• Title/Summary/Keyword: Mixing Factor

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Seepage Characteristics of Domestic Bed Sediments Mixed with Good-quality Soil as Levee Fill Material (양질토와 혼합처리된 국내 하상토의 제체재료로서의 침투특성)

  • Choi, Bong-Hyuck;Kim, Kyung-Min;Kim, Jin-Man;Lee, Dae-Yeong
    • Journal of the Korean Geotechnical Society
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    • v.24 no.10
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    • pp.105-111
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    • 2008
  • To improve the stability of levee structure, it is required to use good quality fill materials, intensive management, appropriate hydraulic structure and construction of cut-off wall. In particular, the most important factor of levee construction technology is to use bed sediment for its safety. In this study, seepage model test and numerical analysis were performed based on a standard section of levee recommended in the river design standard of korea (2005). The results of test and analysis show that most of the bed soil is a sand (SP in USCS), which does not satisfy the permeability criteria for levee materials ($< k=10^{-3}cm/sec$), thus for the safety of levee it is required to adopt a stabilizing method such as good quality soil mixing, water content control.

A Fundamental Study on The Expression of Initial Strength of Injection Materials for Steel Pipe Multi-Stage Method using Circulating Resources (순환자원을 활용한 강관다단공법용 주입재의 초기강도 발현에 대한 기초연구)

  • Sang-Huwon Song
    • The Journal of the Convergence on Culture Technology
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    • v.9 no.5
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    • pp.557-562
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    • 2023
  • This study reviewed the use of soil injection materials using circulating resources as injection materials for the steel pipe multi-stage construction method. The tests performed were homogel time and homogel compressive strength. The steel pipe multi-stage construction method is an auxiliary construction method for tunnels, and the expression of initial strength after construction is an important factor. The better the strength development in the initial stage, the more it can be used as an injection material suitable for the multi-stage steel pipe construction method. As a result of laboratory test, it was found that the homogel time of the injection material using circulating resources required more time than the mixing ratio using cement as the injection material. In addition, it was found that the initial strength curing time satisfying 2MPa was required for more than 24 hours. Therefore, it was confirmed that the injection material using recycled resources required a longer initial curing time than cement of the same mixing ratio.

A Study on the Engineering Characteristics of CLSM (유동성 채움재의 공학적 특성 연구)

  • Jung, Min-Ji;Jeon, Byeong-Won;Kim, Byeong-Jun
    • Journal of the Korean Geotechnical Society
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    • v.40 no.2
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    • pp.19-28
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    • 2024
  • This study explores the long-term decline in the uniaxial compressive strength of Controlled Low Strength Material (CLSM) by preparing a sample with a 1:1 mixing ratio of CLSM and water. Uniaxial compressive strength tests were conducted after 7 and 28 days of curing. The results revealed that the compressive strength at 28 days was reduced by a factor of 2.85 compared to that at 7 days. Additionally, when expansion was introduced under the same mixing conditions, there was a significant reduction in compressive strength. Point load strength tests based on 7 and 28 days of curing indicated a disparity of 29.27 to 58.76 and 48.19 to 95.13 times, respectively, between the point load strength and the uniaxial compressive strength at 7 days. The differences observed in the findings of this study compared to previous studies may be attributed to variations in the precision of the test method and the sample production process. Therefore, it is essential to establish clear testing methods to accurately evaluate CLSM.

The Evaluation of Surface Scaling and Resistance of Concrete to Frost Deterioration with Freezing-Thawing Action by Salt Water (염화물이 함유된 동결수의 동결융해 작용에 따른 콘크리트의 내동해성과 표면열화 평가)

  • Kim, Gyu-Yong;Kim, Moo-Han;Cho, Bong-Suk;Lee, Seung-Hoon
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.11 no.6
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    • pp.143-151
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    • 2007
  • This study presents the experimental results of frost durability including resistance to freezing-thawing and surface scaling of concrete. Mixing design was proportioned with the various water-binder ratio between 0.37 and 0.47 and three different binder compositions corresponding to Type I cement without any supplementary cementitious materials(OPC), Type II cement with 50% blast-furnace slag replacement(BFS50), and ternary cement with Type III cement, 15% fly ash, and 35% slag replacement (BFS35%+FA15%). Test results showed that the mixing design with BFS50% and BFS35%+FA15% exhibited higher durability factor than that made with OPC only. Finally, the use of blend cement containing slag can be used effectively in terms of frost durability of the concrete exposed to severe condition under coastal environment like as flying salt, sea water spray, etc.

Effect of the Broken Red Bricks on the Mechanical Properties of Reinforced Concrete Beams (부순 적벽돌 혼입량에 따른 철근콘크리트 보의 역학적 특성에 관한 연구)

  • Kim, Jeong Sup;Shin, Yong Seok;Cho, Cheol Hee;No, Sung Yeol
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.12 no.2
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    • pp.83-90
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    • 2008
  • The purpose of this study is to attempt to use broken red brick, which is categorized as impurities of circular aggregate to thick aggregate, as a replacement for concrete. Through the material test and performance test for each mixing rate of the broken red brick (0%, 30%, 60%), the following conclusion was reached by studying the material and structural characteristics of circular aggregate to the concrete. Even though broken red brick, which is categorized as impurities of circular aggregate, is mixed 30% with normal rubble, the compression strength, intensity strength, and curving strength was similar to that of concrete that uses normal rubble. Therefore, concrete beam made with broken red brick can be applied to the real construction field. Also, the study regarding the cutting test of the concrete that uses broken red brick and regarding applying and mixing admixture that can increase the ductility factor will be required in the future.

Variability of Water Quality and Limiting Factor for Primary Production in Semi-enclosed Masan Bay, South Sea of Korea (한국 남해 마산만에서 수질환경의 계절적 변동과 기초생산 제한인자)

  • Lim, Dhong-Il;Kim, Young-Ok;Kang, Mi-Ran;Jang, Pung-Kuk;Shin, Kyoung-Soon;Jang, Man
    • Ocean and Polar Research
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    • v.29 no.4
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    • pp.349-366
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    • 2007
  • Seasonal variations of various physicochemical components (temperature, salinity, pH, DO, COD, DOC, nutrients-silicate, DIN, DIP) and potential limiting factor for phytoplankton primary production were studied in the surface water of semi-enclosed Masan Bay. Seasonal variations of nutrient concentrations, with lower values in summer and winter, and higher in fall, are probably controlled by freshwater loadings to the bay, benthic flux and magnitude of occurrence of phytoplankton communities. Their spatial distributional patterns are primarily dependent on physical mixing process between freshwater and coastal seawater, which result in a decreasing spatial gradient from inner to outer part of the bay. In the fall season of strong wave action, the major part of nutrient inputs (silicate, ammonium, dissolved inorganic phosphorus) comes from regeneration (benthic flux) at sediment-water interface. During the summer period, high Si:DIN and Si:DIP and low DIN:DIP relative to Redfield ratios suggest a N- and secondarily P-deficiency. During other seasons, however, silicate is the potential limiting factor for primary production, although the Si-deficiency is less pronounced in the outer region of the bay. Indeed, phytoplankton communities in Masan Bay are largely affected by the seasonal variability of limiting nutrients. On the other hand, the severe depletion of DIN (relatively higher silicate level) during summer with high freshwater discharge probably can be explained by N-uptake of temporary nanoflagellate blooms, which responds rapidly to pulsed nutrient loading events. In Masan Bay, this rapid nutrient consumption is considerably important as it can modify the phytoplankton community structures.

Numerical Study on Flow and Heat Transfer Enhancement in a Cooling Passage with Protrusion-In-Dimples (돌출부를 포함한 딤플 표면을 가진 냉각 유로에서의 유동과 열전달 성능 향상에 관한 수치적 연구)

  • Kim, Jeong-Eun;Ha, Man-Yeong;Yoon, Hyun-Sik;Doo, Jeong-Hoon
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.23 no.12
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    • pp.805-814
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    • 2011
  • In the present study, the detailed flow structure and heat transfer characteristics in the newly-designed heat transfer surface geometry were investigated. The surface geometry proposed in the present study is a traditional dimple structure combining with a protrusion inside the dimple, which is named a protrusion-in-dimple in this study. The basic idea underlying the present surface geometry is to enhance the flow mixing and the corresponding heat transfer in the flow re-circulating region generated by a conventional dimple cavity. The present study was performed by the direct numerical simulation at a Reynolds number of 2800 based on mean velocity and channel height and Prandtl number of 0.71. Three different protrusion heights for protrusion-in-dimples were considered as the main design parameter of the present study. The calculated pressure drop and heat transfer capacity were assessed in terms of the Fanning friction factor and Colburn j factor. The overall performances estimated in terms of the volume and area goodness factor for protrusion-in-dimple cases were higher than the conventional dimple case.

Readeveloping Turbulent Boundary Layer after Separation-Reattachment(I) (박리-재부착 이후의 재발달 난류경계층 I)

  • 백세진;유정열
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.13 no.4
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    • pp.780-788
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    • 1989
  • An experimental study has been performed to investigate the process from nonequilibrium state to equilibrium state in redeveloping turbulent boundary layer beyond separation-reattachment using pitot tube and hot-wire anemometer. The model sued in the experiment has the form of a backward facing step which is assembled by a two-dimensional 4:1 half elipse and a plate. Measurements are carried out up to a distance of about 50 step height downstream of the step, where the reattachment observed at about x/h=6.5. The profiles of the shape factor H the Clauser parameter G and the coefficient of friction $C^{f}$ exhibited the characteristics similar to those of the equilibrium turbulent boundary layer from x/h=25, and the profiles of the trubulent quantities did from x/h=35. However, the wake region of the boundary layer does not seem to recover the equilibrium turbulent boundary layer even at x/h=50. By considering the distributions of the intermittency factor it has been noted that the turbulence structure changes gradually from a mixing layer to a turbulent boundary layer along downstream direction after reattachment. This becomes clearer as we analyse the one-dimensional energy spectra and the dissipation energy spectra which are measured and caculated at various downstream positions after the backward facing step.p.

Evaluation of Effective Dose and Exposure Level of Radon in Process Handling NORM (인산석고 취급공정에서의 라돈농도 및 유효선량 수준 평가)

  • Chung, Eun Kyo;Jang, Jae Kil;Kim, Jong Kyu;Kim, Joon Beom;Kwon, Jiwoon
    • Journal of Korean Society of Occupational and Environmental Hygiene
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    • v.28 no.3
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    • pp.283-291
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    • 2018
  • Objectives: To monitor the radon concentration level in plants that handle phosphorus rock and produce gypsum board and cement, and evaluate the effective dose considering the effect of radon exposure on the human body. Methods: Airborne radon concentrations were measured using alpha-track radon detectors (${\alpha}$-track, Rn-tech Co., Korea) and continuous monitors (Radon Sentinel 1030, Sun Nuclear Co., USA). Radon concentrations in the air were converted to radon doses using the following equation to evaluate the human effects due to radon. H (mSv/yr) = Radon gas concentration x Equilibrium factor x Occupancy factor x Dose conversion factor. The International Commission on Radiological Protection (ICRP) used $8nSv/(Bq{\cdot}hr/m^3)$ as the dose conversion factor in 2010, but raised it by a factor of four to $33nSv/(Bq{\cdot}hr/m^3)$ in 2017. Results: Radon concentrations and effective doses in fertilizer manufacturing process averaged $14.3(2.7)Bq/m^3$ ($2.0-551.3Bq/m^3$), 0.11-0.54 m㏜/yr depending on the advisory authority and recommendation year, respectively. Radon concentrations in the gypsum-board manufacturing process averaged $14.9Bq/m^3$ at material storage, $11.4Bq/m^3$ at burnability, $8.1Bq/m^3$ at mixing, $10.0Bq/m^3$ at forming, $8.9Bq/m^3$ at drying, $14.7Bq/m^3$ at cutting, and $10.5Bq/m^3$ at shipment. It was low because it did not use phosphate gypsum. Radon concentrations and effective doses in the cement manufacturing process were $23.2Bq/m^3$ in the stowage area, $20.2Bq/m^3$ in the hopper, $16.8Bq/m^3$ in the feeder and $11.9Bq/m^3$ in the cement mill, marking 0.12-0.63 m㏜/yr, respectively. Conclusions: Workers handling phosphorous gypsum directly or indirectly can be assessed as exposed to an annual average radon dose of 0.16 to 2.04 mSv or 0.010 to 0.102 WLM (Working Level Month).

Seasonal Variations of Water Quality in the Coastal Sea of Jungmun Resort Complex in Jeiu Island (제주도 중문관광단지 연안해역 수질의 계절변동)

  • Jang Seung-Min;Choi Young-Chan
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.5 no.2
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    • pp.3-18
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    • 2002
  • This study has been carried out to find the water Quality in coastal sea of fungmun area, southern Jeju Island. In-situ observations and water sampling had been made every month from July 1997 to June 2000. The distributions of water temperature and salinity over the study area have been 13.8~27.0℃ and 30.0~34.7‰, respectively. Salinity is showed low salinity from June to September (rainy season) because of rain. Tsushima Warm Waters (TWW) as ≥15℃ and ≥34‰ influence the adjacent sea around Jeju Island all year round. Yangtse Coastal Waters (YCW) influence the surface layer around Jeju from June to September and so strong stratification (termocline, halocline) resulted at the depth of between 20~30m at outer-sea. However the stratification does not happen even in summer at inner-sea, which seem to be caused due to vertical mixing by wind, waves and tides. A water mass of high value of water temperature and salinity (respectively 14.1~17.7℃, 33.9~34.1‰) stayed at the lower layer in outer-sea all the year round. It is probably formed by mixing between TWW and YSBCW(Yellow Sea Bottom Cold Water). The mean value of DO was the lowest in summer and the highest in winter. COD and TH were the highest in summer and the lowest in winter. However, TP showed the lowest value in summer season, because the mean value of N/P ratio was over 16. The mean of N/P ratio was under 16 in other seasons. The phosphate would be a limiting factor in the growth of phytoplanHon in summer. Nitrate would be a limiting factor in other seasons. Distribution of chlorophyll a did not show any seasonal change in the study period, but especially increased during April and May in the first year(1998) and the second year(1999) all over the study area, which suggested that phytoplankton inhabitation distributed widely in the study area. The space averaged values were the highest for TIN in rainy season and lower for TP in rainy season than in other seasons. It suggests that river runoff influences the inner-sea.

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