles in flowing liquefied slopes owing to the dilative behaviour of the liquefied soil. It is shown at least for the particular geometry studied that the current JRA design code can be un-conservative by a factor of three for these dilation-affected transient lateral loads.

• 한국토양비료학회지
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• 제49권6호
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• pp.635-643
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• 2016

Wine consumers desire to drink a high quality wine. For producing high quality wine, high quality soil is required. Conventionally, soil quality is assessed qualitatively. Using traditional laboratory methods, quantitative data can be obtained for management purpose, but it is time consuming and expensive. Therefore, new technology aims to address these limitations, namely portable X-Ray fluorescence spectrometers (pXRF). This instrument can be used directly in the field, requires no soil sample preparations, and can simultaneously measure a wide range of elements qualitatively that are useful for pedological studies. The chemical composition (Ca, Fe, Ti and Zr) of soils at Tallavera Grove vineyard in New South Wales, Australia, was studied using a pXRF. The analysis of the soil's elemental concentration (i.e. Ca and Fe) using pXRF supports management decisions. Measuring the soil's Ca concentration can be used to identify Ca-rich parent materials (limestone). The limestone indicates good soil conditions for vine production. Fe content was used to identify areas of texture-contrast soils or soil with accumulation of clays in the B horizon. In addition, a soil weathering index was calculated using elemental concentrations (i.e. Ti and Zr) to explore the history of soil formation for making decision of management. This index showed that the soil in the vineyard was affected by two processes: the deposition of materials from elsewhere (Aeolian transport or soil erosion) and mixing of materials from upslope.

• 한국지구과학회지
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• 제34권7호
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• pp.605-614
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• 2013

대부분의 급경사지의 붕괴는 지형적으로 불안정한 지역에서 발생한다. 백두산은 전형적인 산악 지역으로 잠재적 폭발 가능성을 지닌 활화산으로 알려져 있다. 본 연구에서는 백두산지역의 수치고도모형을 이용하여 지형요소와 선구조선 분석을 통해 재해 위험도를 작성하였다. 취약도 분석에 사용되는 요소는 지형으로부터 산정된 방위도, 경사도, 상부사면기여면적, 접선구배곡률, 윤곽구배 곡률, 습윤지수의 분포를 이용하였다. 더불어 선구조의 선밀도도를 작성하여 재해 위험도를 평가하는데 이용하였다. 지형요소를 이용한 백두산지역의 재해위험도 분석 결과 남쪽 내지 남서부 지역의 재해 위험도가 4-5등급으로 높게 나타나고 있다.

• 대기
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• 제22권2호
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• pp.209-219
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• 2012

Extreme heavy snowfall episodes have been investigated in case of accumulated snowfall amount larger than 50 cm during the past ten years, in order to understand the association of low-level stability with heavy snowfall in the Yeongdong region. In general, the selected 4 events have similar synoptic setting such as the Siberian High extended to East Sea along with the Low passing by the southern Korean Peninsula, eventually inducing easterly in the Yeongdong region. Specifically moist-adiabatically neutral layer has been observed during the heavy snowfall period, which was easily identified using vertical profiles of equivalent potential temperature observed at Sokcho, whereas convective unstable layer has been formed over the East sea due to relatively warm sea surface temperature (SST) about $8{\sim}10^{\circ}C$ and lower temperature around 1~2 km above the surface, obtained from RDAPS. Difference of equivalent potential temperature between 850 hPa and surface as well as difference between air and sea temperatures altogether gradually increased before the snowfall period. Instability-induced moisture supply to the atmosphere from the East sea, being cooled and saturated by the upper cold surge, would make low-level ice cloud, and eventually move inland by the easterly flow. Heavy snowfall will be enhanced in association with low-level convergence by surface friction and upslope wind against Taebaek mountains. This study emphasizes the importance of low level stability in the Yeongdong region using the radiosonde sounding and RDAPS data, which should quantitatively be examined through numerical model as well as heat and moisture supply from the ocean.

• 대기
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• 제26권3호
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• pp.401-412
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• 2016

A 3D sonic anemometer has been installed at Yongpyong alpine slope since Oct. 23th 2014 to observe the slope winds and to analyze turbulent characteristics with the change in surface cover (grass and snow) and the synoptic wind strength. Eddy covariance method has been applied to calculate the turbulent quantity after coordinate transformation of a planar-fit rotation. We have carefully selected 3 good episodes in the winter season (23 October 2014 to 28 February 2015) for each category (9 days in total), such as grass and snow covers in case of weak synoptic wind condition, and grass cover of strong synoptic wind. The diurnal variations of the slope winds were well developed like the upslope wind in the daytime and downslope wind in the nighttime for both surface covers (grass and snow) in the weak synoptic forcing, when accordingly both heat and momentum fluxes significantly increased in the daytime and decreased in the nighttime. Meanwhile, diurnal variation of heat flux was not present on the snow cover probably in associated with significant fraction of sunlight reflection due to high albedo especially during the daytime in comparison to those on the grass cover. In the strong synoptic regime, the most dominant feature at Yongpyong, only the southeasterly downslope winds were steadily generated irrespective of day and night with significant increases in momentum flux and turbulent kinetic energy as well, which could suggest that local circulations are suppressed by the synoptic scale forcing. In spite of only one season analysis applied to the limited domain, this kind of an observation-based study will provide the basis for understanding of the local wind circulation in the complex mountain domain such as Gangwon in Korea.

• 한국수자원학회논문집
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• 제37권6호
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• pp.467-477
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• 2004

물이 부족한 우리나라는 최근 수자원의 효율적인 이용에 대한 중요성이 강조되고 있으며 특히 지금까지 개발된 저류시설을 통한 수자원의 효율적인 관리가 절대적으로 필요한 실정이다 효율적이고 합리적인 수자원관리와 그 이용 효과를 극대화하기 위해 경북지방의 농업용 저수지에 대한 저류용량과 퇴사량의 현황을 분석한 결과 농업용 저수지의 준설을 통하여 10% 이상에 이르는 저류용량을 추가적으로 확보할 수 있음을 확인하였다. 또한 GIS와 각종 토사발생량 예측기법을 활용하여 산정한 퇴사량을 실제 준설량과 비교 분석한 결과 분산모형과 다방향흐름알고리즘을 이용한 기법이 산지에 위치한 저수지 상류의 지형학적 특성을 잘 반영하며 타 기법에 비해 우수한 예측결과를 제시하는 것을 알 수 있었다.