김옥경 Kim Ok-kyoung , 최진용 Choi Jin-yong , 장민원 Jang Min-won , 유승환 Yoo Seung-hwan , 남원호 Nam Won-ho , 이주헌 Lee Joo-heon , 노재경 Noh Jae-kyoung

DOI: JKWST Vol.48(No.6) 3-13, 2006

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Although the drought impacts are comparably not catastrophic, the results from the drought are fatal in various social and economical aspects. Different from other natural hazards including floods, drought advances slowly and spreads widely, so that the preparedness is quite important and effective to mitigate the impacts from drought. Soil moisture depletion directly resulted from rainfall shortage is highly related with drought, especially for crops and vegetations, therefore a drought can be evaluated using soil moisture conditions. In this study, SMI (Soil Moisture Index) was developed to measure a drought condition using soil moisture model and frequency analysis for return periods. Runs theory was applied to quantify the soil moisture depletions for the drought condition in terms of severity, magnitude and duration. In 1994, 1995, 2000, and 2001, Korea had experienced several severe droughts, so the SMI developed was applied to evaluate applicability in the mid-range hydrologic unit watershed scale. From the results, SMI demonstrated the drought conditions with a quite sensitive manner and can be used as an indicator to measure a drought condition.

권순국 Soon-kuk Kwun , 김관수 Kwansoo Kim , 이정재 Jeong-jae Lee , 이제명 Je-myung Lee , 박창근 Changkeun Park

DOI: JKWST Vol.48(No.6) 17-28, 2006

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We propose an Agricultural Infrastructure Expansion Plan (AIEP) for North Korea following unification from the standpoint of a united Korea's social stability. We predict the food demand after unification, according to four different development scenarios based on the AIEP. These scenarios include meeting a self-sufficient level in the staple food crop, satisfying long-term food supply and demand for the North Korean people, achieving a level of North Korean food consumption comparable to that of South Korea, and maintaining productivity to stabilize of North Korea's rural society. We present the results of a 'benefit-cost' analysis in meeting the production targets of predicted food demands after unification from a civil engineering perspective. We found that the estimated total costs would range from 15.2 to 43.0 billion dollars depending on the particular AIEP scenario. In our analysis, all of the four scenarios presented above demonstrated a high degree of economic validity. We conclude that the AIEP is a necessary and economically valid project for a united Korea's future because it would forestall the collapse of North Korea's rural communities, thereby preventing tremendous economic losses upon unification.

서원명 Suh Won Myung , 윤용철 Yoon Yong Cheol

DOI: JKWST Vol.48(No.6) 31-41, 2006

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The analysis used in this work was cost-benefit analysis method. All future costs and returns of a given mushroom house were discounted to the time of initial investment (present) by means of 3.5% discount rate. Then the cost of ownership was compared to the return from the system. This analysis method has been developed and coded into a balance sheet for use on a EXCEL program. Using this programmed analysis, a large number of the case studies were examined using different combinations of economic conditions. These results will be very useful to individuals considering investment in a mushroom house, or any similar production system. By the way of the sensitivity analysis for each important parameter, the change of the marginal cost-benefit period could be finally determined. These parameters were typically construction cost of mushroom house, cost of cooling system, required cooling and heating energy amounts, unit price of mushroom media bottle, growing number of media bottles, production weight per unit bottle, sale price of mushroom, and annual number of growing period, etc.

류희룡 You Hee-yong , 이재영 Lee Jae-young , 박영택 Park Young-tack

DOI: JKWST Vol.48(No.6) 45-56, 2006

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The finite element method is a practical tool to compute the response of the irregularly layered soil deposit to the base-rock motions. The method is useful not only in estimating the interaction between the structure and the surrounding soil as a whole and the local behavior of the contacting area in detail, but also in predicting the resulting behavior of the superstructure affected by such soil-structure interactions. However, the computation of finite element analysis is marched in the time domain (TD), while the site response analysis has been carried out mostly in the frequency domain (FD) with equivalent linear analysis. This study is intended to compare the results of the TD and FD analysis with focus on the peak response accelerations and the predominant frequencies, and thus to evaluate the applicability and the validity of the finite element analysis in the site response analysis. The comparison shows that one can obtain the results very close to that of FD analysis, from the finite element analysis by including sufficiently large width of foundation in the model and further by applying partial mode superposition. The finite element analysis turned out to be well agreeing with FD analysis in their computed results of the peak acceleration and the acceleration response spectra, especially at the surface layer.

노수각 Noh Soo Kack , 손영환 Son Young Hwan , 장병욱 Chang Pyoung Wuck , 김성필 Kim Seong Pil

DOI: JKWST Vol.48(No.6) 59-67, 2006

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Particles of soil are crushed when soil is compacted in the in-situ or lab. Among many factors that affect the crush of particles, compaction energy is a major factor. Because the crush of particles can change physical properties, the analysis of effect of compaction energy is very important. In this study, the fragmentation fractals were used for determining the change in grain size distribution and the effect due to change in grain size distribution was estimated. Compaction energy was increased by 50, 100, 200 and 300% based on the energy of standard A compaction test. As a result, grain size distribution curves were changed and fine particles increased as compaction energy were increased. Relative compaction were ranged between 93.38~107.67. Fractal dimension of each site increased as compaction energy increased. Relative compaction is proportional to the fractal dimension but coefficients of permeability were in inverse proportional to the involution of fractal dimension.

백원진 Baek Won Jin

DOI: JKWST Vol.48(No.6) 69-77, 2006

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In this study, the large scaled model test improved by sand drain was carried out to clarify the internal behavior of the three-dimensional consolidation under different secondary consolidation periods. From the results of model test, the void ratio in the undrained side was lager than in the drained side. In addition, the unconfined compressive strength in the long-term consolidated specimen was larger than that in the short-term consolidated one. It was also found that the unconfined compressive strength was larger in the drained side than in the undrained side. These reasons are considered to be due to the large effective stress by quick pore water pressure dissipation by the short drainage distance in the drained side. Furthermore, in order to investigate the three-dimensional consolidation behavior of clay ground improved by the vertical drain method, the numerical analysis obtained from the three-dimensional elasto-viscous consolidation theory proposed by author (2006) were compared with the test results. It was found that during the three-dimensional consolidation process not only vertical displacement but also radial displacement occurs inside the specimen.

이행우 Lee Haeng Woo , 장병욱 Chang Pyoung Wuck , 손영환 Son Young Hwan , 김성필 Kim Seong Pil

DOI: JKWST Vol.48(No.6) 79-85, 2006

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A simulation was done to analyze the seepage problems due to seawater intrusion through the embedded rock layers on heterogeneous layers of sea-dike. Numerical analysis with SAMTLE(developed by author) was done by taking various relative permeability ratio(R_r/R_e). These results showed, when the sed-dike is newly designed, operated, and maintained considering the safety of sea-dike in seepage problems, these embankment materials are prudently chosen. The permeability of the soil materials, within the range of salinity management in freshwater, is comparatively high, however, the permeability of rock materials for bottom rock layer is low. Therefore, when the relative permeability ratio(R_r/R_e) is bellow 10 it is safety in seepage problems of sea-dike.

문종필 Jong-pil Moon , 김태철 Tai-cheol Kim

DOI: JKWST Vol.48(No.6) 89-100, 2006

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In order to estimate delivered nutrients load from non-point sources in the Gap stream watershed in Daejeon, a distributed watershed model SWAT2000 was used so that it could predict the impact of land management practices on water, sediments and chemicals yields in large complex watersheds with varing soils, land uses and management condition over long period of time. The SWAT2000 was applied to the Daejeon (Indong), Yudeung (Boksu) and Gap (Hoeduck) streams for TMDL (Total Maximum Daily Load) of nutrients. The observed water quality and streamflow data of the year of 2002 and 2003 were used for calibration, and those of the year 2004 and 2005 were used for validation. Simulated results were evaluated by Estimation Efficiency Analysis (COE), Regression Analysis (R²) and Relative Error (R.E.) for the nutrients amounts on the monthly and yearly basis by comparing observed load with estimated load obtained by using SWAT2000 simulations. The COE value fur T-N was ranged from 0.59 to 0.78, R² values for T-N ranged from 0.65 to 0.84, and R.E values fur T-N load ranged from 4% to 20%. COE value far T-N was ranged from 0.59 to 0.73, R² values for T-P ranged from 0.67 to 0.82, and R.E values for T-P load ranged from 3% to 25%. Estimated results of SWAT2000 simulation for 3 sites (Indong, Boksu, Hoedeok) were reasonably satisfactory. This study indicated that SWAT2000 model could be applicable to estimate the nutrients load from the Gap stream watershed in Korea.

이은정 Lee Eun Jeong , 조영경 Cho Young Kyoung , 박승우 Park Seung Woo , 김학관 Kim Hak Kwan

DOI: JKWST Vol.48(No.6) 101-112, 2006

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A Geographic Information System (GIS) was developed to estimate basin-wide soil losses using the Universal Soil Loss Equation (USLE). It was applied to estimate the annual average soil losses from the Saemangeum watershed. The USLE factors for each subarea of uniform land use and treatments were estimated from the GIS routines from digital topographic maps, land cover and detailed soil maps. A routine was developed to estimate the averaged cropping management factors (C) of USLE for multi-cropping farmlands, based on cropping system records from the district offices. The resulting C factors ranged from 0.28 to 0.35 for multi-cropping areas. The estimated annual average soil loss was approximately 2.9 million tonnes. Typical soil losses from different land uses were 0.8 t/ha at paddies, 33.7 t/ha at uplands and 1.1 t/ha from forested mountains. It was also found that 6.0% of the arable land of the watershed possessed high risks of soil losses, and conservation measures were needed to reduce soil losses.

김형중 Hyung-joong Kim , 윤춘경 Chun-g. Yoon , 권태영 Tae-young Kwun , 정광욱 Kwang-wook Jung

DOI: JKWST Vol.48(No.6) 113-124, 2006

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The feasibility of the up- and down-flow constructed wetland was examined fur rural wastewater treatment in Korea. Many constructed wetland process was suffered from substrate clogging and high plant stresses because of long term operation. The up- and down-flow constructed wetland process used porous granule materials (charcoal pumice : SSR=10:20:70) for promoting intake rate of nutrient to plant, and especially flow type was designed continuously repeating from up-flow to down-flow. BOD₅ and SS was removed effectively by the process with the average removal rate being about 75% respectively. The wetland process was effective in treating nutrient as well as organic pollutant. Removal of TN and TP were more effective than other wetland system and mean effluent concentrations were approximately 7.5 and 0.4mg L^-1 which satisfied the water quality standard for WWTPs. The treatment system did not experience any clogging or accumulations of pollutants and reduction of treatment efficiency during winter period because constructed polycarbonate glass structure prevented temperature drop. Considering stable performance and effective removal of pollutant in wastewater, low maintenance, and cost-effectiveness, the up- and down-flow constructed wetland was thought to be an effective and feasible alternative in rural area.