임성훈 Eam Sung Hoon

DOI: JKWST Vol.55(No.2) 1-8, 2013

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This study was performed for the purpose of analyzing the effect of tide on the stress-strain behavior in the boundary surface of sea dike embankment. Tide is a dynamic condition, but there are not suitable numerical models to solve the dynamic embankment condition caused by tide. So the analysis was simplified to quasi dynamic as follow. First, seepage by tide was analyzed according to elapsed time, and the results of the analysis at every hour during one periodic cycle time of 12 hours were applied to the pore water pressure conditions of stress-strain analysis with hyperbolic model by Duncan and Chang. The place at which maximum shear strain took place in the analysis result moved up and down repeatedly along the boundary of the dredged sand fill section and the crashed stone filter section. The value of maximum shear strain was large at high water level of tide. This result means that contraction and relaxation occur in turn repeatedly at every specific position along the boundary, and the repeated action compact loose position with sand moved down from the upper position by gravity. The experiment with the small sea dike model showed the result consistent with the numerical analysis. The surface of sea side on the dike collapsed at high water level after a couple of repetition of the rising and falling of water.

정한석 Jeong Han Seok , 서교 Suh Kyo , 장태일 Jang Tae Il , 성충현 Seong Choung Hyun , 김학관 Kim Hak Kwan , 박승우 Park Seung Woo

DOI: JKWST Vol.55(No.2) 9-20, 2013

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Many studies have reported additional treatment is needed to use wastewater for agricultural purpose. Economic considerations should be taken into account to establish infrastructure for agricultural reuse because of a large amount of water use in irrigation and relatively low water quality requirement. The objective of this study was to conduct economic analysis of wastewater reclamation and reuse systems for agriculture. A system dynamics approach considering complexity and dynamics in the wastewater reuse systems was used for the economic analysis, which are related with social, environmental, and economic problems. Sensitivity and benefit cost analysis for wastewater reuse systems was conducted through the established economic assessment model. The result of sensitivity analysis showed that water resources development and installation cost were the most sensitive for total benefits and costs, respectively. The scenario-based test of the organized economic assessment model shows marginal cost ranges and enables decision-makers to decide reasonable cost for the wastewater reuse systems for agriculture.

박성직 Park Seong-jik , 안희경 An Hee-kyung

DOI: JKWST Vol.55(No.2) 21-27, 2013

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The present study explored the way to desalinate seawater for agricultural irrigation using forward osmosis (FO) process using liquid fertilizer as draw solution. FO experiments were performed in a cross flow mode using flat sheet FO membrane. The effect of membrane orientation, flow rate, and draw solution concentration on the performance of forward osmosis was investigated by measuring water flux of forward osmosis membrane. The water flux when the draw solution was placed against the membrane active layer was lower than the water flux when the feed solution was placed against the membrane active layer. This results indicated that the decrease of effective osmotic pressure by dilutive internal concentration polarization was less than that by concentrative internal concentration polarization. Increasing flow rate from 66.7 to 133.1 cm3/min resulted in increase of the water flux when the membrane active layer orient to draw solution and feed solution, respectively. The reduction of resistance to water flow increased water flux at higher flow rate. The water flux of FO membrane increased with increasing draw solution concentration from 10000 to 30000 mg/L. The water flux for KH2PO4 draw solution was similar to that for commercial fertilizer. Optimization of FO process would contribute to economically desalinate brackish water for agricultural use.

원철희 Won Chul-hee , 신민환 Shin Min-hwan , 최용훈 Choi Yong-hun , 신재영 Shin Jae-young , 박운지 Park Woon-ji , 이수인 Lee Su-in , 최중대 Choi Joong-dae

DOI: JKWST Vol.55(No.2) 29-36, 2013

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The objective of the research was to describe the effect of straw mat cover and soil amendments on the reduction of runoff and non-point source load from steep sloped highland agricultural fields. Four 5×30 m plots on sandy loam soil with 28 % slope were prepared. Experimental treatments were bare (control), rice straw mat cover (3,000 kg/ha) (S), PAM (5 kg/ha)＋Gypsum (1 ton/ha) (PG) and rice straw mat cover＋PAM＋Gypsum (SPG). A variety of lettuce was cultivated and runoff was monitored during a growing season in 2011. Natural monitoring was conducted to three times. Runoff rate of S, PG and SPG plots were significantly lower than those of control plot. Especially, the runoff rate is zero in SPG plot at a first rainfall events. The reduction rate of runoff from the S, PG and SPG plots was 30.8 %, 29.0 % and 81.8 % compared to control plots, respectively. The reduction rate of NPS pollution load of S, PG and SPG was ranged of 50～90 %, 30～70 % and 90～100 %, respectively. Yield of lettuce from S, PG and SPG plots was respectively 400 (567 kg/ha), 320 (453 kg/ha) and 760 (1,067 kg/ha) that of compared to control plots greater than that from control plots (140 kg/ha). We speculated that the experimental treated plots could hold more nutrients and moisture than the control and helped the crop grow healthier. When analyzing the above results, in terms of reduction of runoff and NPS pollution load and crop yields, SPG experimental treatment had the best effect. It was concluded that the use of rice straw mats cover and soil amendments on soil surface could not only reduce the NPS pollution loads in receiving waters but also help increase the crop yield.

안지현 Ahn Ji-hyun , 송인홍 Song In-hong , 강문성 Kang Moon-seong

DOI: JKWST Vol.55(No.2) 37-45, 2013

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The aim of this study was to investigate chemical characteristic of livestock compost in association with livestock manure types (poultry, cattle, swine, and mixed manure). The livestock compost was collected from local nonghyup branches on a si-gun level. Chemical composition (nutrients, heavy metals etc.) of the samples was analyzed and Pearson's correlation analysis was performed. Quality of most compost samples met the standard of fertilizer specifications. Poultry compost contains greater nutrients especially P2O (p-value＜0.01) and NH4-N (p-value＜0.05). Meanwhile swine compost has higher concentration in water content (p-value＜0.05) and heavy metals (p-value＜0.01 for Cd, Cu and Zn). Overall, poultry compost was correlated positively with nutrients while swine compost has positive correlation with water content and heavy metals. We expect that the study results can provide base data for determining compost types and amount for crop production Keywords: Livestock compost; Animal waste; Nutrients; Heavy

정충길 Jung Chung Gil , 안소라 Ahn So Ra , 김성준 Kim Seong Joon , 양희정 Yang Hee Jeong , 이형진 Lee Hyung Jin , 박근애 Park Geun Ae

DOI: JKWST Vol.55(No.2) 47-57, 2013

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This study is to assess the reduction of non-point source pollution loads for rice straw mulching of upland crop cultivation at a watershed scale. For Byulmi-cheon watershed (1.21 km2) located in the upstream of Gyeongan-cheon, the HSPF (Hydrological Simulation Program-Fortran) and SWAT (Soil and Water Assesment Tool), physically based distributed hydrological models were applied. Before evaluation, the model was calibrated and validated using 9 rainfall events. The Nash-Sutcliffe model efficiency (NSE) for streamflow using the HSPF was 0.62～0.76 and the determination coefficient (R2) for water quality (sediment, total nitrogen T-N, and total phosphorus T-P) were 0.72, 0.62, and 0.63 respectively. The NSE for streamflow using the SWAT were 0.43～0.81 and the R2 for water quality (sediment, T-N, and T-P) were 0.54, 0.87, and 0.64 respectively. From the field experiment of 16 rainfall events, the rice straw cover condition reduced surface runoff average 10.0 % compared to normal surface condition. By handling infiltration capacity (INFILT) in HSPF model, the value of 16.0 mm/hr was found to reduce about 10.0 % reduction of surface runoff. For this condition, the reduction effect of sediment, T-N, and T-P loads were 87.2, 28.5, and 85.1 % respectively. By handling soil hydraulic conductivity (SOL_K) in SWAT model, the value of 111.2 mm/hr was found to reduce about 10.0 point reduction of surface runoff. For this condition, the reduction effect of sediment, T-N, and T-P loads were 80.0, 83.2, and 78.7 % respectively. The rice straw surface covering was effective for removing surface runoff dependent loads such as sediment and T-P.

김동현 Kim Dong-hyun , 김춘수 Kim Chun-soo , 박찬기 Park Chan Gi

DOI: JKWST Vol.55(No.2) 59-64, 2013

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The present study is to evaluate physical and mechanical properties of porous concrete having non cement that mainly causes carbon emission. This study aims to explore eco-friendly concrete technology capable of reducing the amount of carbon emission due to the use of normal cement by substituting it with non cement porous concrete to which alkali-activator and blast-furnace slag powder are impregnated. As experimental variables, 5 %, 6 %, 7 %, 8 %, 9 % and 10 % of alkali-activator were substituted as binders and applied. Testing evaluated in this study were pH value, void ratio, compressive strength and residual compressive strength shown after being immersed in H₂SO₄ solution and Na₂SO₄ solution. The test results were compared with those tested with the use of porous concrete to which 400 kg/m3 of unit cement amount was applied as binder. In consequence, it was concluded that; as for pH value, it was decreased than was the case in which cement was used, but increased with the more the use of alkali activator; as for void ratio and compressive strength, the mix proportion in which 9 % and 10 % of alkali activator were applied in terms of substitution ratio showed the result similar to the mixture in which 400 kg/m3 of unit cement ratio was applied; and, as for residual compressive strength in the case of being immersed in H₂SO₄ solution and Na₂SO₄ solution, the compressive strength was increased, thus leading to improved chemical resistance.

이충원 Lee Chung-won , 장동수 Chang Dong-su , 박성용 Park Sung-yong , 연규석 Yeon Kyu-seok , 김용성 Kim Yong-seong

DOI: JKWST Vol.55(No.2) 65-75, 2013

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In this study, the engineering characteristics of volcanic ash-cement soil mixtures and zeolite-cement soil mixtures are investigated by using unconfined compression test, freezing-thawing test, SEM and XRD analysis. The samples were mixed with volcanic ash from Mt. Baekdusan or porous zeolite, and cement as the ratios of 3.5:1, 4.0:1, 4.5:1, 5.0:1 with and without metakaolin. It is confirmed that compressive strength degraded with increasing of the amount of volcanic ash or zeolite, and increased with addition of metakaolin as a binder. Moreover, test results suggested that the mixtures provided sufficient freezing-thawing resistance. In addition, ettringite as a product of cement hydration was detected by SEM and XRD, and that possibly contributes to the strength of the mixtures.

이충원 Lee Chung-won , 장동수 Chang Dong-su , 박성용 Park Sung-yong , 최중대 Choi Joong-dae , 김용성 Kim Yong-seong

DOI: JKWST Vol.55(No.2) 77-85, 2013

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The aim of this study is to investigate strength and water purification characteristics of effective microorganism-applied volcanic ash block using flexural strength test and water quality analysis. The specimens were prepared with volcanic ash from Mt. Baekdusan and Mt. Hallasan, and cement as the ratios of 3.5:1, 4.0:1, 4.5:1, 5.0:1 with and without metakaolin. Flexural strength degraded with increasing of the amount of volcanic ash, and increased with addition of metakaolin as a binder. Based on these results, the optimal ratio for fabricating volcanic ash-cement mixture block is determined as 3.5:1 with metakaolin. Furthermore, from water quality analysis on contaminated water, removal ability of effective microorganism-applied volcanic ash-cement mixture block and caged volcanic ash block against T-N, T-P and SS was highly evaluated because of adsorption due to the large specific surface area of volcanic ash. Hence, volcanic ash-cement mixture block and caged volcanic ash block possibly contribute to water purification.

이충원 Lee Chung-won , 장동수 Chang Dong-su , 박성용 Park Sung-yong , 김기성 Kim Ki-sung , 김용성 Kim Yong-seong

DOI: JKWST Vol.55(No.2) 87-95, 2013

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The aim of this study is to examine the behavior of reservoir fill dam with the water level raising by use of the centrifugal model test and the numerical simulation. In this study, LIQCA2D-SF based on the cyclic elasto-plastic constitutive model proposed by Oka et al. (1999) is applied for numerical simulation. In order to investigate the displacements and the pore water pressures in the fill dam due to the water level raising velocity, three model tests in centrifugal field of 50g for fill dams were conducted. A comparison between the test result and the simulation result has provided the influence on the displacement and the pore water pressure of the fill dam with increasing up of the water level.