• Journal of the Korean Geotechnical Society
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• v.29 no.8
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• pp.53-63
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• 2013

Bored pre-cast piles using PHC piles is widely used in foundation of building structures constructed in urban areas because noise and vibration due to pile installation are low. However, since slime is formed at the base of borehole and the density of bearing stratum surrounding the base of borehole is decreased due to stress relaxation in drilling process of bored pre-cast pile method, the base load capacity of bored pre-cast piles is very low compared to the strength of bearing stratum. In this study, a new type of PHC pile, which short steel pipe with the same diameter as the PHC pile is attached to the pile tip, is developed to increase the base load capacity of bored pre-cast piles. In order to check the effect of the use of new PHC pile on the base load capacity of bored pre-cast piles, field pile load tests are performed for bored pre-cast piles using the new and existing PHC piles. Results of the pile load tests show that the new PHC pile gives higher base load capacity to bored pre-cast piles than the existing PHC pile, since the tip of new PHC pile is penetrated to undisturbed bearing stratum passing through the slime at the base of borehole and the loosened bearing stratum under the slime by pile driving using light hammer.

• Journal of Korean Society of Forest Science
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• v.107 no.3
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• pp.287-293
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• 2018

This study was carried out to provide surface bearing capacity reinforcement of forest road by sub-base facilities based on a soft ground use of geosynthetics to prevent the damage of the road surface passing heavy logging trucks and to pass smoothly heavy truck against growing timber harvesting. The analysis of the road surface bearing capacity as progressing time and the increase of the number of passage of heavy logging trucks were conducted experimental section of forest road on the soft ground in the Forest Technology and Management Research Center. As a result, it was found that the road surface bearing capacity were stabilized at CBR of 15% or more, the effect of reinforcement by type of geosynthetics showed no significant difference after the lapse of about 1 year. After reaching the passage of 300 times for the heavy logging trucks on the sub-base construction section, the settlements was stabilized below the allowable standard of 50 mm, road surface bearing capacity also improved to more than CBR 20% and there was no significant difference in the thickness of the sub-base. However, in the section where the sub-base is not constructed, it is found that the lack of surface bearing capacity with the settlements more than the allowable standard is not possible to pass the heavy logging trucks. Therefore, in order to reinforce the road surface bearing capacity of the soft ground for the passage of the heavy logging trucks, it is necessary to construct a sub-base of at least 0.2 m when using geosynthetics.

• Journal of the Korean GEO-environmental Society
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• v.18 no.5
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• pp.55-60
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• 2017

It is critical for Korea to make effective use of limited space as it has dense population and high traffic volume compared to its terrestrial area. To resolve this issue, diverse types of underground structures have increasingly been applied so far, and one of the most representative structures is double-deck tunnel. It has upper and lower roads separated by middle slab that shows dynamic behavior according to the vehicle and earthquake loads. In case of the characteristics of earthquake response, it is necessary to have exploratory study as it has high loads, complex working mechanism, and difficult theoretical approach. In order to understand the characteristics of earthquake response based on the supporting conditions of middle slab in double-deck tunnel, this study conducts indoor shaking table test with 3 test cases: (1) fix both brackets, (2) free and fix at each bracket and (3) free at both brackets for 2 seismic waves of artificial and Gyeongju earthquake. The result shows if the middle slab is free at both brackets, the acceleration response is reduced 41% for artificial earthquake and 60% for Gyeongju earthquake compared to the one with fix at both brackets.

• Korean journal of communication and information
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• v.58
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• pp.55-73
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• 2012

This study is critical research on the forming public opinion of SNS and participation behavior. Twitter is a typical SNS service, free school food and 10.26 re-and by-elections during the formation of public opinion on the impact have been investigated. Formation of public opinion about Twitter's analysis of the first research question, The case of free meals to support the Mayor Oh, rather than against Twitter were influential. 10.26 re-and by-elections Twitter in space, the Park' candidate than Na' candidate has formed a favorable opinion. Power twitterian and twitterian on the behavior of the second study involved analysis of the problem, For free meals, power twitterian were responsible for leading the public opinion. For 10.26 re-and by-elections, Power twitterian were more Park' candidates than Na' candidates. In addition, Park' candidates of twitterians were communicating more. Through traditional media in the process of forming public opinion was swayed by public opinion to the target people simply but SNS age people involved in the production and distribution of the issue and the issue has a leading role.

• Journal of the Korean Geosynthetics Society
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• v.15 no.1
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• pp.21-35
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• 2016

It is a current trend that the concrete track is applied for high speed railway. In the case of the railway embankment constructed on soft ground, the damage to concrete track which is sensitive to settlement such as distortion and deflection could be caused by very small amount of long term settlement. Pile Supported Embankment method can be considered as the effective method to control the residual settlement of the railway embankment on soft ground. The Geosynthetics is used inside of the embankment to maximize the arching effect transmitting the load of the embankment to the top of the piles. But, PHC piles that are generally used for bridge structures are also applied as the pile supporting the load of embankment concentrated by the effect of the Geosynthetics. That is very low efficiency in respect of pile material. So, in this study, the cast in place concrete pile was selected as the most suitable pile type for supporting the embankment by a case study and the optimum mixing condition of concrete using a by-product of industry was induced by performing the mixing designs and the compressive strength designs. And it is shown that the cast in place pile with the optimum mixing condition using the by-product of industry is 2.8 times more efficient than the PHC pile for the purpose of Pile Supported Embankment by the finite element analysis method.

• Journal of the Korean Geotechnical Society
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• v.16 no.1
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• pp.131-143
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• 2000

Several theoretical analyses are performed to predict the vertical load on embankment piles with cap beams. The piles are installed in a row in soft ground below the embankment and the cap beams are placed perpendicular to the longitudinal axis of the embankment. Two failure mechanisms such as the soil arching failure and the punching shear failure are investigated according to the failure pattern in embankment on soft ground supported by piles with cap beams. The soil arching can be developed when the space between cap beams is narrow and/or the embankment is high enough. In the investigation of the soil arching failure, the stability in the crown of the arch is compared with that above the cap beams. The factors affecting the load transfer in the embankment fill by soil arching are the space between cap beams, the width of cap beams and the soil parameters of the embankment fill. The portion of the embankment load carried by cap beams decreases with increment of the space between cap beams, while it increases with the embankment height, the width of cap beams, the internal friction angle and cohesion of the embankment fill. Thus, the factors affecting load transfer in embankment should be appropriately decided in order to maximize the effect of embankment load transfer by piles.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.3
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• pp.303-312
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• 2008

Multi-axial compression tests have been frequently adopted for the evaluation of material properties of rock cores and rock fracture model tests. Special care has to be applied on the boundary condition between the specimen and loading platen to draw the precise test results of the multi-axial compression tests. With the use of dry steel platen, the stress rotation will occur, due to the frictional restraint from the boundary between the specimen and loading platen. The restraint will deviate the expected test results under the conditions of the given external pressures. Various methods have been applied to reduce the side restraint along the specimen/loading platen interface. The steel brush type loading platen is one example of the attempts. In this paper, a new type of loading platen is introduced to overcome the limitation caused by the use of the brush type loading platen, which requires some internal space for the installation of the brushes. The new type of loading platen, roller supported steel piston type loading platen. is constituted of shot steel pistons which have sufficient stiffness to deliver the external pressure and the shaft type roller installed at the rear of the pistons. The pistons are designed to follow the local deformation of the specimens. In this paper, structural details of the loading platen are presented and frictional and biaxial compression tests results are shown to verify the required functions of the loading platen. Furthermore, calibration process is followed by a comparison between the test results and numerical analyses.

• Journal of Korean Home Economics Education Association
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• v.25 no.3
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• pp.79-91
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• 2013

The purpose of this study was to investigate the relation among peer support, family strength and self-control. This subjects were the 438 high school students living in Gwangju. Data were analyzed with SPSS 18.0 program. The major findings were as follows; First, the high school students' peer support and family strength scores were higher than median(3.00). Also, long-term satisfaction pursuit scores were higher than median and the immediate satisfaction pursuit scores were lower than median. Second, peer support showed significant difference according to sex. Family strength showed partially significant difference according to standard of living and parents' education achievement. Self-controls showed significant difference according to sex and father's education achievement. Third, family strength and the self-control showed significant correlation. Forth, the high school students' self-control was influenced by role sharing and problem solving, communication and family bonding and fathers' education achievement. And the high school students' self-control was explained about 15% by these variables. In conclusion, the role of home is important. it is necessary to enhance the education of financial stability and to improve self-control in order to help the students enhance solidity among family and communicate affirmatively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.1
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• pp.641-648
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• 2020

This study was undertaken to provide basic data for the development of a mental health promotion intervention program, by confirming the mediating effects of social support in relation to the effect on the life stress and meaning of life in middle-aged women. The subjects of this study were 201 middle-aged women from D and K cities. The data were analyzed with descriptive statistics and Pearson's correlations using a statistical program for structural equation modeling (SEM); fitness of the final model was RMSEA 0.03, CFI 0.98, and NFI 0.95. The major learning from this study was that life stress has a direct effect on meaning of life and social support. Life stress (β=0.05, p< 0.001), meaning of life (β=0.05, p< 0.001), and social support (β=0.05, p< 0.001) have a significant and direct effect on depression. The findings also suggest that life stress indirectly affects the mediating effect between meaning of life and social support, and also depression of middle-aged women. We believe that results of this study encompass basic data that will aid in developing a program to promote the mental health of middle-aged women.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.231-239
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• 2018

This study was conducted to examine the influence of personal characteristics of infant-toddler and mother, social support and mother-child interaction on mother-child attachment. A descriptive study was implemented, and data were gathered from March 1 to September 30, 2016. The subjects were 215 mothers whose children were in infancy or toddlers. A survey was conducted with self-administered questionnaires regarding general characteristics, social support, mother-child interaction and attachment. SPSS 24.0 was used for descriptive statistics, intergroup comparisons of average scores, correlation analysis and multiple regression analysis. Statistically significant differences in average attachment scores according to gender (t=3.200, p<0.002), age (t=4.037, p<0.001) and temperament (F=4.614, p<0.011) were observed among the characteristics of infant-toddlers, as well as according to age (F=18.028, p<0.001) and academic credentials (F=4.241, p<0.016) among the characteristics of mother. Attachment was correlated with social support (r=0.507, p<0.001) and with mother-child interaction (r=0.571, p<0.001). The factors that affected attachment were mother-child interaction (${\beta}=0.361$, p<0.001), social support (${\beta}=0.309$, p<0.001), age (under the age of 30)(${\beta}=-0.370$, p<0.001) and marriage duration (less than 10 years)(${\beta}=-0.179$, p<0.033). Overall, the results indicate that interaction programs that bolster social support and mother-child interactions that exert a crucial influence on attachment should be developed.