• Korean Journal of Soil Science and Fertilizer
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• v.43 no.1
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• pp.8-15
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• 2010

The effect of soil salinity and soil-wetting by rise of water table on the growth of fruit trees was studied to obtain information for orchard establishment in the Saemangeum reclaimed tidal land. Survival ratio of trees was 85%for grape, 31%for fig, 15%for apple and pear, and near zero for peach and blueberry. Wet injury induced by water-logged or flooded condition, rather than salt injury(soil EC was lower than 3.0dS $m^{-1}$ during growing period) is thought to be more responsible for low survival ratio of fruit trees transplanted in Saemangeum area. During the summer raining season in the reclaimed areas, the soil salinity tends to be decreased by natural rainfall effect, and the rainfall acceptable capacity(RAC) of soils dramatically is reduced(10-24 mm) as rainfall is continued to occur. In spite of high hydraulic conductivity(121 cm $day^{-1}$) of soils across the area, low RAC of soils might be due to high soil saturation and elevated water table during summer raining season. Therefore, the installation of effective drainage system should be the primary factor determining successful establishment of orchard in the Saemangeum reclaimed tidal land.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.2
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• pp.194-199
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• 2017

When sea tide and wave velocity change, the behavior of silt protectors underwater changes, and a hydraulic force exceeding the anchor wave force is applied. In this study, the movement mechanism of a silt protector has been analyzed using the mass-spring method. The initial position of the silt protector was in the Jindo area near Gwangpo Port (742-1, Gyupori, Chongdo-myeon, Jindo-gun, Jeonnam, Korea). The tension required to exceed the holding power of the anchor was 0.05 m/s at 318 sec., 0.15 m/s at 77 sec., 0.25 m/s at 43 sec., and 0.3 m/s at 37 sec.. As the anchor started to move from the sea floor and the tide speed increased to 0.01 m/s, anchor movement start time shortened by an average of 11.2 sec.. Compared with when tide was the only affecting factor, the silt protector and anchor were found to have moved 19.7 % at 0.1 m/s, 7.6 % at 0.15 m/s, 5.8 % at 0.2 m/s, 4.3 % at 0.25 m/s and 2.8 % at 0.3 m/s, showing an increase. When wave effect was added to the tide, anchor movement started when the flow rate was slow 7.6 % of the time. With a high flow velocity, anchor movement started without any significant difference less than 4.3 % of the time. When tide speed exceeded 0.13 m/s and the direction of the waves matched, the silt protector was not able to perform due to collisions with surrounding sea structures. When installing a silt protector, the fluid flow situation and the silt protector situation must be carefully analyzed using the mass-spring method to apply the result found in this study.

• Journal of the Korean GEO-environmental Society
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• v.9 no.2
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• pp.39-46
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• 2008

Due to the growth in industrialization, potential hazards in subsurface environments are becoming increasingly significant. The extraction of the contaminant from the soil and movement of the water are restricted due to the low permeability and adsorption characteristics of the reclaimed soils. There are a number of approaches to in-situ remediation that are used in contaminated sites for removing contaminants. These include soil flushing, dual phase extraction, and soil vapor extraction. Among these techniques, soil flushing was the focus of the investigation in this paper. Incorporated technique with PVDs has been used for dewatering from fine-grained soils for the purpose of ground improvement by means of prefabricated vertical drain systems. The laboratory model tests were performed by using the flushing tracer solutions for silty soils and recorded the tracer concentration changes with the elapsed time and flow rates. The modeling was intended to predict the effectiveness and time dependence of the remediation process. Modeling has been performed on the extraction, considering tracer concentration and laboratory model test characteristics. The computer model used herein are SEEP/W and CTRAN/W, this 2-D finite element program allows for modeling to determine hydraulic head and pore water pressure distribution, efficiency of remediation for the subsurface environment. It is concluded that the coefficient of permeability of contaminated soil is related with vertical velocity and extracted flow rate. The vertical velocity and extracted flow rate have an effect on dispersivity and finally are played an important role in-situ soil remediation.

• Journal of the Korean Institute of Gas
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• v.24 no.4
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• pp.62-72
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• 2020

This study presents a methodology of history matching to evaluate the productivity of shale gas reservoir with high reliability and predict future production rate in the Horn-River basin, Canada. Sensitivity analysis was performed to analyze the effect of physical properties of shale gas reservoir on productivity. Based on the results, reservoir properties were classified into 4 cases and history matching were performed considering the classified 4 cases as objective function. The blind test was conducted using additional field production data for 3 years after the history matching period. The error of gas production rate in Case 1(all reservoir parameters), Case 2(influenced parameters for productivity), Case 3(controllable parameters), and Case 4(uncontrollable parameters) were 7.67%, 7.13%, 17.54%, and 10.04%, respectively. This means that it seems to be effective to consider all reservoir parameters in early period for 4 years but Case 2 which considered influenced parameters for productivity shows the highest reliability in predicting future production. The estimated ultimate recovery (EUR) of production well predicted using the Case 2 model was estimated to be 17.24 Bcf by December 2030 and the recovery factor compared to original gas in place (OGIP) was 32.2%.

• Journal of Soil and Groundwater Environment
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• v.22 no.6
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• pp.112-119
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• 2017

In this study, the availability of cow manure as raw material for solid fuel production was investigated. Since the water content of the cow manure was too high, it was dewatered using a laboratory hydraulic compressure ($11.3kg/cm^2$). The moisture content of the cow manure decreased from 82.01% to 73.36 wt.%. The dewatered cow manure was homogenized by the experimental apparatus and then put into the rotating cylindrical apparatus. From the consecutive processes, the cow ball-shaped pellet which size ranged from 3.0 to 25.0 mm was produced. The major factor for making palletized fuel from cow manure was the moisture content. Based on the experimental data, the moisture content of cow manure for pelletizing cow manure was identified as 65~75 wt.%. When the moisture content of the cow manure was lower than 30 wt.%, the diameter of the pellets maded from cow manure was smaller than 3 mm. On the other hand, when the water content of the cow manure was higher than 75 wt/%, the diameter of the processed pellets tended to be larger than 25 mm. The characteristics of the processed cow manure pellets was analyzed to be in accordance with the livestock solid fuel quality standard. The pyrolysis characteristic of the pellet was analyzed by raising the heating temperature of the experimental equipment from 200 to $900^{\circ}C$. The mass change between of 20 and $130^{\circ}C$ corresponds to the amount of moisture contained in the cow manure. The amount of moisture was about 15% of the total weight of cow manure samples. The cow manure pellet was thermally stable up to $280^{\circ}C$. It can be interpreted that combustion of cow manure pellet does not occur until the surface temperature reaches $280^{\circ}C$. The mass change of pellet between of 280 and $450^{\circ}C$ was considered to be due to the vaporization of volatile organic compounds (VOCs) present in the cow manure pellet. The maximum production of VOCs was showed near $330^{\circ}C$.

• Journal of Korea Water Resources Association
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• v.51 no.1
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• pp.35-48
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• 2018

Groynes are installed generally to protect the riverside or the river bank from the erosion caused by water flows by controlling the flow direction and velocity in rivers. In the past, groynes were used to secure enough depth of water in canals. As there has been a growing interest in river restoration and the natural river maintenance since 2000, groynes are proposed as a major environmental hydraulic structure because the flow control and various river bed conditions around the groyne can contribute to habitat functions. Groynes are typically installed in a series. In designing groyne series, groyne spacing is an important factor because the flow changes in the main canal and the flow inside the groyne area occurs variably depending on the groyne spacing. This study provide information to determine the groyne spacing suitable for the purpose of the groyne by examining the flows that variably changes according to the groyne spacing and angle in the recirculation zone of the groyne field. In particular, the formation of vortex, the location of vortex core and the water flow near the river bank, all of which occur in the recirculation zone inside the groyne area, were mainly analyzed to examine the flow characteristics near the river bank that influences the safety of the river bank area. The results of the experiment will serve as important basic data to examine changes in the river bed inside the groyne area as well as the safety of river banks following the installation of groyne series.

• Korean Journal of Environmental Agriculture
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• v.37 no.3
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• pp.166-171
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• 2018

BACKGROUND: Nitrogen leaching depends on the drainage pattern and nitrate content, and those are influenced by soil hydraulic properties and fertility. The purpose of this study was to confirm how soil texture contributed to leaching and balance of nitrogen, as well as to drainage. METHODS AND RESULTS: This study was performed using undisturbed weighing lysimeters which were piled up with clay loam (Songjung series) and sandy loam (Sanju series) soils in National Institute of Agricultural Science experimental field. Chinese cabbage was cultivated from August 30 to October 31, 2017. The application rates of N, $P_2O_5$, and $K_2O$ were 21.5, 7.8, and $15.0kg\;10a^{-1}$, respectively, and irrigation was supplied at -33 kPa in 30 cm soil depth. Drainage in clay loam was not noticeable, although it was increased by rainfall in early September. By contrast, the trend of drainage in sandy loam was strongly dependent upon rainfall pattern. Owing to different drainage patterns between both soil textures, nitrogen leaching was 5-fold higher in sandy loam than in clay loam. Nitrogen use efficiencies in clay loam and sandy loam were represented as 43% and 52%, respectively. CONCLUSION: The pattern of drainage and nitrogen leaching were greatly depended on clay content in soil. From this study, we carefully suggest that soil texture should be considered as an incidental factor to estimate nitrogen balance.

• The Journal of Engineering Geology
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• v.29 no.2
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• pp.99-112
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• 2019

Rainfall infiltration through the unsaturated zone is influenced by a range of factors including topography, geology, soil, rainfall intensity, temperature and vegetation; the actual infiltration varies largely in time and space. The infiltration capacity of soil is a critical factor in identifying groundwater recharge and leakage of surface water. It may differ depending on soil types and geological features of a particular basin or territory as well as on the usage of the land. This study was conducted in forest and farmland region of the mid-mountain area (EL. 50~300 m) of Jeju Island to test soil infiltration capacity of the area where rainfall contributes to groundwater. Results were analyzed using the four soil group classification methods presented by Jeong et al. (1995) and NAS (2007) to discover that the method offered by NAS (2007) is more reliable in the mid-mountain area of Jeju Island. The study compares and reviews the existing classification methods using the results of infiltration capacity tests executed on different soil groups throughout the whole region of the Jeju mid-mountain area. It is expected that this work will serve as a guideline for evaluating surface water recharge and hydraulic characteristics of Jeju Island.

• Journal of Korean Society of Water and Wastewater
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• v.34 no.6
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• pp.503-512
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• 2020

Identifying the water circulation status is one of the indispensable processes for watershed management in an urban area. Recently, various water circulation models have been developed to simulate the water circulation, but it takes a lot of time and cost to make a water circulation model that could adapt the characteristics of the watershed. This paper aims to develop a water circulation state estimation model that could easily calculate the status of water circulation in an urban watershed by using multiple linear regression analysis. The study watershed is a watershed in Seoul that applied the impermeable area ratio in 1962 and 2000. And, It was divided into 73 watersheds in order to consider changes in water circulation status according to the urban characteristic factors. The input data of the SHER(Similar Hydrologic Element Response) model, a water circulation model, were used as data for the urban characteristic factors of each watershed. A total of seven factors were considered as urban characteristic factors. Those factors included annual precipitation, watershed area, average land-surface slope, impervious surface ratio, coefficient of saturated permeability, hydraulic gradient of groundwater surface, and length of contact line with downstream block. With significance probabilities (or p-values) of 0.05 and below, all five models showed significant results in estimating the water circulation status such as the surface runoff rate and the evapotranspiration rate. The model that was applied all seven urban characteristics factors, can calculate the most similar results such as the existing water circulation model. The water circulation estimation model developed in this study is not only useful to simply estimate the water circulation status of ungauged watersheds but can also provide data for parameter calibration and validation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.12
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• pp.845-856
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• 2020

This study proposes a bridge evaluation system for indivisible permit vehicles such as hydraulic cranes. The permit loads for the bridge evaluation are divided into three categories: routine permit loads, special permit 1 loads, and special permit 2 loads. Routine permit and special permit 1 vehicles are allowed to cross a bridge with normal traffic. For these two permits, the standard lane model in the Korean Highway Bridge Design Code was adopted to consider normal traffic in the same lane. Special permit 2 vehicles are assumed to cross a bridge without other traffic. Structural analyses of two prestressed-beam bridges and two steel box girder bridges were conducted for the proposed permit loads. The rating factors of the four bridges for all permit loads were calculated as sufficiently large values for the moment and shear force so that crossing the bridges can be permitted. A reliability assessment of the bridges was performed to identify the reliability levels for the permit vehicles. It was confirmed that the reliability level of the minimum required strength obtained by the load-resistance factors yields the target reliability index of the design code for the permit vehicles.