• The Science & Technology
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• v.31 no.2 s.345
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• pp.11-11
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• 1998

프랑스 남부 해변가엔 하얀 모래, 그리고 하와이 해변가엔 검은 모래와 초록 모래가 지구촌의 피서객을 유혹하고 있다. 이처럼 신비스런 모래들은 어떻게 태어났는가. 하얀 모래는 태고 때부터 이어온 석회질 껍질로 된 해양생물의 유산물이며 검은 모래나 초록 모래는 화산에서 나온 용암이 오랜 세월의 풍화작용을 통해 생성된 것이다.

• Proceedings of the KWS Conference
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• 2004.05a
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• pp.9-11
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• 2004

해변에 있는 모래와 공사판에 있는 모래의 차이는 무엇일까요\ulcorner 해변가나 강가의 모래는 영원히 모래로 남아 있지만, 공사판의 모래는 곧 콘크리트로 변할 것이라는 것입니다. 앞산에 있는 나무는 하느님이 만드시고 우리 모두의 것입니다. (중략)

• 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.

• Journal of Korea Water Resources Association
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• v.54 no.8
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• pp.607-616
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• 2021

The purpose of this study is to simulate the transport of nonuniform sediment considering the hiding-exposure effect numerically. In order to calculate the transport of multi-disperse suspended sediment mixtures, the set of advection-diffusion equations for each particle class is solved. The applicability of the numerical model is examined by comparing the simulation results with experimental data. In this study, we calculate the vertical distribution of total concentration of sediment particles using two approaches: (1) by considering the mixture as represented by a single size; and (2) by combining the concentration of the sediment corresponding to several particle size classes; From the simulation results, it is shown that both approaches calculate reasonable results due to the narrow range of size distribution. Under the condition of nonuniform sediment, the critical shear stress of the sediment particle is influenced by the size-selective entrainment, i.e., hiding-exposure effect. It is shown in this study that the effect of hiding-exposure effect on the erosion rates of fine sand is negligibly small.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.506-510
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• 2009

대수층내의 담수-염수 경계면의 위치와 기울기를 파악하는 것은 해안가의 지하수 개발을 위해 선행되어야 하는 연구이다. 가로 140 cm, 세로 70 cm의 사각형 수조에 모래를 채운 모래염수조를 이용하여 포화된 다공질 매체에서 형성되는 담수-염수 경계면을 모의하였다. 다공질 매체의 입자크기에 따른 수리전도도, 해안가 지형의 지표경사, 해수의 염도에 대한 조건을 각기 달리하여 여러 실험조건에서 각 경우에 따라 형성되는 경계면의 형태를 모의하였고, 각 인자가 경계면의 형성에 어떠한 영향을 미치는지를 분석하였다. 각 조건에 따른 총 31가지의 실험을 수행하였으며, Glover 포텐셜 유도식을 이용한 염수침투 경계면을 비교하였다. 모형에서 측정된 염수침투 경계면은 위의 이론식들의 계산치와 유사한 양상을 보였으며, 경계면의 위치와 기울기는 수리전도도, 지표면경사, 염도에 영향을 받는 것으로 나타났다.

• Economic and Environmental Geology
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• v.57 no.2
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• pp.185-204
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• 2024

This study was conducted for evaluation the geological, physical, and chemical properties of domestic sand by analyzing about 4,800 quality data of natural sand from river and land area surveyed until 2023 through the aggregate resource survey conducted by the Ministry of Land, Infrastructure and Transport. The average depth of the Quaternary unconsolidated sedimentary layer in Korea, which includes a sand layer, is about 10m (maximum depth 66m). The thickness of the sand layer within the sedimentary layer is most dominant in the range of 0.5m to 4.0m. This accounts for about 70% of the entire sand layer. In the sand layer, the ratio of sand, gravel, and clay is 60:20:10. Regardless of the provenance or geology, the sand is mainly composed of quartz, plagioclase, and K-feldspar, and the minor minerals are muscovite, biotite, chlorite, magnetite, epidote. The sand includes in 45~75% of quartz, 5~20% of plagioclase and K-feldspar, each other. And other minor minerals are included in 10%. The average grain size of sand is 0.5mm to 1.0mm, which accounts for 44% of sand samples. The water absorption rate and soundness are estimated to be suitable for aggregate quality standard in almost all sand, and the absolute dry density is suitable for 66%.

• Geotechnical Engineering
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• v.8 no.4
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• pp.67-80
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• 1992

In the analysis of dynamic problem, determination of mazimun shear modulus is essential for the estimation of shear stress at any strain level. Although many models for silica sands were presented, the direct accomodation of those models to crushable sand would be difficult because of crushability during torsion. In this research dynamic behaviour of tested sand is presented. The shear modulus of loose crushable sand shows similar results to silica sand. However, as the density of crushable sand increases the shear modulus decreases because of crushability by increasing surface contact area. And modulus number is expressed in terms of state parameter by Been and Jefferies (1965).

• Journal of the Korean Geotechnical Society
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• v.31 no.7
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• pp.5-12
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• 2015

In this study, the deposition of dredged soils from domestic rivers is simulated in the laboratory using a small soil box. In the tests, small sand with 0.002-0.85 mm, large sand with 0.85-2 mm, and gravel 4.75-5.6 mm are air or water-pluviated into the box. Such various deposition processes are simulated and their dry densities are measured. While dredging or piling such soils, their volume may change. The loss of such soils is calculated by a soil conversion factor C. The C value was determined as 0.91 for small sand, 0.96 for large sand, and 0.91 for gravel. The drainage through soil piles may occur and result in effective stress increase. This may cause the volume change of soils and in order to consider such effect it is necessary to recalculate C values. As a result, dry density increased by 5-12% when the drainage effect is considered. When the drainage effect is considered, the value of soil conversion factor C was 0.81 for small sand, 0.92 for large sand, and 0.82 for gravel. Eventually, the C value decreased up to 4-12%.

• Magazine of the Korean Society of Agricultural Engineers
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• v.29 no.2
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• pp.64-73
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• 1987

효과적인 모래의 다짐 방법으로 진동에 의한 방법이 널리 사용되고 있다. 이 연구의 목적은 모래의 진동 다짐시 영향을 주는 인자의 개별적인 효과를 분석하고 가 인자들이 복합되어 진동다짐에 주는 효과를 분석하는 것이다. 이 연구에서는 진동시간 가속도 과도화중 염수비 시료의 다짐전 밀도등을 변화시켜가며 진동테이블 위에서 제작된 시료를 다짐하였고 시험결과는 상대밀도의 변화애 의하여 분석하였다 진동다짐의 효과는 다짐가속도 진동수 및 모래의 정도에 따라 변하며 과도하중이나 진건은 비교적 적은 영향을 주는 인자였다. 가속도가 1g 보다 큰경우 다짐효과는 진동이 시작되는 초기에 발생하였고 그 후는 면밀하게 진동효과가 나타났다. 효과적인 다짐을 위하여는 최적가속도와 최고 과도하중의 선택이 중요하며 최적치보다 큰경우는 다짐의 효과가 감소한다. 건조된 모래와 포화된 모래 모두 같은 최적가속도에서 최대의 다짐효과를 나타냈다. 각 인자 즉 가속도 진동수 단위 중량 영수비, 균등계수, 유효압경, 과도하중, 및 진동시간등의 효과를 복합하여 진동다짐의 효과를 상대밀도의 변화로 나타낼경우$\Delta$DR=38.0∧0.14 의 관계를 얻었다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.1
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• pp.195-202
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• 1994

In this research, a lot of triaxial test results (CID) are analyzed to study the curvature characteristics of failure envelope of sand and parametric relationship between shear strength and state parameter by Been and Jefferies. In the conventional triaxial tests, correction for the change of sectional area of a sample and for membrane influence is essential especially in order to determine critical state (or steady state) condition more correctly. Based on the test results, a model to express the shear strength of fine sand as a function of density and stress level is presented and curvature characteristics of shear failure envelope and parametric relationship between state parameter and shear strength parameters are evaluated.