• Journal of the Korean Geosynthetics Society
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• v.8 no.3
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• pp.35-44
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• 2009

The purpose of this study was to prevent spreading of contaminants from movement of underground water by creating a barrier using artificial freezing method on a soil contaminated by oils and various NAPLs. Specimens with 80% and 90% degrees of saturation were prepared to form freezing barrier using artificial freezing method. With increasing freezing time of freezing barrier, barrier was formed faster in the specimen with 90% degree of saturation by about an hour compared to the specimen with 80% degree of saturation. In addition, thinnest thickness of frozen barrier in both specimens was 50mm after 12 hours of freezing time, showing expansion of freezing area with time. The results of this study can be applied to barrier in waste reclamation sites and contaminated regions or to flow control of contaminants.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.4
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• pp.555-565
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• 2018

Nowadays, the artificial ground freezing (AGF) method has been used in many geotechnical engineering applications such as temporary excavation support, underpinning, and groundwater cutoff. The AGF method conducts the freezing process by employing a refrigerant circulating through a set of embedded freezing pipes to form frozen walls serving as an excavation support and cutoff wall. Two refrigerants of brine with the freezing temperature of $-20{\sim}-40^{\circ}C$ and liquid nitrogen with the freezing (evaporating) temperature of $-196^{\circ}C$ are commonly being used in geotechnical applications. This paper performed a series of field experiments to evaluate the freezing rate of marine clay in application of the AGF method. The field experiments consisted of the single freezing-pipe test and the frozen-wall formation test by circulating liquid nitrogen, which is a cryogenic refrigerant, into freezing pipes constructed at a depth of 3.2 m in the ground. The temperature of discharged liquid nitrogen was maintained through the automatic valve, and the temperature change induced by AGF method was measured at the freezing pipes and in the ground with time. According to the experimental results, the single freezing-pipe test consumed about 11.9 tons of liquid nitrogen for 3.5 days to form a cylindrical frozen body with the volume of about $2.12m^3$. In addition, the frozen-wall formation test used about 18 tons of liquid nitrogen for 4.1 days to form a frozen wall with the volume of about $7.04m^3$. The radial freezing rate decreased with increasing the radius of frozen body because the frozen area at a certain depth is proportional to the square of the radius. The radial freezing rate was formulated as a simple equation.

• 대한생식의학회:학술대회논문집
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• 2004.11a
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• pp.34-34
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• 2004

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.241-246
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• 2004

매립지 차수층에는 다짐점토층이 사용되고 있지만 건조/수축, 동결/융해 등의 환경적인 영향에 대한 내구성을 향상시키기 위한 기능성 복합차수층에 대한 연구가 진행되고 있다. 본 연구에서는 원지반토양에 고화재를 첨가한 BLT층과 벤토나이트와 미생물 배양액을 첨가한 BLM 층으로 구성된 복합차수층의 차수기능과 BLM층에서 미생물 배양액 첨가에 따른 Bio-barrier 기능을 평가하였다. 원지반토양에 고화재와 벤토나이트를 각각 8, 10%(w/w)를 첨가하였r고, 미생물 배양액은 1%(v/w)을 첨가하였다. 실험결과 원지반토양은 SC계열의 토양으로 분류되었고, BLT, BLM 차수층의 8% 혼합비율에서도 1$\times$ $10^{-7}$cm/sec 보다 낮은 투수계수를 나타내었다. BLM 층에 첨가된 미생물 배양액에 의한 Bio-barrier 기능 실험결과 미생물 배양액 첨가에 의하여 침출수에 대한 내구성이 향상된 것을 확인할 수 있었다.

• Journal of the Korean Geosynthetics Society
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• v.10 no.2
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• pp.29-34
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• 2011

The purpose of this study was to prevent spreading of contaminants from movement of underground water by creating a barrier using artificial freezing method on a soil contaminated by oils and various DNAPLs. Specimens with 80% and 90% degrees of saturation were prepared to form freezing barrier using artificial freezing method. As the results of freezing specimen within soil bin with artificial ground freezing system, artificial contaminated soil cut off wall formed the thinnest wall after 12 hours. It is judged that this cut off wall will control the second soil pollution by intercepting expansion and movement of pollutants and DNAPLs within artificial contaminated soil cut off wall by underground water, intercepting inflow or outflow of underground water. Cut off walls formed by artificial ground freezing system had each other freezing speed according to degree of saturation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.178-178
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• 2004

본 연구에서는 폴리카보나이트의 재료로 만들어진 인장시편과 원형시편을 다목적 광탄성 측정기를 사용하여 프린지 차수를 측정한 후 프린지 상수를 도출하였다. 특히, 새로 개발된 다목적 광탄성기를 이용하여 지랫대 형식으로 프린지 차수를 측정하였고, 시편에 직접 응력을 가하는 방식의 직접(DIRECT) 실험법으로 프린지 차수를 측정하였다. 위와 같은 방식은 나타난 결과를 가지고 프린지 상수를 서로 비교할 수 있다는 장점이 있어 다목적 광탄성기에 대한 신뢰도를 얻을 수 있다 아울러 광탄성 4단계 위상 이동법에서는 주응력 방향, 즉 등경선이 일정한 선상에서는 연속적인 응력분포를 얻을 수 있다.(중략)

• Journal of Energy Engineering
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• v.26 no.3
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• pp.105-112
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• 2017

A lot of piping systems have been used from nuclear power systems to water supply systems. The maintenance of the piping systems is needed to ensure proper operation of the piping systems. Failure of the large pipe systems especially such as KDHC(Korea District Heating Corporation) can be a matter directly related to the enterprise productivity and profitability. It can also lead to very important issues in promoting public safety and convenience. Therefore a method of quick and safety repairs have been emerged as the most important problem. In this study, freezing seal isolation method using liquid nitrogen cryogenic refrigerant was developed for the maintenance of a pre insulated heat transport pipe of KDHC with a diameter of 300 mm. In this study, by employing computational analysis techniques we performed the flow and heat transfer analysis for the targeted pre insulated heat transfer pipe and freezing seal jacket(ice-Plug) and have selected for optimal system. The detailed design model based on the results of the computational analysis finally was produced. A laboratory-scale test apparatus were designed and the freezing seal isolation self-test carried out. Also the performance assessment tests in the test bed of KDHC were carried out for on-site application.

• Journal of the Korean Geosynthetics Society
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• v.10 no.2
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• pp.73-79
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• 2011

Based on the results of Part 1 of our two-parts paper, the possibility on field applicability of CMDS(Coal Mine Drainage Sludge) mixed with bentonite and cement as a liner in landfill sites was investigated. The optimum moisture content that met the landfill liner condition was obtained when the ratio of CMDS: bentonite: cement was 1: 0.5: 0.3 in a lab-scale. The relative compaction was measured in 90.1%, which results for construction field have been generally acceptable. In this study, a large-scale Lysimeter($1.0m{\times}1.5m{\times}2.0m$) was used to simulate the effects of the layer on the freeze/thaw by -20 average temperature. The mixture after freezing/thawing showed compressive strength more than $5kg/cm^2$, which was satisfied with EPA standards. Initial permeability of CMDS was $7.10{\times}10^{-7}cm/s$ and permeability its mixture after freezing/thawing was increased to $9.80{\times}10^{-7}cm/s$. The change of temperature in the layers rises and falls with linear and temperature gradient keep maintain the present state. Moisture contents in the layers have not been radically changed. Through the leaching test determined by KSLT method, it was found that heavy metals excluding Zn and Ni were not leached out or leached out less than the standards during 7 cycles of freezing/thawing process. Since it shows the increased permeability about 1.5 times and slight change in moisture content, but it was satisfied with EPA standar through 7 cycles of freezing/thawing process, this mixture can be applied as a liner in landfill final cover system.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.1
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• pp.31-48
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• 2019

The artificial ground freezing (AGF) method is a groundwater cutoff and/or ground reinforcement method suitable for constructing underground structures in soft ground and urban areas. The AGF method conducts a freezing process by employing a refrigerant circulating through a set of embedded freezing pipes to form frozen walls serving as excavation supports and/or cutoff walls. However, thermal expansion of the pore water during freezing may cause excessive deformation of the ground. On the other hand, as the frozen soil is thawed after completion of the construction, mechanical characteristics of the thawed soil are changed due to the plastic deformation of the ground and the rearrangement of soil fabric. This paper performed a field experiment to evaluate the freezing rate of marine clay in the application of the AGF method. The field experiment was carried out by circulating liquid nitrogen, which is a cryogenic refrigerant, through one freezing pipe installed at a depth of 3.2 m in the ground. Also, a piezo-cone penetration test (CPTu) and a lateral load test (LLT) were performed on the marine clay before and after application of the AGF method to evaluate a change in strength and stiffness of it, which was induced by freezing-thawing. The experimental results indicate that about 11.9 tons of liquid nitrogen were consumed for 3.5 days to form a cylindrical frozen body with a volume of about $2.12m^3$. In addition, the strength and stiffness of the ground were reduced by 48.5% and 22.7%, respectively, after a freezing-thawing cycle.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.3
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• pp.140-148
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• 2016

This study examined the durability of face-slab concrete in Concrete-Faced Rock-filled Dams(CFRDs). The durability of face-slab concrete can be improved by optimizing the amount of fly ash in the cement mixture. Durability tests including plastic shrinkage, permeability, abrasion resistance, and repeated freezing and thawing were done on face-slab concrete specimens with different amounts of fly ash and blended PVA(Poly Vinyl Alcohol) fibre. When the effect of the fly ash content on concrete durability was evaluated, the results showed that a 15% fly ash content and 0.1% blended PVA fiber yielded the optimum durability level for concrete-faced rock-filled dams.