• Geotechnical Engineering
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• v.14 no.6
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• pp.153-166
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• 1998

This paper shows the results of a series of model tests on the behavior of steel pipe pile which is subjected to lateral and inclined loads in homogeneous and non-homogeneous Nak-dong River sands. Non-homogeneous soil consisted of two layers, upper and lower layer. The purpose of the present paper is to investigate the effect of ratio of lower layer height to embedded pile length, ratio of soil modules of upper layer to lower layer and inclined load on the behavior of single pile. These effects can be quantified only by the results of model tests. As a result. in non-homogeneous sand soil, it is shown that the lateral behavior depends upon the ratio of soil modules of upper layer to lower layer more than other factors. And it was found that the relationship between the deflection ratio of non-homogeneous sand to homogeneous sand and the ratio of lower layer height to embedded pile length can be fitted to exponential function of H/L by model tests results. For the inclined load applied, it is shown that the bending moment-depth relationship is not similar to the case of laterally loaded pile and the depth of maximum bending moment at relative density of 90% increases about 70% more than the pile only loaded laterally.

• Journal of the Korean Geotechnical Society
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• v.15 no.5
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• pp.65-80
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• 1999

This paper shows the results of a series of model tests on the behavior of single flexible pile, which is subjected to lateral load, in non-homogeneous Nak-Dong River sands, consisting of two layers. The purpose of the present paper is to investigate the effects of ratio of lower layer thickness to embedded pile length, ratio of soil modulus of upper layer to lower one, and pile head constraint condition on the characteristics of lateral behavior of single pile. These effects can be quantified only by the results of model tests. Based on the results of model tests, in non-homogeneous sand, it was found that the lateral behavior depends upon the ratio of soil modulus of upper layer to lower one. And, in respect of deflection, it was found that the relationship between the deflection ratio of non-homogeneous to homogeneous sand and the ratio of lower layer thickness to embedded pile length can be fitted to exponential function of H/L and lateral load by model tests results. Also, in respect of maximum bending moment, it was found that the relationship H/L and $MBM_{fixed-head}/MBM_{free-head}$ can be fitted to linear function of H/L by model test results.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.2
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• pp.173-182
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• 1993

This paper presents an algorithm to derive the representative unit hydrograph for the real environment of a watershed. For a given watershed, the conventional methods give several different unit hydrographs by storm events. In this study the LP model is somewhat modified based on the previous study by Mays et also as follows: the objective function is designed to minimize the sum of weighted residuals. An additional constraint of moving average is added to prevent the unit hydrograph from the occurence of oscillation which was not active in Mays's paper. Configuration of rainfall matrix was improved to reduce its dimension in accordance with Diskin's review point. In spite of the superiority of LP approach in terms of representativeness, all the methods were very sensitive to the validity of baseflow separation and rainfall-loss. Several methods of the separations for rainfall excesses and direct runoffs were applied and no preferred methods were identified. This is the matter of judgement considering catchment and rainfall characteristics. This algorithm was applied to a real watershed of the Wi stream in the Nak-dong river. Compared with the IHP results by conventional methods, this optimized representative unit hydrograph demonstrated relatively smaller and shorter values in terms of the peak discharge and the basin lag respectively, and the oscillation of its falling limb successfully eliminated owing to the additional constraints of moving averages.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1048-1052
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• 2007

그동안의 하천 유량자료는 주로 홍수방어를 목적으로 구축되어진 관계로 대부분 홍수기에만 의미있는 자료를 갖추고 있으며, 환경관리에 필요한 저갈수기 유량자료는 그 신뢰도가 매우 떨어지고 있다. 다행히 지난 2004년 하반기부터 4대강 물환경 연구소에서 직접 오염총량관리 단위유역 말단부에서 8일 간격으로 유량과 수질을 동시에 측정하기 시작하였고, 사업의 결과 건기 우기의 구별 없이 연중 일정한 간격으로 하천유황 및 수질의 변동여부를 확인하는 것이 가능하게 되었으나, 각 단위유역별 유황곡선을 작성할 목적으로 8일 간격 유량자료를 사용할 수 없다는 단점이 있다. 즉, 현재 관측 중인 8일 간격 유량자료만으로는 동시 관측이 진행 중인 수질항목과 유량 사이의 상관관계 정도를 파악한다거나, 어떤 방법으로든 수문모형을 구축한 후 이를 부분적으로 검정할 때 참고자료로 사용하는 정도로 그 용도가 한정될 수밖에 없는 실정이다. 이에 본 연구에서는 낙동강 오염총량관리 41개 단위유역 전체를 대상으로 관측된 8일 간격 유량자료를 이용하여 이를 1일 간격 유량자료로 확장을 시도하였다. 이를 위하여 기존의 TANK 모형에 하도추적기능을 추가한 보다 진보된 TANK 모형을 구성하였다. 낙동강 단위유역별 취수량과 방류량을 바탕으로 한 물수지 자료 또한 구비하여 모형에 고려되도록 하였다. 모형의 매개변수 추정을 위하여 국립환경과학원 낙동강물환경연구소에서 8일 간격으로 관측한 유량자료가 이용되었다. 분석결과 모의된 일유량이 실제 유량을 비교적 잘 재현하는 것으로 나타남에 따라 8일간격 유량관측자료의 일유량으로의 확장 가능성을 확인할 수 있었다. 구축된 모형은 적용에 앞서 10년 평균 저수량을 기준으로 1차 오염총량관리 기준유량과의 비교를 시도하였으며, 상류 댐 방류의 영향 및 물수지의 영향을 배제한 상태의 자연유량을 산정하여 이를 현재 유황과의 비교를 수행하였다. 현재유량과의 비교 결과 다목적 댐의 방류효과로 인한 유량 증가효과 및 대규모의 취수로 인한 유량 감소효과가 뚜렷하게 나타남을 알 수 있었다. 산정된 자연유량을 통하여 비유량을 산정한 결과 $5,000km^2$이하인 유역 면적의 경우 비유량 $0.0048m^3/s/km$를, $5,000km^2$이상인 경우에는 비유량 $0.0043m^3/s/km$를 적용하는 것이 바람직할 것으로 분석되었다. 여기에 유역의 물이용 및 상류의 댐 방류 효과가 고려되면 실제 유역의 저수량을 개략적으로 산정할 수 있을 것으로 기대된다.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.5
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• pp.246-254
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• 2017

Microcystin-LR (MC-LR) is one of most abundant microcystins, and is derived from blue-green algae bloom. Advanced oxidation processes (AOPs) are effective process when high concentrations of MC-LR are released into a drinking water treatment system from surface water. In particular, UV-based AOPs such as UV, $UV/H_2O_2$, $UV/O_3$ and $UV/TiO_2$ have been studied for the removal of MC-LR. In this study, UV-LED was applied for the degradation of MC-LR because UV lamps have demonstrated some weaknesses, such as frequent replacements; that generate mercury waste and high heat loss. Degradation efficiencies of the MC-LR (initial conc. = $100{\mu}g/L$) were 30% and 95.9% using LED-L (280 nm, $0.024mW/cm^2$) and LED-H (280 nm, $2.18mW/cm^2$), respectively. Aromatic compounds of natural organic matter changed to aliphatic compounds under the LED-H irradiation by LC-OCD analysis. For application to raw water, the Nak-dong River was sampled during summer when blue-green algae were heavy bloom in 2016. The concentration of extracellular and total MC-LR, geosmin and 2-MIB slightly decreased by increasing the LED-L irradiation; however, the removal of MC-LR by UV-LED (${\lambda}=280nm$) was insufficient. Thus, advanced UV-LED technology or the addition of oxidants with UV-LED is required to obtain better degradation efficiency of MC-LR.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.6
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• pp.691-696
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• 2001

The first bloom of Cochlodinium polykrikoides was observed in the estuary of Nak-dong river near Pusan in Korea in 1982. Since then, there have been irregular blooms, sometimes spread over the adjoining .to Jinhae Bay even though it was confined to the bay and its vicinites until 1988. It had been outbroken frequently in the adjacent to Tongyeong, Geoje, Namhae and Yeosu coast since 1989. It became widespread along the coast of the South Sea to the East Sea of Korea in 1995. And in October in 1998 and 1999, the bloom had been taken place in Kunsan coast of Yellow Sea. According to the observations in situ, the frequency of occurrence has been increased year by year. The prevailing bloom season was from July to October with peak in September. The duration of the bloom became longer with the year, and sometimes lasted more than one month. The density of the bloom did not exceed 5,000 cells $mL^{-1}$until 1991, but it increased year by year to the highest of 43,000 cells $mL^{-1}$ in 1999. With respect to the assembleges of species in dinoflagellate blooms, C. polykrikoides was one of the important species with diatoms and the other dinoflagellates in 1980s. But since then, C. polykrikoides made an almost monospecific bloom. Based on two decadal observations of C. polykrikoides blooms, it became widespread throughout whole coast of the Korea, persistent for about one or two month long in some year, and monospecisc high density blooms. It was reported that significant fish mortalities were caused by this harmful dinoflagellate blooms especially in the fishfarms accomodating intensive fish cages such as Tongyeong, Namhae-do, Geoje, Yeosu and Geomun-do fishfarming yards. This widespread and persistent harmful algal blooms impede the development of marine aquaculture industries.