• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.1
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• pp.15-20
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• 2009

Marine concrete structure is exposed to salt injury and deteriorated by steel corrosion due to chloride ions diffusion. It, therefore, is very important to estimate the chloride diffusivity in concrete. In this paper the compressive strength and permeable pore volume of concrete are measured and the diffusion coefficient and penetration depth of chloride ions in concrete were investigated to estimate the chloride diffusivity efficiently. To correlate these results each other, regression analysis was done. The results showed a good linear relation between chloride diffusivity and the fundamental properties of concrete and the chloride diffusivity of concrete with water-cement ratios of $40%{\sim}60%$ were about $2.5{\sim}6.6{\times}10^{-12}m^2/s$.

• Journal of the Korean GEO-environmental Society
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• v.24 no.9
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• pp.5-13
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• 2023

Cement-based reinforcement materials, which are representative slope reinforcement materials, can cause contamination of ground and groundwater when ground injection or surface application is applied. Accordingly, slope reinforcement materials using eco-friendly biopolymers are attracting attention as a means of replacing existing materials, but the biopolymers currently used are easily dissolved when exposed to groundwater or rainfall environments, reducing strength. In order to solve this problem, the cross-linking of protein between sodium casein and Transglutaminase (TGase, C₂₀H₁₆N₄O₂S₂) was used to increase the water resistance of biopolymers, and a rainfall slope test was conducted to evaluate their usability and applicability as a slope reinforcing material. In the case of reinforcement with only sodium casein, the precipitation dissolved sodium casein, and the slope was completely destroyed in 1 hour. On the other hand, it was observed that the slope reinforced by adding a small amount of TGase (0.5%) do not collapse even after 80 hours of rainfall duration due to increased water resistance. Strength and water resistance increases due to the addition of a small amount of TGase, and its applicability as an eco-friendly reinforcement is confirmed.

• Journal of the Korean Geotechnical Society
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• v.30 no.7
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• pp.5-15
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• 2014

Abandoned mine deposits are exposed to various physico-chemical geo-environmental hazards and disasters, such as acid mine drainage, water contamination, erosion, and landslides. This paper presents the ring shear characteristics of waste materials. The ring shear box with a rotatable O-ring was used in this study. Three tests were performed: (i) Shear stress-time relationship for given normal stress and shear speed, (ii) shear stress as a function of shear speed, and (iii) shear stress as a function of normal stress. For a given normal stress (50 kPa) and speed (0.1 mm/sec), the materials tested exhibit a strain softening behavior, regardless of drainage condition. The peak and residual shear stresses were determined for each normal stress and shear speed. The shear stress was measured when shear speed is equal to 0.01, 0.1, 1, 10, 50, 100 mm/sec or when normal stress is equal to 20, 40, 60, 80, 100, 150 kPa. From the test results, we found that the shear stress increases with increasing shear speed. The shear stress also increases with increasing normal stress. However, different types of shearing mode were observed in drained and undrained conditions. Under drained condition, particle crushing was observed from the shearing zone to the bottom of lower ring. Under undrained condition, particle crushing was observed only at the shearing zone, which has approximately 1 cm thick. It means that a significant high shear speed under undrained condition can result in increased landslide hazard.

• Asian Journal of Turfgrass Science
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• v.19 no.1
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• pp.27-38
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• 2005

This study was conducted to find out withering and dying trends of turfgrasses on the base of tree, and to investigated how much area of turfgrasses withering and dying were progressed on angle of inclination at golf course. Turfgrasses withering and dying on base of trees on slope was extended more to the down-solpe direction than to the up-solpe direction. This trend was common in all experiment plot. Turfgrasses on the base of trees were withered and dead by competing with tree root fur nutrients and moisture in soil. But the trend of the withering and dying in some experiment plots occurred by soil erosion following turfgrass withering and dying occurring on upside ridge. This trend was generally appeared in region of tree community at upside ridge. The form of turfgrass withering and dying on the base of tree in some experiment plots was similar to that of the tree crown. This withering and dying from occurred at the $11^{th}$ experiment plot in Ji San Golf Course and the $6^{th}$ experiment plot in East valley Golf Course.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.4
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• pp.393-400
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• 2012

In recent years, nano-structured thin film systems are often applied in industries such as MEMS/NEMS device, optical coating, semiconductor or like this. Thin films are used for many and varied purpose to provide resistance to abrasion, erosion, corrosion, or high temperature oxidation and also to provide special magnetic or dielectric properties. Quite a number of articles to evaluate the characterization of thin film structure such as film density, film grain size, film elastic properties, and film/substrate interface condition were reported. Among them, the evaluation of film adhesive to substrate has been of great interest. In this study, we fabricated the polymeric thin film system with different adhesive conditions to evaluate the adhesive condition of the thin film. The nano-structured thin film system was fabricated by spin coating method. And then V(z) curve technique was applied to evaluate adhesive condition of the interface by measuring the surface acoustic wave(SAW) velocity by scanning acoustic microscope(SAM). Furthermore, a nano-scratch technique was applied to the systems to obtain correlations between the velocity of the SAW propagating within the system including the interface and the shear adhesive force. The results show a good correlation between the SAW velocities measured by acoustic spectroscope and the critical load measured by the nano-scratch test. Consequently, V(z) curve method showed potentials for characterizing the adhesive conditions at the interface by acoustic microscope.

• Journal of the Korean Geotechnical Society
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• v.18 no.5
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• pp.251-260
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• 2002

Geotextile tribes are made of sewn geotextile sheet and hydraulically or mechanically filled with dredged materials. They have been applied in hydraulic and coastal engineering in recent years(shore protection structure, detached breakwater, groins, and jetty). Therefore, it is composed of geotextile and confined fill material. Recently, new preliminary design criteria supported by model and prototype tests, and some stability analysis calculations have been studied. The stability analysis of geotextile tube is composed of geotechnical and hydrodynamic analysis. The stability check points are sliding failure, overturning, bearing capacity failure against the wave attack. In this paper are presented the stability analysis method by empirical equation and 2-D equilibrium analysis for geotextile tube. Also, the hydraulic model tests were performed to verify the theoretical stability analysis with geotextile tube shape, filling ratio, significant wave height, and so on. The results of this study show that the stability of geotextile tube depends on the tube shape, contact area, projection area. The theoretical analysis and hydraulic model test show almost the same results.

• Journal of the Korean Geotechnical Society
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• v.20 no.5
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• pp.49-58
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• 2004

Consolidation properties of Shihwa deposits were analysed by means of depositional environments. Depositional environments including particle size distributions, sediment structures, geochemical properties, porewater chemistries and carbon age dating were analysed using undisturbed samples retrieved successively from a boring hole in the study area. Laboratory oedometer tests and anisotropic consolidated triaxial tests (CKoUC) for undisturbed samples were performed to examine the overconsolidation phenomena. Based on the results of analysis of depositional environments, it was found that the upper silt/clay mixed layer was deposited under marine condition while underlying sand and clay layers were deposited under fluvial condition. Planar laminated structures of silts and clays were dominant in marine deposits. Although there was no clear evidences that geological erosion had occurred in marine deposits, overconsolidation ratios of the upper marine samples were greater than unity Stress Paths of the upper marine samples behaved similarly to those of normally consolidated clays. Data plotted in stress state charts showed that the marine deposits were normally consolidated in geological meaning. These apparent overconsolidation of the marine deposits can be explained by the structures i.e. chemical bonding due to the difference of the rate of deposition, not by geological erosions and ground water fluctuations.

• Journal of the Korean GEO-environmental Society
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• v.19 no.3
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• pp.25-33
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• 2018

Piping is one of the most frequently occurring collapse type of a levee, and is often caused by roofing (backward erosion piping) at the ground-structure interface. Roofing is generally evaluated using creep ratio. However, creep ratio does not take into account the characteristics of the ground-structure interface. In this study, the roofing risk was investigated by using model test and numerical analysis considering the ground-structure interface characteristics. In the model test, it was confirmed that the piping potential decreased as the interface roughness increased, and this was applied to the numerical analysis. Existing numerical methods can not adequately simulate the particle behavior at the ground-structure interface because only the water level difference is considered. In this paper, particle behavior at the interface was investigated by performing seepage analysis and then, carrying out particle analysis technique simulating the boundary condition of the ground-structure interface. Analysis results have shown that the roofing resistance decreases as the ground-structure interface roughness decreases.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.465-465
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• 2011

강우가 발생하거나 관개를 함에 따라 농경지의 토양침식물, 잔류 비료나 농약 등의 비점오염원은 지표 및 지하 유출과 함께 거동함으로써 지표수 뿐 아니라 지하수 수질에도 영향을 미칠 수 있다. 특히, 최근 고부가가치 농산물 수요의 증가로 전국적으로 시설재배 농업이 확대되고 있으나 시설재배 내에서의 비점오염원 유출특성에 관한 연구는 미흡하다. 따라서 시설재배 농업과 관행농업의 비점오염원의 거동 및 지하침투 오염부하를 비교 평가하고 비점오염원을 저감하기 위한 적절한 방안 마련이 필요하다. 따라서 본 연구에서는 시설 및 관행재배 지역의 지하침투 오염부하량을 평가하기 위하여 주변 영향이 배제되어 시설재배와 관행재배의 비교 평가 가능한 포장 및 광역 단위 시험포장을 선정하고 모니터링 시스템을 구축하였다. 먼저 필지 단위와 광역 단위 단위에서의 모니터링 시스템을 설계하고, 수문 및 수질 분석 항목을 설정하였다. 이를 바탕으로 관행재배지에서의 물수지 모니터링을 위하여 기상 및 강우량, 지하수위, 토양수분, 관개 및 배수량을 측정하기 위한 장비를 설치하고, 토양수 및 지하수의 물질 수지 분석을 분석하기 위한 토양수, 지하수, 논담수 등의 수질 샘플망을 구축하였다. 또한 시설재배지에서의 물수지 모니터링을 위하여 기상, 지하수위, 토양수분 및 관개량을 측정하기 위한 장비를 설치하고, 토양수 및 지하수의 물질 수지 분석을 분석하기 위한 토양수, 지하수, 관개용수 등의 수질 샘플망을 구축하였다. 향후 본 시험 포장에 대한 지속적인 모니터링과 샘플링 실시하여 다양한 항목에 대한 조사 및 분석이 이루어진 다면 시설재배지 비점오염원 모니터링 및 정량화 기술개발을 통해 시설재배지에서의 비점오염에 대한 정량적 자료구축이 가능할 것으로 판단되며, 기초적인 자료를 제공함으로써 국내 농업비점오염총량 추정 기술에 기여할 수 있을 것으로 판단된다.

• Journal of Sericultural and Entomological Science
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• v.19 no.1
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• pp.19-23
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• 1977

In the previous short communication, the authors reported the applicability of Sodium Hyplochoride solution to silkworm rearing industry as a disinfectant after confirmed the fact that the chemical agent is capable to kill most of the pathogens of silkworm diseases. The authors, in the present study, attempted to investigate the influence of the chemical on the growth of silkworm larvae and the effect on the disinfection of silkworm larvae to inactivate the pathogen of yellow muscardine disease, Isaria farinosa and the results obtained are summarized as fellows. 1. The chemical agent did not affect the growth of silkworm larvae, when it was applied on silk-worm body with the concentration of 1,3,5 per cent of the agent during the rearing period. 2. The Sodium Hypochloride solution did not give any damage to silkworm larvae when larvae were fed up with 1,3,5 per cent of the solution. 3. In the bioassay of the solution on disinfection of larvae inoculated with yellow muscardine disease pathogen, the fact that the agent could control the disease was observed by showing much low infection rate in 3.5 per cent treatment compared to non-treatment control.