• Geomechanics and Engineering
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• v.12 no.4
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• pp.639-655
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• 2017

The binary mixture consists of two types of granular media with different physical attributes and sizes, which can be characterized by the percentage of large granules by weight (P) and the particle size ratio (${\alpha}$). Researchers determine that two thresholds ($P_S$ and $P_L$) exist for the peak shear strength of binary mixtures, i.e., at $P{\leq}P_S$, the peak shear strength is controlled by the small granules; at $P{\leq}P_L$, the peak shear strength is controlled by the large granules; at $P_S{\leq}P{\leq}P_L$, the peak shear strength is governed by both the large and small granules. However, the thresholds of binary mixtures with different ${\alpha}$ values, and the explanation related to the inner details of binary mixtures to account for why these thresholds exist, require further confirmation. This paper considers the mechanical behavior of binary mixtures with DEM analysis. The thresholds of binary mixtures are found to be strongly related to their coordination numbers $Z_L$ for all values of ${\alpha}$, where $Z_L$ denotes the partial coordination number only between the large particles. The arrangement structure of the large particles is examined when P approaches the thresholds, and a similar arrangement structure of large particles is formed in both 2D and 3D particle systems.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.1125-1126
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• 2010

• Journal of the Korean GEO-environmental Society
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• v.14 no.1
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• pp.33-42
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• 2013

In this paper, a series of monotonic undrained shear tests were carried out on four kinds of sand-fine mixtures with various fines content. Two kinds of sands (Silica sand V3, V6) and fines (Iwakuni natural clay, Tottori silt) were mixed together in various proportions, while paying attention to the void ratio expressed in terms of sand structure $(F_c{\leq}F_{cth})$. The undrained shear strength of mixtures below the threshold fines content was observed so that as the plastic fines content increases, maximum deviator stress ratio decrease for dense samples while an increase is noted for loose samples. For non-plastic fines, the increase in the amount of fines leads to an increase in density of the soil, which results in an increase in strength. Then, the monotonic shear strength of the mixtures was estimated using the concept of granular void ratio. It was found that the shear strength of mixtures is greatly dependent on the skeleton structure of sand particles.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.911-912
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• 2010

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.10a
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• pp.459-460
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• 2009

• Journal of Bio-Environment Control
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• v.2 no.1
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• pp.37-45
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• 1993

The purpose of this research was to develop ideal substrates for the production of good quality tomatoes in bag culture system and also to improve media with low or no environmental pollution by blending and mixing artificial substrate including peatmoss, perlite, vermiculite, granular rockwool, polyphenol resin foam, bark, and smoked rice hull. The highly efficient media proved by experiments were vermiculite, smoked rice hull, polyphenol resin foam, granular rockwool, and perlite, which showed good results in the early growth as well as the marketable yield of tomato in the bag culture. Tomato plants grown in the media mixed with peatmoss, vermiculite and granular rockwool at the ratio of 3 : 1 : 1(by volume) showed the highest marketable yield, and the next at the ratio of 2 : 1 : 1. The perlite-granular rockwool mixtures at the ratio of 2 : 3 and 1 : 4, and the peatmoss vermiculite mixtures at the ratio of 2 : 3 and 3 : 2, seemed to be promising media for bag culture.

• Journal of Bio-Environment Control
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• v.16 no.2
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• pp.101-107
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• 2007

This experiment was carried out to develop the substrate mixtures for the production of high quality plug seedlings of cucumber. Peatmoss based substrates, rice hull, carbonized rice hull, decomposed sawdust, perlite and granular rockwool were mixed by five different mixing ratioes (M1, M2, M3, M4 and M5). The cultivars used were cucumber (Cucumis sativus L. cv. Janghyung heukjinju) plants. The higher the content of peatmoss added, the higher the plant growth in terms of plant height, leaf area and total dry weight, which leading to the production of high quality plug seedlings. Seedlings growth of cucumber were greater in M5 mixtures [peatmoss:rice hull:decomposed sawdust=40:40:20(v/v)], M4 mixtures [peatmoss:rice hull:decomposed sawdust:granular rockwool=30:25:20:25(v/v)] and M2 mixtures [peatmoss:rice hull:decomposed sawdust:granular rockwool=20:20:15:25:20(v/v)] The concentrations of nutrient solution (EC) had a great influence on plant height, leaf area, total fresh and dry weight of cucumber seedlings growth. As the concentration of nutrient solution increased from 0.1 to $1.5dS{\cdot}m^{-1}$, the growth and seedling quality of cucumber in plant height, leaf area and dry weight were significantly improved.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.419-426
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• 2000

The purpose of this study is to present the application of WFS co-mixtures for retaining wall as flowable backfill. The fly ash, generated at the Tae-An thermoelectric power plant, was used in this research and was classified as Class F. Green Sand, Furane Sand, and Coated Sand, which had been used at a foundry located in Pusan, were used. Couple of laboratory tests and small scale retaining wall tests were performed to obtain the physical properties of the WFS co-mixtures and the possibility of backfill materials of retaining wall. The range of permeability for all the co-mixtures was from 3.0${\times}$10$\^$-3/ cm/s to 6.0${\times}$10$\^$-5/ cm/s. The unconfined strength of the 28-day cured specimens reached around 550kPa. Results of the consolidated-undrained triaxial test showed that the internal friction angle is between 33.5$^{\circ}$ and 41.8$^{\circ}$. The lateral earth pressure against wall decreased up to 80% of initial pressure within a 12 hours and the total lateral earth pressure is less than that of typical granular soil. It was enough to construct the backfill for the standard retaining of 6m with just two steps, like fill the co-mixtures for half of retaining wall, and then fill the others after 1 day. The stability of retaining wall for overturning and sliding increased as the curing time elapsed.

• Journal of the Korean Geotechnical Society
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• v.24 no.1
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• pp.51-59
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• 2008

In this study, cyclic shear characterics of sand-clay mixtures were analyzed. In order to perform cyclic triaxial tests on sand clay mixtures, natural clays with activity and silica sand were mixed variously to reproduce soils with wide range of grain size compositions. Test specimens with various fines contents were prepared by the moisture compaction and pre-consolidation methods, while paying attention to the void ratio expressed in terms of the sand structure and clay structures, and undrained cyclic shear tests were performed. In the test results, cyclic shear strength decreased with increasing of sand granular void ratio below 20% of fine contents. When the granular void ratio of the test specimen exceeded the maximum void ratio of the silica sand, the clay matrix dominated the soil structure, and soil structures were not influenced by compaction energy. It was observed that, the matrix structure of the coarse particles has great effect on the undrained cyclic shear strength characteristics for sand-clay mixtures, and therefore, it is more appropriate to pay more attention to the density of the sand structure, rather than to the fines content.

• Journal of the Korean Geotechnical Society
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• v.23 no.4
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• pp.91-100
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• 2007

In most design codes, soils are classified as either sand or clay, and appropriate design equations are used to represent their behavior. For example, the behavior of sandy soils is expressed in terms of the relative density, whereas consistency limits are often used for clays. However, sand-clay mixtures, which are typically referred to as intermediate soils, cannot be easily categorized as either sand or clay and therefore a unified interpretation of how the soil will behave at the transition point, i.e., from sandy behavior when fines are low to clay behavior for high fines content, is necessary. In this study, active natural clays are mixed with sand, and the fines content varied in order to produce different structures, ranging from one state where only sand particles form the soil structure to another where the matrix of fines make-up the structure. While paying attention to the granular void ratio in order to clarify the shear properties of sand-clay mixtures with increasing fines content monotonic, shear tests were performed on isotropically, and anisotropically consolidated specimens. From the test results, it was observed that the monotonic shear strength of sand-clay mixtures is dependent on the granular void ratio.