강민구 Kang Min Goo , 박승우 Park Seung Woo , 박종민 Park Jong Min

DOI: JKWST Vol.46(No.3) 3-14, 2004

---

A two-dimensional numerical model based on a finite volume method was formulated to solve the shallow water equations and applied for evaluating drainage characteristics at large-sized paddy fields. Manning roughness coefficient was calibrated using the observed inundating depths at drainage tests, and used for validating the model with the results from another drainage test. The simulated results were in good agreement with the observed inundating depths. The result of surface drainage showed that the longer width of the outlet was or the more the number of drainage outlet was, the shorter the drainage time was taken, and the larger the size of the field become, the longer the drainage time was taken, and the field shape had little effect on drainage time. To reduce the drainage time to 24 hours, the outlet is located lower than the elevation of the basin and small drainage ditch is constructed at the field. The results showed that the drainage time was taken short as the small drainage ditch was constructed. The comparison of drainage time as to the size of field constructed small drainage ditch showed the field, 100m x 200 m, can be drained in 24 hours.

장민원 Jang Min Won , 정하우 Chung Ha Woo , 최진용 Choi Jin Yong , 박기욱 Park Ki Wook , 배승종 Bae Seung Jong

DOI: JKWST Vol.46(No.3) 17-30, 2004

---

This study aimed to develop an agricultural drought assessment methodology for irrigated paddy field districts from a single reservoir. Agricultural drought was defined as the reservoir storage shortage state that cannot satisfy water requirement from the paddy fields. The suggested model, SRADEMP (a Single Reservoir Agricultural Drought Evaluation Model for Paddy), was composed of 4 submodels: PWBM (Paddy Water Balance Model), RWBM (Reservoir Water Balance Model), FA (Frequency and probability Analysis model), and DCI (Drought Classification and Indexing model). Two indices, PDF (Paddy Drought Frequency) and PDI (Paddy Drought Index) were also introduced to classify agricultural drought severity. Both values were divided into 4 steps, i.e. normal, moderate drought, severe drought, and extreme drought. Each step of PDI was ranged from +4.2 to -1.39, from -1.39 to -3.33, from -3.33 to -4.0 and less than -4.0, respectively. SRADEMP was applied to Jangheung reservoir irrigation district, and the results showed good relationships between simulated results and the observed data including historical drought records showing that SRADEMP explains better the drought conditions in irrigated paddy districts than PDSI.

이순혁 Lee Soon-hyuk , 김병준 Kim Byeong-jun , 맹승진 Maeng Sung-jin , 류경식 Ryoo Kyong-sik

DOI: JKWST Vol.46(No.3) 31-42, 2004

---

This research seeks to derive the design rainfalls through the L-moment with the test of homogeneity, independence and outlier of data on annual maximum daily rainfall at 38 rainfall stations in Korea. To select the appropriate distribution of annual maximum daily rainfall data by the rainfall stations, Generalized Extreme Value (GEV), Generalized Logistic (GLO), Generalized Pareto (GPA), Generalized Normal (GNO) and Pearson Type 3 (PT3) probability distributions were applied and their aptness were judged using an L-moment ratio diagram and the Kolmogorov-Smirnov (K-S) test. Parameters of appropriate distributions were estimated from the observed and simulated annual maximum daily rainfall using Monte Carlo techniques. Design rainfalls were finally derived by GEV distribution, which was proved to be more appropriate than the other distributions.

이종형 Lee Jong Hyeong , 윤석환 Yoon Seok Hwan

DOI: JKWST Vol.46(No.3) 43-54, 2004

---

For a given watershed that consists of urbanized areas, it was essential to predict how the runoff characteristics, such as runoff peak and volume, and travel time, change with time for planning and designing various kinds of hydraulic facilities with given recurrence interval. In this study, Mushim stream watershed was simulated using HEC-HMS model to get runoff characteristics of an urbanization basin. The results was showed that runoff was increased 1794.20∼2104.65 m³/s and 1751.90∼1961.30 m³/s according to the increased of rainfall and CN value recurrence interval in years. Observed storm was increased 497.91∼581.71 m³/s and 506.57∼537.01 m³/s for increased of CN value and impervious area. This paper is also possible to evaluate the effect of urbanization quantitatively.

성찬용 Sung Chan Yong , 임성수 Lim Sung Soo

DOI: JKWST Vol.46(No.3) 57-63, 2004

---

This study was performed to evaluate the engineering properties of cement mortar brick with loess and fly ash. The unit weight was in the range of 2,068∼2,137 kgf/m³ and 1,899∼2,045 kgf/m³ in water and dry curing, respectively. It was decreased with increasing the loess content. The absorption ratio was in the range of 5.2∼13.1% and 8.5∼13.2% in water and dry curing, respectively. The compressive strength was decreased with increasing the loess content. The compressive strength of the 193 kgf/cm² in water and 188 kgf/cm² in dry curing at the curing age 28 days of the binder volume ratio 35% was exceeded in 163 kgf/cm² of standard compressive strength about cement bricks. The carbonation depth was in the range of 0.9∼1.4 mm, 1.2∼3.6 mm, 1.4∼6.7 mm and 2.4∼12.5 mm in dry curing of curing age 14days, 28days, 90days and 360days, respectively.

원종필 Won Jong-pil , 백철우 Baek Chul-woo , 박찬기 Park Chan-gi , 전언중 Jun Oun-jung

DOI: JKWST Vol.46(No.3) 65-72, 2004

---

Modern underground and tunnel works that the wet type shotcrete is getting widely designed and applied in a large scale project. Further to its applications, the needs of improving the performance of the shotcrete, such as new and developed additives and accelerators for increasing the performance of shotcrete, become the most important issue in the field. The main objective of this study evaluated to performance of steel fiber reinforced shotcrete using alkali free based accelerator for the durability and high quality of shotcrete. The major test variables are accelerator type and its dosage. One type silicate based accelerator and one type aluminate based accelerator and one type alkali free based accelerator were used. The dosage of accelerators is determined by the manufactures and laboratory test condition. Compressive strength test results showed that the dosage of silicate and aluminate based accelerators caused reduction of mechanical properties of shotcrete. Compressive strength of alkali free based accelerator is more stable than of silicate and aluminate based accelerators. Also, according to the compressive strength and flexural test results, it was found that steel fiber reinforced shotcrete used alkali free based accelerator could attain significant improvement in the mechanical and flexural performance.

박찬기 Park Chan-gi , 원종필 Won Jong-pil

DOI: JKWST Vol.46(No.3) 73-81, 2004

---

FRP reinforcing bars(rebars) are produced through a variety of manufacturing process includes pultrusion, and filament winding and braiding etc. Each manufacturing method produces a different surface condition of FRP rebar. The surface properties of FRP rebar is an important property for mechanical bond with concrete. Current methods of providing surface deformation to FRP rebars include helical wrapping, surface sand coating and rib molding. The problem with the helical wrapping method is that it can not provide enough surface deformation for good bond and it can be easily sheard off from the FRP rebars. Sand coating and rib molding provide surface deformation only to the outer FRP skins. Therefore, FRP rebar has about 60% of bond strength of steel rebar. The main objective was to evaluate the bond properties of FRP rebar after environmental exposure. Five types of FRP rebar includes CFRP ISO, GFRP Aslan, AFRP Technora, CFRP(Korea), and GFRP(Korea) rebars performed direct bond tests. Also, FRP rebar bond specimens were subjected to exposure conditions including alkaline solution, acid solution, salt solution and deionized water etc. According to bond test results, CFRP(Korea) and GFRP(Korea) rebars were found to have better bond strength with concrete than previous FRP rebars. Also, FRP(Korea) rebar had more than about 70% in bond strength of steel rebar.

홍성구 Hong Seonggu

DOI: JKWST Vol.46(No.3) 85-92, 2004

---

Biomass is considered to be a major potential fuel and renewable resource for the future. In fact, there is high potential to produce significant amount of energy from biomass around the world. In spite of the potential, there are a few efforts in biomass utilization in this nation. In this study, elemental biomass data was obtained with respect to the amount and calorific values of agricultural residues. Rice straw and husks were not included in the evaluation due to their demand from alternative uses such as livestock feedings, bedding materials, and so forth. Dry basis high calorific values are about 4,500 kcal/kg for all the agricultural residues investigated, similar to literature data. Energy densities or unit area energy value, from pepper and sesame were significant and comparable to those of woody biomass. These elemental data for biomass resources will provide the background of planning and development of biomass energy program, which is getting more feasible along with advances in energy conversion technologies such as micro gas turbines.

권순국 Soon-kuk Kwun , 이우신 Woo-shin Lee , 우건석 Kun-suk Woo , 심재한 Jae-han Shim , 허위행 Wee-haeng Hur , 최현정 Hyun-jung Choe , 이상철 Sang-chul Lee

DOI: JKWST Vol.46(No.3) 93-105, 2004

---

The Shihwa wetland, a newly developed constructed wetland prototype in Korea with an area of approximately 104 ha, was established to improve the water quality severely polluted inflow streams into Lake Shihwa. Because this wetland could play a role as an ecological park in addition to improving the water quality, an ecological impact of the Shihwa constructed wetland has been a national concern. This paper focused on reporting the survey results for fauna among the entire investigation results for 3 years. A total of 129 terrestrial insect species have been observed from August 2001 to June 2002. Among them, Ischnura asiatica (Brauer) (order Odonata), Scymnus species (order Coleoptera) and Orthopteran species were frequently found in the reed bushes. A total of 77 bird species were recorded in a seasonal count, the maximum number of species was 34 in winter and the maximum number of individuals was 4,599 in summer. For the freshwater fish, only 4 species were found in 2000, however in 2001 and 2002, 12 species and 459 individuals were collected at four survey points. Among these12 species, the dominant species were Mugil cephalus(36%), followed by Carassius auratus (25%) and Rhinogobius brunneus (22%). Meanwhile, 12 individuals of Oryzias latipes were observed nearby, mostly downstream of the wetland. For the Herpetofauna at four survey areas, 3 species of amphibians and 3 species of reptiles were recorded. Because of remaining salinity in the soil of the Shiwha constructed wetland, Herpetofauna inflow to the wetland was scanty and mainly inhabited the upstream area. A total of 8 mammal species were recorded. Small-sized species were the striped field mouse, the Ussurian harvest-mouse, the Manchurian reed vole and the brown rat. Middle- and large-sized species were Korean water-deer, Korean raccoon dogs, Korean yellow weasels and feral cats.