• Journal of The Korean Society of Grassland and Forage Science
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• v.25 no.3
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• pp.205-210
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• 2005

This study was conducted from March 21 to July 9 in 2004 at JeJu Island to investigate the effect of different particle sizes (0.3-0.5, 0.5-0.8, 0.8-1.0, 1.0-1.5 and 1.5-2.0mm) on creeping bentgrass vegetation. The results obtained were summarized as follows; plant height became shorter as particle size was increased from 0.3-0.5 to 1.5-2.0 n. Root length, Minolta SPAD-502 chlorophyll reading value, leave and root weight were directly proportional plant height response. Degree of land cover and density of creeping bentgrass decreased as the particle size was increased from 0.3-0.5 to 1.5-2.0nm, and degree land cover and density of weed increased. The number of weed species were increased as the sand particle size was increased. Then ranking of the dominant weeds were Portulaca oleracea, Trifolium repens and Cyperus amuricus (at 0.3-0.5 and 0.5-0.8mm particle size), Trifolium repens, Portulaca oleracea and Polygonum hydropiper (at 0.8-1.0mm particle size), Portulaca oleracea, Polygonum hydropiper and Poa annua (at 1.5-2.0mm particle size). Based on the these findings, the optimum sand particle size for growth of creeping bentgrass seems to be about 0.3-0.5m in volcanic ash soils of Jeju island.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.2053-2057
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• 2009

본 연구에서는 국내하천을 대상으로 하상재료에 따른 조도계수 변화를 분석하였다. 조도계수 분석은 수위, 유량, 하천 단면 등을 직접 측정하여 미지질조사국에서 개발한 ncalc모형을 이용하였고 하상재료 분석은 ISO4364, ISO9195 기준으로 실시하였다. 조사 대상하천은 총 17개 하천으로 거석, 호박돌, 자갈, 모래 등 다양한 하상재료 특성을 반영할 수 있는 지점으로 선정하였다. 하상 재료 크기 $D_{50}$을 기준으로 하여 모래 자갈 혼합 하천이라 할 수 있는 2mm${\sim}$32mm 구간, 자갈 하천인 32mm${\sim}$64mm 구간, 호박돌 하천인 64mm${\sim}$128mm, 거석 하천인 128mm 이상으로 구분하였다. 분석 결과 실측 자료를 이용하여 계산된 조도계수는 유량에 따라 감소하는 경향을 보였으며, 고유량에서 0.04이하로 수렴하는 결과를 보였다. 이를 하상재료 크기에 따라 구분 지을 경우 입경이 커질수록 유량에 따른 변화 폭이 커지는 것으로 나타났다. 하상재료 입경의 크기가 64mm 이하인 하천의 경우 조도계수 변화 범위가 최대 0.02 로 나타난 반면 입경크기가 64mm이상인 하천에서는 최대 0.20 까지 나타나는 결과를 보였다. 조도계수는 일반적으로 수위 증가에 따라 흐름에 저항을 주는 요인들이 침수되면서 감소한다고 보고되었다. 하천의 하상재료 입경이 클 경우 저수위에서 하상재료에 의한 저항요인이 크게 발생되어 수면경사, 흐름 특성 등 조도계수에 영향을 주는 요인들이 생기는 것으로 판단된다.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.7
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• pp.833-838
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• 2007

In this study, adhesion and transport of bacteria in positively-charged media was investigated with batch and column experiments. Bacterial species used in this study was Escherichia coli ATCC 11105(length: 2.2 ${\mu}m$, diameter: 0.6 ${\mu}m$) and media used were quartz sand(particle size distribution: 0.5-2.0 mm, mean diameter: 1.0 mm) and iron-coated sand. Batch results indicate that bacterial adhesion increased as the content of iron-coated media increased. At iron-coated media 0%(quartz sand 100%), around 46% of bacteria was adhered to media while at iron-coated media 100%(quartz sand 0%) about 97% was attached. Column results also show that bacterial adhesion was enhanced with an increase of iron-coated media content. As the iron-coated media content increased from 0 to 100%, bacterial adhesion increased from 8 to 94%. The experimental results demonstrate that positively-charged media could influence transport of bacteria in porous media.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.210-210
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• 2011

하도에서의 하천정비 및 안전하도 유지를 위해서는 하상변동 특성을 면밀히 파악하는 것이 중요하다. 상류유역에서 하천으로 내려온 유사(流砂)는 하천의 흐름과 생태환경에 영향을 미친다. 이중 하천흐름은 사련(ripple)이나 사구(dune)의 형성에 영향을 미쳐, 하천의 지형변동인 사주에 영향을 주고 하천 식생의 성장과 발달에 직 간접적으로 간섭하게 된다. 또한, 교량, 취수장의 취수장애, 호안블럭의 침식 등과 같이 수리구조물의 안정에 영향을 주게 된다. 하천의 유사량 변화에 따라 생태계의 서식환경이 변하게 된다. 또한, 저수지에서 유입 유사량의 변화에 따라 저수지의 용적이 변하게 되어 댐의 설계 및 운영에 많은 영향을 끼치게 되며 특히 저수지 탁수관리에 매우 중요하다. 본 연구에는 4개 대권역의 주요지천 및 댐 직 하류하천 지점 중 적정구간을 선택하여 하상재료조사를 실시하였다. 하상재료 조사는 하도를 구성하는 모래와 자갈의 물리적 성질 중 유사의 이동량 및 하상의 변동, 하도설계 등에 관련 있는 입도분포, 비중 등을 측정하며 자갈하천은 표층 하상재료를 조사하고, 모래 재료는 체분석, 실트이하 재료는 BW관 등을 이용한 침강속도 분석을 실시한다. 주요지점의 중 남강의 안의 수위 우량관측소 지점의 상 하류 2km 구간을 200m마다 21개 지점의 하상재료를 채취하여 입도분석을 실시하였다. 분석결과 남강 안의지점의 표층은 여느 하천과 마찬가지로 상 하류 굵은 자갈로 구성되어 있으며 전형적인 자갈하천의 특성을 보었다. 상류200m(2000m)에서는 최소 50mm(10mm), 최대 440mm(75mm), 평균입경은 174mm(34.7mm) 이었고, 하류200m(2000m)에서의 표층입경은 최소 8mm(25mm), 최대 50mm(110mm)이며 평균입경은 27.3mm(62.5mm)로 구성되어 있었다. 전체적으로 상류지역의 입경이 하류지역보다 큰 것을 관찰할 수 있었으며 유수 흐름의 일시적인 저항이 발생하는 안의교 지점의 자갈 입경이 인근 부근보다 큰 것을 확인할 수 있었다.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.334-334
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• 2017

Representative particle sizes(RPS) are commonly used for particle size distribution of heterogeneous sediment such as bed material. RPS can provide not only information of mean characteristics of sediment, but also other properties like sorting, skewness, kurtosis. For sediment including sand and clay material, RPS is estimated through two steps. The first is experimental step for calculating weight of each size class, the next is interpolation step to get RPS by using the graph plot. At the second step, graph method known as direct reading of value along the interpolation line in the graph plot is commonly used. This method is often time-consuming job. In this study we developed a new program to get RPS by using MS Excel. Simple linear and semi-log interpolation are used. When compared with conventional graph method(direct reading), simple linear shows 5.31%, while semi-log 1.29% of relative difference. We developed MS Excel program for estimation of RPS automatically.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.3
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• pp.241-250
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• 2006

In the present study, a beach survey such as sand sizes, swim zone widths, and slopes of swash zone has been accomplished for 39 beaches along the Gangwon coastline. The data analysis presents that the swim zone width has a strong correlation with the sand size, showing that the swim zone width is reversely proportional to the 1.1 power of a grain size. The profile factor A has been analyzed using the beach profile form of $h=Ay^{2/3}$, where A was resulted to be proportional to the 0.77 power of a gram size.

• Korean Journal of Soil Science and Fertilizer
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• v.18 no.3
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• pp.240-246
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• 1985

This study was conducted to estimate the proper particle size of Zeolite particle as the soil conditioner for sandy soil. On sand columns filled with different size of sand fractions, Zeolite particles of different size were applied. Tap water was percolated through those columns under the same water level as paddy soil during rice growth. The > 0.1mm fraction of Zeolite was not vertically moved although the water was percolated for 96 hours. The < 0.1mm fraction of Zeolite was moved out 85.7% in 2-1mm, 32.64% in 1-0.5mm, and 24.5% in 0.5-0.25mm sand column, respectively. The proper diameter of Zeolite particle for amelioration of sandy soils widely distributed around river side in Korea was estimated as 0.25-0.1mm fraction in consideration of its pore size.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.11 no.2
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• pp.75-86
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• 1999

호안전면에서의 양빈의 거동이 연구, 조사되며 모래로 이루어진 해변에서의 양빈과 비교하였다. 조건이 서로 다른 6개의 양빈특성이 연구되며 각 조건에 대하여 반복실험이 수행된다. 실험조건에는 모래해변, 호안을 가진 해변, 해안에 직각인 파랑, 그리고 해안에 비스듬한 파랑을 포함한다. 호안을 가진 해안인 경우, 모래입경의 영향이 연구에 포함된다. 또한 호안을 가진 해안에서 모래가 완전히 물에 잠기는 양빈구역의 양단에서 표사이동율을 각각 해변에 직각인 파랑, 해변과 일정한 각도를 이루는 파랑에 대하여 정량화 하였다. 각기 다른 두 개의 표사이동 관계식이 제시되고 검사된다. 비록 약간의 차이가 있더라도 모델에 의한 표사이동율은 실측한 표사이동율과 비교적 잘 일치함을 보여준다.

• Ecology and Resilient Infrastructure
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• v.4 no.1
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• pp.34-43
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• 2017

The Naeseong Stream as a tributary of Nakdong River has conserved the unique structure and function of a typical sand-bed stream ecosystem. However, it is expected to change the stream bed environments and then the fish fauna in the downstream of the dam after the operation of the Yeongju Dam from 2016. We collected fishes and investigated their habitat environments from 2014 to 2016 in the downstream of the Yeongju Dam under construction in order to monitor changes in habitat environment, fauna and community structure of fishes in the Naeseong Stream. The size of the bed materials increased immediately downstream of the Yeongju Dam under construction. Before the operation of the Yeongju Dam, Zacco platypus was dominated and Opsarichthys uncirostris amurensis, Coreoleuciscus splendidus, Hemibarbus longirostris and Pseudogobio esocinus were sub-dominated according to the different sampling sites. Hemibarbus labeo, H. longirostris, Pseudogobio esocinus, Gobiobotia nakdongensis, Cobitis hankugensis and Leiocassis ussuriensis were found as a psammophilous fish specific to sand stream in the Naeseong Stream. At the downstream of the dam, the fish community was classified into a group of gravel-bed fishes such as Microphysogobio yaluensis, Coreoleuciscus splendidus and Coreoperca herzi and a group of sand-bed fishes such as Hemibarbus labeo, Cobitis hankugensis and Gobiobotia nakdongensis. These fish communities gradually tended to change from sand-bed fish community to gravel-bed fish community during the construction of the Yeongju Dam. Therefore, it is necessary to collect the baseline data for the stream ecosystem conservation in the sandy stream by continuously monitoring changes in the environment and fish in the downstream of the Youngju Dam.

• Journal of the Korean Geotechnical Society
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• v.34 no.7
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• pp.5-15
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• 2018

The unconfined compressive strength (UCS) test through coring is widely used to determine the reinforcement effect of the ground with grouting. However, the UCS test through coring can disturb the ground, is expensive and takes a lot of time to prepare the specimen. In this study, the factors affecting UCS of microfine cement grouted sand are evaluated and an empirical equation of UCS of microfine grouted sand is suggested. It is observed that UCS increases linearly until 28 days, however, the increasing rate of strength decreases sharply after that 28 days. The W/C ratio is dominant factor influencing UCS and UCS increases exponentially with the decrease of water/cement (W/C) ratio. Also, UCS increases linearly with increasing the relative density ranging from 30% to 70% and with decreasing median particle size. However, in case of W/C ratio=1 and K6 ($D_{50}=0.47mm$), UCS is lower than that of K4 ($D_{50}=1.08mm$) and K5 ($D_{50}=0.80mm$) due to filtration effect. Based on the experimental results, the empirical equation of UCS of microfine cement grouted sand can be expressed as the function of median particle size ($D_{50}$), porosity (n) and W/C ratio.