• Korean Journal of Fisheries and Aquatic Sciences
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• v.16 no.4
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• pp.335-340
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• 1983

The effects of water temperature, salinity, and silt and clay on the photosynthetic activity of Porphyra yezoensis were measured. The rate of photosynthesis of P. yezoensis increases as the water temperature rises in the range of $8{\sim}16^{\circ}C$ and begin to decrease at $18^{\circ}C$. In the salinity range of $21.5{\sim}33.5\%0$, the rate of photosythesis of P. yezoensis was increased in the sea water of $29.5\%0$ salinity and decreased in $21.5\%0$ salinity. The rates of photosynthesis of P. yezoensis were significantly decreased with increase of the concentration of silt and clay and the time of exposure to suspended silt and clay. Of the combined effects of salinity, and silt and clay on the photosynthetic activity of P. yezoensis, the effects of silt and clay were higher in the low salinity of $21.5\%0$ and $33.5\%0$. The wet weight of P. yezoensis showed a remarkable loss with increase of the concentration of silt and clay and the time of exposure to silt and clay.

• Journal of the Korean GEO-environmental Society
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• v.11 no.3
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• pp.43-51
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• 2010

In the downstream areas of the Nakdong river, Pusan clays are commonly found and thickness may reach to maximum of 100m. From geological point of view, Pusan clay are characterized as holocene clays, deposited for approximately 20,000 years ago. Recently, there have been many construction projects based on these soft ground areas. It is needed to know clearly soil properties of the areas for design and safety analysis, especially undrained shear strength of soft clays. However, Pusan clay have not been studied systematically because the clay layers are usually very deep, having high sensitivity characteristic. In this study, undisturbed UD samples obtained from the downstream areas of the Nakdong river were researched using laboratory tests (CthUE, CKcUC, CIUC, UU and UC) and in-situ tests (Field Vane, CPTu). The undrained shear strength characteristics of the samples were depicted using stress-strain relationship.

• Journal of the Korean Society of Clothing and Textiles
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• v.13 no.3 s.31
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• pp.207-222
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• 1989

New process for the preparation of the artificially soild cloth (ASC) used for detergency evaluation was developed and its detergency was also studied. ASC was prepared by the dipping of cotton cloth in the water in which oily soil, protein (gelatine), carbon black and clay had been dispersed. The clay used for this ASC was red yellowish soil around Mt. Kumjung and was a typical soil in Pusan area. Adhesive status of soil at prepared ASc was examined by an electron microscope, and crystallyzation and color change of used clay were evaluated with the determination of X-ray diffraction and surface reflectance. For the evaluation of detergency by the washing with commercial and model detergents, the behavior of soil removal from this ASC comparing with naturally soiled collar cloth was examined. Those results are summerized as followings; 1) Adhesive ststus of soil at prepared ASc was very similar to that of naturally soiled collar cloth. 2) A crystalline of clay calcined at $800^{\circ}C$ was disappeared in part and color of calcined clay changed into reddish yellow by the decomposition of organic matters. 3) More uniform ASc was prepared with clay calcined at $800^{\circ}C\;that\;200^{\circ}C$ however its detergency prepared from clay calcined at $800^{\circ}C$ was poor 4) A significant relationship between the content of inorganic matter in ASc and K/S value was found, however no significant result between the content of protein contaminated and K/S value was observed. 5) Detergency of prepared ASc had a very similar to that of naturally soiled collar cloh.

• Journal of the Korean Geotechnical Society
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• v.22 no.12
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• pp.57-65
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• 2006

In the Nakdong River estuary soft and thick clay, which called Pusan clay, are deposited. Despite a number of great reclaimed projects that have been performed in the area, the consolidation settlement and time have been significantly underestimated due dominantly to sample disturbance, since the last decade. In order to resolve the underestmation, it was necessary to examine the compressibility characteristics through a systematic geotechnical investigation on the clay. In this study an advanced sampling technique was adopted on two sites chosen along the coastline, and then oedometer testing and geological investigation were performed for the undisturbed and reconstituted samples. As the results, the compressibility parameters of the clay were representatively determined, as well as their correlation. Particularly the effects of depositional environment on the physical indexes, level of structure, sample disturbance and compressibility parameters were analyzed for the clay.

• 한국석유지질학회:학술대회논문집
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• autumn
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• pp.45-45
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• 2000

• Journal of the Mineralogical Society of Korea
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• v.18 no.1
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• pp.1-9
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• 2005

The electrocatalytic reduction of O₂ was investigated with methyl viologen and methylene blue incorporated clay-modified electrodes. Clay suspensions were prepared with Na-montmorillonite, Ca-montmorillonite, and kaolinite. The methyl viologen-clay modified electrodes were made by coating clay suspensions adsorbing methyl viologen on a glassy carbon electrode. Cyclic voltammetry were performed in aqueous media to investigate the electrocatalytic property of the modified electrode in reducing O₂. A Na-montmorillonite modified electrode showed the greatest adsorption capacity for methyl viologen. The modified electrode made of Na-montmorillonite suspension of 0.87 g/10 mL and a 2.5 mM of methyl viologen solution showed the most effective electrocatalytic property, where the catalytic reduction potential was shifted by 242.6 mV toward the positive potential. The electrocatalytic ability was more significant in acidic (pH=3.7) and alkaline (pH=12.7) media than the neutral pH range (6.3∼8.3). The methyl viologen-Na-montmorillonite modified electrode had the good reproducibility and maintain the electrocatalytic property over 20 times reuse.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.21 no.4
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• pp.246-258
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• 1988

Semi-quantitative analysis of $less-than-2{\mu}m$ clay minerals in thirty-nine superficial sediments from the Chinju Bay, southern coast of Korea, was made to reveal the distribution, provenance and dispersal pattern of fine-grained sediments. Additional nine samples were also taken from the Choryang Cheon (a river draining the kaolin-rich Hadong area) to investigate the influence of river a discharge. Grain size analysis for the Chinju Bay sediment samples was performed simultaneously as an aid to understand the sediment types and depositional environments. Except for the northeastern part, clayey mud predominates the entire bay. Average relative abundance of the four major clay minerals, I. I., illite, kaolinite, chlorite and smectite, is $55.1\%,\;23\%,\;21.5\%\;and\;0.4\%$, respectively. Although illite dominant clay mineral, the average content is about $10\~20\%$ tourer than that of the nearby continental shelf area. On the contrary, kaolinite content in the bay is about $10\%$ higher than that of the shelf area. Recent clay minerals of the Chinju Bay are mainly derived from the nearby inland area through numerous rivers and streams. Transport from shelf area, however. also seems to be important.

• Geomechanics and Engineering
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• v.14 no.2
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• pp.175-185
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• 2018

Sand Compaction Piles (SCPs) are constructed by feeding and compacting sand into soft clay ground. Sand piles have been installed with irregular cross-sectional shapes, and mixtures of both sand and clay, which violate the design requirement of circular shape according to the replacement area ratio due to various factors, including side flow pressure. Therefore, design assumptions cannot be satisfied according to the conditions of the ground and construction and the replacement area ratio. Two case histories were collected, examined, and interpreted in order to study the effect of the shape of SCPs. The effects of the distortion of SCP shape and the mixture of sand and clay were studied with the results of large direct shear tests. The design internal friction angle was secured with the irregular cross-sectional sand piles regardless of the replacement area ratio. The design internal friction angle was secured regardless of mixed condition when the mixture of sand and clay was higher than the replacement area ratio of 65%. Therefore, systematic construction management is recommended with a replacement area ratio below 65%.

• Journal of the Korean Geotechnical Society
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• v.33 no.10
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• pp.15-24
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• 2017

A self-supported temporary excavation method called Inclined Earth Retaining structure (IER) has been developed by improving an existing excavation method. The stability of the IER was proved with both model tests and field tests. Especially, the results of the model tests proved that the lateral displacement of a model retaining wall was significantly reduced in clay. In this study, the applicability of the IER installed in the soft clay ground is estimated by analyzing survey data collected in the construction field. The results of FE analysis show that the lateral displacement of the IER decreased by 70.9% of that of a single row, self-supported retaining wall using the same number of H-piles. Thus, using the IER method in the soft clay ground will increase the stability of the excavated ground with the effect restraining its lateral displacement. Furthermore, using Deep Cement Mixing (DCM) to the upper half embedded depth of front support is recommended as a subsidiary method of reducing the lateral displacement of IER in the soft clay ground based on FE analysis results.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.505-512
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• 1999

Soft marine clay deposits pose several foundation problems. Generally, lime stabilization is used worldwide for solidifying of soft marine clay deposits. In this paper, a series of laboratory tests were conducted to verify clay-lime reaction. A clay was collected from Pusan, which was mixed with various quantities of quick lime and slaked lime. Various compounds produced by clay-lime reaction were identified by X-ray diffraction analysis. The physico-chemical properties of the clay were also investigated. Compounds such as calcium silicate hydrate (CSH), calcium aluminate hydrate (CAH), calcium aluminate (CA), hillebrandite, and gehlenite were identified. It is likely that such compounds were mainly produced by pozzolanic reaction. Based on the change of physico-chemical properties obtained by the reaction, the water content was considerably decreased when lime was added to the clay. In addition, unconfined strength was increased. In the other hand, quick lime was more effective than slaked lime in decreasing and increasing of the water content and unconfined strength, respectively. Fewer cracks were produced when the clay was mixed with quick lime. It is suggested that these beneficial changes produced by the mixing of the clay and lime depend on the properties of compounds obtained by chemical reaction.