• Journal of Ocean Engineering and Technology
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• v.25 no.6
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• pp.110-115
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• 2011

Numerouslong-term consolidation and secondary compression settlements may occur in Busan clay, which is astructured soft clay and consists of a thick clay deposit. As a surcharge load is applied to soils, soils experience different stress paths with depth. Therefore, it is necessary to study the long-term consolidation behavior of Busan clay considering stress conditions such as OC or NC states. In this study, a series of long-term consolidation tests were performed to investigate the consolidation characteristics of Busan clay for 20 days. The undisturbed clay samples were taken from 3 sites located in the Nakdong River estuary. The results showed that the creep rate of the Busan clay gradually decreased with time, which indicated that the secondary compression settlement decreased with time. In addition, the experimental results for 3 samples showed that the ratios were about 0.0363 and 0.051, respectively.

• Journal of the Korean Applied Science and Technology
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• v.34 no.4
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• pp.799-806
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• 2017

The potential use of modified clays in the adsorption of vapor phase benzene and toluene was investigated. The modified clays OC-CPC, IOC, and Al-PILC were prepared for comparative purposes and were characterized using infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction. It was confirmed the intercalation of the aluminium pillar in IOC and Al-PILC, as well as the introduction of cetylpyridinium. The adsorption studies showed a great affinity of benzene and toluene for OC-CPC due to the hydrophobic character that resulted and also to the increase in the interlaminar distance. IOC showed a lower affinity for the benzene and toluene, followed by Al-PILC. Natual clay had no affinity for benzene and toluene due to its hydrophilic nature. Clay materials having a laminar structure can be chemically modified, changing their physiochemical characteristics, such as interlaminar distance, surface area, pore size, and chemical affinity. In this study, it was focused on obtaining modified clays to be used for the adsorption of volatile organic chemicals.

• Geomechanics and Engineering
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• v.29 no.1
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• pp.1-11
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• 2022

A semi-analytical solution to responses of overconsolidated (OC) unsaturated soils surrounding an expanding spherical cavity under constant suction condition is presented. To capture the elastoplastic hydro-mechanical property of OC unsaturated soils, the unified hardening (UH) model for OC unsaturated soil is adopted in corporation with a soil-water characteristic curve (SWCC) and two suction yield surfaces. Taking the specific volume, radial stress, tangential stress and degree of saturation as the four basic unknowns, the problem investigated is formulated by solving a set of first-order ordinary differential equations with the help of an auxiliary variable and an iterative algorithm. The present solution is validated by comparing with available solution based on the modified Cam Clay (MCC) model. Parametric studies reveal that the hydraulic and mechanical responses of spherical cavity expanding in unsaturated soils are not only coupled, but also affected by suction and overconsolidation ratio (OCR) significantly. More importantly, whether hydraulic yield will occur or not depends only on the initial relationship between suction yield stress and suction. The presented solution can be used for calibration of some insitu tests in OC unsaturated soil.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.2
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• pp.219-226
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• 2020

Over the last decades, great efforts have been devoted to reuse industrial wastes and by-products from various industries as supplementary cementitious materials in order to reduce carbon dioxide(CO₂) emission by reducing the use of Portland cement in construction. Oyster shell waste, originating from the fishery industry, is available in huge quantities in certain areas, and is generally discarded or landfilled. In this study, we aimed to reuse oyster shell as an alternative to limestone in limestone calcined clay cement(LC³). The oyster shell calcined clay cement(OC³) paste were produced and were characterized via X-ray diffraction, isothermal calorimetry, compressive strength tests, and thermogravimetry. The results revealed that OC³ pastes exhibited similar strength development and reactivities by pozzolanic reaction with LC³, which implies that oyster shell could be used as a substitute for limestone in LC³.

• Journal of the Korean Geotechnical Society
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• v.26 no.11
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• pp.47-61
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• 2010

To predict the settlement rate of a ground area that incorporates vertical drains, it is desirable to conduct various kinds of advanced field and laboratory tests for hydraulic properties. However, it is urgently needed to appropriately evaluate the hydraulic properties using the results of conventional soil tests which are extensively used for local practice. To achieve this purpose, a number of CPT dissipation test, laboratory permeability and consolidation tests were performed at five sites in the floodplain of the Nakdong River delta, and the test data were comprehensively analyzed. As a result, it is found that the coefficients of horizontal consolidation ($C_{h,NC}$) and permeability ($k_{h,OC}$) of the clay agreed well with those of the CPT-based methods proposed by Baligh and Levadoux (1986). The values of $C_{h,NC}$ and $k_{h,OC}$ were in the range of $0.4{\sim}3.0\;cm^2/sec$ and $0.40{\sim}2.50\;cm^2/sec$, each of which slightly increases or decreases with depth, respectively. It was also inferred that these trends seem to reflect the depositional environments of the clay.

• Proceedings of the KSRS Conference
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• 2009.03a
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• pp.121-125
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• 2009

농업과 환경분야에서 토양 상태를 신속하고 주기적으로 모니터링하는 것에 대한 관심이 높아지고 있다. 토양의 특성을 측정하는 기존의 화학분석 방식은 분석의 정밀도, 시료의 수, 분석항목 등에 따라 시간, 인력, 비용적 소모가 커진다. 최근에는 식품, 농업, 환경 분야에서 신속하고 비파괴적 분석 방법으로 가시 근적외선 분광학을 도입하고 있다. 가시 근적외선 영역(VNIR, 400-2400 nm)에는 다양한 물질의 고유한 흡수분광형태가 존재한다는 이론적 토대로부터 물질의 정성 정량적 분석이 가능하다고 알려져 있다. 본 연구에서는 VNIR 분광 스펙트럼으로부터 Al, organic carbon (OC), clay, silt, sand, CEC (Cation exchange capacity), CEC/clay 등의 토양 특성을 정량하고자 하였다. 농경지에서 채취한 94개 토양시료를 기존의 화학분석 방법으로 분석하고 실내에서 VNIR 스펙트럼을 측정하였다. 스펙트럼은 원시형태와, 1차, 2차 도함수로 변환된 형태 모두 partial least square regression (PLSR) 모델에 적용하였다. PLSR에 의한 토양특성 추정식은 RMSE, $R^2$, SDE, RPD 값을 이용하여 검증하였다. Al, OC, silt, sand 함량에 대해서는 통계적으로 유의한 수준의 추정값을 산출하였고, clay와 CEC/clay에 대해 추정한 값은 실측값과 약한 상관성을 나타내었다. 이러한 분광학적인 추정 기법은 영상을 이용한 정성 정량분석에 활용될 수 있을 것으로 사료된다.

• Elastomers and Composites
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• v.41 no.4
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• pp.252-259
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• 2006

A new route for making rubber/clay nanocomposites was suggested based on skim natural rubber latex (SNRL), which is a protein rich by-product obtained during the centrifugal concentration of natural rubber (NR) latex. NR/acrylonitrile butadiene rubber (NBR) based nanocomposites were prepared from SNRL and NBR latex of 26 % acrylonitrile content by blending of aqueous dispersion of organoclay (OC) followed by coagulation, drying, mill mixing and vulcanization. X-ray diffraction(XRD) studies revealed that NR/NBR blend nanocomposites exhibited a highly intercalated and exfoliated structure, especially for NBR-rich blends. Dynamic mechanical studies showed that more compatible behavior was observed for NBR-rich blends. The 25/75 NR/NBR blend nanocomposite showed the best mechanical properties.

• Journal of Animal Science and Technology
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• v.65 no.1
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• pp.113-131
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• 2023

The objective of this study was to investigate the effect of supplementing clay minerals and organic chromium in feed on broiler chicken under heat stress (HS). A total of 90 one-day-old broiler chicken (Arbor Acres) with an initial body weight of 45.0 ± 0.2 g were assigned to five treatment groups (six replications, three birds each cage): 1) NC group, basal diet under room temperature environment; 2) PC group, basal diet under high temperature (HT) environment; 3) ILT group, basal diet + 1% illite + HT; 4) ZLT group, basal diet + 1% zeolite + HT; 5) OC group, basal diet + 400 ppb/kg organic chromium + HT. The ILT and ZLT groups had significantly higher body weight than the PC group in 4 weeks. Apparent total tract digestibility of gross energy was increased in the ILT, ZLT, and OC groups compared to the PC group. The NC group had lower foot-pad dermatitis score than other groups. Escherichia coli population in the cecum and feces was decreased in the ZLT group than in the PC group. Lactobacillus in cecum and feces was significantly increased in the ZLT group than in the PC group. Regarding blood profiles, blood cortisol was decreased in the NC and ILT groups compared to the PC group. Water holding capacity and pH were increased in the ZLT group than the PC group. In conclusion, according to the results of growth performance, nutrients digestibility, bacteria counts, and meat characteristics, supplementation of the ZLT in broiler diet can alleviate HS.

• Journal of the Korean Geotechnical Society
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• v.22 no.11
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• pp.75-87
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• 2006

A series of calibration chamber tests are performed to investigate the spatial distribution of the excess porewater pressure due to piezocone penetration into overconsolidated clays. It was observed that the excess porewater pressure increases monotonically from the piezocone surface to the outer boundary of the shear zone and then decreases logarithmically, approaching zero at the outer boundary of the plastic zone. It was also found that the size of the shear zone decreases from approximately 2.2 to 1.5 times the cone radius with increasing OCR, while the plastic radius is about 11 times the piezocone radius, regardless of the OCR. Based on the modified Cam clay model and the cylindrical cavity expansion theory, the expressions to predict the Initial porewater pressure at the piezocone were developed, considering the effects of the strain rate and stress anisotropy. The method of predicting the spatial distribution of excess porewater pressure proposed in this study was verified by comparing it with the porewater pressure measured in overconsolidated specimens in the calibration chamber.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.10a
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• pp.312-333
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• 2006

This paper presents the results of an analysis of the excess porewater pressure distribution due to piezocone penetration in overconsolidated clays. From piezocone test results for moderately and heavily overconsolidated clays, it was observed that the excess porewater pressure increases monotonically from the piezocone surface to the outer boundary of the shear zone and then decreases logarithmically to the outer boundary of the plastic zone. It was also found that the size of the shear zone decreases from approximately 2.2 to 1.5 times the cone radius with increasing OCR, while the plastic radius is about 11 times the piezocone radius, regardless of the OCR. The equation developed in this study based on the modified Cam clay model and the cylindrical cavity expansion theory, which take into consideration the effects of the strain rate and stress anisotropy, provide a good prediction of the initial porewater pressure at the piezocone location. The method of predicting the spatial distribution of excess porewater pressure proposed in this study is based on a linearly increasing ${\Delta}u_{shear}$. In the shear zone and a logarithmically decreasing ${\Delta}u_{oct}$, and is verified by comparing with the excess porewater pressure measured in overconsolidated specimens at the calibration chamber.