• 한국지반공학회지:지반
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• 제14권4호
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• pp.61-76
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• 1998

보강토공법의 효시일 테일알메(Terre Armee)공법이 개발된 이래로 다양한 종류의 보강토공법이 그 경제적 이점에 주목되어 개발되었다. 보강토공법 중 특히 보강토벽공법의 기본 메카니즘은 보강재를 각 중에 다수 배치하여 인장에 약한 각의 특성을 보완하고자 하는 것이다. 띠상의 금속보강재를 이용하는 테일알메공법 등 대부분의 보강토공법에서 흙과 보강재 사이의 마찰력에 의해 흙의 변형을 구속하게 되므로 충분한 마찰력을 확보하기 위하여 양질의 사질토를 성토제로 사용하도록 제한하고 있다. 즉 점성토와 같은 배수성이 불량한 토질재료를 금속성의 보강재로 보강할 경우 과잉간극수압의 발생에 따른 유효음력의 감소로 인한 흙과 보강재간의 마찰력이 크게 감소하여 보강 효과를 기대하기 어렵기 때문이다. 그러나 양질의 사질토를 건설현장 인근에서 구할 수 없을 경우 운반비의 과대로 보강토공법의 경제적 이점을 최대한으로 살릴 수 없다. 본 연구에서는 현장발생 점성토를 배수성이 양호한 부직포(nonwoven geotextile)로 보강하였을 때의 보강효과를 조사하기 위하여 일련의 직접전단시험을 실시하였다. 그 결과 함수비가 높은 점성토를 이용하여 성토체를 구 축할 경우 상대적으로 인장강성이 작더라도 배수성이 좋은 면상의 부직포를 보강재로 이용하면 소 요의 보강효과를 기대할 수 있는 것으로 분석되었다.

• Food Science and Biotechnology
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• 제15권6호
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• pp.925-930
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• 2006

Chitosan-based nanocomposite films were prepared using a solution intercalation method incorporating varying amounts of organically modified montmorillonite (Cloisite 30B) from 0 to 30 wt%. The nanocomposite films prepared were optically clear despite a slight decrease in the transmittance due to the spatial distribution of nanoclay. X-ray diffraction patterns indicated that a certain degree of intercalation or exfoliation formed when the amount of clay in the film was low and that microscale tactoids formed when the clay content in the sample was high (more than 10 wt%). The tensile strength (TS) of the chitosan film increased when the clay was incorporated up to 10 wt% and then decreased with further increases in the clay content of the film. The elongation at break (E) increased slightly upon the addition of low levels of clay up to 5 wt% and then decreased with further increases in the amount of the clay in the film. The water vapor permeability (WVP) decreased exponentially with increasing clay content. The water solubility (WS) and swelling ratio (SR) of the nanocomposite films decreased slightly, indicating that the water resistance of the chitosan film increased due to the incorporation of the nanoclay.

• 한국지하수토양환경학회지:지하수토양환경
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• 제16권3호
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• pp.17-27
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• 2011

Recently, a physically based model of water-table fluctuation due to precipitation is developed based on aquifer water balance model. In the model, it was assumed that the water infiltration into ground surface is advection dominant and immediately reaches to water-table. The assumption may be suited for the sites where the water-table is shallow and/or the permeability of the unsaturated zone is high. However, there are more cases where the model is not directly applicable due to thick and low permeable unsaturated zone. For the low permeability unsaturated zone, the pattern of water flux passing through unsaturated zone is diffusive as well as advective. In this study, to improve the previously developed water-table fluctuation model, we combined the delayed drainage model, which has long been used in well hydraulics, to the water-table fluctuation model. To test the validity of the development, we apply the developed model to 5 different domestic sites. The model parameters are calibrated based on the groundwater hydrograph and the precipitation time series, and the correlation analyses among the parameters are pursued. The overall analyses on the delineated model parameters indicate that the delayed drainage parameters or delay index used in the developed model are able to reveal drainage information in the unsaturated zones.

• 한국지반공학회논문집
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• 제16권2호
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• pp.115-123
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• 2000

Piezocone Penetration Test has been performed in the soft ground over the site preparation area at Inchon International Airport(IIA). With the pore pressure dissipation test results, the changes in the permeability and the coefficient of consolidation in clayey soil were checked and the differences of the undrained shear stength verified the soft ground improvement effect from vane test and piezocone test both before and after the improvement. From the results, thin sand seam was found and this caused a big difference in the coefficient of permeability and consolidation. The coefficient of consolidation was high in the upper marine deposit and relatively low in lower marine deposit. It was found that the reduction of void ratio by preloading resulted in the reduction of coefficient of consolidation after the ground improvement. In addition, there were some variations of undrained shear strength when the number of 15 or 18 was used as the coefficient of piezocone(Nkt). However, when the average value of undrained shear strength calculated using Nkt=10 was applied, the result indicated the similar average value with the result of vane test and the increasing rate of strength( Δsu/Δ$\sigma$≒0.38) also showed the similar distribution.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.814-815
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• 2011

A surfaced permanent magnet spherical motor is capable of operating as three degree of freedom that used for the joints of the robot's arm, leg, and eyes. Ongoing research like new concept is essential part of motor field, it will make a great contribution in the future the overall portion of the motor, is becoming expected. The author analysis torque characteristics in spherical motor with state of rotating and positioning. And future design direction is smaller motors with equivalent or higher output. Solutions as torque and efficiency improvements are selecting the core with special processing type like powder metallurgy materials. Their special characteristic is high permeability and low eddy current losses at high speed, so improved the torque and efficiency.

• Journal of the Korean Wood Science and Technology
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• 제22권1호
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• pp.66-71
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• 1994

To increase drying rate and reduce drying degradation, pretreatments such as prefreezing and presteaming have been widely used in wood industries. Presteaming lumbers prior to kiln drying is known positively to improve its permeability, to increase diffusion coefficient and to reduce discoloration, but negatively to increase collapse. Prefreezing lumbers prior to kiln drying is also known to reduce significantly its drying defects and its shrinkages. Thus it is no doubt that the pretreated lumbers shrink diversely from the untreated. In this study the shrinkage behaviors of the pretreated specimens are investigated by drying two tropical hardwoods (Apitong and Taun) in three different dying conditions: high temperature and slow drying rate (drying in a closed cylinder), high temperature and rapid drying rate (drying in an oven) and low temperature and slow drying rate(drying at room temperature). The prefrozen specimens show the least volumetric shrinkages in most drying conditions. The specimens dried in cylinders shrink most among all drying conditions. In general the pretreated specimens reached the 30 % moisture content faster than the untreated by about 30 %.

• 한국지반환경공학회 논문집
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• 제23권5호
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• pp.33-39
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• 2022

오염물질이나 지하수의 흐름 및 유출의 차단, 해수 침투 방지 및 노후화된 제체의 보수·보강 등을 목적으로 활용되는 Cement-Bentonite 차수벽에 혼합되는 시멘트 일부를 GGBS로 치환하여 사용하는 Slag-Cement-Bentonite 차수벽은 높은 강도와 낮은 투수계수, 우수한 내구성 및 내화학성 등의 여러 장점으로 지하수 제어가 필요한 여러분야에서 다양하게 활용되고 있다. 그러나 이와같은 장점에도 불구하고 국내에서는 Slag-CB 차수벽에 대한 다양한 연구가 이루어지지 않아 적용사례가 많지 않으며, 특히, 시멘트를 대체하여 혼합되는 GGBS는 생산되는 국가에 따라 성질이 상이하여 국내 Slag-CB 차수벽의 활용성을 높이기 위해서는 국내에서 생산되는 GGBS를 활용한 Slag-CB 차수벽에 대한 다양한 연구가 필요한 실정이다. 이에 본 연구에서는 Slag-CB 차수벽의 활용성을 향상시키기 위해 국내에서 생산되는 GGBS를 혼합한 Slag-CB 차수벽의 GGBS 치환율에 따른 블리딩율, 응결시간, 강도 및 차수성 등을 평가하였다. 그 결과, 국내에서 생산된 GGBS를 혼합한 Slag-CB 차수벽은 CB 차수벽에 비해 낮은 블리딩율과 우수한 강도 및 차수성을 보였으며, 이러한 성능향상은 GGBS 치환율이 높을수록 더욱 효과적인 것으로 분석되었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
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• pp.144-149
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• 2000

Porous cement concrete was developed to prevent hydroplaning of airway pavement or to reduce noise emission in highway. In has been introduced in domestic since early 1980' and applied to a pedestrian road or bike way. The concrete, however, has problems such as lack of optimized mix design, low strength and deterioration, etc. The purpose of this study is to manufacture porous cement concrete using blast-furnace slag to enhance mechanical properties. The results of this study are as follows; the compressive strength range is 102∼247kgf/㎠, the tensile strength range is 16∼70kgf/㎠, the bending strength range is 43∼70kgf/㎠, and the coefficient permeability range is 6.79 ×10-2∼1.17∼10-1cm/sec. To develope high-performance porous concrete, further studies are needed on optimum mixture of fineness modulus and admixture.

• International Journal of Concrete Structures and Materials
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• 제10권4호
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• pp.539-553
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• 2016

Polymer concrete (PC) has been favoured over Portland cement concrete when low permeability, high adhesion, and/or high durability against aggressive environments are required. In this research, a new class of PC incorporating Multi-Walled Carbon Nanotubes (MWCNTs) is introduced. Four PC mixes with different MWCNTs contents were examined. MWCNTs were carefully dispersed in epoxy resin and then mixed with the hardener and aggregate to produce PC. The impact strength of the new PC was investigated by performing low-velocity impact tests. Other mechanical properties of the new PC including compressive, flexural, and shear strengths were also characterized. Moreover, microstructural characterization using scanning electron microscope and Fourier transform infrared spectroscopy of PC incorporating MWCNTs was performed. Impact test results showed that energy absorption of PC with 1.0 wt% MWCNTs by weight of epoxy resin was significantly improved by 36 % compared with conventional PC. Microstructural analysis demonstrated evidence that MWCNTs significantly altered the chemical structure of epoxy matrix. The changes in the microstructure lead to improvements in the impact resistance of PC, which would benefit the design of various PC structural elements.

• Geomechanics and Engineering
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• 제20권6호
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• pp.537-546
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• 2020

Oil and natural gas reserves have been recognised abundantly in clayey rich rock formations in deep costal reservoirs. It is necessary to understand the sedimentary history of those reservoir rocks to well explore these natural resources. This work designs a group of laboratory experiments to mimic the physical process of the sedimentary clay-rich rock formation. It presents characterisation results of the physical properties of the artificial clayey rocks synthesized from illite clay, quartz sand and brine water by high-pressure consolidation tests. Special focus is given on the effects of illite clay content and high-stress consolidation on the physical properties. Multi-step loaded consolidation experiments were carried out with stress up to 35 MPa on mixtures constituting of the illite clay, quartz sand and brine water with five initial illite clay contents (w=85%, 70%, 55%, 40% and 25%). Compressibility and void ratio were characterised throughout the physical compaction process of the mixtures constituting of five illite clay contents and their water permeability was measured as well. Results show that the applied stress induces a great reduction of clayey rock void ratio. Illite clay contents has a significant influence on the compressibility, void ratio and the permeability of the physically synthesized clayey rocks. There is a critical illite clay content w=70% that induces the minimum void ratio in the physically synthesised clayey rocks. The SEM study indicates, in the high-pressure synthesised clayey rocks with high illite clay contents, the illite clay minerals are located in layers and serve as the material matrix, and the quartz minerals fill in the inter-mineral pores or are embedded in the illite clay matrix. The arrangements of the minerals in microscale originate the structural anisotropy of the high-pressure synthesised clayey rock. The test findings can give an intuitive physical understanding of the deep-buried clayey rock basins in energy reservoirs.