• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.162-162
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• 2016

본 연구에서는 한국 낙동강에 위치한 강정-고령보에 설치된 by-pass 어도의 유인효율을 유량 변화에 따라 살펴보고, 어도 유인효율을 극대화할 수 있는 최적의 본류 방류량을 산정하였다. 강정-고령보는 고정보와 가동보로 구성된 혼합식 보로 유량조절이 가능하며, 가동보의 조작에 따라 by-pass 어도 내의 유량이 결정된다. 유인효율의 지표로 목표어종의 HSC(Habitat Suitability Criteria) 지수에 기반한 WUA(Weighted Usable Area)를 삼았다. WUA는 평면 2차원 물리서식처 모형인 River2D를 활용하여 계산하였다. 또한 River2D로 계산된 유속장은 GPS Floater를 활용한 현장관측 자료로 검증하였으며, 어망을 이용한 월별 어류 모니터링 자료로 유인효율 평가의 타당성을 간접적으로 검증하였다. 결과적으로 본 연구 대상인 강정-고령보의 by-pass 어도에서 가장 효과적으로 목표 어류를 유인하기 위해서는 본류의 유량이 190 cms내외를 유지해야 한다. 특히 목표 어류인 모래무지가 봄철(4월~6월)에 산란기를 맞아 상하류로 이동하려는 경향을 띄므로, 이때 적절한 가동보 운영을 통해 본류 유량을 190 cms로 유지하는 것이 필요하리라 사료된다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.2
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• pp.153-156
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• 2010

The effective thermal conductivity of two-phase materials such as unbonded silica sands saturated with a nanofluid was measured at high temperature using the transient thermal probe method. The nanofluid used in this study was a water-based mixture of 0.1 vol% $Al_2O_3$ nanoparticles with a diameter of 45 nm. The convection problem for fluids was prevented with this measurement method because the fluid was confined to within very small pore spaces. Based on the prediction model for unbonded sands, the thermal conductivities of the saturating nanofluid at high temperatures could be determined with the measured effective thermal conductivities for the two-phase material. In the results, increases in the thermal conductivity ratios of the nanofluid to pure water when temperatures were varied from $30^{\circ}$ to $80^{\circ}C$ were within the range of 4.87%~5.48%.

• Journal of the Korean GEO-environmental Society
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• v.21 no.11
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• pp.21-26
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• 2020

Natural soil is composed of particles of various sizes, and the shear behavior which is a kind of mechanical behavior of the soil is affected by the particle size distribution. In addition, since the natural soil contains a large mixture of coarse and fine grained soil, it is difficult to clearly understand the shear behavior of the soil. Therefore, a ring shear test was conducted on sandy soils that has various particle size distribution in order to identify the effect of the distribution on shear characteristics of soils. At this time, sand and silt were used for coarse and fine grained soils, respectively, to make sandy soils by changing the silt content. Also the water was supplied during the test to confirm shear characteristics of sandy soils with various particle size distributions. The result shows that the shear strength increases as the silt content increases, and the strength decreases as the silt content increases over the sand. Besides, residual shear strength gradually decreases because of the silt content when the water is supplied.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.2
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• pp.89-98
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• 1988

This research evaluated factors on cement-based solidification process designed for hazardous sludge produced from electroplating industry. Four factors of sand/cement ratio, water/cement ratio, amount of wet sludge and amount of a precipitator, were investigated in terms of leachability and compressive strength of the solidified materials. Results of triplicate tests and statistical analysis indicated that sand/cement ratio(S/C) had the greatest effect on leaching of Cr(VI) from the solidified materials while water/cement ratio(W/C) on Zn and compressive strength. Cr(VI) was fixed better than Zn by portland cement. An experimental modeing was developed to estimate leached metal concentration and compressive strength at a given condition. Proper mixing criteria were also suggested for the use of the solidified mixture as construction materials. In solidification of 30g dry sludge, optimal condition was studied for S/C ratio, W/C ratio and the weight of precipitator which were 1, 1.5 and 1.075g respectively.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.6
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• pp.405-411
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• 2013

A sediment transport calculation considering cohesive force is proposed to deal with the transport phenomena of cohesive sediment. In the proposed calculation, each sand particle is assumed to be surrounded by a thin layer of mud. The critical Shields parameter and bed-load sediment transport rate are modified to include the cohesive force acting on the sand particle. The proposed calculation is incorporated into a two-way coupled fluid-structure-sediment interaction model, and applied to wave-induced topographic change of artificial shallows. Numerical results show that an increase in the content ratio of the mud, cohesive resistance force per unit surface area and water content cause increases in the critical Shields parameter and decreases in the bed-load sediment transport rate, reducing the topographic change of the shallow without changing its trend. This suggests that mixing mud in the pores of the sand particles can reduce the topographic change of shallows.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.179-184
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• 2008

Silt or clay alluvium fully saturated with water generally shows low resistivity. Sometimes it is believe that the low resistivity layer is considered as good aquifer but this makes problems in the development of groundwater. To overcome this problem, we adopted induced-polarization(IP) method with resistivity method. Laboratory experiments and resistivity/IP field surveys with non-polarization electrodes were conducted for the study. Laboratory experiments shows that the increase of clay contents in the sample mixed with sand and clay give low resistivity and high chargeability. We used this experiment results in the interpretation of resistivity/IP field data which were obtained in riverbank filtration. Finally, the layer which has low resistivity and chargeabilty would be regarded as a good aquifer for the development of groundwater intake.

• Journal of the Korean GEO-environmental Society
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• v.6 no.4
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• pp.5-12
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• 2005

In this study, the geotechnical applicability of permeable barriers that could filter the leachate from a landfill was evaluated. Specimens were cast from sand, loess and bentonite according to the specific weight ratios of them. A series of experiments are performed to determine the unconfined compressive strength and permeability of various mixing ratio of bentonite, loess, and sand. From the laboratory test, optimum mixing ratio that satisfied the regulations of unconfined compressive strength($5kgf/cm^2$) and coefficient of permeability ($10^{-3}{\sim}10^{-4}cm/sec$) in landfill was found when the weight ratio of sand and loess was 8:2 with 2% of bentonite. Using the laboratory test data and in situ test results, the applicability of the wall will be tested for various conditions.

• Asian Journal of Turfgrass Science
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• v.17 no.1
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• pp.13-17
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• 2003

This study was conducted to figure out the effect of KOB Soil on creeping bentgrass‘Cobra’, Kentucky bluegrass (KB)‘Midnight’75% + Perennial ryegrass (PR)‘Palmer III’25%. This experiment was conducted from September 1, 2001 to August 31, 2002 at Hwajoulryong in Jeongsun County, Gwangwon-do. Treatments were Sand 80% + Peatmoss 20%, Sand 80% +KOB-Soil (No. 1) 20%, and Sand 80% +KOB-Soil (No. 2) 20%. Treatments with KOB Soils was superior to control fer the leaf length, number of leaf, turf quality and root length in Creeping bengrass and Kentucky bluegrass + Perennial ryegrass.

• Journal of the Korean GEO-environmental Society
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• v.11 no.9
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• pp.39-45
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• 2010

Controlled low strength material(CLSM) is produced by mixing portland cement, fine aggregates, water and chemical admixtures. Sand is the most commonly used as the fine aggregates in the conventional CLSM. It is getting more and more difficult to obtain sand in Korea so it is required that the alternative materials be developed as the replacement of sand. Since the engineering characteristics of coal ash are similar to the sand, it becomes necessary to examine the application of the coal ash as the alternative material for CLSM and as the environment-friendly material. When the results meet the optimum pH level that plants can live, it can be expanded the scale of application of the study on the plant as the important field. This study was subjected to present the method to reduce the pH range of CLSM to a suitable condition that plants can survive. To verify this method, the care of neutralization was conducted by immersing the specimen to Ammonium monohydrogen phosphate. Before curing and neutralization, the maximum pH of developmental CLSM is approximately 11. However, the pH value of developmental CLSM has under 9.5 after peaceful curing and neutralization management.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1C
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• pp.39-51
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• 2011

A large number of small particles may surround large gravels which are non-contact and dispersed within the ground. The strength of such soil may be influenced by the mechanical properties of a few coarse gravels. A specimen or gravel size can impact the shear characteristics of sand with dispersed gravels. In this study, the size of gravel and specimen varies and its effect on shear characteristics of a granular soil was evaluated. Five sizes of gravels with 7, 12, 15, 18, and 22 mm were used repeatedly and inserted in the middle of each compacted layer. A specimen consists of five or ten equal layers depending on gravel size, which is 5 cm or 10 cm in diameter and 10 cm or 20 cm in height. An embedded gravel ratio by weight is 3% and constant for all cases with gravel. After consolidation, a series of undrained triaxial compression tests under three confining pressures was performed on sand with dispersed gravels. The maximum deviator stress of a specimen with 10 cm in diameter was at average 30% higher than that with 5 cm in diameter and increased up to 90% for a specimen with gravel. When a gravel size of 7 and 12 mm used, the maximum deviator stress of a specimen with 10 cm in diameter was higher than that of one without gravel, whereas the maximum deviator stress of a specimen with 5 cm was higher or lower than that without gravel. The gravel size and specimen diameter influenced the undrained behavior of sand. The maximum deviator stress of a specimen with gravel either increased or decreased compared to that without gravel, depending on the ratio of gravel size to specimen diameter, 1/5.