• Journal of Korean Tunnelling and Underground Space Association
• /
• v.21 no.1
• /
• pp.31-48
• /
• 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 Korean Tunnelling and Underground Space Association
• /
• v.18 no.5
• /
• pp.401-412
• /
• 2016

It is extremely difficult to apply conventional grouting methods to subsea tunnelling construction in the high water pressure condition. In such a condition, the rapid artificial freezing method can be an alternative to grouting to form a watertight zone around freezing pipes. For a proper design of the artificial freezing method, the influence of salinity on the freezing process has to be considered. However, there are few domestic tunnel construction that adopted the artificial freezing method, and influential factors on the freezing of the soil are not clearly identified. In this paper, a series of laboratory experiments were performed to identify the physical characteristics of frozen soil. Thermal conductivity of the frozen and unfrozen soil samples was measured through the thermal sensor adopting transient hot-wire method. Moreover, a lab-scale freezing chamber was devised to simulate freezing process of silica sand with consideration of the salinity of pore-water. The temperature in the silica sand sample was measured during the freezing process to evaluate the effect of pore-water salinity on the frozen rate that is one of the key parameters in designing the artificial freezing method in subsea tunnelling. In case of unfrozen soil, the soil samples saturated with fresh water (salinity of 0%) and brine water (salinity of 3.5%) showed a similar value of thermal conductivity. However, the frozen soil sample saturated with brine water led to the thermal conductivity notably higher than that of fresh water, which corresponds to the fact that the freezing rate of brine water was greater than that of fresh water in the freezing chamber test.

• Geomechanics and Engineering
• /
• v.15 no.4
• /
• pp.997-1004
• /
• 2018

The brine leakage is a tough problem in artificial freezing engineering. This paper takes the common soft clay in Wujiang District as the study object, and calcium chloride solutions with six salinity levels were considered. The 'classic' cooling curve method was employed to measure the freezing point of specimens after freeze-thaw. Results indicate that four characteristic stages can be observed including supercooling, abrupt transition, equilibrium and continual freezing, strongly dependent on the variation of unfrozen water content. Two characteristic points were found from the cooling curves, i.e., freezing point and initial crystallization temperature. A critical value for the former exists at which the increment lowers. The higher the saline content approximately linearly, lower the freezing point. In the initial five cycles, the freezing point increases and then stabilizes. Besides, the degree of supercooling was calculated and its correlations with water, salt and freeze-thaw cycles were noted. Finally, an empirical equation was proposed for the relationship of freezing point and three main factors, i.e., water content, saline content and freeze-thaw cycles. Comparison of calculated and measured data proves that it is reliable and may provide guidance for the design and numerical analysis in frozen soil engineering.

• Proceedings of the KSAR Conference
• /
• 2004.06a
• /
• pp.278-278
• /
• 2004

The purpose of this study was to establish the convenient freezing method for more cheap and simple. Semen quality was evaluated the motility, viability, abnormality, acrosome intactness and membrane integrity. And there were also examined the developmental rates of IVM/IVF embryos using frozen-thawed boar semen in each treatment group. (omitted)

• The Journal of Engineering Geology
• /
• v.11 no.1
• /
• pp.13-23
• /
• 2001

Rock slope near the road or railroad is affected by the outside temperature and iterative freezing-thawing process during winter and early spring. The purpose of this study is to analyze the stability of rock slope which is iniluenced by deterioration due to the freezing-thawing. Method of analysis is homogenization method which find the strength property of discontinuous rock mass and as a strength failure criterion, Drucker-Prager failure criterion is used, The deterioration property of real rock is obtained by a freezing-thawing labordtory test of tuff and this quantitative property is used as a basic data of stability analysis of rock mass. To evaluate the deterioration depth due to the freezing-thawing in the field rock slope, one dimensional heat conductivity equation is used and as a a result we can find the depth of which is affected by a temperature. After determined the freezing-thawing depth of model slope, the pattern of rock mass strength value of model rock slope which excess the limit of self-load is analyzed.

• Proceedings of the KSME Conference
• /
• 2000.04b
• /
• pp.51-56
• /
• 2000

The Finite Element Solutions Is reported on solid-liquid phase change in porous media with natural convection including freezing. The model is based on volume averaged transport equations, while phase change is assumed to occur over a small temperature range. The FEM (Finite Element Method) algorithm used in this study is 3-step time-splitting method which requires much less execution time and computer storage the velocity-pressure integrated method and the penalty method. And the explicit Lax-Wendroff scheme is applied to nonlinear convective term in the energy equation. For natural convection including melting and solidification the numerical results show reasonable agreement with FDM (Finite Difference Method) results.

• Food Science of Animal Resources
• /
• v.35 no.1
• /
• pp.27-34
• /
• 2015

The ultrastructure in the beef muscle of the electro-magnetic resonance and air blast freezing during the frozen storage, and the changes in the quality characteristics after thawing were evaluated. The size of ice crystal was small and evenly formed in the initial freezing period, and it showed that the size was increased as the storage period was elapsed (p<0.05). The beef stored by the electro-magnetic resonance freezing showed the size of ice crystal with a lower rate of increase than the air blast freezing during the frozen storage. The thawing loss of beef stored by the electro-magnetic resonance freezing was significantly lower than the air blast freezing during frozen storage (p<0.05), and it showed that the thawing loss of the round was higher than the loin. Water holding capacity decreased as the storage period became longer while the electro-magnetic resonance freezing was higher than the air blast on 8 month (p<0.05). As a result of sensory evaluation, the beef stored by the electro-magnetic resonance freezing did not show the difference until 4 months, and it showed higher acceptability in comparison with the beef stored by the air blast freezing. Thus, it is considered that the freezing method has an effect on the change in the ultrastructure and quality characteristics of the beef.

• Journal of Biosystems Engineering
• /
• v.40 no.3
• /
• pp.271-276
• /
• 2015

Purpose: Quick freezing is widely used in commercial food storage. Well-known freezing techniques such as individual quick freezing require a low-temperature coolant and small cuts for the heat-transfer efficiency. However, the freezing method for bulk food resembles techniques used in the 1970s. In this study, electromagnetic (EM) heating was applied to improve the quick freezing of bulk food. Methods: During freezing, the surface of food can be rapidly cooled by an outside coolant, but the inner parts of the food cool slowly owing to the latent heat from the phase change. EM waves can directly heat the inner parts of food to prevent it from freezing until the outer parts finish their phase change and are cooled rapidly. The center temperature of garlic cloves was probed with optical thermo sensors while liquid nitrogen (LN) was sprayed. Results: When EM heating was applied, the center cooling time of the garlic cloves from freezing until $-10^{\circ}C$ was 48 s, which was approximately half the value of 85 s obtained without EM heating. For the white radish cubes, the center cooling time was also improved, from 288 to 132 s. The samples frozen by LN spray with EM heating had a closer hardness to the unfrozen samples than the samples frozen by LN only. Conclusions: The EM heating during quick freezing functions to maintain the hardness of fresh food by reducing the freezing time from 0 to $-10^{\circ}C$.

• Korean Journal of Animal Reproduction
• /
• v.13 no.3
• /
• pp.141-148
• /
• 1989

The effects of seeding method and optimum time for freezing embryos according to the developmental stages on embryo survival rates after rapid freezing were determined using the FDA-test. The summarized results are as follows : 1. In the rapid freezing of embryos, the sucrose added medium together with Co-seeding or non-seeding showed the FDA scores of 4.67 and 4.20, respectively, but, raffinose addition obtained FDA scores of 4.27 and 3.97. 2. The developmental stage of embryos at freezing was most critical on the survival of embryos after thawing. Higher FDA scores were obtained in the order of blastocyst stage(4.94), morula stage(3.82) and ealy stage(2.65) in sucrose added medium. The same trend was observed in the raffinose added medium with an order or 4.91, 4.47 and 2.32. 3. Microscopic study of embryo before freezing and post-thawing indicated that the embryo showed shrinkage within 5 minutes after the embryo was transfer to the freezing medium. When thawed embryo was tranfered to the dilution medium, swelling of the embryo was observed and there after it reshrank indicating the removal of cryoprotectant from the embryo. The size of the embryo recovered to the original state when it was moved into a PBS-solution.

• Journal of Embryo Transfer
• /
• v.4 no.1
• /
• pp.1-13
• /
• 1989

This paper reviews the most important steps that have generated consistent progress in principles and developmental progress of embryo cryopreservation, and also study on freezing procedure and its application by conventional method and current improved method for freezing procedure and its appilcation of embryo cryopreservation in farm animals. Four were of particular interest: 1.The transport of water across the ccli membrane (zona pellucida) during freezing and thawing accordinglyplays a role in determing whether the celi survives. This movement of water is controlied mainly by extracellular phase changes and by the nature and concentration of any cryoprotective agent present. Therates of cooling, freezing and warming, and the intervals over which they are applied are further decisi've factors in determining whether a cryopreservation procedure allows survival after thawing. 2.The first successful deep freezing experiments with sheep morula and blastocysts during the seventies were based on the early procedures used for mouse embryos.Current research during the eighties is developed with the aim of simplifying and improving current procedures such as one-step dilution and rapid or ultra-rapid cooling by using the model of laboratory animals. 3.The conventional method for the embryo cryopreservation is described. An alternative to this method which may result in high survival and also in reducing of the freezing and thawing time is done by combing a permeable cryoprotectant such as glycerol, DMSO or propanediol and a non-permeable compound such as sucrose, trehalose, raffinose or lactose. 4.Finally a different approach to the preservation of embryos, named vitrification, is introduced. This procedure depends upon the ability of concentrated solutions of cryoprotective agents such as glycerol and propanediol to supercool to very low temperature (-196$^{\circ}C$) during rapid cooling before solidifying without formation of ice. However, more complete data are necessary for successful vitrification of blastocysts.