• Title, Summary, Keyword: 영구동토층

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Evaluation of Active Layer Depth using Dynamic Cone Penetrometer (동적 콘 관입기를 이용한 활동층 심도평가)

  • Hong, Won-Taek;Kang, Seonghun;Park, Keunbo;Lee, Jong-Sub
    • Journal of the Korean Geoenvironmental Society
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    • v.17 no.1
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    • pp.49-54
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    • 2016
  • An active layer distributed on surface of an extreme cold region causes a frost heave by repeating the freezing and thawing according to the seasonal temperature change. Since the height of frost heave is greatly affected by the thickness of active layer, an accurate evaluation of the thickness of active layer is necessary for the safe design and construction of the infrastructure in the extreme cold region. In this study, dynamic cone penetrometer, which is miniaturized in-situ penetration device, is applied for the evaluation of active layer depth distribution. As the application tests, two dynamic cone penetration tests were conducted on the study sites located in Solomon and Alaska. In addition, ground temperature variations were obtained. As the results of the application tests, the depth of interface between the active layer and the permafrost was evaluated from the difference in dynamic cone penetration indexes of the active layer and the permafrost, and a layer was detected around the interface considered as an ice lens layer. Also, the interface depths between the above zero and the below zero temperature determined from the ground temperature variations correspond with the interface depths evaluated from the dynamic cone penetration tests. This study demonstrates that the dynamic cone penetrometer may be a useful tool for the evaluation of the active layer in the extreme cold region.

Seismic Amplification Characteristics of Eastern Siberia (동시베리아 지역의 지진 증폭 특성)

  • Park, Du-Hee;Kwak, Hyung-Joo;Kang, Jae-Mo;Lee, Yong-Gook
    • Journal of the Korean Geotechnical Society
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    • v.30 no.10
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    • pp.67-80
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    • 2014
  • The thickness of permafrost in Eastern Siberia is from 200 to 500 meters. The seasonally frozen layer can vary from 0 to 4m depending on ground temperature and its location. The shear wave velocity varies from 80m/s in summer to 1500m/s in winter depending on soil type. When melted, large impedence will occur due to the difference between the shear wave velocity of seasonally frozen soil and that of permafrost layer. Large displacement may occur at the boundary of the melted and the frozen layer, and this phenomenon should be considered in a seismic design. In this research, one-dimensional equivalent linear analyses were performed to investigate the effects of the seasonally frozen layer on ground amplification characteristics. Soil profiles of Yakutsk and Chara in Eastern Siberia were selected from geotechnical reports. 20 recorded ground motions were used to evaluate the effect of input motions. As the thickness of seasonally frozen layer and the difference in the shear wave velocity increases, the amplification is shown to increase. Peat, very soft organic soil widely distributed throughout Eastern Siberia, is shown to cause significant ground motion amplification. It is therefore recommended to account for its influence on propagated motion.

Finite Element Analysis of Gas Pipelines Depend on the Arctic of Active Region (극한지 활동층 변화에 따른 천연가스배관의 유한요소해석)

  • Yeom, Kyu Jung;Kim, Kyung Il;Kim, Young-Pyo;Oh, Kyu Hwan;Kim, Woo Sik
    • Journal of the Korean Institute of Gas
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    • v.18 no.5
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    • pp.72-77
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    • 2014
  • It is known that there is no demand for building the arctic environment in Korea. However, it is important to use the different energy source instead of fuel source due to global warming. It is now demanded of using gas of Alaska and Siberia for long term developing the natural gas. The design of gas pipelines in Korea is very different from the arctic region. The operation of gas in arctic region have to consider of arctic region such as permafrost and active regions. It is needed to understand of gas pipeline design with different arctic soil properties. Nowadays, the pipelines is designed with stress-based and but there is demanded for strain based design with more deformed pipeline. We study of arctic environment with different active region using Finite Element Method of thermal elasto-plastic analysis.

Evaluation on Thermal Performance of Thermosyphon by Numerical Analysis (열사이펀의 열성능 산정을 위한 수치해석 연구)

  • Jang, Changkyu;Choi, Changho;Lee, Jangguen;Lee, Chulho
    • Journal of the Korean Geotechnical Society
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    • v.30 no.9
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    • pp.57-66
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    • 2014
  • The ground in cold region consists of active and permafrost layers. The active layer at the unstable state may cause ground corrosion and uplift, when the temperature of frozen ground increases due to seasonal changes. The thermosyphon is one of the stabilization methods to maintain the ground stability in the frozen ground. The thermosyphon is a closed two-phase convection device that extracts heat from the ground and discharges it into the atmosphere. In this study, ground freezing experiment using a thermosyphon and simulated ground with the isolation material was conducted to evaluate the thermal performance of the thermosyphon. In order to consider the thermal performance of the thermosyphon, commercial numerical program (TEMP/W) was adopted. Likewise, the thermal performance of thermosyphon and thermal properties of ground were applied in the numerical model. In a series of comparisons with experiment results and numerical study, thermal performance of thermosyphon can be evaluated.

A Case Study of Test Production of Gas from Hydrate Bearing Sediments on Nankai Trough in Japan (일본 난카이 해구 가스하이드레이트 퇴적층으로부터의 가스 시험생산 사례분석)

  • Kim, A-Ram;Lee, Jong-Won;Kim, Hyung-Mok
    • Tunnel and Underground Space
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    • v.25 no.2
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    • pp.133-143
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    • 2015
  • Gas hydrate is a solid substance composed of natural gas constrained in water molecules under low temperature and high pressure conditions. The existence of hydrates has been reported to be world-widely distributed, mainly at permafrost and deep ocean floor. Test productions of small amount of natural gas from the on-shore permafrost have been accomplished in U.S.A and Canada, but, world-first and the only production case from off-shore hydrate bearing sediments was in Nankai trough, Japan. In this study, we introduce key technologies in gas production from hydrates by analyzing the Japanese off-shore gas production project in Nankai trough in terms of depressurization- induced dissociation so as to utilize planned domestic gas production test in Ulleung basin.

Experimental and Numerical Investigation of the Performance of Vertical Thermosyphon for Frozen Ground Stabilization (실험과 수치해석을 통한 동토지반 안정화용 수직형 열사이펀의 성능평가)

  • Lee, Jangguen;Lee, Chulho;Jang, Changkyu;Choi, Changho
    • Journal of the Korean Geosynthetics Society
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    • v.13 no.4
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    • pp.45-56
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    • 2014
  • Frozen ground in cold region consists of an upper active layer and lower permafrost which is permanently frozen land. During the summer season, the air temperature is high enough to make the frozen ground melt, which causes the reduction of soil strength and thaw settlement. These phenomena result in structural instability, so it is necessary to apply frozen ground stability techniques. Thermosyphon is a closed natural two-phase convection device to maintain the ground temperature below $0^{\circ}C$ by extracting heat from the ground and discharges it into the atmosphere. Experimental and numerical investigation has been performed to estimate the effect of the refrigerant filling ratio in thermosyphon using R-134a refrigerant and the thermal conductance of the thermosyphon.

Sharing the Experience of Mars Desert Research Station

  • Kim, Byung Man;Moon, Kyung Soo
    • The Bulletin of The Korean Astronomical Society
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    • v.43 no.2
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    • pp.31.2-31.2
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    • 2018
  • 미국 유타주 유타사막에 설치된 MDRS(Mars Desert Research Station)는 미국의 비영리기구인 화성학회(The Mars Society)에서 운영하는 화성탐사연구기지다. 화성학회는 1998년 우주비행사, 천문학자, 과학자 4000여명이 모여 만든 비영리연구단체다. 2001년 미국 유타주에 문을 연 MDRS에서는 토양 미생물 검출실험, 태양에너지 조리실험, 영구동토층 연구, 해빙 연구, 드론 정찰 및 지도 작성 등 인류가 화성에 도착했을 때 실제 수행할 연구들을 진행하고 있다. tVN <갈릴레오 : 깨어난 우주> 촬영 차 MDRS에 머물며 과학실험을 수행한 사례를 공유하고 이를 통해 천문학 및 우주탐사에 대한 대중화 방안에 대해 논의해 보고자 한다.

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Morphogenetic Environment of Jilmoe Bog in the Odae Mountain National Park (오대산국립공원 내 "질뫼늪"의 지형생성환경)

  • Son, Myoung-Won;Park, Kyeong
    • Journal of the Korean association of regional geographers
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    • v.5 no.2
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    • pp.133-142
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    • 1999
  • The wetland is very important ecologically as a habitat of diverse organisms. The purpose of this paper is to elucidate the morphogenetic environment of Jilmoe Bog found in the Odae Mountain National Park Jilmoe Bog is located in the high etchplain(1,060m) where Daebo Granite which had intruded in Jura epoch of Mesozoic era has weathered deeply and has uplifted in the Tertiary. The annual mean temperature of study area is $5.3^{\circ}C$, the annual precipitation is 2,888mm. The minimun temperature of the coldest month(january) is below $-30^{\circ}C$ and the depth of frozen soil is over 1.6m. Jilmoe bog consists of a large bog and a small bog. The length of the large bog is 63m and its width is 42m. The basal surface of Jilmoe bog is uneven. Jilmoe bog is a string bog fanned due to frost actions. In String bog, its surface is wavy with stepped dry hills and net-like troughs crossing hill slope. It seems that string bog is related to the permofrost or seasonal permofrost of cold conifer forest(taiga) zone(where the depth of frozen soil is very deep in the least in winters). String bog is a kind of thermokarst that frozen soil thaws differentially locally in declining permofrost and ground surface becomes irregular. There is turf-banked terracette of width $30{\sim}40cm$ in the headwall of small cirque-type nivation hollow formed at footslope of Maebong mountain around Jilmoe bog. This turf-banked terracette is formed by the frost growth of soil water below grass mat in periglacial climate environment. Where water is plentiful such as a nivation follow${\sim}$valley corridor and a headwall of valley, turf patterned grounds of width $30{\sim}50cm$ are found. This turf patterned ground is 'unclassified patterned ground', earth hummock. In conclusion, Jilmoe bog is a string bog of thermokarst that the relief of ground surface is irregular according to locally differentially thawing of permofrost(frozen soil). Jilmoe bog is high moor, its surroundings belongs to periglacial environment that turf-banked terracette and turf patterned ground are fanned actively.

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Experimental and Field Investigations for the Accuracy of the Frost Depth Indicator with Methylene Blue Solution (실내실험과 현장실험을 통한 Methylene Blue 동결깊이 측정장치 신뢰성 검토에 관한 연구)

  • Kim, Hak Seung;Lee, Jangguen;Kim, Young Seok;Kang, Jae-Mo;Hong, Seung-Seo
    • Journal of the Korean Geosynthetics Society
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    • v.12 no.3
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    • pp.75-79
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    • 2013
  • The frost depth is one of important factors in the design of structures such as roadways, buried pipeline, and foundations. A frost indicator with methylene blue solution has several advantages with respect to installation cost, maintenance, and simple measurement. However, as a geotechnical engineering aspect, the accuracy of the frost indicator has not been proved yet. This paper presents experimental and field investigations of the accuracy of the frost indicator and contour maps of maximum frost depth. The contour maps of maximum frost depth can be applied to design geo-infrastructure in South Korea.

A Patent Analysis on the Gas Hydrate Exploration and Development (특허정보를 통한 가스하이드레이트 기술동향 분석)

  • Lee, Jae-Wook;Kim, Seong-Yong
    • 한국신재생에너지학회:학술대회논문집
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    • pp.403-406
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    • 2006
  • 최근 막대한 매장량으로 인해 미래의 비재래형 에너지원으로 주목받고 있는 천여가스 하이드레이트는 고압 저온 환경에서 수소결합을 하는 고체상 격자 내에 객체분자인 가스분자가 포획되어 형성된 가스하이드레이트의 일종으로 영구 동토지역과 심해저의 퇴적층에 광범위하게 분포되어 있다. 본 연구에서는 이러한 가스하이드레이트의 개발기술과 천연가스의 저장과 운송기술에 관한 미국 일본 유럽 등 특허 3극 및 한국 특허 총 357건을 추출하고 특허정보 분석을 실시하여 국내외 기술개발 동망 및 기술변화 추이를 살펴보았다. 특허 검색에 사용된 DB와 분석도구는 특허청 선행기술 전문조사기관 등으로 지정된 (주)윕스사의 WIPS와 ThinKlear이며, 미국/일본/유럽 등 특허 3극과 한국에서 공개 또는 등록된 특허를 검색대상으로 하였다 자원으로서 천연가스 하이드레이트를 개발하는 기술과 관련하여 총 193건의 특허가 추출되었으며, 이 때 사용하는 방법에는 감압법, 열처리법, 억제제 주입법 등이 있었다. 또한 연료용 가스, 특히 메탄가스의 수송 및 저장에는 통상 액화하여 액화천연가스로 수송하는 방법이 사용되고 있으나 가스하이드레이트를 이용할 경우 액화천연가스를 이용하는 것보다 더 경제적임이 보고되면서 이와 관련된 연구가 활발히 진행 중이며, 총 164건의 특허가 추출되었다. 상기 추출된 총 357건을 대상으로 연도별 출원동향, 국가별 점유율 및 시계열 분석, 분류기술별 출원동향 등의 특허정보 분석을 수행하였다.

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