• Journal of the Mineralogical Society of Korea
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• v.29 no.2
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• pp.35-45
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• 2016

Clays, which are abundant in nature and eco-friendly, have been utilized throughout human history due to their characteristic physicochemical properties. Recently, a variety of clays such as montmorillonite, kaolinite, sepiolite and layered double hydroxide with or without chemical modification have been extensively studied for potential application in industries. Clays that possess a large specific surface area, high aspect ratio, nanometer sized layer thickness and controllable surface charge could be utilized as polymer fillers after appropriate chemical modifications. These modified clays can improve mechanical and gas barrier properties of polymer materials but also provide sustained antibacterial activity to polymer films. Furthermore, engineered clays can be utilized as scavengers for chemical or biological pollutants in water or soil, because they have desirable adsorption properties and chemical specificity. In this review, we are going to introduce recent researches on engineered clays for potential applications in future industries such as food packaging and environmental remediation.

• YAKHAK HOEJI
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• v.34 no.2
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• pp.139-146
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• 1990

Streptococcus sp. TR-1 which has inducible resistance to MLS antibiotics was isolated from soil samples in Korea. Streptococcus sp. TR-1 was cultured in Lysis broth, then a plasmid was isolated by modified Elliker method. Bacillus subtilis UOTO277 was transformed with that plasmid. This result showed that the plasmid has the gene relating with inducible resistance to MLS antibiotics. It was named pMB4 and its size was determined about 2.4 Kb by results of digestion with various restriction enzymes. Restriction endonuclease cleavage site map of pMB4 plasmid was made by double digestion of the plasmid. pMB4 plasmid has different restriction endonuclease site map from the other plasmids that have been discovered in Streptococcus sp. so far. And it could be identified that pMB4 plasmid does not have homology with ermK of Bacillus licheniformis EMR but has homology with ermC of Staphylococcus aureus from the results of Southern hybridization.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.281-292
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• 2008

Prefabricated Board Drains (PBDs) recently become more widely used than conventional sand drains in improving soft ground because the PBD is more time and cost effective. The performance of PBDs is affected by disturbance in the adjacent soil formation during inserting mandrels, the intrusion of fine particles into filter fabric, and necking of the drain by excessive lateral pressure especially occurring in very deep clay formation such as the Busan New Port site. In this study, the PBD with double-core is introduced, which seems to overcome the shortcomings of usual single-core PBDs. An in-situ test program was established in the Busan New Port site, in which a set of the double-core PBDs and the single-core PBDs was installed to compare the efficiency of each of the drains. The discharge capacity of the double-core and the single-core PBDs was compared for various confining pressures in the modified Delft test and the chamber test. A series of CRS consolidation tests was performed in order to obtain profiles of void ratio-effective stress and void ratio-permeability relationships in the Busan New Port site that are used as input date in performing a numerical program ILLICON. The numerically simulated settlements of ground surface in the test site are in good agreement with those of in-situ measurements. In addition, the performance of the double-core and single-core PBDs has been experimentally and numerically compared in this paper.

• Journal of the Korean GEO-environmental Society
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• v.7 no.5
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• pp.31-39
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• 2006

In this study, modified triaxial compression tests were carried out to investigate the characteristics of shear strength of unsaturated dredged soils. The variation of shear strength generally depends on more matric suction than drained conditions, and then is gradually converged in matric suction 100kPa. It indicates that the effective angle of internal friction and effective cohesion in unsaturated conditions increase due to degree of saturation, namely, matric suction than those of saturated conditions. Therefore, it shows that apparent friction angle, ${\phi}^b$ due to the variation of matric suction to evaluate reasonable shear strength parameters in unsaturated soils should be considered.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.6
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• pp.575-586
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• 2015

In NATM tunnel, the Ground-Lining Interaction model(GLI model) had been proposed a one of the numerical analysis as the ground load estimation method of the concrete lining. But this model was not applied with the interface mechanism between the ground and the support member or concrete lining. Therefor in this study, it is implemented as a model for closer than actual states that the interface element applied to the existing GLI model. And the modified GLI formula is proposed with the ground load estimation that is from the numerical results for each ground and rock cover conditions. Based on the numerical results, the ground load acting on concrete lining is reduced to ave. 88~106% in case of IV ground condition and ave. 47~57% in case of weathered soil condition comparing with the existing GLI model. It can be anticipated that the results obtained from this study can be applied to an estimation of the ground load on the concrete lining modeled like as real states, consistent and economical design.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.17 no.6
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• pp.1-15
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• 2014

A dredging on erosion control dam has been enforced without evaluation the factors that affect the dredging. In addition, there is the negative effect much more than positive effect by dredging on erosion control dam. Therefore, this study was carried out to develop evaluation indicators and to suggest fieldbook in order to determine whether sand deposits at erosion control dam should be dredged up or not. The most important six evaluation indicators that can decide to dredge up at erosion control dam were obtained from three round delphi technique and were selected in the following order: the current sand deposit ratio(0.339), existence of cultivated land and house downstream(0.276), the slope of streambed(0.162), the amount of movable soil and gravel(0.118), the history of any disasters(0.063), the basin area(0.043). The weighted score for each evaluation indicator were acquired from AHP analysis with respect to the degree of importance and then the modified weighted score for actual measurements were classified as three categories: large(2.53), medium(1.60) and small(1.01). Based on delphi technique, erosion control dam dredging evaluation fieldbook introduced the four evaluation indicators out of the total six evaluation indicators and two low effected evaluation indicators were excluded. This results showed that the values for reliability analysis and consistency ratio were acceptable.

• Geotechnical Engineering
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• v.12 no.2
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• pp.19-32
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• 1996

Based on Trifuilac's empirical model to transform earthquake acceleration time history in the time domain into Fourier amplitude spectrum in the frequency domail an earthquake scaling technique for simulating the earthquake record of certain magnitude as the required magnitude earthquake was suggested. Also, using the earthquake record of magni dude(M) 5.8, the simulated earthquake of magnitude(M) 8.0 was established and its application to dynamic testing system was proposed. The earthquake scaling technique could be considered by several terms : earthquake magnitude(M), earthquake intensity(MMI), epicentral distance, recording site conditions, component direction and confidence level required by the analysis. Albo, it had an application to the various earthquake records. The simulated earthquake in this study was established by two orthogonal horizontal components of earthquake acceleration-time history. The simulated earthquake shaking could be applied to the dynamic pile load test for the model tension pile and the model compressive open -ended piles driven into the pressure chamber. In the static pile load test, behavior of two piles was very different and after model tension pile experienced 2 or 3 successive slips of the pile relative to the soil, it was failed completely. During the simulated earthquake shaking, dynamic behavior and pile capacity degradation of two piles were very different.

• Geotechnical Engineering
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• v.12 no.2
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• pp.107-114
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• 1996

A series of shear tests is performed to measure friction coefficients of the interface between different reinforcements and weathered granite soils. The reinforcements tested are smooth steel strip, Paraweb(friction tie) and geotextile with rough surface, while the weathered granite soils are composed of different, grain size distribution. Soils are compacted with the energy of 95% modified AASHTO and fully saturated before testing to simulate the worst site condition. Because of characteristics of the direct shear apparatus, shear strength is obtained in terms of drained condition. Test results show that the more fines the soils contain, the larger ratio of friction coefficient ($\mu=\frac{tan{\delta}}{tan{\Psi}}$) is obtained. Also the ratios are much higher for the Friction tie and the geotextile compared to the smooth steel strip. Those suggest that even weathered granite soils with 36% fines are possible to use as backfill of reinforced earth structures for the two reinforcements when a drainage system is provided.

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.5
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• pp.643-648
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• 2005

Near infrared reflectance spectroscopy (NIRS) has become increasingly used as a rapid, accurate method of evaluating some chemical constituents in cereal grains and forages. If samples could be analyzed without drying and grinding, then sample preparation time and costs may be reduced. This study was conducted to develop robust NIRS equations to predict fermentation quality of corn (Zea mays) silage and to select acceptable sample preparation methods for prediction of fermentation products in corn silage by NIRS. Prior to analysis, samples (n = 112) were either oven-dried and ground (OD), frozen in liquid nitrogen and ground (LN) and intact fresh (IF). Samples were scanned from 400 to 2,500 nm with an NIRS 6,500 monochromator. The samples were divided into calibration and validation sets. The spectral data were regressed on a range of dry matter (DM), pH and short chain organic acids using modified multivariate partial least squares (MPLS) analysis that used first and second order derivatives. All chemical analyses were conducted with fresh samples. From these treatments, calibration equations were developed successfully for concentrations of all constituents except butyric acid. Prediction accuracy, represented by standard error of prediction (SEP) and $R^2_{v}$ (variance accounted for in validation set), was slightly better with the LN treatment ($R^2$ 0.75-0.90) than for OD ($R^2$ 0.43-0.81) or IF ($R^2$ 0.62-0.79) treatments. Fermentation characteristics could be successfully predicted by NIRS analysis either with dry or fresh silage. Although statistical results for the OD and IF treatments were the lower than those of LN treatment, intact fresh (IF) treatment may be acceptable when processing is costly or when possible component alterations are expected.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.2
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• pp.209-222
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• 2006

Odor problems brought about by deteriorating air quality occur in areas surrounding landfills because VOCs emissions from landfills are exhausted through surface soil and gas vents. Due to these factors, monitoring of VOCs emissions from landfills are essential. However, only a few studies have been carried out to assess VOCs emissions from landfills. A comprehensive approach to this problem is definitely warranted. In this study, we estimated BTEX emissions from 7 landfill sites in Korea using field experiments and LandGEM(Landfill Gas Emission Model), which is the USA EPA(Environmental Protection Agency)-recommended model for landfill gas emission estimation. For this purpose, we suitably modified the model's major input parameters $L_0$ and k according to 3 classes based on landfill scale after considering the characteristics of field experiments and LandGEM data. Consequently, we estimated VOCs emissions from landfills for cities, provinces and all of Korea alter modifying $L_0$ & k using LandGEM. Through the results of this study, we obtained essential basic data with respect to present conditions which will help us understand VOCs emissions from landfills in Korea.