• Geomechanics and Engineering
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• v.12 no.3
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• pp.523-539
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• 2017

Clay soils are typical for their swelling properties upon absorption of water during rains and development of cracks during summer time owing to the profile desorption of water through the inter-connected soil pores by water vapour diffusion leading to evaporation. This type of unstable soil phenomenon by and large poses a serious threat to the strength and stability of structures when rest on such type of soils. Even as lime and cement are extensively used for stabilization of clay soils it has become imperative to find relatively cheaper alternative materials to bring out the desired properties within the clay soil domain. In the present era of catastrophic environmental degradation as a side effect to modernized manufacturing processes, industrialization and urbanization the creative idea would be treating the waste products in a beneficial way for reuse and recycling. Bottom ash and ecosand are construed as a waste product from cement industry. An optimal combination of bottom ash-eco sand can be thought of as a viable alternative to stabilize the clay soils by means of an effective dispersion dynamics associated with the inter connected network of pore spaces. A CATIA model was created and imported to ANSYS Fluent to study the dispersion dynamics. Ion migration from the bottom ash-ecosand pile was facilitated through natural formation of cracks in clay soil subjected to atmospheric conditions. Treated samples collected at different curing days from inner and outer zones at different depths were tested for, plasticity index, Unconfined Compressive Strength (UCS), free swell index, water content, Cation Exchange Capacity (CEC), pH and ion concentration to show the effectiveness of the method in improving the clay soil.

• Journal of the Korean Geosynthetics Society
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• v.16 no.2
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• pp.55-66
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• 2017

The standard piezocone penetration rate of 2 cm/s is proposed in specifications regardless of soil type. However, conditions of standard Piezo Cone Penetration (CPTU) Testings in silty soils with low plasticity vary from undrained to partially drained or fully drained penetration conditions. The partially drained shear strengths of Incheon, Hwaseong and Gunsan silty soils were estimated from the analysis results of the distributions of CPTU-based shear strengths. The CPTU-based shear strengths were compared between the undrained shear strength line and the fully drained shear strength line, which were determined from approximately ${\varphi}^{\prime}=3^{\circ}$ and ${\varphi}^{\prime}=15^{\circ}$, respectively. The internal friction angles obtained from the back analysis and UU-tests tended to increase with decreasing plasticity index, which range approximately from ${\varphi}^{\prime}=2^{\circ}$ to ${\varphi}^{\prime}=14^{\circ}$. The results matchs well with CPTU-based estimation results.

• Journal of the Korean GEO-environmental Society
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• v.8 no.4
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• pp.57-65
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• 2007

Earthquake is one of the factors to affect the stability of geotechnical structures. Numerous past earthquakes have shown that earthquakes have taught that damage of soil structures could occur on fine soils as well as coarse soils. For that reason, earthquake-induced decreasing tendency for strength on both coarse and fine soils has been investigated using direct simple shear (DSS) tests in laboratory. Based on the testing results the decreasing tendency for strength on coarse and fine soils is clearly identified in terms of the concept of volume decrease potential and plasticity index, respectively. Most of the soils except the weathered soil have shown similar reduction tendency of strength with the increasing number of cycles. Liquefaction strength of coarse and fine soils appears to decrease with the increment of volume decrease potential and the decrement of plasticity index, respectively. Reduction of strength on the weathered soil is particularly remarkable rather than others, which might be owing to the collapse phenomenon. From the DSS test results for soils, proposed is a simple method to evaluate strength decrement with the increasing number of cycles, and it can help estimate decrement of strength with the number of cycles easily.

• The Journal of Korean Physical Therapy
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• v.22 no.3
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• pp.31-35
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• 2010

Purpose: The aim of this study was to use fMRI and clinical prognosis criteria to evaluate therapeutic interventions in stroke patients with corona radiata infarct and acquire fundamental information about recovery mechanisms. Methods: Four subjects (2 men, 2 women) who had strokes with corona radiata infarct were recruited. For all subjects, motor functions such as motricity index (MI), modified brunnstrom classification (MBC), functional ambulatory category (FAC), and bathel index (BI) were evaluated. Evaluations were done at least 4 times over a period of approximately 6~7 months from stroke onset. We compared the final evaluation with the first. Results: All patients with corona radiata infarct showed improvement in motor outcomes with the passing of time. The strength of all patients improved from zero or trace levels to normal or good levels in the MI (Motricity Index) test. Other motor outcomes including the modified brunnstrom classification (MBC), the functional ambulatory category (FAC), and the bathel index (BI) also improved with the passing of time. Conclusion: Stroke patients with corona radiata infarcts change for the better over time. Therefore, one can introduce clinical interventions by the aspect of progress in functional motor recovery.

• Korean journal of food and cookery science
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• v.7 no.3
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• pp.1-6
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• 1991

Potato starches are obtained from Irish Cobbler (the dry type), Shepody and superior (the intermediate type) and Dejima (the moist type). Rheological properties of heat-gelatinized potato starch paste were studied to elucidate difference of various potato starches. Heat-gelatinized 3 to 7% potato starch paste showed pseudo plasticity in yield stress. As starch paste concentration increased, the values of consistency index was increased. Relationship between logarithmic consistency index and concentration of potato starch paste was linear at 5% starch concentration. Concentration dependence of consistency index and yield stress of Shepody was highest. As measuring temperature increased, the value of consistency index was decreased. Irish Cobbler starch paste at $50^{\circ}C$, Shepody, Superior and Dejima starch paste at $60^{\circ}C$ showed linear relationships with different slopes. The activation energies of Shepody starch paste was 3.97㎉l/㏖.

• Journal of Industrial Technology
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• v.25 no.A
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• pp.57-65
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• 2005

In this paper, for the highly plastic marine soft clay distributed in west and southern coast of Korean peninsula of Kwangyang and Busan New Port areas, correlation between compression index and other indices representing geotechnical engineering properties such as liquid limit, void ratio and natural water content were analyzed. Appropriate empirical equations of being able to estimate the compressibility of clays in the specific areas were proposed and compared with other existing empirical ones. For analyses of the data and test results, data for marine clays were used from areas of the South Container Port of the Busan New Port, East Breakwater, Passenger Quay, Jungma Reclamation and Reclamation Containment in the 3rd stage in Kwangyang. In order to find the best regression model by using the commercially available software, MS EXCEL 2000, results obtained from the simple linear regression analysis, using the values of liquid limit, initial void ratio and natural water content as independent variables, were compared with the existing empirical equations. Multiple linear regression was also performed to find the best fit regression curves for compression index and other soil properties by combining those independent variables. On the other hands, another software of SPSS for non-linear regression was used to analyze the correlations between compression index and other soil properties.

• Geomechanics and Engineering
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• v.1 no.1
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• pp.75-84
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• 2009

Artificial neural networks (ANNs) are a new type of information processing system based on modeling the neural system of human brain. The prediction of swell pressures from easily determined soil properties, namely, initial dry density, initial water content, and plasticity index, have been investigated by using artificial neural networks. The results of the constant volume swell tests in oedometers, performed on statically compacted specimens of Bentonite-Kaolinite clay mixtures with varying soil properties, were trained in an ANNs program and the results were compared with the experimental values. It is observed that the experimental results coincided with ANNs results.

• Geomechanics and Engineering
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• v.7 no.6
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• pp.633-647
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• 2014

Biopolymers, polymers produced by living organisms, are used in various fields (e.g., medical, food, cosmetic, medicine) due to their beneficial properties. Recently, biopolymers have been used for control of soil erosion, stabilization of aggregate, and to enhance drilling. However, the inter-particle behavior of such polymers on soil behavior are poorly understood. In this study, an artificial biopolymer (${\beta}$-1,3/1,6-glucan) was used as an engineered soil additive for Korean residual soil (i.e., hwangtoh). The geotechnical behavior of the Korean residual soil, after treatment with ${\beta}$-1,3/1,6-glucan, were measured through a series of laboratory approaches and then analyzed. As the biopolymer content in soil increased, so did its compactibility, Atterberg limits, plasticity index, swelling index, and shear modulus. However, the treatment had no effect on the compressional stiffness of the residual soil, and the polymer induced bio-clogging of the soil's pore spaces while resulting in a decrease in hydraulic conductivity.

• Journal of the Korean Geotechnical Society
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• v.27 no.9
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• pp.37-46
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• 2011

The compression index, which represents the compressibility of clay, is generally obtained from the consolidation test, or has been predicted by empirical correlations with soil properties. In this study, the results of consolidation tests on natural and reconstituted Busan and Inchon clays are analyzed to figure out the sedimentation state and its effect on empirical correlations. Results of analysis show that the void index of Busan clay is higher than SCL while the void index of Inchon clay is lower than SCL. By comparing prediction errors with ${\Delta}e_r$, which represents the sedimentation state of clay, it is shown that errors predicting the compressibility based on the liquid limit and plasticity index decrease as ${\Delta}e_r$ increases. Supplemented correlations predicting the compression index of Busan and Inchon clays are suggested using these relationships.

• Structural Engineering and Mechanics
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• v.64 no.6
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• pp.819-826
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• 2017

The effects of thermocycling procedure and material shade on the mechanical properties and wear resistance of resin-based dental restorative materials are investigated. The modulus of elasticity, hardness, plasticity index and wear resistance are determined for the conventional composite, the nanohybrid composite and the nanofilled dental composites. Disc-shape samples are prepared from each material to investigate the effects of thermocycling procedure on the mechanical properties and wear resistance of different types of dental restorative materials. In this respect, a group of samples is thermocycled and the other group is stored in ambient conditions. Then nano-indentation and nano-scratch tests are performed on the samples to measure their mechanical properties and wear resistance. Results show that the A1E shade of the dental nanocomposite possesses higher modulus of elasticity and hardness values compared to the two other shades. According to the experimental results, the mean values for the modulus of elasticity and hardness of the A1E shade of the nanocomposite are 13.71 GPa and 1.08 GPa, respectively. The modulus of elasticity and hardness of the conventional dental composite increase around 30 percent in the oral environment due to the moisture and temperature changes. The wear resistance of the dental composites is also significantly affected by moisture and temperature changes in the oral conditions. It is observed that thermocycling has no significant effect on the hardness, plasticity index and wear resistance of the nanohybrid composite and the nanocomposite dental materials.