• Title/Summary/Keyword: High permeability

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Considerations of Permeability of Converter Slag for Recycling in vertical drainage method (연직배수공법에 있어서 제강슬래그의 재활용을 위한 투수성 연구)

  • 이광찬;정규향;김영남;이문수
    • Proceedings of the Korean Geotechical Society Conference
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    • 2000.02a
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    • pp.93-112
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    • 2000
  • The permeability of converter slag, replacing material of sand mat on improving soft clay foundation, was evaluated in the laboratory. The effects of grain size, flow water time and aging were investigated using sea and fresh water. Converter slag being submerged with fresh water, the coefficients of permeability in A and B samples less than 10mm grain sizes were measured as 6.52${\times}$10$\^$-2/cm/sec and 5.99${\times}$10$\^$-1/cm/sec, while changed as 1.88${\times}$10$\^$-2/cm/sec, 3.86${\times}$10$\^$-1/cm/sec under sea water condition. Also, the condition of turbulent flow may exit and was experimentally identified from the relationship between hydraulic gradient and seepage velocity. After 180 days on using sea water, the coefficients of permeability of sample A and B samples decreased ten times smaller than those initial values. And after that time continually decreased as for till 360 days. The reduction of permeability coefficient was considered to influence filled with voids in high-calcium quicklime(CaO). However, in-situ coefficient of permeability was practically satisfactory.

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Considerations of Permeability of Converter Slag for Recycling in vertical drainage method (연직배수공법에 있어서 제강슬래그의 재활용을 위한 투수성 연구)

  • 이광찬;정규향;김영남;이문수
    • Proceedings of the Korean Geotechical Society Conference
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    • 2000.02a
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    • pp.12-31
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    • 2000
  • The permeability of converter slag, replacing material of sand mat on improving soft clay foundation, was evaluated in the laboratory. The effects of grain size, flow water time and aging were investigated using sea and fresh water. Converter slag being submerged with fresh water, the coefficients of permeability in A and B samples less than 10mm grain sizes were measured as 6.52${\times}$10$\^$-2/cm/sec and 5,99${\times}$10$\^$-1/cm/sec, while changed as 1,88${\times}$10$\^$-2/cm/sec, 3.86${\times}$10$\^$-1/cm/sec under sea water condition. Also, the condition of turbulent flow may exit and was experimentally identified from the relationship between hydraulic gradient and seepage velocity. After 180 days on using sea water, the coefficients of permeability of sample A and B samples decreased ten times smaller than those initial values. And after that time continually decreased as for till 360 days. The reduction of permeability coefficient was considered to influence filled with voids in high-calcium quicklime(CaO). However, in-situ coefficient of permeability was practically satisfactory.

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Permeability Measurement of a Circular Braided Preform for Resin Transfer Molding

  • Cho, Yun Kyoung;Song, Young Seok;Kang, Tae Jin;Chung, Kwansoo;Youn, Jae Ryoun
    • Fibers and Polymers
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    • v.4 no.3
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    • pp.135-144
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    • 2003
  • Permeability of the preform is one of key factors in design of RTM (Resin Transfer Molding) mold, determination of processing conditions, and modeling of flow in the mold. According to previous studies, permeability measured in the unsaturated fiber mats are higher than that in the saturated fiber mats by about 20% because of the capillary pressure. In this study, permeabilities of several fiber preforms are measured for both saturated and unsaturated flows. A saturated experiment of radial flow has been adopted to measure the permeability of anisotropic fiber preforms with high fiber content, i.e., circular braided preforms. In this method, four pressure transducers are used to measure the pressure distribution. Permeabilities in different directions are determined and the experimental results show a good agreement with the theory. Since permeability is affected by the capillary effect, permeability should be measured in the unsaturated condition for the textile composites to be manufactured under lower pressure as in the Vacuum Assisted Resin Transfer Molding (VARTM).

Numerical study on PEM fuel cell performance with variation of GDL permeability and channel geometry (기체확산층의 유동투과율과 채널 형상 변화에 따른 고분자 전해질 연료전지 성능변화 수치연구)

  • Koh, Soo-Gon;Sohn, Sang-Ho;Nam, Jin-Hyun;Kim, Charn-Jung
    • Proceedings of the KSME Conference
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    • 2008.11b
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    • pp.3114-3119
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    • 2008
  • Relatively high convective flow exists in the under-rib regions of a gas diffusion layer (GDL) when serpentine flow fields are employed in a PEMFC. This under-rib convection is believed to be favorable for the performance of PEMFCs, by enabling more effective use of catalysts in the under-rib regions. From the fact that the under-rib convection in a GDL is directly proportional to the permeability of the GDL, computational fluid dynamics (CFD) simulations were performed to discover the relationship between the GDL permeability and the PEMFC performance. Single-, triple-, and quintuple-path parallel serpentine flow fields for $9\;cm^2$ active cell area were considered while changing the GDL permeability from $1{\times}10^{-12}$ to $5{\times}10^{-11}m^2$. The results showed that higher GDL permeability generally resulted in better performance of PEMFCs, but the degree of performance enhancement became smaller as the parallel path number increased. The effects of the permeability on the local variables were also discussed.

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Nondestructive Evaluation for Mechanical Degradation of Ultrasuper-Critical Heat-Resistance Steel by Reversible Permeability (가역투자율를 이용한 초초임계압 내열강의 기계적 열화에 관한 비파괴평가)

  • Ahn, SeongBin;Kim, JaeJin;Seo, DongMin;Kim, ChungSeok
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.17 no.6
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    • pp.46-52
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    • 2018
  • Nondestructive evaluation for mechanical degradation of ultrasuper-critical (USC) heat-resistance steel, which is attractive to the next generation of power plants is studied by magnetic reversible permeability. The interrelationship between reversible permeability and high-temperature mechanical degradation has been investigated by precise measurement of permeability nondestructively. Also, the effects of microstructural variation on reversible permeability are discussed. Isothermal aging was observed to coarsen the tempered carbides ($Cr_{23}C_6$), generated the intermetallic phases ($Fe_2W$), and grow rapidly during aging. The dislocation density also decreases steeply within lath interior. The peak to peak interval (PPI) of reversible permeability profile decreased drastically during the initial 500 h aging period, and was thereafter observed to decrease only slightly. The variation in PPI is closely related to the decrease in the number of pinning sites and the degradation in tensile strength.

Experimental study on seepage characteristics of large size rock specimens under three-dimensional stress

  • Sun, Wenbin;Xue, Yanchao;Yin, Liming;Zhang, Junming
    • Geomechanics and Engineering
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    • v.18 no.6
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    • pp.567-574
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    • 2019
  • In order to study the effect of stress and water pressure on the permeability of fractured rock mass under three-dimensional stress conditions, a single fracture triaxial stress-seepage coupling model was established; By using the stress-seepage coupling true triaxial test system, large-scale rock specimens were taken as the research object to carry out the coupling test of stress and seepage, the fitting formula of permeability coefficient was obtained. The influence of three-dimensional stress and water pressure on the permeability coefficient of fractured rock mass was discussed. The results show that the three-dimensional stress and water pressure have a significant effect on the fracture permeability coefficient, showing a negative exponential relationship. Under certain water pressure conditions, the permeability coefficient decreases with the increase of the three-dimensional stress, and the normal principal stress plays a dominant role in the permeability. Under certain stress conditions, the permeability coefficient increases when the water pressure increases. Further analysis shows that when the gob floor rock mass is changed from high stress to unloading state, the seepage characteristics of the cracked channels will be evidently strengthened.

A predicting model for thermal conductivity of high permeability-high strength concrete materials

  • Tan, Yi-Zhong;Liu, Yuan-Xue;Wang, Pei-Yong;Zhang, Yu
    • Geomechanics and Engineering
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    • v.10 no.1
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    • pp.49-57
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    • 2016
  • The high permeability-high strength concrete belongs to the typical of porous materials. It is mainly used in underground engineering for cold area, it can act the role of heat preservation, also to be the bailing and buffer layer. In order to establish a suitable model to predict the thermal conductivity and directly applied for engineering, according to the structure characteristics, the thermal conductivity predicting model was built by resistance network model of parallel three-phase medium. For the selected geometric and physical cell model, the thermal conductivity forecast model can be set up with aggregate particle size and mixture ratio directly. Comparing with the experimental data and classic model, the prediction model could reflect the mixture ratio intuitively. When the experimental and calculating data are contrasted, the value of experiment is slightly higher than predicting, and the average relative error is about 6.6%. If the material can be used in underground engineering instead by the commonly insulation material, it can achieve the basic requirements to be the heat insulation material as well.

A Nitrogen Permeability Experiment with the Various Thickness of Concrete (콘크리트 두께에 따른 질소투과계수 영향실험)

  • 이명규;정상화;김도현
    • Proceedings of the Korea Concrete Institute Conference
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    • 2002.05a
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    • pp.767-772
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    • 2002
  • Using the diffusion cell, a experimental study on the nitrogen permeability was performed with the various thickness of concrete. This is important with relating to the carbonation study because the study of $CO_2$ diffusivity needs to use thin concrete specimen. Experimental results show that the nitrogen permeability is few affected by concrete specimen's thickness. But, specimens with 1cm thickness have a high permeability and deviation relatively. Also, specimens with w/c ratio 0.40 have a low permeability than 0.58. Consequently, the 3cm thickness is the better stable than others but the 1cm thickness specimens will be stable in case having a lot of specimens.

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Influence of Theoretical Void Ratio, Grading of Aggregate and Curing Method on Strength and Water Permeability of Porous Concrete (이론공극율, 골재입도 및 양생방법이 포러스콘크리트의 강도 및 투수성능에 미치는 영향)

  • 김재환;유범재;최세진;백용관;박정호;김무한
    • Proceedings of the Korea Concrete Institute Conference
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    • 2000.10a
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    • pp.373-378
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    • 2000
  • The objective of this study was to investigate the influence the influence of theoretical void ratio(T.V.R), grading of aggregate and curing method on the strength and water permeability of porous concrete, and the reduction proportion of water permeability by these factors. The results of the study showed that its strength and water permeability were greatly depended on the T.V.R and grading of aggregate, but didn't on the curing method. And, when the T.V.R and grading of aggregate were increased, the reduction proportion of water permeability was small. As the relation ship between its physical properties and non-destruction test values was very high, its use for the estimation of the physical properties will be useful.

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Permeability of Self-Consolidating Concrete (고유동 콘크리트의 투수성에 관한 연구)

  • 김민석;최석환
    • Proceedings of the Korea Concrete Institute Conference
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    • 2003.11a
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    • pp.156-159
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    • 2003
  • Large amount of binders and high-range AE water-reducing (HRWR) agent are required for self-consolidating concrete in order to achieve flowability and segregation resistance. In this study, the initial permeability of SSC(self-consolidating concrete) until the age of 28 days is measured and compared with those of other SSCs, in which some parts of cement are substituted with fly ash or blast furnace slag. The strengths of SSC samples are also examined along with the permeability change.

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