The purpose of this study was to investigate the effects of ponding depth treatment on water balance in paddy fields. Three ponding depth treatments, very shallow, shallow, and deep were used. The experimental plots were three 80m $\times$ 8m rectangular plots. Daily values of rainfall amount, ponding depth, irrigation water, drainage water, evapotranspiration, and infiltration were measured in the field. The ponding depth was continuously observed by water level logger during the growing season. The ET was measured by 1-m diameter PVC lysimeters. Irrigation water volume was measured by 75 mm pipe flowmeters and the drainage water volume by 75 mm pipe flowmeters and a recording Parshall flume. The results showed that irrigation water depths were 688.9 mm, 513.6 mm, and 624.4 mm in very shallow, shallow, and deep ponding, respectively. The effective rainfall amounts (effective ratio) were 243.7 mm(48.8%), 344.6 mm(68.9%), and 272.9 mm(54.6%) in very shallow, shallow, and deep ponding, respectively. The three treatments did not show any statistical difference in growth and yields. But the shallow depth treatment showed the largest yield.

관개 저수지의 특성에 맞도록 가뭄을 평가하기 위하여 누가 강수량, 유역 토양수분량, 저수율, 급수 제한강도 등의 방법으로 가뭄이 한창 문제가 되었던 2001년 6월 13일을 기준일로 택하여 예당저수지의 가뭄을 평가한 결과는 다음과 같다. 누가 강수량에 의한 방법으로는 30년 빈도로 평가되었고, 1978년과 유사한 패턴을 나타내었고, 유역 토양수분량에 의한 방법으로는 30년 빈도로 평가되었고, 1981년과 유사한 패턴을 나타내었고, 저수율에 의한 방법으로는 20년 빈도로 평가되었고, 1981년과 유사한 패턴을 나타내었고, 급수 제한강도에 의한 방법으로는 10년 빈도로 평가되었고, 1988년과 유사한 패턴을 나타내었다. 각 방법간의 평가가 다르기 때문에 가장 가시적이고 현실적인 저수율에 의한 방법으로 20년 빈도가뭄으로 종합평가 하였고, 이후의 가뭄이 1981년도와 유사하게 진행될 것으로 예측하여, 향수 저수지 가뭄대책에 참고하도록 하였다.

The condition of initial movement far the river bank protection using rip rap is a limit condition beyond which the lining is progressively destroyed as the separate elements are removed by the flow. In the case of the river bank protection using gabion mattress, however, after the initial movement the containment offered by the mesh remains. A new situation of equilibrium with a deformed river bank protection using gabion mattress is obtained, allowing it to withstand more severe conditions without compromising the resistance and without further deformation. Shield's coefficient for the river bank protection using gabion mattress is twice the value of that fur river bank protection using rip rap. This means that with the same hydraulic behavior conditions, the average dimension of the rocks to be used in the river bank protection using gabion mattress is half that of river bank protection using rip rap rock. When the same size rocks are used the allowable velocity for the river bank protection using gabion mattress is more than twice, even as much as 3 or 4 times that for river bank protection using rip rap.

This study is performed to examine pH reduction by neutralization treatment and curing condition of porous concrete using rice straw ash for planting. Test results show that pH of porous concrete without neutralization treatment in the dry and water curing is 10.34 ∼ 10.57 and 9.42 ∼ 9.72, respectively. pH of porous concrete by neutralization treatment in the dry and water curing is 9.72 ∼ 10.03 and 9.00 ∼ 9.37, respectively. Accordingly, the best method for pH reduction of porous concrete for planting is to use water curing and neutralization treatment.

The amount used of aggregates for concrete is increasing rapidly since the mid-1980s in Korea. The natural gravels from river are already displaced with crushed stone, and use of crushed sand as a substitute of natural river sands, also, is getting increased day by day. This paper is presented fur analysis on mechanical properties of high strength concrete using fly ash and crushed sand. The material functions in mixing design of concretes are various water-cement ratios(w/c) such as 0.25, 0.40, 0.55 and different replacement ratio of crushed sand to natural sands such as 0%, 20%, 40%, 60%. As a results, it has been shown that compressive strengths of concretes with W/C lower than 0.40 and 0.25 are higher than 400 kgf/$\textrm{cm}^2$ and 600 kgf/$\textrm{cm}^2$ respectively. It is also concluded that the results of rapid chloride permeability tests of concrete are evaluated to negligible. The conclusions of this study is that it is possible to use fly ash and crushed sand fur high strength concrete.

Concrete containing discontinuous discrete steel fiber in a normal concrete is called steel fiber reinforced concrete(SFRC). Tensile as well as flexural strengths of concrete could be substantially increased by introducing closely spaced fibers which delay the onset of tension cracks and increase the tension strength of cracks. However, many properties of SFRC have not been investigated, especially properties on repeated loadings. Thus, the purposes of this dissertation is to study the flexural fatigue characteristics of SFRC considering cumulative damage. A series of experimental tests such as compressive strength, splitting tensile strength, flexural strength, flexural fatigue, and two steps stress level fatigue were conducted to clarify the basic properties and fatigue-related properties of SFRC. The main experimental variables were steel fiber fraction (0, 0.4, 0.7, 1, 1.5%), aspect ratio (60, 83). The principal results obtained through this study are as follows: The results of flexural fatigue tests showed that the flexural fatigue life of SFRC is approxmately 65% of ultimate strength, while that of plain is less than 58%. Especially, the behavior of flexural fatigue life shows excellent performance at 1.0% of steel-fiber volume fraction. The cumulative damage test of high-low two stress levels is within the value of 0.6 ∼ 1.1, while that of low-high stress steps is within the value of 2.4 ∼ 4.0.

Due to the fact that the design of a reinforced concrete structure changes in accordance with its shape and assigned load, total automation of the design system has not been achieved. For instance, since there is no general rule about setting up reinforcing steel quantity and arrangement location, it is simply not feasible to automatically decide the reinforcing arrangement location. In this study, the ESO(evolutionary structural optimization) technique and its related issues will be discussed. The ESO techniques is determined the reasonable load path which is traveling of load between in-flow and out-flow at a concrete structure using numerical analysis. And the results applied to the steel arrangement in reinforced concrete structures. The optimal algorithm, which determines the terminal criteria during ESO process, has been updated by using the obtained results. And the load path within the member has been determined automatically.

Characteristics of unit loads of pollutants were investigated at a paddy fields area(Soro-ri) with large-scaled plots on loam soil during irrigation seasons of 1999 ∼2000. The average irrigation requirement of experimental paddy area are estimated at over 3,000 mm. The unit loads of pollutants in paddy fields area are determined by subtracting irrigation water load from outflow load (percolated and surface outflow loads). Surface outflow load in rainy days was calculated using the relationships of discharge and load, which are grouped into fertilizing and non-fertilizing periods. The ratios of the surface outflow load in rainy days to the total surface outflow load are 16.4% for T-N, 26.8% for T-P, and 23.3% far CODc,. The unit loads of pollutants show month-to-month and year-to-year variations, and monthly unit load of pollutants can show negative values, indicating that the paddy area acts as the pollutants sink. The average unit loads of the pollutants during irrigation seasons were estimated at 18.2 kg/ha fur T-N, 0.31 kg/ha for T-P, and 43.3 kg/ha for CODc,, which are smaller than the reported values for Kosei area in Japan.

Lake water quality assessment information is useful to anyone involved in lake management, from lakeshore owners to lake associations. 11 provides lake water quality, which can improve how to manage lake resources and how to measure current conditions. It also provides a knowledge base that can be used to protect and restore lakes. SWMM was applied to simulate the discharge and pollutant loads from Boryeong watershed, and WASP5 was applied to analyze the changes of water quality in Boryeong freshwater lake. In each model, the most suitable parameters were calculated through sensitive analysis and some parameters used default data. Simulated in SWMM and measured discharge showed the accuracy of 88.6%. T-N and T-P exceeds the criteria in the simulation of water quality in Boryeong freshwater lake, and control of pollutant loads in the main stream showed the most effective way. Integrated water quality management system was developed to give convenience in the operation of SWMM and WASP5 and data acquisition.

Recently, absorbent biofilters, which are inexpensive and easy to manacle, have been supplied to the rural areas, but have limitations in removing the nutrients effectively. Accordingly, as an alternative plan. natural zeolites were arranged in front or at the rear of the absorbent biofilters, and their removal efficiency for nitrogen and, ultimately, their applicability to the on-site wastewater treatment system were studied. Furthermore, the same experiments were carried out on artificial zeolites, made from coal ashes at National Honam Agricultural Experiment Station, to compare natural zeolites with artificial ones. Treated wastewater through the Absorbent Biofilter showed 22.6% nitrogen removal efficiency, while 64.6% was attained when natural Zeolites were placed in front of the absorbent biofilters (Zeolite-Aerobic process). As an addition, phosphorus was also efficiently removed. On the other hand, Aerobic-Zeolite process, which arranged natural zeolites at the rear of the biofilters, did not have significantly higher nitrogen removal as compared to the treatment using only the absorbent biofilters. Furthermore, upon regeneration of the natural zeolite, the ion exchange rate was fecund to increase over 10% as compared to before regeneration. Our results show that natural zeolites, applied to the on-site wastewater treatment system through the Zeolite-Aerobic process, not only increase the removal efficiency of nutrients, but, by choosing the appropriate regeneration time, can also be cast-effective. Artificial zeolites, on the other hand, though more efficient in removing nutrients, cannot be regenerated and, therefore, are not cost-effective.