• Korean Journal of Soil Science and Fertilizer
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• v.31 no.1
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• pp.67-71
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• 1998

This study was carried out to granulate artificial zeolite powder that remove ammonium nitrogen and phosphorous simultaneously in wastewater treatment. Optimum water content was required for 30 percent volume to granulate artificial zeolite with 1.7mm diameter and 1~2cm length using granulator. Portland cement could remove much $NH_4{^+}$ and $PO_4{^{3-}}$ from the wastewater than other binding materials. Mixed 33, 25. 20. 16 percent of portland cement to artificial zeolite powder(v/v), cation exchange capacity of the granulars were 66.5, 81.4, 126.8, $151.2cmol^+kg^{-1}$ and hardness of that were 176.1, 24.4, 4.1, $0.4kg\;cm^{-2}$, respectively. Content of portland cement in the granular were related with removal of $PO_4{^{3-}}$ positively and that of $NH_4{^+}$ negatively. Shaked 1g of the granulars that made of portland cement 33 percent with 40ml synthetic wastewater containing $NH_4{^+}$ $1545mgl^{-1}$ and $PO_4{^{3-}}$ $417mgl^{-1}$, 99.4 percent of $NH_4{^+}$ and 90.3 percent of $PO_4{^{3-}}$ were removed simultaneously after 48 hours shaking. The longer shaking, the more $NH_4{^+}$ and $PO_4{^{3-}}$were removed. The artificial zeolite granular had both micropore and macropore that could be useful in the wastewater purification.

• Korean Journal of Soil Science and Fertilizer
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• v.28 no.2
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• pp.123-129
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• 1995

For the propose of increasing the value added, zeolite powder was granulated by adding Polyvinyl Alcohol (PVA) as cementing material. The optimal concentration of PVA for granulation and the physical properties of the prepared granule were investigated. Four percent PVA stock solution was made by adding distilled water at $90^{\circ}C$ water bath and incorporated with zeolite. The contents of water stable granule above 2.0mm in diameter was 98.0% in the case of 0.3% PVA addition and almost 100% in the case of 0.6% PVA addition. Increasing PVA concentration of granules increased the hardness and decreased the infiltration rate and the maximum water holding capacity of granules, However, the drying method hardly affected the physical properties of granules. With the increase in the mixing ratios of kaolinite or bentonite to zeolite, the hardness of granules increased but high water contents of granules resulted in rapid decrease in the hardness of granules. However, when smectite or perlite was mixed with zeolite, the increase in mixing ratios to zeolite resulted in the decrease in hardness, the increase in the infilteration rate and maximum water holding capacity of granules.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.6
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• pp.1063-1070
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• 2011

In this study, total of 5 different chemical amendments were evaluated for determining kinetic parameters and stabilization efficiency of heavy metals in aqueous phase. Standard solution of Cd and Pb ($100mg\;L^{-1}$) was mixed with various ratio of amendments (1, 3, 5, 10%) and heavy metal stabilization efficiency was monitored for 24hrs. All examined amendments showed over 90% of removal efficiency for both Cd and Pb except zerovalent iron (ZVI) for Cd (43-63%). Based on result of heavy metal stabilization efficiency, it was ordered as $CaCO_3$ > Dolomite > Zeolite > Steel slag > ZVI for both Cd and Pb in aqueous phase. For kinetic study, first order kinetic model was adapted to calculate kinetic parameters. In terms of reaction rate constants (k), zeolite showed the fastest reaction rate (k value from 0.4882 for 1% to 2.0105 for 10%) for Cd and ZVI (k value from 0.2304 for 1% to 0.5575 for 10%) for Pb. Considering reaction rate constant and half life for heavy metal stabilization, it was ordered as Zeolite > $CaCO_3$ > Dolomite > Steel slag > ZVI for Cd and $CaCO_3$ > Dolomite > Steel slag > Zeolite > ZVI for Pb. Overall result in this study can be interpreted that lime containing materials are more beneficial to remove heavy metals with high efficiency and less time consuming than absorbent materials.

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.5
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• pp.369-376
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• 2007

This experiment was carried out to investigate optimum conditions of coir-based substrates for the red pepper plug seedlings. Eleven different coir based substrates prepared by mixing of coir, vermiculite, rice hull, perlite, zeolite, mixed at different ratios were tested. The physical and chemical properties of the substrates were analyzed by the CEN (European committee for standardization) method. Fresh and dry weights of shoot and root, leaf area, root length, and T/R ratio (dry shoot weight/dry root weight) were determined at 55 days after sowing. The results showed that the growing media CRZ 8(coir:rice hull: vermiculite=8:1.9:0.1) and CVSZ 6(coir:silver vermiculite: zeolite=6:3.9:0.1) can successfully be used for pepper plug seedlings judging from dry weight and T/R ratio of the plug seedlings. The optimal range of total pore space, water volume, air volume, easily available water content and water buffering capacity of the coir-based growing substrates for pepper plug seedlings were in the range of 92~94%, 52~60%, 32~43%, 18~21%, and 0.9~8%, respectively.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.6
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• pp.553-581
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• 2022

Shortly after tunnel boring machine (TBM) was introduced in the tunneling industry, the use of TBM has surprisingly increased worldwide due to its performance together with the benefit of being safely and environmentally friendly. One of the main cost items in the TBM tunneling in rock and soil is changing damaged or worn cutters. It is because that the cutter change is a time-consuming and costly activity that can significantly reduce the TBM utilization and advance rate and has a major effect on the total time and cost of TBM tunneling projects. Therefore, the importance of accurately evaluating the cutter life can never be overemphasized. However, the prediction of cutter wear in soil, rock including mixed face is very complex and not yet fully clarified, subsequently keeping engineers busy around the world. Various prediction models for cutter wear have been developed and introduced, but these models almost usually produce highly variable results due to inherent uncertainties in the models. In this study, a case study of design and construction of disc cutter change is introduced and analyzed, rather than proposing a prediction model of cutter wear. As the disc cutter is strongly affected by the geological condition, TBM machine characteristic and operation, authors believe it is very hard to suggest a generalized prediction model given the uncertainties and limitations therefore it would be more practical to analyze a real case and provide a detailed discussion of the difference between prediction and result for the cutter change. By doing so, up-to-date idea about planning and execution of cutter change in practice can be promoted.

• Korean Journal of Plant Resources
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• v.34 no.5
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• pp.470-477
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• 2021

Amsonia ellipotica (Thumb.) Roem. & Schult. has less than 10 native places nationwide and is evaluated as an endangered species (EN) on the Korean Red List, so systematic breeding and cultivation methods are required. This study was carried out to establish an effective method for seedling production in A. elliopotica that can be developed as a genetic resource conservation and new ornamental material. This experiment was performed by varying the seedling production container (72, 105 and 128 cell trays), number of seeds sown in a cell (1, 2, and 4 per cell), soil type [horticultural soil and neutralized peat-moss: perlite mixed in 3:1, 4:1 (v:v)], additional fertilizer concentrations (0, 250, 500 and 1000 mg/L) and shading degrees (0, 55 and 75%). As a result of the study, growth increased with the increased in measuring capacity per cell of sowing container. According to number of seeding growth, sowing one seed per cell was the best. Seedling growth increased as the treatment concentrations increased, higher growth was in 1000 mg/L. On the other hand, during the shading treatment, growth significantly decreased regardless of shading degrees.

• Journal of the Korean GEO-environmental Society
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• v.23 no.9
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• pp.17-23
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• 2022

Using cement as a road subbase is economical, easily modified and supplemented and has excellent road pavement quality control. In addition, cement adheres well to sandy soils without adhesion, and it plays a role of permanently preserving adhesion in viscous soils with adhesion, so it can be widely applied as stable treatment with the advantages of increased strength, reduced compressibility. and improved durability. However, while cement is excellent in terms of strength for a road subbase, the material properties mean that it is difficult to maintain and reinforce when cracks or fractures occur due to dry shrinkage, and the pH increases in the ground due to hexavalent chromium eluting from cement. which can cause environmental problems such as groundwater contamination. Therefore, this study evaluates the usability of alternatives in the road base layer such as environmentally cementitious stabilizer and on-site soil generated from the site. We intend to reduce the environmental damage and evaluate the durability. To evaluate the applicability of the site, Environmental stability test and freeze-thaw test and wetting-drying test was conducted to evaluate the strength characteristics of alternative materials on the road through the limited performance evaluation of environmentally cementitious stabilizer. The test ranges were set at mixing ratios of 10%, 20%, and 30% and ages of three days, and 28 days old to evaluate the early strength and reference strength according to the mixing ratio of the environmentally cementitious stabilizer.

• Journal of the Korean GEO-environmental Society
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• v.24 no.1
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• pp.15-23
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• 2023

The grouting method is a method of construction for the purpose of waterproofing and reinforcing soft ground. When grout is injected into the ground, there are various types of penetration and diffusion of grout depending on the shape of the ground, the size of soil, the porosity, and the presence or absence of groundwater. the current situation. Therefore, in this study, to investigate the penetration performance of the grouting to conductive material, laboratory tests were performed on the addition of the conductive material. In the injection test, 0%, 3%, and 5% of the mixed water were added as conductive materials to the grout, and the original ground condition was composed of various types of ground composed of gravel and silica sand. Conductive grout is injected by pressure into the model ground using a dedicated injection device, and the injection time (t), pressure (p), flow rate (v) and injection amount (q) are measured, and the hardened body injected in the model ground is collected. Penetration performance was evaluated. In the results of the grout injection experiment, the amount of conductive material used and the grout injection rate showed an inverse relationship, and it was confirmed that the penetration pattern was changed according to the size of the soil particles in the model ground. The grout containing the conductive material has relatively good penetration into the ground and excellent strength and durability of the hardened body, so it was judged that it could be used as an additive for measuring the penetration range of the grout.

• 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.