• Title/Summary/Keyword: 간극량

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Occurrence of Sand Liquefaction on Static and Cyclic Loading (정적 및 동적 하중에서 모래의 액상화 발생)

  • 양재혁
    • Journal of the Korean Geotechnical Society
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    • v.17 no.6
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    • pp.235-244
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    • 2001
  • Liquefaction may be caused by sudden decrease in the soil strength under undrained conditions. This loss of soil strength is related to the development of excess pore pressures. During this study, fines content affects the maximum and minimum void ratios are investigated. The results of static and cyclic triaxial test on silty saturated sands are presented. These tests are performed to evaluate liquefaction strength and static and cyclic behavior characteristics. The samples are obtained from Saemangeum and drying on air. The main results are summarized as follows : 1) The maximum and minimum void ratio lines follow similar trends. 2) Maximum and minimum void ratios are established at 20~30% fines content. 3) As confining pressures and overconsolidation ratio are increased, the resistance to liquefaction are increased. 4) Instability friction angles are increased with increasing initial relative density. 5) The resistance to liquefaction are decreased with increasing effective stress ratio.

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Settlement Behavior Characteristics of CFRD in Construction Period - Case of Daegok Dam - (콘크리트 표면 차수벽형 석괴댐의 축조 중 침하거동 특성 - 대곡댐을 중심으로 -)

  • Park Han-Gyu;Kim Yong-Seong;Seo Min-Woo;Lim Heui-Dae
    • Journal of the Korean Geotechnical Society
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    • v.21 no.7
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    • pp.91-105
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    • 2005
  • In this study, the deformation behavior of Daegok dam during the construction was analyzed based on the measurement data and a comparative analysis with foreign CFRD measurements was performed. From measuring settlements of Daegok dam with depth, overall behavior was evaluated to be consistent with measured data of other CFRD dams. In addition, construction modulus, void ratio and shape factor were also evaluated to be major factors in predicting the settlement behavior during construction of CFRD-typed dam from measured data of 38 CFRD-typed dams, and the maximum internal settlement is proportional to the void ratio. From the relationship between the maximum internal settlement and the height of a dam, 26 dams were assessed to have its relative modulus ranging between 0.001 and 0.01. In case of general CFRD, the average modulus of maximum internal settlement to the height of a dam is estimated to be 0.005. In case of a low void ratio, the construction modulus was high with its shape factor below 4. On the other hand, in case of a high void ratio, the relative settlement rate was high with its shape factor more than 4.

Groundwater inflow rate estimation considering excavation-induced permeability reduction in the vicinity of a tunnel (터널 굴착으로 인한 터널인접 절리암반 투수계수 감소를 고려한 터널 내 지하수 유입량 산정방법)

  • Moon, Joon-Shik
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.15 no.3
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    • pp.333-344
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    • 2013
  • This paper discussed about the effect of permeability reduction of the jointed rock mass in the vicinity of a tunnel which is one of the reasons making large difference between the estimated ground-water inflow rate and the measured value. Current practice assumes that the jointed rock mass around a tunnel is a homogeneous, isotropic porous medium with constant permeability. However, in actual condition the permeability of a jointed rock mass varies with the change of effective stress condition around a tunnel, and in turn effective stress condition is affected by the ground water flow in the jointed rock mass around the tunnel. In short time after tunnel excavation, large increase of effective tangential stress around a tunnel due to stress concentration and pore-water pressure drop, and consequently large joint closure followed by significant permeability reduction of jointed rock mass in the vicinity of a tunnel takes place. A significant pore-water pressure drop takes place across this ring zone in the vicinity of a tunnel, and the actual pore-water pressure distribution around a tunnel shows large difference from the value estimated by an analytical solution assuming the jointed rock mass around the tunnel as a homogeneous, isotropic medium. This paper presents the analytical solution estimating pore-water pressure distribution and ground-water inflow rate into a tunnel based on the concept of hydro-mechanically coupled behavior of a jointed rock mass and the solution is verified by numerical analysis.

The Changes of Aperture Variation and Hydraulic Conductivity for Compression Variability (압력에 따른 균열 간극변화와 수리전도도 변화 관찰)

  • 채병곤;이철우;정교철;김용제
    • Journal of Soil and Groundwater Environment
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    • v.8 no.4
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    • pp.1-11
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    • 2003
  • In order to measure aperture variation dependent on normal stress and to characterize on relationship between aperture variation and hydraulic conductivity this study measured apertures of rock fractures under a high resolution confocal laser scanning microscope (CLSM) with application of five stages of uniaxial normal stresses. From this method the response of aperture can be continuously characterized on one specimen by different loads of normal stress. The results of measurements showed a rough geometry of fracture bearing non-uniform aperture. They also revealed different values of aperture variations according to the load stages on each position along a fracture due to the fracture roughness. Laboratory permeability tests were also conducted to evaluate the changes of permeability coefficients related to the aperture variations by different loads. The results of permeability tests revealed that the hydraulic conductivity was not reduced at a fixed rate with increase of normal load. Moreover, the rates of aperture variations did not match to those of hydraulic conductivity. The hydraulic conductivity calculated in this study did not follow the cubic law, representing that the parallel plate model is not suitable to express the fracture geometry corresponding to the results of aperture measurements under the CLSM.

Consolidation Behavior of Agricultural Reservoir under Embankment on Soft Ground (연약지반상(軟弱地盤上)에 축조(築造)된 농업용저수지(農業用貯水池) 제체의 압밀거동(壓密擧動))

  • Oh, Beom-Hwan;Lee, Dal-Won;Eam, Sung-Hoon
    • Korean Journal of Agricultural Science
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    • v.29 no.2
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    • pp.53-66
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    • 2002
  • This study was performed to evaluation the consolidation behavior of agricultural reservoir in the very soft ground. The final settlement prediction methods by Terzaghi, Hyperbolic and Asaoka methods were used to compare with the degree of consolidation estimated by exess pore water pressure. The dissipated excess pore water pressure during embankment construction and peak excess pore water pressure on the completed embankment were suggested for the estimation of the degree of consolidation. It was concluded that the degree of consolidation estimated from dissipated excess pore water pressure was more reliable than that from the peak excess pore water pressure. The stability methods for agricultural reservoir was used to compare and analyze with various condition by limit equilibrium method.

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Affecting Analysis of Air Content on the Freeze-Thaw Durability of Concrete (콘크리트의 동결융해 내구성에 공기량이 미치는 영향 분석)

  • Lee, Beung-Duk;Kim, Hyun-Joong;Kang, Hye-Jin
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.565-568
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    • 2008
  • Domestic area of most be happened chloride deicer damage. Because daily mean temperature is below 0$^{\circ}C$ from the area of domestic most. Concrete durability influence Air Content. Presently, We used to AE(air-entraining agent) for increase freeze-thaw durability. So, on concrete Air Spacing ratio used $200{\mu}m{\sim}230{\mu}m$ in Canada and under $250{\mu}m$ in Japan institution. Use of Air content has been and will continue to be a major part of concrete durability and scaling. Chloride-containing chemicals such as calcium chloride or rock salt are main deicers for the road. The prepared optimum mix concrete in this study show that freeze-thaw and scaling resistance of Non-AE(air content 1.5%) and AE (air content 4.5%, 7.2%). Solution concentrations of deicing agent were good result, and the pore system and change of hydration products is not difference comparing before freeze-thaw test.

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A Study on Determination of the Degree of Consolidation and Time Factor Considering Site Ground Characteristics (현장 지반특성을 고려한 압밀도 및 시간계수 결정에 관한 연구)

  • Choi, Min-Ju;Kim, Hung-Nam;Lee, Kang-Il
    • Journal of the Korean Geosynthetics Society
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    • v.21 no.1
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    • pp.23-32
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    • 2022
  • This study is conducted to minimize the problems caused by the difference between the settlement and settlement time of the one-dimensional consolidation analysis by the Terzaghi's consolidation theory, which is generally used in domestic soft soil design, from the settlement and settlement time measured at the field site. Consolidation-time factor considering the field site characteristics can be determined using the relationship among the degree of consolidation, settlement time, and time factor, the time-settlement curve measured at the field is reverse- analysis using a numerical-analysis technique to reproduce the same consolidation behavior as in the field. Time-settlement and time-excessive pore water pressure data when the same consolidation behavior as the site is reproduced Consolidation-time factor of the soil of Songsan Green City by settlement and excess pore water pressure was calculated using the settlement and excess pore water pressure for each settlement time. If the results of this study use the Terzaghi consolidation-time factor, which does not consider the consolidation characteristics of the soft ground target area, it is difficult to determine the end time of the soft ground during construction. It is necessary to use the established settlement-time factor.

Sensitivity Analysis of the Leachate Level of a Landfill to Hydraulic Properties of Cover Soil and Waste (매립장의 복토재와 폐기물 수리특성에 대한 침출수위의 민감도 분석)

  • 주완호;장연수;김용인
    • Journal of the Korean Society of Groundwater Environment
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    • v.5 no.2
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    • pp.110-115
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    • 1998
  • In this paper, the sensitivity of the leachate level is analyzed using the program HELP to reduce the high leachate level on the landfill. Hydraulic parameters analyzed were porosity, field capacity, wilting point and initial water content of cover soil and waste. Also, the influence of the difference between the initial water content and the field capacity on the leachate level in the landfill was analyzed. The results of the sensitivity analysis show that the increase of the porosity and the wilting point decreases the leachate level, while the increase of the field capacity and the hydraulic conductivity increases the leachate level. Major parameters to the change of the leachate level were the hydraulic conductivity in the case of cover soil and the porosity, the field capacity and the initial water content in the case of waste.

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Relation between Groundwater Inflow into the Waterway Tunnel and Hydrogeological Characteristics in Hyeonseo-myeon, Cheongsong-gun, Korea (청송군 현서면 일대 도수로터널내 지하수 유입량과 수리지질 특성의 관련성)

  • 박재현;함세영;성익환;이병대;정재열
    • The Journal of Engineering Geology
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    • v.11 no.2
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    • pp.141-152
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    • 2001
  • The waterway tunnel zone (length 1,484m) in the Hyeonseo-myeon area that is a part of Yeongcheon dam waterway tunnel has been studied to characterize the relationship between groundwater inflow into the waterway tunnel and hydrogeologic characteristics. The effects of sandstone thickness in the tunnel section. fracture density, fracture aperture and spacing, fault zone width and hydraulic conductivity on the early inflow (inflow prior to the lining and grouting) are investigated. The relationship between fracture density and hydraulic conductivity is also considered. The result of the study suggests that fault zone width has the greatest effect on groundwater inflow into the tunnel, and sandstone thickness, hydraulic conductivity and fracture density in order shows an influence on the inflow.

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Comparative Study of Tip Clearance Loss in Impulse and Reaction Turbine Cascades (충동터빈과 반동터빈 캐스케이드에서의 팁 간극 손실에 대한 비교 연구)

  • Park, Kyung-Wook;Jung, Eun-Hwan;Song, Seung-Jin
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.11a
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    • pp.145-148
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    • 2008
  • Korea Aeronautics Research Institute (KARI) is developing a turbo pump that has 1-stage impulse turbine and relatively high tip clearance for safety. The objective of this research is to investigate the effect of reaction on tip clearance loss in axial turbines. Both cascades were tested in a subsonic wind tunnel. In each cascade, total pressure was measured for tip clearance ranging from 1% to 20% of chord. In results, increasing tip clearance, total pressure loss in reaction turbines is continually increased but impulse turbines keep almost same level of mass averaged total pressure loss. When tip clearance becomes more than 10% of chord, mass-averaged total pressure loss in impulse turbines is less than in reaction. This means that when tip clearance is more than 10% of chord, impulse turbines have better efficiency than reaction turbines.

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