• 대한토목학회논문집
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• 제38권4호
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• pp.555-565
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• 2018

최근 임시 지보, 보강 및 지하수 차수와 같은 다양한 지질공학분야에서 차수 및 지반보강 공법으로 인공동결공법(artificial ground freezing method)이 적용되고 있다. 인공동결공법은 지중에 매설된 동결관 내로 냉매를 순환시켜 대상 지반에 차수벽 및 지지체의 역할을 할 수 있는 동결벽체(frozen wall)를 형성한다. 본 연구에서는 해성 점토지반(marine clay)에 대한 인공동결공법 현장실증시험을 수행함으로서 인공동결공법에 따른 해성 점토지반에서의 동결속도(freezing rate)를 평가하였다. 현장실증시험은 지중에 3.2m 깊이로 매설된 동결관 내로 초저온 냉매인 액화질소를 순환시키는 방법으로 단일공 시험과 동결벽체 형성 시험을 수행하였다. 자동밸브를 통해 유출되는 액화질소의 온도를 일정하게 유지시켰으며, 동결과정에서 동결관 외벽 및 지중의 온도변화를 측정하였다. 시험결과, 단일공 시험은 부피가 약 $2.12m^3$인 원기둥 모양의 동결체를 형성하는데 총 3.5일 동안 약 11.9ton의 액화질소가 소요되었고, 동결벽체 형성 시험은 부피 약 $7.04m^3$의 동결벽체를 형성하는데 총 4.1일 동안 약 18ton의 액화질소가 소요된 것으로 산정되었다. 임의의 깊이에서 동결면적이 동결반경의 제곱에 비례하기 때문에 동결반경이 증가할수록 방사방향 1차원 동결속도가 감소하였고, 이를 바탕으로 방사방향 1차원 동결속도 예측식을 제시하였다.

• 한국축산식품학회지
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• 제34권1호
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• pp.33-39
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• 2014

This study investigates the effects of the gelatin concentration (10-40%, w/v), freezing temperatures (from $-20^{\circ}C$ to $-50^{\circ}C$) and freezing methods on the structural and physical properties of gelatin matrices. To freeze gelatin, the pressure-shift freezing (PSF) is being applied at 0.1 (under atmospheric control), 50 and 100 MPa, respectively. The freezing point of gelatin solutions decrease with increasing gelatin concentrations, from $-0.2^{\circ}C$ (10% gelatin) to $-6.7^{\circ}C$ (40% gelatin), while the extent of supercooling did not show any specific trends. The rheological properties of the gelatin indicate that both the storage (G') and loss (G") moduli were steady in the strain amplitude range of 0.1-10%. To characterize gelatin matrices formed by the various freezing methods, the ice crystal sizes which were being determined by the scanning electron microscopy (SEM) are affected by the gelatin concentrations. The ice crystal sizes are affected by gelatin concentrations and freezing temperature, while the size distributions of ice crystals depend on the freezing methods. Smaller ice crystals are being formed with PSF rather than under the atmospheric control where the freezing temperature is above $-40^{\circ}C$. Thus, the results of this study indicate that the PSF processing at a very low freezing temperature ($-50^{\circ}C$) offers a potential advantage over commercial atmospheric freezing points for the formation of small ice crystals.

• 유기물자원화
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• 제18권2호
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• pp.93-100
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• 2010

본 연구는 하수슬러지 전처리 방법으로 분쇄, 동결 해동, 동결 분쇄 조작을 한 후, 각각의 슬러지 특성의 변화를 고찰하였다. 분쇄 슬러지, 동결 해동 슬러지, 동결 분쇄 슬러지는 하수슬러지 부피에 비해 각각 2.08배, 3.37배, 3.54배 감소하여 동결 분쇄한 경우가 가장 슬러지 감소량이 컸으며 그 다음으로 동결 후 해동한 경우, 분쇄만 한 경우 순이었다. 또한 하수슬러지의 SCOD 농도, SBOD 농도, protein 농도는 동결하지 않은 것보다 동결 하는 것이 높았고, 그 중에서도 동결 후 분쇄하는 것이 가장 높은 경향을 보였다. TS, VS의 제거율은 동결한 것이 높았지만, 동결 분쇄보다 동결 해동이 높은 경향을 보였다. 이상의 결과로부터 동결 분쇄 방법이 슬러지 전처리 방법으로 매우 효과적이며 2012년부터 발효되는 슬러지 해양 투기 전면 금지에 대한 대안이 될 수 있을 것으로 기대된다.

• 한국식품영양과학회지
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• 제28권4호
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• pp.871-875
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• 1999

This study was carried out to investigate the effects of freezing temperature on the quality of thawing aged beef loin. Drip loss was higher at 3oC freezing than at 20oC freezing, showing 17.21% drip loss after 6 days aging by 3oC freezing, 14.92% drip loss 12 days aging by 20oC freezing. Cooking loss by both water bath and pan boiling were decreased with increased in aging days. The salt soluble protein extractability of the beef loin was increased until 9 days aging by both 3oC and 20oC freezing, after that was decreased. The L value of the beef loin was high until 9 days aging by 3oC freezing, after that the L value of that was decreased. And the aging at 20oC freezing was high significantly with increased aging days. The a value of the beef loin was low significantly in 6 and 9 days aging by 3oC freezing, 20oC freezing was low significantly with increased aging days. The b value of the beginning of aging was higher with increased aging days. The percentage of denatured myoglobin of the beginning of aging was the highest, then those of 3oC and 20oC freezing showed 89.70% and 88.00%, respectively. The shear force of the beef loin was decreased with aging days, but the myofibrillar fragmentation index increased with aging days. The pH of the beef loin increased until 6 days of aging by both 3oC and 20oC freezing, after that the pH decreased.

• 한국지반신소재학회논문집
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• 제22권1호
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• pp.97-107
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• 2023

본 연구에서는 국내 동상피해 발생지역 중 동결지수가 높은 강원산간지역의 콘크리트도상 현장에 대하여 동상피해 원인과 동결심도를 분석하고 동결심도 자료를 바탕으로 콘크리트도상의 동결심도 산정식 및 강원지역의 동결심도 산정식을 고찰하였다. 강원산간지역의 콘크리트도상 동결심도와 강원지역의 동결심도 경향성을 비교한 결과 콘크리트도상은 동결지수 400(℃×일)이하에서는 동결심도가 강원지역의 동결심도보다 높게 나타났으며, 동결지수400(℃×일)이상의 구간에서는 강원 지역의 동결심도가 콘크리트도상의 동결심도보다 높게 나타났다. 본 연구를 통해 강원지역의 동결심도 산정식을 제시하여 강원지역의 철도 및 도로 건설사업 시 동상 방지대책 수립에 활용될 수 있도록 기초자료를 제공하였다.

• 대한토목학회논문집
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• 제29권1D호
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• pp.55-61
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• 2009

이 연구는 지역별 환경변수 및 도로포장재료의 물리적 특성을 토대로 하여 국내에서 최근에 개발된 동결해석모델인 FrostAM을 사용하여 최근에 사업시행중인 전국 9개 사업지구에 대해 동결깊이 분석을 실시하였다. 동결깊이 분석에 필요한 자료중 환경변수는 기상청 사이트의 측정자료를 사용하였으며, 물리적 특성중 수리특성 분석을 위해 전국 각 지역으로부터 시료를 채취하여 불포화토 물성측정 장치를 사용하여 실내실험 및 분석을 실시하였다. FrostAM을 사용하여 분석된 동결깊이는 동결지수를 사용하여 결정된 각 사업지구의 동결깊이와 비교한 결과 14cm~44cm 작게 나타났다. 이러한 결과로 볼 때 동결지수에 의한 동결깊이는 전반적으로 크게 계상되었으며, 사업지구별로 설계자가 다르다는 점을 고려할 때 동결깊이 산정이 설계자에 따라 상당한 편차가 있는 것으로 보인다.

• 한국식품과학회지
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• 제21권6호
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• pp.735-741
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• 1989

For the accurate prediction of freezing time, probably the most difficult factor to measure and major error source is the surface heat transfer coefficient. In this work, surface heat transfer coefficient were determined for still air freezing and immersion freezing methods by theory of the transient temperature method and confirmed by using a modification of plank's equation to predict the freezing time of ground lean beef. The results showed the cooling rate of immersion freezing was about 11 times faster than that of still air freezing method. A comparison of surface heat transfer coefficient of copper plate and ground lean beef resulted an difference of 25-30% because the food sample surface is not smooth as copper plate. Also, when h-values measured by ground lean beef were applicated to modified model, the accuracy of its results is very high as difference of about 8%.

• 한국해양공학회지
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• 제15권3호
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• pp.128-133
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• 2001

It is generally known that the concrete structure subjected to severe environment is much affected by the corrosion of reinforcement, the freezing and thawing action of concrete structure. The main objective of this study is to investigate the freezing and thawing resistance of concrete including fly ash. The effect of the air content in concrete using fly ash is investigated. The experimental study is conducted for 10 mix-ratio cases of concrete of which variables are content of fly ash, concrete compressive strength and containment of air-entrained admixtures. Test results show that the freezing and thawing resistance improves as the amounts of fly ash increase, and concrete with air-entrained admixtures has good freezing and thawing resistance. The concrete with fly ash is to be included air-entrained admixture according to content of fly ash in order to increase the freezing and thawing resistance.

• 한국건축시공학회지
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• 제2권2호
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• pp.151-156
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• 2002

When fresh concrete is exposed to low temperature, the concrete may suffer frost damage due to freezing at early ages and strength development may be delayed. One of the solution methods for resolve these problems is to reduce freezing temperature of concrete by the use of chemical admixture called Accelerators for freezing resistance. In this study, we investigate the effect on strength development of cement mortar using accelerators for freezing resistance with the variance curing condition. As the result of this study, the mortar using accelerators for freezing resistance show that continuously strength development in curing condition of -5$^{\circ}C$. And compressive strength under the variance temperature condition was higher than constant temperature condition in same maturity.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2001년도 추계학술대회 논문집
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• pp.520-525
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• 2001

It's strongly recommended to check upon the slope stability of soil nearby railroad, since the freezing-thawing repeat in long term may cause decrease of slope stability. The study is, therefore, focused on the strength characteristic transformation of soil, measuring it experimentally, throughout physical and mechanical tests operated by the freezing-thawing repeat tests. The sampling of weathered soil used for the embankment materials along the domestic railway lines are classified by parent-rock, and then collected after it in the first hand. It tells that Uniaxial strength and axial strain were decreased simultaneously as the frequency of freezing-thawing repeat increased and its range was reduced into 25～85 percentage off comparing to uniaxial strength of unfreezing-soils when about 100 times of freezing-thawing repeats occurred. Following the result of direct shear tests, the cohesion of freezing-soil with freezing-thawing repeats shows 11∼60 percentage less than that of unfreezing-soil but the change of internal friction angle of the soil is extremely slight, enough to ignore. As a result. it could be found that strength characteristic transformation has highly correlated with freezing-thawing repeat.