• Title, Summary, Keyword: 평균응력

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Recruitment and Succession of Riparian Vegetation in Alluvial River Regulated by Upstream Dams - Focused on the Nakdong River Downstream Andong and Imha Dams - (댐 하류 충적하천에서 식생이입 및 천이 - 낙동강 안동/임하 댐 하류하천을 중심으로 -)

  • Woo, Hyo-Seop;Park, Moon-Hyung;Cho, Kang-Hyun;Cho, Hyung-Jin;Chung, Sang-Joon
    • Journal of Korea Water Resources Association
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    • v.43 no.5
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    • pp.455-469
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    • 2010
  • Changes of geomorphology in alluvial river and vegetation recruitment on its floodplain downstream from dams are investigated both qualitatively and quantitatively focusing on the downstream of Andong dam and Imha dam on the Nakdong River. Results of the analyses of river morphology and bed material in the study site show a general trend of riverbed degradation with a max scour of 3 m and bed material coarsening from pre-dam value of 1.5 mm in D50 to post-dam value of 2.5 mm. Decrease in bed shear stress due to the decrease in flood discharge have caused vegetation recruitment on the once-naked sandbars. As result, the ratio of area of vegetated bars over total area of bars has drastically changed from only 7% in 1971 before the Andong dam (constructed in 1976) to 25% after it, and increased to 43% only three year after the Imha dam (constructed in 1992) and eventually to 74% by 2005. Analysis of the vegetation succession at Wicjeol subreach, one of the three subreaches selected in this study for detailed investigation, has clearly shown a succession of vegetation on once-naked sand bars to a pioneering stage, reed and grass stage, willow shrub and eventually to willow tree stages. At the second subreach selected, two large point bars in front of Hahoe Village seem to have maintained their sand surfaces without a signifiant vegetation recruitment until 2005. The sand bars, however, seem to have been invaded by vegetation recently, which warns river managers to have a countermeasure to protect the sand bars from vegetation invasion in order to conserve them for the historical village of Hahoe. On the other hand, recruitment and establishment of vegetation on the sand bars by artificial disturbance of the river, such as damming, can create an unique habitat of backmarsh in the sandy river, as shown in the case of Gudam Wetland, and may increase the biodiversity as compared with relatively monotonous sand bars. Last, the premise in this study that decrease in flood discharge due to upstream dams and decrease in bed shear stress can induce vegetation recruitment on the naked sand bars in the river has been verified with the analyses of the distribution of dimensionless bed shear stress along the selected cross section in each subreach.

Structural Safety Test and Analysis of Type IP-2 Transport Packages with Bolted Lid Type and Thick Steel Plate for Radioactive Waste Drums in a NPP (원자력발전소의 방사성폐기물 드럼 운반을 위한 볼트체결방식의 두꺼운 철판을 이용한 IP-2형 운반용기의 구조 안전성 해석 및 시험)

  • Lee, Sang-Jin;Kim, Dong-hak;Lee, Kyung-Ho;Kim, Jeong-Mook;Seo, Ki-Seog
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.5 no.3
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    • pp.199-212
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    • 2007
  • If a type IP-2 transport package were to be subjected to a free drop test and a penetration test under the normal conditions of transport, it should prevent a loss or dispersal of the radioactive contents and a more than 20% increase in the maximum radiation level at any external surface of the package. In this paper, we suggested the analytic method to evaluate the structural safety of a type IP-2 transport package using a thick steel plate for a structure part and a bolt for tying a bolt. Using an analysis a loss or dispersal of the radioactive contents and a loss of shielding integrity were confirmed for two kinds of type IP-2 transport packages to transport radioactive waste drums from a waste facility to a temporary storage site in a nuclear power plant. Under the free drop condition the maximum average stress at the bolts and the maximum opening displacement of a lid were compared with the tensile stress of a bolt and the steps in a lid, which were made to avoid a streaming radiation in the shielding path, to evaluate a loss or dispersal of radioactive waste contents. Also a loss of shielding integrity was evaluated using the maximum decrease in a shielding thickness. To verify the impact dynamic analysis for free drop test condition and evaluate experimentally the safety of two kinds of type IP-2 transport packages, free drop tests were conducted with various drop directions. For the tests we examined the failure of bolts and the deformation of flange to evaluate a loss or dispersal of radioactive material and measured the shielding thickness using a ultrasonic thickness gauge to assess a loss of shielding integrity. The strains and accelerations acquired from tests were compared with those by analyses to verify the impact dynamic analysis. The analytic results were larger than the those of test so that the analysis showed the conservative results. Finally, we evaluated the safety of the type IP-2 transport package under the stacking test condition using a finite element analysis. Under the stacking test condition, the maximum Tresca stress of the shielding material was 1/3 of the yielding stress. Two kinds of a type IP-2 transport package were safe for the free drop test condition and the stacking test condition.

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The research for the yachting development of Korean Marina operation plans (요트 발전을 위한 한국형 마리나 운영방안에 관한 연구)

  • Jeong Jong-Seok;Hugh Ihl
    • Journal of Navigation and Port Research
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    • v.28 no.10
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    • pp.899-908
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    • 2004
  • The rise of income and introduction of 5 day a week working system give korean people opportunities to enjoy their leisure time. And many korean people have much interest in oceanic sports such as yachting and also oceanic leisure equipments. With the popularization and development of the equipments, the scope of oceanic activities has been expanding in Korea just as in the advanced oceanic countries. However, The current conditions for the sports in Korea are not advanced and even worse than underdeveloped countries. In order to develop the underdeveloped resources of Korean marina, we need to customize the marina models of advanced nations to serve the specific needs and circumstances of Korea As such we have carried out a comparative analysis of how Austrailia, Newzealand, Singapore, japan and Malaysia operate their marina, reaching the following conclusions. Firstly, in marina operations, in order to protect personal property rights and to preserve the environment, we must operate membership and non-membership, profit and non-profit schemes separately, yet without regulating the dress code entering or leaving the club house. Secondly, in order to accumulate greater value added, new sporting events should be hosted each year. There is also the need for an active use of volunteers, the generation of greater interest in yacht tourism, and the simplification of CIQ procedures for foreign yachts as well as the provision of language services. Thirdly, a permanent yacht school should be established, and classes should be taught by qualified instructors. Beginners, intermediary, and advanced learner classes should be managed separately with special emphasis on the dinghy yacht program for children. Fourthly, arrival and departure at the moorings must be regulated autonomically, and there must be systematic measures for the marina to be able, in part, to compensate for loss and damages to equipment, security and surveillance after usage fees have been paid for. Fifthly, marine safety personnel must be formed in accordance with Korea's current circumstances from civilian organizations in order to be used actively in benchmarking, rescue operations, and oceanic searches at times of disaster at sea.

[ $^{40}Ar/^{39}Ar$ ] Ages of the Tertiary Dike Swarm and Volcanic Rocks, SE Korea (한반도 남동부 제3기 암맥군과 화신암류의 $^{40}Ar/^{39}Ar$ 연대)

  • Kim Jong-Sun;Son Moon;Kim Jin-Seop;Kim Jeongmin
    • The Journal of the Petrological Society of Korea
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    • v.14 no.2
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    • pp.93-107
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    • 2005
  • We determined $^{40}Ar/^{39}Ar$ ages of the Tertiary dike swarms and volcanic rocks distributed in the SE Korea where the most prevalent crustal-deformation and volcanism occurred during the period. In previous study, it was disclosed that the mafic dike swarms on both sides (east and west) of the Yeonil Tectonic Line (YTL) were originated from a same magma although they are consistently aligned with different intrusion directions of NS and NE, respectively. Ages of the mafic dike swarms of this study are $47.3\pm0.8Ma$ and $48.0\pm1.3Ma$, respectively and confirm such conclusion. These facts clarify that the YTL acted as a westernmost limit of the crustal deformation, especially clockwise crust-rotation, during the Miocene. Frequent occurrence of basic dikes indicate strongly that the southeastern part of the Korean Peninsula was under E-W extensional stress field at about 48 Ma, intimately related to the India-Asia collision and subsequent sudden change of the Pacific Plate motion. The ages of the uncommonly appearing intermediate and felsic dikes were determined as $55.9\pm1.5Ma$ and $53.0\pm1.0Ma$, respectively. Ages of the andesitic lava of the Hyodongri Volcanics, the dacitic lava of the Yongdongri Tuff, and dacitic rocks intruding and covering the Churyeong Breccia were determined as $24.0\pm0.5Ma,\;21.6\pm0.4Ma$, $21.8\pm0.1Ma,\;and\;22.0\pm0.5Ma$ respectively. The ages from the volcanics agrees well with the stratigraphy established by the latest field survey, which confirms that the $andesitic\~dacitic$ volcanism was followed by the basaltic volcanism during the Early Miocene.

The Bonggil Pseudotachylyte, SE Korea: Its occurrence and characteristics (봉길 슈도타킬라이트: 산상과 특성)

  • Kang, Hee-Cheol;Han, Raehee;Kim, Chang-Min;Cheon, Youngbeom;Cho, Hyeongseong;Yi, Keewook;Son, Moon;Kim, Jong-Sun
    • Journal of the Geological Society of Korea
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    • v.53 no.1
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    • pp.173-191
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    • 2017
  • Pseudotachylytes, i.e., solidified friction-induced melts, are strong evidence of seismic slip on faults. Here we report pseudotachylyte (PT)-bearing faults studied in outcrops of granodiorite (SHRIMP U-Pb zircon age, $75.0{\pm}1.5Ma$) and biotite granite (SHRIMP U-Pb zircon age, $58.4{\pm}1.1Ma$) on the coast of Bonggil-ri, Yangbuk-myeon, Gyeongju, SE Korea. Three types of pseudotachylyte are identified on the basis of thickness and morphology: Single dyke-, fault vein-, and injection vein-type PT. The single dyke-type PT shows a variation of thickness from 15~40 centimeters along its strike and has an average thickness of 21 cm, which is the largest in the world, as far as we know. The PT is dark gray and neighbors with several tens meters-thick cataclasite zone. At a first glance it looks like a mafic dike, but it has a chemical composition almost identical to the wall rock of granodiorite. Also, it has many subrounded clasts which consist predominantly of quartz and feldspar and newly crystallized tiny grains (submicrometers to several micrometers in size) such as plagioclase, K-feldspar, quartz, biotite, and Fe-oxides. The feldspars and biotite are euhedral and some plagioclase grains show zoning. Flow structures and embayed clasts are also observed. A number of fault vein-type PTs occur as thin (as thick as 2 cm) layers generated on the fault plane, and striations, such as slickensides indicating slip direction, develop along the fault planes and formed during co-seismic slip at the interface between the wall rock and frictional melt. Smaller injection vein-type PTs are found along the single dyke-type PT and the fault vein-type PTs, and appear in a variety of shapes (bleb, lens, sigmoid, network, and breccia) based on field occurrence and vein geometry. All of these observations indicate the PT formed due to frictional melting of the wall rock minerals during fault slip. We propose to call the single dyke type-PT to "Bonggil Pseudotachylyte" considering the thickness of the PT and the locality of the study area. The Bonggil PT-bearing fault strikes $N54^{\circ}W$, dips to NE with an angle of $65{\sim}72^{\circ}$, shows sinistral-reverse oblique-slip sense, and can be traced continuously over ~110 m. Since $^{40}Ar/^{39}Ar$ whole rock age of the Bonggil PT is $47.3{\pm}1.4Ma$, the age of seismic faulting which is responsible for the formation of the Bonggil PT should be younger than the Middle Eocene. Further work will be conducted to understand the mechanical aspect of the PT formation.