• Fashion & Textile Research Journal
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• v.17 no.6
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• pp.1020-1029
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• 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.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.1
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• pp.52-60
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• 2013

Ejector-diffuser system makes use of high-pressure primary stream to entrain the low-pressure secondary stream through pure shear action between two streams. In general, the flow field in the ejector-diffuser system is highly complicated due to turbulent mixing, compressibility effects. A fatal drawback of the ejector system is in its low efficiency. Many works have been done to improve the performance of the ejector system, but not yet satisfactory. In the present study, a mixing guide vane was installed at the inlet of the secondary stream for the purpose of the performance improvement of the ejector system. A CFD method has been applied to simulate the supersonic flows inside the ejector-diffuser system. The present results obtained were validated with existing experimental data. The mixing guide vane effects are discussed in terms of the entrainment ratio, total pressure loss as well as pressure recovery.

• Journal of the Korean Geosynthetics Society
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• v.8 no.2
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• pp.55-62
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• 2009

Recently, new development projects are being carried out with the soft ground located along the West coast and the South coast. As soft grounds have complex engineering properties that the load bearing capacity is low and high compressibility, it needs to solve this problems Prior to structures are constructed by the method of improvement of soft ground. The sand mat is usually being used for improvement of soft ground as a horizontal drain material and loading base. But, as the volume is enormous and an amount of demanded sand is increased, it is state of short in supply. This paper presents the feasibility study to use of precious slag ball instead of sand mat as the replacing material through the basic soil property tests, the medium of discharge capacity test and analysis of settlement character.

• Journal of the Korean GEO-environmental Society
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• v.14 no.9
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• pp.57-65
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• 2013

Carbonate sands can be crushed under low confining pressure to achieve high compressibility. So particle crushing has significant influence on characteristics of strength and deformation. Trial embankment and hydrotest are conducted on Sabkha layer, consisting of carbonate sand to build tank structure. In this paper the settlement behavior was analyzed from each test. Particle crushing happened from 80 to 170kPa stress under compression test, and calcium was detected from chemical test. The test result came out Sabkha soil was very weak and easy to be crushing. About trial embankment test, particle crushing was not happen, and then extinction of pore water pressure and settlements were finished just during 2 days. On the other hand, the long-term settlement was happened in hydrotest. So the two test results did not correspond to each other. If loading stress is higher than yielding stress, instant settlement and secondary compression settlement are happened as a result of the particle crushing.

• Geomechanics and Engineering
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• v.7 no.2
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• pp.183-200
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• 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
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• v.17 no.5
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• pp.453-464
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• 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.

• Journal of the Korean GEO-environmental Society
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• v.12 no.6
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• pp.43-51
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• 2011

Marine clays are widely distributed in Korean eastern, western and southern coastal areas. Understanding engineering characteristics of the soft ground is very important, whenever civil structures are constructed in those coastal areas. It is because the ground is composed of highly compressible marine clay. In this paper, the physical and compression characteristics of Incheon, Mokpo, Gwangyang and Busan marine clay were analyzed and the characteristics between western and southern coastal marine clays were compared. For this, test results of 1,471 samples from 114 sites were used. As a result, Incheon clay showed the lowest plasticity and the highest unit weight due to influx of silt from the Yellow River and the turn of the tide of Incheon area. However, Gwangyang clay showed highly compressible characteristic due to extensive reclamation. On the other hand, Mokpo and Busan clay showed partially similar levels of characteristics. The compression index of Mokpo and Busan clay was high more than twice in comparison with Incheon clay and that of Gwangyang clay was higher than seventy percents in comparison with Mokpo and Busan clay.

• Geomechanics and Engineering
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• v.27 no.6
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• pp.551-560
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• 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
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• v.27 no.6
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• pp.583-594
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• 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.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.2C
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• pp.133-140
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• 2010

A series of triaxial test was performed in order to determine critical state parameters of calcareous Jeju sand, which comprises angular shape particles with many pores in the surface. It is observed that Jeju sand mainly shows the contractive behavior during triaxial shear due to high extreme void ratios and large compressibility. The peak friction angle of Jeju sand decreases slightly with increasing mean effective stress due to the particle crushing of carbonate materials. However, the peak friction angle of Jeju sand is higher than that of other silica sands because of the more angular particle shape. The critical state friction angle of Jeju sand gradually decreases when the mean effective stress at a critical state increases. Whereas, there is not a clear influence of void ratio on the critical state friction angle. Critical state parameters of Jeju sand are similar to those of calcareous sands, but significantly larger than those of common sands.