김경호 Kim Kyoung-ho , 박재성 Park Jae-sung , 이호진 Lee Ho-jin , 연주흠 Youn Ju-heum

DOI: JKWST Vol.47(No.5) 3-13, 2005

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The present study examined the 3 dimensional space distribution characteristics of sea water intrusion using data available from previous observations. For this study, we used 3D FEMWATER, which is a 3 dimensional finite element model. The target area was around Daechang-ri, Gimje-si, Jeollabuk-do. The area is relatively easy to formulate a conceptual model and has observation wells in operation for surveying sea water intrusion. Considering the uncertainty of numerical simulation, we analyzed sensitivity to hydraulic conductivity, which has a relatively higher effect. According to the result of the analysis, the variation of TDS concentration had an error range of -1,336~+107mg/ ℓ. Taking note that the survey data from observation wells were collected when the boundary between fresh water and sea water in the aquifer was in equilibrium, we set the range of time for numerical simulation and estimated the spatial distribution of TDS concentration as the range of sea water intrusion. According to the result of estimation, the spatial distribution of TDS concentration calculated when 1,440 days were simulated was taken as the range of sea water intrusion. Using the result of calculation, we can draw not only vertical views for a certain section but also horizontal views of different depth. These views will be greatly helpful in understanding the spatial distribution of the range of sea water intrusion. In addition, the result of this study can be used rationally in proposing an optimal quantity of water pumping through investigating the moving route of sea water intrusion over time in order to prevent excessive water pumping and to maintain an optimal number of water pumping wells per interval.

조진구 Cho Jin Goo , 박진환 Park Jin Hwan

DOI: JKWST Vol.47(No.5) 17-26, 2005

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The objectives of this study are to determine the behavior of simply supported skew RC slabs subjected to a point load. The p-version nonlinear skew RC FE model has been used. Integrals of Legendre polyno-mials are used for shape functions with p-level varying from 1 to 10. In the nonlinear formulation of this model, the material model is based on the Kupfer's yield criterion, hardening rule, and crushing condition and layered model is used through the thickness. The cracking behavior is modeled by a smeared crack model and the fixed crack approach is adopted as the crack model. It is shown that the proposed model is able to adequately predict the deflection and ultimate load of nonlinear skew RC slabs with respect to steel arrangements and steel ratios.

김윤용 Kim Yun Yong , 김정수 Kim Jeong Su

DOI: JKWST Vol.47(No.5) 27-39, 2005

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In the recent design of high ductile fiber-reinforced ECC (engineered cementitious composite), optimizing both processing and mechanical properties for specific applications is critical. This study presents an innovative method to develop new class ECCs, which possess the different fluid properties to facilitate diverse types of processing (i.e., self-consolidating or shotcrete processing) while maintaining ductile hardened properties. In the material design concept, we employ a parallel control of fresh and hardened properties by using micromechanics and cement rheology. Control of colloidal interaction between the particles is regarded as a key factor to allow the performance of the specific processing. To determine how to control the particle interactions and the viscosity of cement suspension, we first introduce two chemical admixtures including a highly charged polyelectrolyte and a non-ionic polymer. Optimized mixing steps and dosages we, then, obtained within the solid concentration predetermined based on micromechanical principle. Test results indicate that the rheological properties altered by this approach were revealed to be highly effective in obtaining the desired function of the fresh ECC, allowing us to readily achieve hardened properties, represented by pseudo strain-hardening behavior in uniaxial tension.

임성훈 Eam Sung Hoon

DOI: JKWST Vol.47(No.5) 43-49, 2005

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In this study. it was suggested that the elastic model to analyze the behavior of pore water pressure in saturated sand specimen on the condition of non-drainage. The model based on the experiments which were performed for the relationships between the pore water pressure and the grain size of specimen, and effective stress, respectively. The suggested model embodied the pore water and soil grain as separate elastic springs of different stiffness. The springs were joined parallel and the axial strains were restricted to the same deformation. The suggested model was well consistent with the experiments.

김용성 Kim Yong-seong , 김기영 Kim Ki-young , 전제성 Jeon Je-sung

DOI: JKWST Vol.47(No.5) 51-61, 2005

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In this study, borehole records were analyzed to verify the amplification of seismic motion at the soft reclaimed ground before and after the main event of the 1995 Hyogoken Nambu Earthquake at Port Island, Japan. From the analysis, it was shown that the amplification of seismic motion occurred near the soft ground surface (within 30 m below) where confining stress is low. Moreover, it was found that recovery of dynamic soil stiffness at the liquefied ground began gradually 3 hours after the liquefaction and completed in 10 days, when the ground exhibited the same seismic motion characteristics as those before the liquefaction.

이행우 Lee Haeng Woo , 장병욱 Chang Pyoung Wuck , 강병윤 Kang Byung Yoon , 김현태 Kim Hyun Tae

DOI: JKWST Vol.47(No.5) 63-71, 2005

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In-situ soil remediation mechanism through the vertical drains (VDs) is analyzed with numerical model as the error and complementary error function. Results from in-situ test and analysis indicate that the contaminant concentration ratio as initial one ( C/C₀) increases as the radius ratio ( r/R) increases from the injection well, and also increases as the depth ratio ( z/H) increases from the top of contaminated area. The elapse time needed to attain 50% and 90% clean up level (t₅₀, t₉₀) increases as the radius ratio (r/R) and the depth ratio (z/H) increase. As above results, the procedure of soil flushing in contaminated area using vertical drains makes progress from the top of injection well to the bottom of extraction well.

방천희 Bang Cheon-hee , 박재로 Park Jae-roh , 권혁 Kwon Hyok

DOI: JKWST Vol.47(No.5) 75-86, 2005

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Recently since urbanization has brought about a dried stream and a worse water quality, Anyang city discharged the third treated sewage into the upper stream of Anyancheon and Hakuicheon. As the result, Hakuicheon had the water level and velocity enough for a living thing in the water to live in but water quality was worse than it had been. Therefore in case of meeting the water level and velocity of the second grade water-quality which living things in the water can live in, the discharge and water quality to secure in-stream flow must be at least 0.350 ㎥/s and BOD₅ 3.2mg/ℓ respectively. In Anyancheon the water level was increased a little higher than it had been but the velocity was almost unchanged in comparison with it before. On the other hand the water quality was a little better than it had been. Therefore in case of meeting the water level and velocity of the third grade water-quality that people can do water-friendly activity, the discharge and water quality to secure in-stream flow must be at least 0.688 ㎥/s and BOD₅ 4.8mg/ℓ respectively. The water-quality prediction on the suggested eight scenarios was simulated in all satisfying the third grade water-quality.

함종화 Jong-hwa Ham , 윤춘경 Chun G. Yoon , 구원석 Won-seok Koo , 김형철 Hyung-chul Kim , 신현범 Hyum-bhum Shin

DOI: JKWST Vol.47(No.5) 87-97, 2005

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The field scale experiment was performed to examine the effect of physical design parameters on the constructed wetland performance and recommend the feasible design of constructed wetland in Korean polder areas. Four sets (each set of 0.85 ha) of wetland (0.8 ha) and pond (0.08 ha) systems were used. Two different wetland systems, a wetland-pond system and a pond-wetland system, were studied to examine the effect of wetland and pond configuration. And two different length-to-width ratios were used, 2:1 and 0.8:1, to examine the effect of aspect ratio. A pond-wetland system was more preferable than a wetland-pond system, and also requires a smaller area than a wetland-pond system or a wetland system to reduce T-P. There was no difference in effluent concentration between the 2:1 system and the 0.8:1 system. Although the linear velocity of the 2:1 aspect was higher than the 0.8:1 aspect, resuspension was not a factor in this study due to a very low linear velocity. From this study and other literature review, it was found that design method of paddy rice field could be applied and expanded to the design of constructed wetland in Korea. Further investigation for the detailed design parameters of constructed wetland needs be continued for design method of paddy rice to be applied in full scale.