이종형 Lee Jong Hyeong , 윤석환 Yoon Seok Hwan

DOI: JKWST Vol.47(No.6) 3-14, 2005

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Accurate estimation of the spatial distribution of rainfall is critical to the successful modeling of hydrologic processes. The objective of this study is to evaluate the applicability of spatially distributed rainfall data. Spatially distributed rainfall was calculated using Kriging method and Thiessen method. The application of spatially distributed rainfall was appreciated to the runoff response from the watershed. The results showed that for each method the coefficient of determination for observed hydrograph was 0.92~0.95 and root mean square error was 9.78~10.89 CMS. Ordinary Kriging method showed more exact results than Simple Kriging, Universal Kriging and Thiessen method, based on comparison of observed and simulated hydrograph. The coefncient of determination for the observed peak flow was 0.9991 and runoff volume was 0.9982. The accuracy of rainfall-runoff prediction depends on the extent of spatial rainfall variability.

박승기 Park Seung Ki

DOI: JKWST Vol.47(No.6) 15-24, 2005

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The normalization on the characteristics of water level change at the upstream gauging station was attempted according to the operation of drainage sluice gate of the Geumgang estuary dam. The characteristics were normalized by the analysis of water level change and by the linear-regression of the water level data measured at the inner station of Geumgang estuary dam and upstream gauging station. The results of normalization may be referred to the management of Geumgang estuary lake, the operation of pumping and drainage stations in the shore of the lake. The mean response time of water level change on Ibpo, Ganggyeong and Gyuam water level station were 39,81 and 160 minutes, when sluice gate was opened respectively. The mean velocity of surface wave, the mean displacement of water level change, the mean time of water level change and the mean rate of water level change varied largely depending on the location of gauging station and the characteristics of stream section of the water level gauging station.

원종필 Won Jong Pil , 박찬기 Park Chan Gi

DOI: JKWST Vol.47(No.6) 27-34, 2005

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The purpose of this study is to improve the durability performance of polymer modified cement composites for repair of concrete under combined aging conditions. The experimental procedure was divided into three parts. First, the replacement level of mineral admixtures in polymer modified cement composites were determined in an experimental study based on a Box Behnken design. Second, the flow value, compressive strength and chloride permeability test of sixteen types of mixtures were conducted. Test results show that the polymer modified cement composites were effected on the improvement of the compressive strength and permeability performance. Third, the effects on the replacement level of silica fume mixture was evaluated by the compressive strength, chloride permeability, chemical resistance and repeated freezing and thawing cycles test. They demonstrated that the polymer modified cement composites using mixture of silica fume, fly ash, and blast furnace slag improved the durability performance.

차경섭 Cha Kyung Seob , 장병욱 Chang Pyoung Wuck , 우철웅 Woo Chull Woong , 김성필 Kim Seong Pil

DOI: JKWST Vol.47(No.6) 37-45, 2005

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Almost every year, Korea has been suffered from serious damages of lives and properties, due to landslides that are triggered by heavy rains in monsoon season. In this paper, we systematized the physically based landslide prediction model which consisted of 3 parts, infinite slope stability analysis model, groundwater flow model and soil depth model. To evaluate its applicability to the prediction of landslides, the data of actual landslides were plotted on the predicted areas on the GIS map. The matching rate of this model to the actual data was 84.8%. And the relation between hydrological and land form factors and potential landslide were analyzed.

이인형 Lee In Hyung , 임종석 Lim Jong Seok

DOI: JKWST Vol.47(No.6) 47-57, 2005

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Stress distribution in soils is the very important element to design and to solve the problems of settlement, safety of foundations and trafficability of constructing vehicle in civil engineering. This research presents the comparative estimation of the actual and theoretical measurement on the underground stress of outer layer for each soil after the observation of each top soil layer fur its vertical and horizontal stresses in (1) homogeneous sand ground (2) weak stratum with the sand soil (3) weak stratum with gravel of the soil model, and it also investigates the effect of subsidence of ground by the repeated load. The underground stresses fumed out to be different in the value of theoretical and actual measurement after the trial examination of model. This study has the purpose of suggesting the better construction method of running equipment on weak stratum by comparing the estimated value of trial experiment and theory on underground stress of the weak ground surface area and of raising up the necessity of the continuous research hereafter.

허준 Heo Joon , 장병욱 Chang Pyoung Wuck

DOI: JKWST Vol.47(No.6) 59-70, 2005

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A series of resonant column test was performed to investigate the dynamic deformation characteristics of silty sand soils mixed with polypropylene fibrillated type fiber. Results show that optimum mixing ratios were 0.2% for 19mm of cut fiber for shear modulus and 0.1% for 60mm cut fiber fur damping ratio. As shear strain was increased, normalized values of shear modulus (G(Reinforced)/ G(Unreinforced)) of fiber reinforced soil were increased up to 10^-3%~10^-1% ranges. However, normalized damping ratio (D(Reinforced/D(Unreinforced)) was diminished with an increase in strain beyond 10^-3%~10^-1% for the damping capacity of soils mixed with fiber. Normalized shear modulus (G/G_max) obtained from the test was plotted in the chart suggested by Seed and Idriss. The shear modulus of silty sand was located between sand and gravel curves.

권순국 Soon-kuk Kwun , 전기설 Gi-seol Cheon , 김성배 Song-bae Kim

DOI: JKWST Vol.47(No.6) 73-82, 2005

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This study was performed to evaluate the need for heating wastewater to enhance treatment efficiency of organic matter (BOD, SS) during cold winter in newly developed Absorbent Biofilter System (ABS) which was established in the Suwon Campus of the Seoul National University. Treatments consisted of non-heating (2000 year) and heating(2001, 2002 year), and sampled data were analyzed during cold winter period as well as post winter period to investigate the influence of heating after winter season. Even the average air temperature showed only 0.4℃ difference between two experimental years, the difference in the average effluent temperature during cold winter period between heating and non-heating experiment was approximately 11℃. The average effluent concentration of organic matter in non-heating treatment exceeded the Korean standards for water quality of discharged effluent in riparian area (BOD and SS 10 mg/L); however, the standards were met in case of heating treatment during both winter and post winter period. Therefore, the need for heating wastewater during cold winter season in ABS was justified. On the other hand, there was no improvement of treatment efficiency in T-N and T-p, but we observed the more activated nitrification as increasing the wastewater temperature. Because the average underground temperature was 5℃ higher than the average air temperature during cold winter period, we recommend that the ABS can be established in the underground rather than on-ground for saving the heating cost.

신용철 Shin Yongchul , 최중대 Choi Joongdae , 임경재 Lim Kyoungjae , 심혁호 Shim Hyeokho , 류창원 Lyou Changwon , 양재의 Yang Jae E. , 유경열 Yoo Kyung-yoal

DOI: JKWST Vol.47(No.6) 83-92, 2005

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Natural environment of the Wolgokri stream watershed, located in Chuncheon, Gangwon province, Korea, has been well preserved as a traditional agricultural watershed. To analyze characteristics of NPS pollution generated from an mountainous agricultural watershed, the flow and water qualities of the study watershed were monitored and were analyzed to estimate pollution loads. Annual runoff volume ratio was 70.4%. Concentrations of T-N, T-p, COD, and TOC were higher when monthly rainfall was between 0~30mm than those when monthly rainfall was between 30~70mm. However, the concentrations varied considerably when monthly rainfall was higher than 100mm. The flow weighted mean concentrations(mg/L) of BOD, COD, TOC, NO₃-N, T-N, T-P and SS were 1.96, 2.72, 3.32, 1.41, 4.70, 0.187 and 13.36, respectively. The BOD, SS, T-N and T-P loads of July, 2004 were 48%, 17%, 51% and 32% of annual load, respectively. The BOD, COD, TOC, NO₃-N, T-N, T-p, and SS loads (kg/ha) from Mar. 2004 to Apr. 2005 were 19.09, 26.55, 32.39, 13.85, 45.92, 1.887 and 130.18, respectively. The highest concentrations of BOD, NO₃-N, T-N, T-p, SS, COD and TOC were found before the flow reached the peak runoff, possibly due to the first flushing effect. Generally, pollution loads of the Wolgokri watershed were not that significant. Phosphorus load, however, was higher enough to cause eutrophication in the receiving water body. It was recommended that best management practices need to be implemented to reduce phosphorus sources.