• Title/Summary/Keyword: 간극량

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Characterization of Physical Factor of Unsaturated Ground Deformation induced by Rainfall (강우를 고려한 불포화 지반변형의 영향인자 평가)

  • Kim, Man-Il;Jeon, Gyo-Cheol
    • The Journal of Engineering Geology
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    • v.18 no.2
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    • pp.127-136
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    • 2008
  • Geophysical survey for establishing a wide site for the distribution of water content, wetting front infiltration due to the rainfall, and distribution of groundwater level has been performed by using 8round penetration radar (GPR) method, electrical resistivity method, and so on. On the other hand, a narrow area survey was performed to use a permittivity method such as time domain reflectometry, frequency domain reflectometry, and amplitude domain reflectometry methods for estimating volumetric water content, soil density, and concentration of contaminant in surface and subsurface. The permittivity methods establish more corrective physical parameters than different found survey technologies mentioned above. In this study for establishment of infiltration behaviors for wetting front in the unsaturated soil caused by an artificial rainfall, soil physical parameters for volumetric water content, pore water pressure, and pore air pressure were measured by FDR measurement device and pore water pressure meter which are installed in the unsaturated weathered granite soil with different depths. Consequently, the authors were proposed to a new establishment method for analyzing the variations of volumetric water content and wetting front infiltration from the responses of infiltrating pore water in the unsaturated soil.

A Study on Settlement Prediction of Concrete-faced Rockfill Dam Using Measured Data During Construction and After Impounding (시공 중 및 담수 후 계측데이터를 이용한 CFRD의 침하량 예측 연구)

  • Lee, Chungwon;Kim, Yongseong
    • Journal of the Korean GEO-environmental Society
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    • v.16 no.2
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    • pp.5-13
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    • 2015
  • In the present study, the prediction methods of the crest settlement after impounding and the maximum internal settlement during dam construction were proposed through the analysis on settlement data at 38 monitored points of 36 Concrete-Faced Rockfill Dams (CFRDs). The results from this analysis provided that the crest settlement and the maximum internal settlement are increased in proportion to the dam height and the void ratio. However, the relationship between internal settlement and dam height for each void-ratio range plotted in semi-logarithmic scale is the nearly same. Also, the prediction of the crest settlement of the CFRD is possible through the maximum internal settlement during dam construction. In addition, it seems that the valley shape highly affects the dense dam body with high construction modulus. The results of this study will provide the useful tool for the design, construction and management of CFRDs.

Structural Analysis of Built-in Side-by-Side Refrigerator with Ice Dispenser and Home Bar and Evaluation of Door Differences and Gasket Gap (얼음디스펜서와 홈바가 있는 빌트인 양문형 냉장고의 구조해석 및 도어 단차와 개스킷 간극의 평가)

  • Ryu, Si-Ung;Lee, Boo-Youn
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.19 no.9
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    • pp.465-473
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    • 2018
  • A cabinet-door integrated finite element model for a built-in side-by-side refrigerator with an ice dispenser and home bar was constructed, and its deformation was analyzed by ANSYS. As loads, the food load in the shelf and baskets, and thermal load occurring during the normal operation condition were considered. From results of the analyses, the door height difference (DHD) and door flatness difference (DFD) between the two doors, and the increase in the gap of the door gasket, which affects the sealing of cool air in the cabinet, were derived. As results of an evaluation of the differences, the DHD and DFD under the assembled condition satisfied the acceptance criteria of the manufacturer. The food and thermal loads increased the DHD and DFD due to thermal deformation, and the DFD increased significantly. In addition, the increase in the gap of door gasket located between the cabinet and doors was derived from the results of displacements under the food and thermal loads. The evaluation showed that the maximum increase in gap appeared at the left edge of the freezing compartment gasket, which satisfied the acceptance criteria of the manufacturer.

Experimental Studies of Shearing Properties on Compacted Nakdong River Silty Sands under Unconsolidated Undrained Condition (비압밀비배수조건에서 다져진 낙동강 실트질 모래의 전단거동에 대한 실험적 연구)

  • Khin, Swe Tint;Kim, Young-Su
    • Journal of the Korean GEO-environmental Society
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    • v.11 no.12
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    • pp.57-62
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    • 2010
  • In this study, the effect of different silt contents on the shear characteristics of silty sands was evaluated. Two series of triaxial compression tests were performed on the cylindrical specimens of compacted Nakdong river sand with 10% and 30% silt contents under unconsolidated undrained condition. All identical specimens were prepared to compact with same initial water content for five layers and saturated using control panel and then sheared under initial effective confining pressure, 100 to 400kPa. All specimens exhibited a strain softening tendency after failure in stress-strain curves and deviator stresses of specimens with 10% silt content were greater than those of specimens with 30% silt content. Pore water pressures of specimens with 10% silt content were observed negative(i.e. swelling) due to increasing void ratio after failure but those of specimens with 30% silt content were shown only positive. The behavior of compacted cylindrical specimens with low silt content was more dilative than that of high silt content. Peak deviator stresses decreased as increasing silt content and peak pore water pressures increased as increasing silt content.

Monitoring of Fill Dams for Internal Defect via Centrifuge Model Tests (원심모형시험을 이용한 필댐 취약부 모니터링)

  • Choo, Yun Wook;Cho, Sung Eun;Shin, Dong Hoon
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.32 no.2C
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    • pp.37-47
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    • 2012
  • In this study, three centrifuge tests were performed to evaluate the feasibility of three physical quantities for detecting internal defect of earth core fill dam: pore water pressure, temperature, and electrical resistance. For this purpose, the measurement system for pore water pressure, temperature and electrical resistance on centrifuge model dams was established. Three centrifuge tests included a fill dam without internal defect and two other dams with artificial internal defect in the core. The effectiveness of seepage monitoring was examined during the centrifuge test. Test results showed the applicability of monitoring techniques to detect internal defect by monitoring pore water pressure, temperature, and electrical resistance.

Behaviour of the Excess Pore Pressure Induced by Sand Mat on the Soft Clay (점토지반 샌드매트의 간극수압 거동)

  • Kim, Hyeong-Joo;Lee, Min-Sun;Paek, Pil-Soon;Jeon, Hye-Sun
    • Journal of the Korean Geotechnical Society
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    • v.22 no.8
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    • pp.55-62
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    • 2006
  • The design of sand mat should be reviewed by the behaviour of excess pore pressure which is obtained by combining characteristics of soft ground with the permeability of sand mat. In this paper, in order to investigate the distribution of hydraulic gradient of sand mat, a banking model test was performed using dredged sand as materials of sand mat, and these results were compared by the numerical analysis results utilizing Terzaghi's consolidation equation. The results show that the pore pressure was influenced by the settlement increasing in the central area of sand mat as the height of embankment increases, and uprising speed of excess pore pressure due to residing water pressure is delayed compared with the results of numerical analysis. Finally, the construction of sand mat should be spreaded to reduce the increased hydraulic gradient at the central area of embankment.

Centrifuge Test and Its Numerical Modeling for Reliquefaction (재액상화에 관한 원심모형실험과 수치해석)

  • Park, Sung-Sik
    • Journal of the Korean Geotechnical Society
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    • v.22 no.12
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    • pp.89-98
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    • 2006
  • In this paper the behavior of saturated sand deposits where liquefaction occurred before is studied for successive earthquakes. The relationship between past pore pressure generation and reliquefaction resistance is examined by using cyclic direct simple shear tests. If the soil sample in direct simple shear produced nearly 90% of excess pore pressure during first time loading, its liquefaction resistance increased during following cyclic loading after consolidation. However, a fully liquefied soil during first time loading has a densely packed condition but shows less liquefaction resistance for the following cyclic loading. UBCSAND model that can account for pore pressure change and stiffness loss of soil during shaking is used to analyze the centrifuge test simulating reliquefaction. The pore pressure rise during first time cyclic loading controls liquefaction resistance. The measurements from reliquefaction centrifuge test are compared with numerical predictions. By considering frequent earthquakes having occurred at the Southern Korea near Japan, such effective stress approach is necessary for reliquefaction study.

Assessment of groundwater inflow rate into a tunnel considering groundwater level drawdown and permeability reduction with depth (터널굴착 중 지하수위 강하 및 깊이별 투수계수 변화를 적용한 지하수 유입량 변화 분석)

  • Moon, Joon-Shik;Zheng, An-Qi;Jang, Seoyong
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.19 no.2
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    • pp.109-120
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    • 2017
  • Groundwater seepage into a tunnel is one of the main causes triggering tunnel collapse and the consequent ground subsidence. Thus, it is important to estimate adequately the groundwater inflow rate and porewater pressure change during tunneling with time elapse. In current practice, Goodman's analytical solution (or image tunnel method) assuming homogeneous ground condition around a tunnel is commonly used for estimating groundwater inflow rate. However, the generally-used analytical solution for estimating groundwater inflow rate does not consider groundwater level drawdown and permeability change with depth, and the inflow rate can be overestimated in design phase. In this study, parametric study was performed in order to investigate the effect of groundwater level drawdown and permeability reduction with depth, and transient flow analysis was carried out for studying the inflow rate change as well as groundwater level and porewater pressure change around a tunnel with time elapse.

Estimation of the Permeability Variation in Saturated Sand Deposits Subjected to Shaking Load Using 1-g Stinking Table Test (1-g 진동대시험을 이용한 진동하중을 받는 포화된 모래지반의 투수계수 변화 추정)

  • 하익수;김명모
    • Journal of the Korean Geotechnical Society
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    • v.19 no.6
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    • pp.363-369
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    • 2003
  • The purpose of this study is to understand the dissipation pattern of excess pore pressure after liquefaction and to estimate the variation in permeability during shaking load, which should be known for settlement predictions of the ground undergoing liquefaction. In this study, 1-g shaking table tests were carried out for 5 different kinds of sands, all of which had high liquefaction potentials. During the tests excess pore pressure at various depths, and surface settlements were measured. The measured dissipation curve of the excess pore pressure after liquefaction was linearly simulated using the solidification theory, and from the analysis of the slopes of linearly simulated curves, the correlation between dissipation velocity and the gradation characteristics was obtained. By substituting this correlation and the measured settlement to the dissipation velocity equation recommended in solidification theory, the permeability during dissipation was calculated, which was used for estimating the permeability variation during shaking load. The dissipation velocity of excess pore pressure after liquefaction had a linear correlation with the effective grain size divided by the coefficient of uniformity. The permeability during dissipation and liquefaction increased by 1.1∼2.8 times and 1.4∼5 times compared to the initial permeability of the original ground, respectively. And the amount of increase became greater as the effective grain size of the test sand increased and the coefficient of uniformity decreased.

Inception of Tip Vortex Cavitation on Ducted Rotors (덕트 로터의 날개끝 보오텍스 캐비테이션 초기발생특성)

  • K.S. Kim;K.Y. Kim;J.W. Ahn;J.T. Lee;E.D. Park;H.B. Chae;H.S. Lee
    • Journal of the Society of Naval Architects of Korea
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    • v.36 no.1
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    • pp.37-46
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    • 1999
  • The influence of the tip clearance upon the cavitation inception were investigated by experiments for ducted rotors having different tip clearances The axial and tangential mean velocities around the ducted rotors were measured using an L.D.V. system to investigate the correlation between tip vertex cavitation inception and hub vortex cavitation. Observation results for tip vortex cavitation and hub vortex cavitation show good agreement in trend with the analysis results of velocity measurement. An optimum tip clearance for ducted rotor was selected to delay the tip vortex cavitation.

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