• 한국의류산업학회지
• /
• 제17권6호
• /
• pp.1020-1029
• /
• 2015

This paper investigated the wearing performance of knitted fabrics made of air vortex yarns using PTT/tencel/cotton fibres in comparison with ring and compact yarns for emotional garment. Wicking property of knitted fabric made of MVS yarns was worse than those by ring and compact yarns, however, drying property of knitted fabric made of MVS yarns was better than those by ring and compact yarns, which was explained as more water vapor transport due to larger openness between fibres in the MVS yarns than those in the ring and compact yarns. Thermal conductivity of knitted fabric made of MVS was lower than those of ring and compact yarns and maximum heat flow(Q_max) at the transient state of MVS knitted fabric was lower than those of ring and compact yarns, which may be attributed to MVS yarn structure that has parallel fibres in the core part of the yarn and fasciated fibre bundles on the sheath part with roughness on the yarn surface. However, pilling of MVS knitted fabric was better than those by ring and compact yarns, which was caused by less and shorter hairy fibres protruded from MVS yarn surface than those of ring and compact yarns. It was observed that tactile hand of MVS yarn knitted fabrics was stiffer than those of ring and compact yarns knitted fabrics. It was explained by low extensibility and compressibility and high bending and shear rigidities of the MVS yarn knitted fabrics, which resulted in bad wearing performance of MVS knitted fabric.

• 한국추진공학회지
• /
• 제17권1호
• /
• pp.52-60
• /
• 2013

이젝터-디퓨져 시스템은 두 유동 사이의 순수전단운동을 통해 저압의 2차유동을 동반하여 고압의 주된 유동을 만들어 낸다. 일반적으로, 이젝터-디퓨져 시스템에서 유동장은 난류 혼합, 압축 효과로 인해 매우 복잡하게 되며, 저효율의 큰 문제점을 가지고 있다. 현재까지 이젝터 시스템의 성능을 향상시키기 위한 많은 연구가 수행 되어 왔지만 만족스럽지 않은 실정이다. 본 연구에서는 이젝터 시스템의 성능향상을 위해 2차유동의 입구에 혼합 안내깃을 설치하였으며, CFD는 이젝터-디퓨져 시스템의 초음속 내부 유동을 모사하여 수행하였다. 얻어진 결과는 기존의 실험결과를 입증하였으며, 본 논문에서 혼합 안내깃 효과를 전압 손실, 유인비 및 압력회복에 대해서 논의되었다.

• 한국지반신소재학회논문집
• /
• 제8권2호
• /
• pp.55-62
• /
• 2009

최근 국토의 균형 있는 발전을 위하여 서해안 및 남해안 지역에 주로 분포되고 있는 연약지반에 대한 건설공사가 활발히 이루어지고 있다. 이러한 연약지반은 지반의 강도가 약하고, 압축성이 강해서 구조물을 축조하기 전에 반드시 표층안정처리, 압밀촉진, 치환공법 등의 지반개량이 선행되어야 한다. 이러한 연약지반 개량공법 중 표층처리공법은 샌드매트의 포설을 이용한 처리가 주를 이루었다. 그러나, 샌드매트공법에 요구되는 모래의 양이 증가함에 따라 공급이 원활하게 이루어지고 있지 않은 상태이다. 본 연구에서는 이러한 문제점을 해결하고자 샌드매트 대체제로서 풍쇄 슬래그의 사용이 적합한지를 판단하기 위하여 기본 물성시험, 실내 통수능 시험, 침하특성 분석을 통해서 확인하고자 한다.

• 한국지반환경공학회 논문집
• /
• 제14권9호
• /
• pp.57-65
• /
• 2013

탄산질 모래는 낮은 구속압에서도 입자파쇄가 발생하며 이로 인해 높은 압축성을 나타내기 때문에 입자파쇄가 강도 및 변형특성에 중요한 영향을 미친다. 본 논문은 탄산질 모래로 구성된 Sabkha층에 Tank 설치를 위하여 시험성토 및 Hydrotest를 수행한 후 지반의 침하거동을 비교 분석한 것이다. 현장 Sabkha층 시료는 압밀시험결과 80~170kPa에서 입자파쇄가 발생하였고, 화학조성을 분석한 결과 석영질 모래에서 검출되지 않은 칼슘성분이 다량 검출되어 입자파쇄가 잘 일어날 수 있음을 알 수 있었다. 입자파쇄가 발생하지 않은 시험성토에서는 성토완료 이틀만에 간극수의 소산과 침하가 완료되었으나 입자파쇄응력보다 큰 200kPa의 하중이 재하된 Hydrotest에서는 충수 후 장기침하거동이 발생하여 시험성토의 침하거동과는 상이한 결과를 나타내었다. 따라서 현장 Sabkha층에 입자파쇄하중 이상의 하중이 재하될 경우 입자파쇄로 인한 즉시침하와 파쇄된 입자의 재배열로 인한 이차압축침하가 발생됨을 알 수 있었다.

• Geomechanics and Engineering
• /
• 제7권2호
• /
• pp.183-200
• /
• 2014

The expansivity of clayey soils is a complicated phenomenon which may affect the stability of geotechnical structures and geo-environmental projects. In all common factors for the monitoring of soil expansion, less attention is given to anion type of pore space solutions. Therefore, this paper is concerned with the impact of various concentrations of different inorganic salts including NaCl, $Na_2SO_4$, and $Na_2CO_3$ on the macro and microstructure behavior of the expandable smectite clay. Comparison of the responses of the smectite/NaCl and smectite/$Na_2SO_4$ mixtures indicates that the effect of anion valance on the soil engineering properties is not very pronounced, regardless of the electrolyte concentration. However, at presence of carbonate as potential determining ions (PDIs) the swelling power increases up to 1.5 times compared to sulfate or chloride ions. The samples with $Na_2CO_3$ are also more deformable and show lower osmotic compressibility than the other mixtures. This demonstrates that the barrier performance of smectite greatly decreases in case of anions with the non-specific adsorption (e.g., $Cl^-$ and $SO{_4}^{2-}$) as the salinity of solution increases. Based on the results of the X-ray diffraction and sedimentation tests, the high soil volumetric changes upon exposure to carbonate is attributed to an increase in the repulsive forces between smectite basic unit layers due to the PDI effect of $CO{_3}^{2-}$ and increasing the pH level which enhance the buffering capacity of smectite. The study concluded that the nature of anion through its influence on the re-arrangement of soil microstructure and osmotic phenomena governs the hydro-mechanical parameters of expansive clays. It seems not coinciding with the double layer theory of the Gouy-Chapman double layer model.

• Geomechanics and Engineering
• /
• 제17권5호
• /
• pp.453-464
• /
• 2019

Soft marine soil has high fine-grained soil content and in-situ water content. Thus, it has low shear strength and bearing capacity and is susceptible to a large settlement, which leads to difficulties with coastal infrastructure construction. Therefore, strength improvement and settlement control are essential considerations for construction on soft marine soil deposits. Biopolymers show their potential for improving soil stability, which can reduce the environmental drawbacks of conventional soil treatment. This study used two biopolymers, an anionic xanthan gum biopolymer and a cationic ${\varepsilon}-polylysine$ biopolymer, as representatives to enhance the geotechnical engineering properties of soft marine soil. Effects of the biopolymers on marine soil were analyzed through a series of experiments considering the Atterberg limits, shear strength at a constant water content, compressive strength in a dry condition, laboratory consolidation, and sedimentation. Xanthan gum treatment affects the Atterberg limits, shear strength, and compressive strength by interparticle bonding and the formation of a viscous hydrogel. However, xanthan gum delays the consolidation procedure and increases the compressibility of soils. While ${\varepsilon}-polylysine$ treatment does not affect compressive strength, it shows potential for coagulating soil particles in a suspension state. ${\varepsilon}-Polylysine$ forms bridges between soil particles, showing an increase in settling velocity and final sediment density. The results of this study show various potential applications of biopolymers. Xanthan gum biopolymer was identified as a soil strengthening material, while ${\varepsilon}-polylysine$ biopolymer can be applied as a soil-coagulating material.

• 한국지반환경공학회 논문집
• /
• 제12권6호
• /
• pp.43-51
• /
• 2011

국내의 동 서 남해안에는 해성점토층이 폭넓게 분포되어 있으며, 해안지역에서 기반시설물을 설계할 때 압축성이 큰 해성점토로 구성된 연약지반의 공학적 특성을 파악하는 일은 매우 중요하다. 본 논문에서는 인천, 목포, 광양 및 부산지역 해성점토의 물리적 압축특성을 분석하여 각 지역 및 우리나라 서 남해안 점토특성을 비교하였다. 이를 위하여 114구역 1,471개 샘플의 실험결과를 이용하였다. 비교결과, 인천점토의 경우 중국 황하로부터 유입된 세립실트 및 높은 조수간만의 차로 가장 낮은 소성 및 높은 단위중량을 보였고, 광양점토는 광범위한 준설매립의 영향으로 압축성이 가장 컸다. 그와 비교할 때 목포 및 부산의 경우는 부분적으로 비슷한 수준의 특성을 나타내었다. 목포와 부산점토의 압축지수는 인천에 비하여 2배 이상, 광양점토의 경우는 목포 및 부산에 비해 70% 이상 높게 나타났다.

• Geomechanics and Engineering
• /
• 제27권6호
• /
• pp.551-560
• /
• 2021

Due to the low strength and high compressibility characteristics, the loess deposits tunnels are prone to large deformations and collapse. An accurate stability evaluation for loess deposits is of considerable significance in deformation control and safety work during tunnel construction. 37 groups of representative data based on real loess deposits cases were adopted to establish the stability evaluation model for the tunnel project in Yan'an, China. Physical and mechanical indices, including water content, cohesion, internal friction angle, elastic modulus, and poisson ratio are selected as index system on the stability level of loess. The data set is randomly divided into 80% as the training set and 20% as the test set. Firstly, principal component analysis (PCA) is used to convert the five index system to three linearly independent principal components X1, X2 and X3. Then, the principal components were used as input vectors for probabilistic neural network (PNN) to map the nonlinear relationship between the index system and stability level of loess. Furthermore, Leave-One-Out cross validation was applied for the training set to find the suitable smoothing factor. At last, the established model with the target smoothing factor 0.04 was applied for the test set, and a 100% prediction accuracy rate was obtained. This intelligent classification method for loess deposits can be easily conducted, which has wide potential applications in evaluating loess deposits.

• Geomechanics and Engineering
• /
• 제27권6호
• /
• pp.583-594
• /
• 2021

The gas permeability behavior of unsaturated bentonite-based materials is of major importance for ensuring effective sealing of high-level radwaste repositories. This study investigated this by taking a sample of Granular Bentonite Material (GBM) at the end of the Engineered Barrier Emplacement (EB) experiment in the Opalinus Clay, placing it under different humidity conditions until it achieved equilibration, and testing the change in the gas permeability under loading and unloading. Environmental humidity is shown to have a significant effect on the water content, saturation, porosity and dry density of GBM and to affect its gas permeability. Higher sensitivity to confining pressure is exhibited by samples equilibrated at higher relative humidity (RH). It should be noted that for the sample at RH=98%, when the confining pressure is raised from 1 MPa to 6 MPa, gas permeability can be reduced from 10^-16 m² to 10^-19 m², which is close to the requirements of gas tightness. Due to higher water content and easier compressibility, samples equilibrated under higher RH show greater irreversibility during the loading and unloading process. The effective gas permeability of highly saturated samples can be increased by 2-3 orders of magnitude after 105℃ drying. In addition, cracks possibly occurred during the dehydration and drying process will become the main channel for gas migration, which will greatly affect the sealing performance of GBM.

• 대한토목학회논문집
• /
• 제30권2C호
• /
• pp.133-140
• /
• 2010

본 연구에서는 제주해사에 대한 일련의 삼축압축시험을 수행하여 파쇄성이 큰 제주 탄산염 모래의 한계상태정수를 결정하였다. 제주해사는 입자의 모난 정도가 크고 입자표면과 내부에 다수의 공극이 발달되어 전형적인 탄산염 모래의 특성을 보인다. 제주해사는 큰 최대, 최소 간극비와 큰 압축성 때문에 전단 시 압축거동이 지배적이었다. 구속압이 증가할수록 입자가 파쇄되어 제주해사의 첨두마찰각이 다소 감소하였으나, 일반적인 규산염 모래의 마찰각보다는 다소 큰 것이 관찰되었다. 제주해사의 한계상태 마찰각은 평균유효응력이 증가할수록 점차 감소하였으나, 시료의 간극비가 제주해사의 한계상태에 미치는 영향은 미미하였다. 제주해사의 한계상태 정수는 여타의 탄산염 모래와 유사하였으나, 일반적인 규산염 모래보다는 매우 크게 결정되었다.