• Korean Journal of Plant Resources
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• v.19 no.4
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• pp.517-520
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• 2006

The effects of culture soil combinations on growth of native pteridophyte (Pteris multifida, Cyrtomium falcatum and Cheilanthes argentea) were investigated in this study. Six different culture soil mixtures used for cultivating the pteridophytes under 30% shading condition. Pteris multifida was showed the most growth at the culture soil mixtures of peatmoss : living moss (5 : 5), and peatmoss : perlite (7 : 3). Cyrtomium falcatum and Cheilanthes argentea showed the best growth in the culture soils mixtures of sand : soil : leaf mold (2 : 5 : 3) and peatmoss : perlite (7 : 3, 5 : 5), respectively.

• Geomechanics and Engineering
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• v.25 no.1
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• pp.49-58
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• 2021

The resistance of soil to the tractive force of flowing water is one of the essential parameters for the stability of the soil when directly exposed to the movement of water such as in rivers and ocean beds. Biopolymers, which are new to sustainable geotechnical engineering practices, are known to enhance the mechanical properties of soil. This study addresses the surface erosion resistance of river-sand treated with several biopolymers that originated from micro-organisms, plants, and dairy products. We used a state-of-the-art erosion function apparatus with P-wave reflection monitoring. Experimental results have shown that biopolymers significantly improve the erosion resistance of soil surfaces. Specifically, the critical shear stress (i.e., the minimum shear stress needed to detach individual soil grains) of biopolymer-treated soils increased by 2 to 500 times. The erodibility coefficient (i.e., the rate of increase in erodibility as the shear stress increases) decreased following biopolymer treatment from 1 × 10-2 to 1 × 10-6 times compared to that of untreated river-sands. The scour prediction calculated using the SRICOS-EFA program has shown that a height of 14 m of an untreated surface is eroded during the ten years flow of the Nakdong River, while biopolymer treatment reduced this height to less than 2.5 m. The result of this study has demonstrated the possibility of cross-linked biopolymers for river-bed stabilization agents.

• Journal of Environmental Science International
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• v.31 no.7
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• pp.665-675
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• 2022

The purpose of this study was to provide basic information for judging cultivation suitability by analyzing the growing environment of Zanthoxylum schinifolium habitats in Gyeongnam-do. The site environment, soil environment and community structure were analyzed in habitats of 7 cities and counties. The habitats were distributed in slopes at 87~764 m above sea level. It was found habitats was distributed in the well-drained soil with high content of sand and soil texture of habitats was mainly loamy sand and sandy loam. Bulk density and particle density were 0.89 g/cm³ and 2.65 g/cm³ on average, respectively. The soil had 5.10 of pH, 6.41% of OM content, 0.29% of TN content, 3.84 ppm of available P content, and CEC of 12.3 cmol⁺/kg on average. The habitats were classified into four communities (Z. schinifolium-Lindera erythrocarpa, Castanea crenata-L. erythrocarpa, Pinus densiflora-Z. schinifolium, P. thunbergii-Z. schinifolium by clustering analysis. Ecological niche breadth was highest of 0.885 in site (T VI ongyeong) and lowest of 0.608 in site (Goseong).

• Geomechanics and Engineering
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• v.12 no.5
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• pp.831-847
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• 2017

Conventional geotechnical engineering soil binders such as ordinary cement or lime have environmental issues in terms of sustainable development. Thus, environmentally friendly materials have attracted considerable interest in modern geotechnical engineering. Microbial biopolymers are being actively developed in order to improve geotechnical engineering properties such as aggregate stability, strength, and hydraulic conductivity of various soil types. This study evaluates the geotechnical engineering shear behavior of sand treated with xanthan gum biopolymer through laboratory direct shear testing. Xanthan gum-sand mixtures with various xanthan gum content (percent to the mass of sand) and gel phases (initial, dried, and re-submerged) were considered. Xanthan gum content of 1.0% sufficiently improves the inter-particle cohesion of cohesionless sands 3.8 times and more (up to 14 times for dried state) than in the untreated (natural) condition, regardless of the xanthan gum gel condition. In general, the strength of xanthan gum-treated sand shows dependency with the rheology and phase of xanthan gum gels in inter-granular pores, which decreases in order as dried (biofilm state), initial (uniform hydrogel), and re-submerged (swollen hydrogel after drying) states. As xanthan gum hydrogels are pseudo-plastic, both inter-particle friction angle and cohesion of xanthan gum-treated sand decrease with water adsorbed swelling at large strain levels. However, for 2% xanthan gum-treated sands, the re-submerged state shows a higher strength than the initial state due to the gradual and non-uniform swelling behavior of highly concentrated biofilms.

• Journal of Soil and Groundwater Environment
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• v.9 no.1
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• pp.63-69
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• 2004

Hematite-coated sand was examined for the application of the PRB (permeable reactive barrier) to the arsenic-contaminated subsurface in the metal mining areas. The removal efficiency of As in a batch and a flow system was investigated through the adsorption isotherm, removal kinetics and column experiments. Hematite-coated sand followed a linear adsorption isotherm with high adsorption capacity at low level concentrations of As (＜1.0 mg/L). In the column experiments, high content of hematite-coated sand enhanced the removal efficiency, but the amount of the As removal decreased due to the higher affinity of As (V) than As (III) and reduced adsorption kinetics in the flow system. Therefore. the amount of hematite-coated sand, the adsorption affinity of As species and removal kinetics determined the removal efficiency of As in a flow system.

• Geomechanics and Engineering
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• v.9 no.6
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• pp.757-774
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• 2015

Reinforcing soils with the geosynthetics have been shown to be an effective method for improving the uplift capacity of granular soils. The pull-out resistance of the reinforcing elements is one of the most notable factors in increasing the uplift capacity. In this paper, a new reinforcing element including the elements (anchors) attached to the ordinary geogrid for increasing the pull-out resistance of the reinforcement, is used. Thus, the reinforcement consists of the geogrid and anchors with the cylindrical plastic elements attached to it, namely grid-anchors. A three-dimensional numerical study, employing the commercial finite difference software FLAC-3D, was performed to investigate the uplift capacity of the pipelines buried in sand reinforced with this system. The models were used to investigate the effect of the pipe diameter, burial depth, soil density, number of the reinforcement layers, width of the reinforcement layer, and the stiffness of geogrid and anchors on the uplift resistance of the sandy soils. The outcomes reveal that, due to a developed longer failure surface, inclusion of grid-anchor system in a soil deposit outstandingly increases the uplift capacity. Compared to the multilayer reinforcement, the single layer reinforcement was more effective in enhancing the uplift capacity. Moreover, the efficiency of the reinforcement layer inclusion for uplift resistance in loose sand is higher than dense sand. Besides, the efficiency of reinforcement layer inclusion for uplift resistance in lower embedment ratios is higher. In addition, by increasing the pipe diameter, the efficiency of the reinforcement layer inclusion will be lower. Results demonstrate that, for the pipes with an outer diameter of 50 mm, the grid-anchor system of reinforcing can increase the uplift capacity 2.18 times greater than that for an ordinary geogrid and 3.20 times greater than that for non-reinforced sand.

• Geomechanics and Engineering
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• v.36 no.4
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• pp.317-328
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• 2024

Adopting a rational engineering methodology for building structures on sandy-clay soil layers has become increasingly important since it is crucial when structures erected on them often face seismic and cyclic wave loads. Such loads can cause a reduction in the stiffness, strength, and stability of the structure, particularly under un-drained conditions. Hence, this study aims to investigate how the dynamic properties of sand-clay mixtures are affected by loading frequency and clay content. Cyclic triaxial tests were performed on a total of 36 samples, comprising pure sand with a relative density of 60% and sand with varying percentages of clay. The tests were conducted under confining pressures of 50 and 100 kPa, and the samples' dynamic behavior was analyzed at loading frequencies of 0.1, 1, and 4 Hz. The findings indicate that an increase in confining pressure leads to greater inter-particle interaction and a reduced void ratio, which results in an increase in the soil's shear modulus. An increase in the shear strength and confinement of the samples led to a decrease in energy dissipation and damping ratio. Changes in loading frequency showed that as the frequency increased, the damping ratio decreased, and the strength of the samples increased. Increasing the loading frequency not only reflects changes in frequency but also reduces the relative permeability and enhances the resistance of samples. An analysis of the dynamic properties of sand and sand-clay mixtures indicates that the introduction of clay to a sand sample reduces the shear modulus and permeability properties.

• Geomechanics and Engineering
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• v.12 no.6
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• pp.935-948
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• 2017

An experimental program was conducted to investigate the effects of the static compaction pressure, cement content, water/cement ratio, and curing time on unconfined compressive strength (UCS) of the cement treated sand. UCS were conducted on samples prepared with 4 different cement/sand ratios and were compacted under the lowest and highest static pressures (8 MPa and 40 MPa). Each sample was cured for 7 and 28 days to observe the impact of curing time on UCS of cement treated samples. Results of the study showed the unconfined compressive strength of sand increased as the cement content (5% to 10%) of the cement-sand mixture and compaction pressure (8 MPa to 40 MPa) increased. UCS of sand soil increased 30% to 800% when cement content was increased from 2.5% to 10%. Impact of compaction pressure on UCS decreased with a reduction in cement contents. On the other hand, it was observed that as the water content the cement-sand mixture increased, the unconfined compressive strength showed tendency to decrease regardless of compaction pressure and cement content. When the curing time was extended from 7 days to 28 days, the unconfined compressive strengths of almost all the samples increased approximately by 2 or 3 times.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1290-1295
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• 2008

The relative density of soil indicate loose and dense state of sand. Because sand is low compressibility, initial relative density of sand is important effect factor of compression and shear behavior. To measure exactly relative density, the exactly maximum and minimum void ratio was determinated by laboratory tests. Generally, vibrating table method is adapted for minimum void ratio(KS F 2345). However KS F 2345 is not consider the particle break during the vibrating table test. In this study, The minimum void ratio is compared with a method of Pluviation and Vibrating table test results using the K-7(crushed sand). It is concluded that the K-7 sand particles were crushed during the vibrating table test and vibrating table test is not a suitable test for a crushed sand $e_{min}$.

• Environmental Analysis Health and Toxicology
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• v.17 no.4
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• pp.333-339
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• 2002

Yellow sand (YS) storms were observed about ten times in the Korean peninsula during March and April in 2002. Twenty four hour fine particle (PM$\_$2.5/) samples were collected onto the 47 mm Teflon - coated quartz filters over 9 days during and after the events using the MiniVol Portable Air Sampler at a flow rate of 5 liters per minute. The highest PM$\_$2.5/ concentration measured during the YS period was 289 $\mu\textrm{g}$/㎥, which is 13 times higher than the lowest of the values for the samples collected during the non-yellow sand period. The filter samples were analyzed for inorganic ions using the IC, AAS and Autoanalyzer, and for metals using the ICP-MS. The results showed that the concentrations of some inorganic ions (e.g., Ca$\^$2+/ and SO$_4$$\^$2-/) and metals (e.g., Fe, Mn) of soil origin were elevated during the yellow sand events.