김성필 Kim Seong-pil , 허준 Heo Joon , 봉태호 Bong Tae-ho

DOI: JKWST Vol.53(No.6) 1-6, 2011

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The conventional factor of safety as used in geotechnical engineering does not reflect the degree of uncertainty of the relevant parameters. Then in the geotechnical engineering, there have been efforts to reflect the uncertainties of the geotechnical properties through probabilistic analysis. In this study, a practical method for probabilistic analysis using the Hasofer-Lind reliability index is introduced. The method is based on the perspective of an ellipsoid that just touches the failure surface in the original space of the variables. The method is applied to prefabricated vertical drains (PVD) and compared with the result of Monte Carlo Simulation method.

장민원 Jang Min-won , 이현정 Lee Hyeon-jeong , 김이현 Kim Yi-hyun , 홍석영 Hong Suk-young

DOI: JKWST Vol.53(No.6) 7-16, 2011

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This study discussed the applicability of satellite SAR (Synthetic Aperture Radar) imagery with regard to reservoir monitoring, and tried the extraction of reservoir storage from multi-temporal C-band RADARSAT-1 SAR backscattering images of Yedang and Goongpyeong agricultural reservoirs, acquired from May to October 2005. SAR technology has been advanced as a complementary and alternative approach to optical remote sensing and in-situ measurement. Water bodies in SAR imagery represent low brightness induced by low backscattering, and reservoir storage can be derived from the backscatter contrast with the level-area-volume relationship of each reservoir. The threshold segmentation over the routine preprocessing of SAR images such as speckle reduction and low-pass filtering concluded a significant correlation between the SAR-derived reservoir storage and the observation record in spite of the considerable disagreement. The result showed up critical limitations for adopting SAR data to reservoir monitoring as follows: the inappropriate specifications of SAR data, the unreliable rating curve of reservoir, the lack of climatic information such as wind and precipitation, the interruption of inside and neighboring land cover, and so on. Furthermore, better accuracy of SAR-based reservoir monitoring could be expected through different alternatives such as multi-sensor image fusion, water level measurement with altimeters or interferometry, etc.

홍성구 Hong Seong Gu , 왕용 Wang Long

DOI: JKWST Vol.53(No.6) 17-22, 2011

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Biomass gasification provides synthesis gas or syngas that can be used for internal combustion engines as fuel or chemical synthesis as feedstock. Among different types of gasifiers, downdraft gasifier can produce relatively clean syngas with lower tar contents. In this study, a downdraft gasifier was fabricated with 150 mm of hearth diameter to gasify woodchip that is commercially available in this country. After drying woodchip to about 20 %, gasification experiments were conducted measuring temperature, pressure, air and gas flow rates. The volumetric concentrations of CO, H₂, CO₂, CH₄ were 10.7～14.5, 16.5～21.4, 12.5～16.6, and 2.3～2.9, respectively. They were overall within the ranges of the results that the previous studies showed. However, CO concentration was relatively lower and H2 was slightly higher than those from other studies. It seemed that water gas shift reaction was occurred due to the moisture in the fuel woodchip. Additional drying process coupled with syngas cooling would be required to improve the overall efficiency and syngas quality.

정혁 Jung Hyuk , 신형진 Shin Hyung Jin , 박종윤 Park Jong Yoon , 정인균 Jung In Kyun , 김성준 Kim Seong Joon

DOI: JKWST Vol.53(No.6) 23-29, 2011

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This study was conducted to identify the effect of lapse rate application according to elevation on the estimation of large scale watershed rainfall. For the Han river basin (26,018 ㎢), the 11 years (2000-2010) daily rainfall data from 108 AWS (Automatic Weather Station) were collected. Especially, the 11 heavy rain and typhoon events from 2004 to 2009 were selected for trend analysis. The elevation effect by IDW (Inverse Distance Weights) interpolation showed the change up to ＋62.7 % for 1,200～1,600 m elevation band. The effect based on 19 subbasins of WAMIS (Water Resources Management Information System) water resources unit map, the changes of IDW and Thiessen were －8.0 % (Downstream of Han river)～ ＋19.7 % (Upstream of Namhan river) and －5.7 %～＋15.9 % respectively. It showed the increase trend as the elevation increases. For the 11 years rainfall data analysis, the lapse rate effect of IDW and Thiessen showed increase of 9.7 %～15.5 % and 6.6 %～9.6 % respectively.

오윤경 Oh Yun-gyeong , 최진용 Choi Jin-yong , 유승환 Yoo Seung-hwan , 이상현 Lee Sang-hyun

DOI: JKWST Vol.53(No.6) 31-41, 2011

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This study was conducted to predict future land-cover changes under climate change scenarios and to cluster analysis of regional land-cover characteristics. To simulate the future land-cover according to climate change scenarios - A1B, A2, and B1 of the Special Report on Emissions Scenarios (SRES), Dyna-CLUE (Conversion of Land Use Change and its Effects) was applied for modeling of competition among land-use types in relation with socioeconomic and biophysical driving factors. Gyeonggi-do were selected as study areas. The simulation results from 2010 to 2040 suggested future land-cover changes under the scenario conditions. All scenarios resulted in a gradual decrease in paddy area, while upland area continuously increased. A1B scenario showed the highest increase in built-up area, but all scenarios showed only slight changes in forest area. As a result of cluster analysis with the land-cover component scores, 31 si/gun in Gyeonggi-do were classified into three clusters. This approach is expected to be useful for evaluating and simulating land-use changes in relation to development constraints and scenarios. The results could be used as fundamental basis for providing policy direction by considering regional land-cover characteristics.

노수각 Noh Soo-kack , 손영환 Son Young-hwan , 봉태호 Bong Tae-ho , 박재성 Park Jae-sung

DOI: JKWST Vol.53(No.6) 43-50, 2011

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The fractal method has recently been applied to a model for determining soil grain size distribution. The objective of this study is to review the applicability of the fractal method for a analysis of submarine sedimentary environments by comparing fractal constants with grain size statistical analysis for the soil samples of Pohang (PH) and Namhae (NH). The y-interception of log (grain size)-log (passing) equation was also used because grain size distribution couldn’t be expressed with fractal dimension only. The result of comparison between fractal constants (dimension, y-interception) and grain size statistical indices, the fractal dimension was directly proportional to the mean and the sorting. And the y-interception showed high correlation with the mean. The fractal dimension and y-interception didn’t show significant correlation with the skewness and the kurtosis. Thus regression equations between fractal constants and two statistical indices (mean, sorting) were derived. All classifications of the mean and the sorting could be determined using the regression equation based on the fractal dimension and y-interception. Therefore, fractal constants could be used as an alternative index representing the sedimentary environments instead of the mean and sorting.

김상민 Kim Sang Min , 안병일 Ahn Byeong Il

DOI: JKWST Vol.53(No.6) 51-58, 2011

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The objective of this study is to identify whether or not the ground water level is decreasing. We suggest a method of estimating the change in groundwater level using newly developed groundwater pumping station data. The Goseong area located in Gyeongnam province was selected considering three factors. First, this area demands relatively large amount of irrigation water because most of the land is used as a paddy field and the proportion of the paddy field within total arable land is increasing. Second, groundwater level data in nearby area are available since these are monitored by Water Management Information System (WAMIS). Third, many groundwater pumping stations have been developed in this area in order to overcome droughts thus detail information for pumping stations are available. Regression results indicate groundwater level has been decreased for over 20 years. This decreasing trend is due to the shortage of surface irrigation water which was caused by the decrease in rainfall.

성찬용 Sung Chan Yong , 김태호 Kim Tae Ho

DOI: JKWST Vol.53(No.6) 59-65, 2011

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This study was performed to evaluate the compressive and flexural strength, void ratio and permeability coefficient used powdered waste glass, CaCO₃, recycled coarse aggregate and unsaturated polyester resin to find optimum mix design of permeable polymer concrete for pavement. The compressive and flexural strength of permeable polymer concrete for pavement using powdered waste glass were in the range of 16.8∼19.7 MPa and 4.7∼6.1 MPa, respectively. it was satisfied the regulation of permeable concrete for pavement (18 MPa and 4.5 MPa). The void ratio and permeability coefficient were decreased with increasing the powdered waste glass, respectively. The void ratio and permeability coefficient were satisfied national regulation of permeable concrete for pavement (8 % and 1×10^－2 cm/s). In addition, this study found out that required amount of binder was decreased with increasing the powdered waste glass. This fact is expected to have economical effects during the use of powdered waste glass in the manufacture of permeable polymer concrete for pavement. Accodingly, the powdered waste glass can be used for permeable concrete material.

장훈 Jang Hoon , 김진수 Kim Jin Soo , 김영현 Kim Young Hyeon , 송철민 Song Chul Min

DOI: JKWST Vol.53(No.6) 67-74, 2011

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The objective of this study was to compare concentrations of nutrients such as total nitrogen (TN), nitrate nitrogen (NO₃-N) total phosphorous (TP), and phosphate phosphorous (PO₄-P) in groundwater under paddy and upland fields, and surface water recharging from a rural mixed land-use watershed. Chinese cabbage and hot pepper were cultivated on the upland field plot. The TN concentrations in upland groundwater showed double peaks (4.7, 4.3 mg/L, respectively) in April 2009 shortly after fertilizer application, indicating that TN concentrations are greatly influenced by fertilization. However, the TN concentrations in paddy groundwater were always lower than 2.0 mg/L irrespective of fertilization. Whereas the mean concentrations of TN and NO₃-N in upland groundwater significantly (p＜0.05) higher than those in surface water, the mean concentrations of TP and PO₄-P in upland groundwater were significantly lower than those in surface water. On the other hand, the mean concentrations of TN, NO₃-N, TP and PO₄-P in paddy groudwater were significantly (p＜0.05) lower than those in surface water. The TN concentrations in upland groundwater were generally higher than those in surface water during early April to early December due to the effect of fertilization, but vice versa in the other periods. In contrast, the TP concentrations in upland groundwater were always lower than those in surface water due to the sorption of inorganic phosphorous by soil. Moreover, the TN and TP concentrations in paddy groundwater were always lower than those in surface water, and therefore paddy groundwater may dilute nutrient concentrations in surface water when paddy groundwater and surface water mix.

김학관 Kim Hak Kwan , 강문성 Kang Moon Seong , 이은정 Lee Eun Jeong , 박승우 Park Seung Woo

DOI: JKWST Vol.53(No.6) 75-84, 2011

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The objective of this study is to evaluate the hydrologic impacts of climate and land use changes in a rural small watershed. HadCM3 (Hadley Centre Coupled Model, ver.3) A2 scenario and LARS-WG (Long Ashton Research Station - Weather Generator) were used to generate future climatic data. Future land use data were also generated by the CA-Markov (Cellular Automata-Markov) method. The Soil and Water Assessment Tool (SWAT) model was used to evaluate hydrologic impacts. The SWAT model was calibrated and validated with stream flow measured at the Baran watershed in Korea. The SWAT model simulation results agreed well with observed values during the calibration and validation periods. In this study, hydrologic impacts were analyzed according to three scenarios: future climate change (Scenario Ⅰ), future land use change (Scenario Ⅱ), and both future climate and land use changes (Scenario Ⅲ). For Scenario Ⅰ, the comparison results between a 30-year baseline period (1997～2004) and a future 30-year period (2011～2040) indicated that the total runoff, surface runoff, lateral subsurface runoff, groundwater discharge, and evapotranspiration increased as precipitation and temperature for the future 30-year period increased. The monthly variation analysis results showed that the monthly runoff for all months except September increased compared to the baseline period. For Scenario Ⅱ, both the total and surface runoff increased as the built-up area, including the impervious surface, increased, while the groundwater discharge and evapotranspiration decreased. The monthly variation analysis results indicated that the total runoff increased in the summer season, when the precipitation was concentrated. In Scenario Ⅲ, the results showed a similar trend to that of Scenario Ⅱ. The monthly runoff for all months except October increased compared to the baseline period.

함종화 Ham Jong Hwa , 김형중 Kim Hyung Joong , 김동환 Kim Dong Hwan , 홍대벽 Hong Dae Byuk

DOI: JKWST Vol.53(No.6) 85-91, 2011

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Three different types of wetlands (unplanted wetland, reed planted wetland, cattail planted wetland) were constructed at the mouth of Seokmoon reservoir with 910 ㎡ each to examine the effects of wetland plant on pollutant removal rate in constructed wetland, and operated for 9 years (2002～2010). Water depth of the wetland was maintained at 0.3～0.5 m, flow rate was about 40～200 ㎥/day, and retention time was managed at about 1～5 days. There was no difference in removal rate of SS, TN, and TP between reed wetland and cattail wetland. Removal rate of SS and TN in planted wetland with reed and cattail were higher than unplanted wetland, whereas removal rate of TP in unplanted wetland was higher then planted wetland. The monthly variation of removal rate in planted wetlands was high compared with unplanted wetland. From the long term monitoring results, SS and TN removal rates of period3 (2008～2010) were higher than period1 (2002～2004) in planted wetland, whereas TP removal rate was decreased as time goes on. Overall, pollutant removal rate in constructed wetland was more influenced by existence of plants than by plant species. Although constructed wetland is operated long term period, SS, TN, and TP removal rate (SS 90 %, TN 60 %, TP 40 %) can be maintained high values.

김기성 Kim Keesung

DOI: JKWST Vol.53(No.6) 93-100, 2011

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김상민 Kim Sang Min , 김성재 Kim Sung Jae , 김용완 Kim Yong Wan , 박태양 Park Tae Yang , 김성민 Kim Sung Min , 박기욱 Park Ki Wook , 장민원 Jang Min Won

DOI: JKWST Vol.53(No.6) 101-109, 2011

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The purpose of this study was to establish the methodology for providing the environmental flows from irrigation reservoir. Reservoir water budget for study area was analyzed to simulate the water supply scenarios for environmental flows. Bonghyun and Hi reservoirs area, located in Gyeongnam, Gosung-gun, Hi-myeon, were selected for study watersheds and streams for this study. Reservoir operation was simulated to determine the envionmental flows supply amount from March to October with the constraint that environmental flow supply was restrained when the storage of reservoir were below the half or one-third of effective storage. The simulated results indicated that the supply of environmental flows with the amount of 200 ton/day and 600 ton/day resulted in up to 15 mm and 29 mm of runoff depth increase in the downstream, respectively. The effect of environmental flows supply from existing irrigation reservoir was not significant because the irrigation reservoir was not designed to supply the environmental flows. It is necessary to remodel the irrigation reservoir and develop the reservoir operation technique, to meet the need for the environmental flows.

장승우 Chang Seungwoo , 강문성 Kang Moon Seong , 송인홍 Song Inhong , 장정렬 Jang Jeong Ryeol , 이은정 Lee Eun Jeong , 박승우 Park Seung Woo

DOI: JKWST Vol.53(No.6) 111-119, 2011

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The main objective of this study was to evaluate the effects of control-release fertilizer (CRF) on pollutant loadings from a small watershed. The Baran watershed, 386 ha in size, was selected as the study site, and the AGNPS (Agricultural Non-point Source Pollution) model was used to evaluate the effects of fertilizer types. Digital maps of digital elevation (DEM), slope distribution, channel, flow direction, landuse, soil, and curve number were extracted from the study watershed. Model parameters related to hydrology and water quality were calibrated and validated by comparing model predictions with the observed data collected for 2 years (1999 to 2000). Calibration and validation resulted in R² values of 0.75-0.91 for all the water quality parameters. All the paddy fields (21.2 %) of the study watershed were sprayed by either CRF or NPK (standard fertilizer). In CRF application, total nitrogen (TN) load was 4.9% less than NPK application, however total phosphorus (TP) load was 0.7 % more than NPK application. In CRF application, considering only paddy fields in the study area, TN load was 38.7 % less than NPK application. Using CRF in paddy fields could be one of the ways to reduce pollutant loadings from agricultural watersheds, however, in order to confirm it, more researches about effects of using CRF are necessary.

손영권 Son Yeong Kwon , 윤춘경 Yoon Chun Gyeong , 김형중 Kim Hyung Joong , 함종화 Haam Jong Hwa

DOI: JKWST Vol.53(No.6) 121-128, 2011

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Long-term water treatment performance analysis was conducted for the constructed wetland treating agricultural tailwater. Studied wetland was established in 2001 and operated from June, 2002 to November, 2010. Wetland vegetation cover was shown over 90 % coverage after 2005. According to vegetation development, accumulation of sediment nutrient was observed; Organic Carbon, T-P and T-N. In addition, DO concentration and temperature was decreased in the constructed wetland output. An infiltration rate also significantly decreased due to compaction of wetland soil. A runoff coefficient was increased due to the low infiltration rate after 2005. A T-N, TSS and Chl.a removal rate was maintained constantly. However, the T-P removal rate was slightly decreased along to wetland operation because low DO concentration could increase elution of phosphorus from sediment. After constructing open water, the T-P removal rate was increased. This is because open water could accelerate the reaearation process. Consequently, over three years of vegetation development could be helpful for wetland performance. In addition, DO concentration is important factor to maintain the T-P treatment.

신민환 Shin Min Hwan , 원철희 Won Chul Hee , 박운지 Park Woon Ji , 최용훈 Choi Young Hun , 신재영 Shin Jae Young , 임경재 Lim Kyoung Jae , 최중대 Choi Joong Dae

DOI: JKWST Vol.53(No.6) 129-136, 2011

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To measure effects of surface cover on runoff and sediment discharge reduction using rainfall simulator, four(5 m×30 m scale) plot experiments were conducted in this study. Surface covers made with straw mat, Polyacrylamide (PAM), chaff, and sawdust were simulated 4 times under 31.1～44.4 mm/hr rainfall intensities. Compared with results from control plot, the time of runoff generation is delayed and outflow volume decreased with surface cover. Effects on runoff reduction of straw mat, PAM, sawdust and chaff ranged 4.7～81.5 % and runoff rate reduced by 6.5～76.1 % respectively, when compared with those from control plot. The percentage of decrease in sediment discharge were 99.7～99.8 % from straw mat＋sawdust＋PAM plots, 85.9～95.6 % from straw mat＋PAM plots, and 98.5～99.4 % from straw mat＋chaff＋PAM plots. The runoff, sediment discharge, and SS concentration reduction efficiencies of the cover materials were outstanding when compared to control plot. It was analyzed that reduction of runoff and sediment discharge were mainly contributed by decrease in rainfall energy impact and flow velocity and increase of infiltration due to the surface cover materials. The results could be used as a base for the development of best management practices (BMPs) to reduce runoff, sediment discharge from sloping field.

원철희 Won Chul-hee , 최용훈 Choi Yong-hun , 박운지 Park Woon-ji , 신민환 Shin Min-hwan , 최중대 Choi Joong-dae

DOI: JKWST Vol.53(No.6) 137-144, 2011

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We have examined the pollutant load of combined sewer in dry days. Two monitoring sites (C-1, C-2) were equipped with an flowmeter. Monitoring was conducted from September 2004 to April 2006 for 20 months during dry days. Flowrate and concentration of pollutants are lowest from 3 to 6 o’clock, and it is high at 9, 12 and 21 o’clock. Most of organic matters exist in the dissolved state. The results show that pollution loads in C-2 area were 4.5-7.2 times higher than in C-1. Pollutant loads were high on Saturdays. Pollutant loads (kg/ha/day) of C-2 were 1.1-3.1 times higher those of C-1. However there was no significant difference in winter. Analysis of correlation coefficient of water quality parameter indicates that besides of flowrate all items in C-1 site have tight relationship respectively (p＜0.01). In C-2 site, correlation coefficient of TP-SS, TP-TN, TP-flowrate, BOD-flowrate, BOD-SS and TN-TP are statistically significant (p＜0.01).

문종필 Moon Jongpil , 이성현 Lee Sunghyoun , 권진경 Kwon Jin-kyung , 강연구 Kang Younku , 유영선 Ryou Youngsun , 이수장 Lee Sujang

DOI: JKWST Vol.53(No.6) 145-152, 2011

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In order to heat greenhouse nearby river channel, riverbank filtration water source heat pump was developed for getting plenty of heat flux from geothermal energy. Recharging well, thermal storage tank with separating insulation plate and filtering tank for eliminating iron, manganese were mainly developed for making the coefficient of performance (COP) of heat pump higher. Heating system using riverbank filtration water source heat pump was installed at a paprika greenhouse in the Jinju region where a single fold of vinyl cover and 2 layers of horizontal thermal curtain were installed as a part of temperature keeping and heat insulation with a greenhouse area of 3,185 ㎡. 320,000 kcal/h was supplied for performing a site application tests. A greenhouse heating test was performed from Feb. 1, 2011 to Apr. 30, 2011. As the result of that, COPh of the heat pump was measured in the range of 4.0～4.5, while COPS of the system was represented as 2.9～3.3. COP measured of the heat pump was very good and well responded to indoor heating temperature of the environment control system of a greenhouse.

김시환 Kim Shi Hwan , 윤성수 Yoon Seong Soo , 박진선 Park Jin Seon , 전정배 Jeon Jeong Bae

DOI: JKWST Vol.53(No.6) 153-163, 2011

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This research describe improved algorithm that is able to decide terminal criterion of Evolutionary Structural Optimization (ESO), reducing load of calculation to search load path of concrete beam, and apply to agricultural facilities. The ESO method is that make to discrete structure, structural analyze each element stress through FEM. And repeat generation with next material condition to become for most suitable composing. Individual element introduces concept of zero stiffness, but zero stiffness decisions are gone to direction of exclusion. In this stduy, improve algorithm to be convergence by ‘Rule of Alive or Die’ in arrival because is most suitable. Also, existing terminal criterion lack consistency because that used depend on experience of researcher. This research procedure is fellowed. First, all modulus of elasticity assume a half of elasticity modulus of material, Second, structural analysis by FEM, Third, apply to the remove ratio and restoration ratio for the ‘rule of alive or die’. Forth, reconstruct the element and material conditions. And repeat the first to forth process. The terminal time of evolutional procedure is the all elastic modulus of element changed to blank value or elasticity modulus value of original. Therefore, in this study, consist the algorithm for programming, and apply to the agricultural facilities with concrete.

박민지 Park Min Ji , 신형진 Shin Hyung Jin , 최영돈 Choi Young Don , 박재영 Park Jae Young , 김성준 Kim Seong Joon

DOI: JKWST Vol.53(No.6) 165-170, 2011

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Recently natural disasters such as the frequency and intensity of drought have been increasing as a result of climate change. This study suggests a drought index, WADI (Water Availability Drought Index), that considers water availability using 6 components (water intake, groundwater level, agricultural reservoir water level, dam inflow, streamflow, and precipitation) using the Z score and data monitoring on a nationwide level. SPI (Standardized Precipitation Index) was applied in coastal area. For the severe droughts of 2001 spring and 2008 autumn, the index was evaluated by comparison with reported damage areas. suggested to combine The spatial concordance rate of WADI in 2001 and 2008 for estimation of the degree of drought severity was 50 % and 24 % compared to the actual recorded data respectively.

전지홍 Jeon Ji-hong

DOI: JKWST Vol.53(No.6) 171-183, 2011

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Temporal and spatical surface runoff by heavy rainfall during 25～28 July, 2011 causing urban flooding at Seoul were analyzed using Long-Term Hydrologic Impact Assessment (L-THIA). L-THIA was calibrated for 1988～1997 and validated for 1998～2007 using monthly observed data at Hangangseoul watershed which covers 90 % of Seoul city. As a results of calibration and validation of L-THIA at Hangangseoul watershed, Nash-Sutcliffe coefficients were 0.99 for calibration and 0.99 for validation. The simulated values were good agreement with observed data and both calibrated and validated levels were “very good” based on calibration criteria. The calibrated curve number (CN) values of residential and other urban area represented 87 % and 93 % of impervious area, respectively, which were maximum percentage of impervious area. As a result of L-THIA application at Seoul city during 2 5～28 July, 2011, most of rainfall (54 %, 287.49 mm) and surface runoff (65 %, 247.32) were generated at 27 July, 2011 and a significant amount of rainfall and surface runoff were occurred at southeastern Seoul city. As a result of bi-hourly spatial and temporal analysis during 27 July, 2011, surface runoff during 2:00～4:00 and 8:00～10:00 were much higher than those during other times and surface runoff located at Seocho-gu during 6:00～8:00 represented maximum value with maximum rainfall intensity which caused landslide from Umyun mountain.