• Journal of the Korea Concrete Institute
• /
• v.13 no.4
• /
• pp.397-405
• /
• 2001

In clod weather regions, a strong seasonal wind brings sea salts to the land. In addition to it, recently, the spreading amount of deicing salts has increased numerously for purpose of removing snow and ice. Thus the salts environment around concrete structures becomes so severe that various damages of concrete due to applied salts will be brought up. Much of countries such as America, Europe etc. is carried out study for effects of deicing salts on concrete. However, there are not test methods for deterioration of concrete subjected to both freezing-thawing and chloride in Korea. In this study, we carried out test for the compound deterioration subjected to both freezing-thawing and chloride attack, to investigate the effects of sodium chloride on the deterioration of concrete. The test was performed to investigate the effects of cement type, strength and air content on the scaling deterioration of concrete. As a result, the scaling deterioration was accelerated in the presence of salts. And the resistance to scaling was strongly influenced by the type of cement, the strength and air content of concrete.

• 한국방재학회:학술대회논문집
• /
• 2010.02a
• /
• pp.90.1-90.1
• /
• 2010

우리나라는 계절적 특성으로 인하여 겨울에서 봄에 이르기까지 도로포장의 동결 융해가 반복되어 도로 파손을 유발 시키고 있다. 동결 융해로 인한 피해를 줄이기 위하여 도로포장 설계시 동상방지층을 별도로 설치를 하고 있으나 실효성 검증 없이 무분별하게 적용되고 있어 국가적으로 예산을 낭비하고 있다. 본 연구에서는 효과적인 동상방지층의 설계를 목적으로 계측된 온도 및 함수비 데이터를 효율적으로 관리하고 모니터링하는 기반을 마련하고자 한다.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.11 no.3
• /
• pp.43-47
• /
• 2011

Korea has seasonal weathers which result in the frosting of soil in winter times, and the thawing of soil in spring. These climate characteristics result in the damaging of pavements, due to the repeated freezing and thawing of road pavements during winter and spring. In order to reduce these pavement damages, anti-frost heave layers are being specially installed, however it is being applied based on foreign researches, and therefore result in the waste of national budget. With this study, a database system was constructed for effective management and monitoring of measured temperatures and function data of 2 meters below the embankment, cut slope, and the cutting-embankment boundary, which are 15 regions picked by the frost index diagram. As the study result, an effective storage and management-purpose database was established for easy data searching and downloading for the pavement design engineers.

• Journal of Wetlands Research
• /
• v.25 no.4
• /
• pp.257-266
• /
• 2023

Amphibian populations are declining globally, pushing many species to the brink of extinction. To promote biodiversity and sustainable management, countries are actively researching amphibian reproductive ecology. Sperm cryopreservation is a crucial assisted reproductive technology that aids in preserving the genetic diversity of amphibians. However, because amphibian sperm cells are sensitive to osmotic stress, the optimal cryopreservation method therefore differs from species to species. This literature review offers an overview of the significance of developing cryopreservation techniques for amphibian conservation and highlights the need to create optimal cryopreservation methods and the introduction of long-term monitoring (e.g., fertilization success and offspring reproduction) to advance cryopreservation technology development. This review can be used as basic research data for amphibian conservation methods.

• Tunnel and Underground Space
• /
• v.17 no.1 s.66
• /
• pp.56-65
• /
• 2007

A new underground LNG storage concept in the rock mass has been developed by combining underground cavern construction and new ice-ring harrier technologies with the conventional cryogenic insulation system. Technical feasibility of the storage system has been verified through construction and operation of the pilot storage cavern and a full-scale project is expected to start in the near future. One of the most important issues in the LNG storage system is the operational efficiency of the storage to minimize heat loss during a long period of operation due to the cryogenic heat transfer. This paper presents several important results of heat transfer and coupled hydro-thermal analyses by a finite element code Temp/W and Seep/W. A series of heat transfer analyses for full-scale caverns were performed to determine design parameters such as boil-off gas ratio (BOR), insulation thickness and pillar width. The result of the coupled hydro-mechanical analysis showed that BOR for underground storage system remains at about 0.04 %/day during the early stage of the operation. This value could be even much lower when the discontinuities in the rock masses are taken into consideration.

• International Journal of Highway Engineering
• /
• v.13 no.1
• /
• pp.21-32
• /
• 2011

The frost penetration depth of pavement is usually estimated from the freezing index that made temperature data analysis of 30 years and decided the thickness of anti-frost layer. The field monitoring region in study was divided into five regions by freezing index 550~650$^{\circ}C{\cdot}$day, 450~550$^{\circ}C{\cdot}$day and 350~450$^{\circ}C{\cdot}$day. Each region has three-section of road pavement such as cutting area, boundary area of cutting and banking, and lower area of banking. The field monitoring system was established both in the section of anti-frost layer and in the section without anti-frost layer. The data analysis was conducted for determination of frost penetration depth within the paved road by the field monitoring system. The result showed that The temperature of subgrade without anti-frost layer shows below zero in centigrade for the region of freezing index 550~650$^{\circ}C{\cdot}$day, up and down around zero degree in subgrade for the region of freezing index 450~550$^{\circ}C{\cdot}$day, and there is no place existed below zero degree in subgrade for the region of freezing index below 450$^{\circ}C{\cdot}$day. With comparison of field frost penetration depth for the cross-sections of pavement, the cutting area shows the greatest frost penetration depth, and less influence of frost penetration depth for the boundary area of cutting and banking, and the least influenced for the lower area of banking.

• Journal of the Korean Geotechnical Society
• /
• v.32 no.12
• /
• pp.59-67
• /
• 2016

The strength of frozen soils is affected by size and shape of particles, and the amount of ice and unfrozen water. The objective of this study is to characterize the unfrozen water content and the unconfined compressive strength of the frozen soils according to the degree of saturations and silt fractions. The specimens are mixtures of sand, silt, and water. The silt fractions (SF), which are the ratio of the silt weight ($W_{silt}$) to the sand weight ($W_{sand}$), are 10% and 30%. In addition, the degrees of the saturation are 5%, 10%, 15%, and 20%. The specimens are frozen under the temperature of $-10^{\circ}C$ conditions. The uniaxial compression tests are conducted for 24 hours, 48 hours, and 72 hours after freezing to determine proper freezing time. The freezing time of 24 hours is chosen because the unconfined compressive strengths of specimens after 24 hours freezing times are similar to each other. Furthermore, the unfrozen water content is monitored during freezing using the TDR system. The unfrozen water content increases with the increase of the silt fraction and degree of saturation. The unconfined compressive strength of the frozen soils exponentially increases with increasing the degree of saturation. This study shows that the amount of ice has more influence on the strength of the frozen soils than the amount of unfrozen water.

• Journal of the Korean Geotechnical Society
• /
• v.15 no.6
• /
• pp.297-306
• /
• 1999

In this research, the frost heave mechanism of the weathered tuff soil sampled from the area tying between Ulanbator and Beijing was studied. The frost heave tests were carried maintaining the constant temperature at both upper$(+5^{\circ}C)\; and\; lower(-5^{\circ}C)$ ends of the sample. Here, main emphasis is given on variation of the freezing point depression with the variation of applied overburden pressure. The expansion of ice lens and migration of the pore water towards freezing front were observed in the test. It was found that with the increase in overburden pressure there is decrease in heave rate and increase in the absolute value of a segregation-freezing temperature. Hence the equation between segregation-freezing temperature and overburden pressure could be suggested. Also the water content of the samples at the frozen side was shown to be higher than those at the unfrozen side. Similarly, the water at warmer part of the frozen tuff was found much higher than that of the cooler part.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.1
• /
• pp.229-236
• /
• 2003

Ultrasonic propagation velocities of both the dilatational and shear waves through the weathered tuff soil sampled from the area tying between Ulanbator and Beijing were measured under temperature condition of near subzero by means of sing-around method. After comparing the results with obtained data on unfrozen water content, a linear relation between velocities and unfrozen water content was performed with high coefficient value. Experimental results of two kinds of rather uniform materials, namely, glass-beads and silica micro-beads, testified the similar linear relations. In addition, the change rate of dilatational wave velocities with the change of volumetric unfrozen water content was not dependent on soil type. Although a rational theory of the ultrasonic velocities dependence on the unfrozen water content is not yet proposed, the presented empirical relationships may suggest the appropriate evaluation to the effect of unfrozen water on dynamic characteristics of frozen soil.

• International Journal of Highway Engineering
• /
• v.12 no.2
• /
• pp.107-113
• /
• 2010

In this study, the relative effects of low-chloride deicier(LCD) and two other deicing agents on the scaling of concrete were conducted in a series of tests at laboratory accordance with the ASTM C 672. The solutions concentration of deicers tested included 1, 4, 10%. Tap water was used as control. The amount of scaling was evaluated gravimetrically. As test result of deicer solution types, when applied to 4% solutions, surface scaling of concrete after 56 freeze-thaw cycles was produced significantly as about 9 times on LCD solution, as about 18 times on $CaCl_2$ solution, and as about 33 times on NaCl solution comparing with tap water. As test result of deicer solution concentrations, relatively low concentrations (of the 4% by weight) of deicer were produced more surface scaling than higher concentrations (of the 10% by weight) or lower concentrations (of the 1% by weight) of deicer. It show that the damaging concentration is of the order of 3~4% for previous research result. It appears that the mechanism of surface scaling is primarily physical rather than chemical. Also, the effect of chloride deicier types, freeze-thaw cycling, and air contents on the performance of concrete was experimentally investigated. The results show that the concrete specimens subjected to freeze-thaw cycling scaled more severely in exposure to deicing salt than those in non-exposure to deicing salt, weight losses of the specimens tested in exposure to deicing salt were twice as much as those tested in non-exposure to deicing salt. Relative dynamic modulus of elasticity of concrete specimens decreased more quickly in exposure to deicing salt than in non-exposure to deicing salt. Also, relative dynamic modulus of elasticity of concrete specimens in exposure to sodium chloride deicing salt was decreased more quickly comparing with exposure to LCD salt. It is also shown that the chloride contents according to concrete specimen depths was more largely in exposure to LCD salt. When concrete specimen is exposed to chloride deicing salts and freeze-thaw cycling, performance degradation in the entrained air concrete(AE concrete) retarded more considerably comparing with non-entrained air concrete(Non-AE concrete).