• Journal of the Korean Society of Environmental Restoration Technology
• /
• v.4 no.3
• /
• pp.66-74
• /
• 2001

The main purpose of this thesis is to select the appropriate plants for the ecological restoration of coastal land. The soil and vegetation environment survey of the beach where the halophytes live now was executed for the sake. Firstly, the soil survey was done by the physical and chemical survey of beach soil and dumped soil. The soil is mostly sandy loam and sandy clay loam which has silty much. The beach soil where the salt plants live has more organic matters in the content than dumped soil because of the influx of the dead halophytes, a pioneer plant to this area. Secondly the vegetation survey was executed by the halophytes survey in the beach area in order to select the appropriate plants for ecological restoration. The shows two different areas in the vegetation divided by the salt density of soil. Artemisia fukudo, Juncus haenkei, Carex pumila, Silene armeia, Polyponum aviculare etc live in the less salt density area and it doesnt show collected. Salicornia herbacea, Suaeda asparagoides, Aster tripolium, Limonium tetragonum, Suaeda maritima, Scirus fluvitilis, Phragmtes communis, Suaeda japonica, Zoysia sinica etc halophytes live in the more salt density area and there are a few advent plant but many collected. So the salt density of soil limits the vegetation. The selection of appropriate plants for the ecological restoration programs was designed with 3 different standards considering the salt density of soil in the dumped soil area. The plan selection guidelines of thick salt density due to the salt density of soil, and economical efficiency and maintenance because the area is large. The guidelines of middle salt density area were made considering economical efficiency and maintenance because there are salt as well, and it is effective for the scenery if they have normal ecology but their leaves have good color and the flowers are beautiful. However I suggest beautiful flowery plants for the neutral plan area because this area is the entry point of the airport so the view is very important.

• Korean Journal of Soil Science and Fertilizer
• /
• v.30 no.3
• /
• pp.265-271
• /
• 1997

The salt accumulation, and chemical properties of 90 samples of the plastic film house soil in the area of Cheongju and Chungju were surveyed. Soil textural distribution of soil samples was 30% for sandy loam, 27% for loam and 43% for silty loam. Percentage distribution of electrical conductivity(EC) of surface soil was 23% below $2dS\;m^{-1}$, 30% for $2{\sim}4dS\;m^{-1}$, 25% for $4{\sim}6dS\;m^{-1}$ and 22% over $6dS\;m^{-1}$. Salt affected soil, which EC was higher than $4dS\;m^{-1}$, covered nearly 50% of all field surveyed. However subsoils(20~30cm) below $2dS\;m^{-1}$ was 68%. Salts in plastic film house soil was accumulated by increasing the cultivation period. After 5 years of cultivation electrical conductivity in plastic house soil was generally higher than $4.47dS\;m^{-1}$ in EC that was 2.8~5.6 times higher than that in the field soil in the outside of plastic film house. As the result of temporary removal of plastic film cover from the house during the rainy summer season, salt content in soil was decreased from $3.54{\sim}7.36dS\;m^{-1}$ to $0.71{\sim}2.92dS\;m^{-1}$ in EC due to the desalinization by runoff and percolating water. Contents of $NO_3-N$, $SO_4-S$ and Cl in plastic film house soil were 2.5. 7.0 and 3.4 times higher than those of open field respectively.

• Korean Journal of Soil Science and Fertilizer
• /
• v.49 no.3
• /
• pp.275-281
• /
• 2016

The aim of this study was to examine the selected soil chemical properties of paddy fields in different topographic areas to efficiently manage nutrient valances of the paddy fields in Jeonbuk Province. Three-hundred soil sampling sites in paddy fields were selected from the different topographic areas in Jeonbuk Province. The soil samples were collected every four years from 1999 to 2015. Soil pH and exchangeable K and Mg concentrations declined during the experimental periods. However, almost all the chemical properties were within the proper levels for paddy soil, except exchangeable Mg concentration. Distributed areas of the paddy fields with soil pH below 5.5 continuously increased, but the paddy fields with lower concentrations of soil organic matter and available $P_2O_5$ than the proper levels declined after 2007. In addition, the paddy fields with available $SiO_2$ below the proper concentration decreased from 83.3% of the total paddy fields studied in 1999 to 61.0% of the total fields investigated in 2015. The paddy fields with lower exchangeable K and Mg than the proper levels increased after 2003 whereas the fields with lower exchangeable Ca concentration decreased. Dominant landform of coastal and plain areas was fluvio-marine plains that was distributed in 53.7% and 40.9%, respectively. Local valley and fans was a dominant landform of mountainous and middle-mountainous areas, which was 51.8% and 67.6%, respectively. Dominant soil textures distributed in coastal and plain areas were silty loam and loam. Those in mountainous and middle-mountainous areas were sandy loam and loam, respectively. Soil pH was relatively higher in coastal area and the comparatively higher content of soil organic matter was found in costal area than other areas. The concentrations of available $P_2O_5$, exchangeable Ca, and exchangeable Mg were generally higher in mountainous, coastal, plain areas, respectively, but available $SiO_2$ and exchangeable K concentrations were not significantly different among the different topographic areas.

• Korean Journal of Soil Science and Fertilizer
• /
• v.47 no.4
• /
• pp.262-268
• /
• 2014

The management of soil chemical properties is very important to sustainable agriculture of many horticultural crops, including cucumber. This study was conducted to find the optimal soil properties of environmentally friendly agriculture in controlled horticulture. Soil chemical properties of 267 samples were collected from soil in Chungnam Province. The average of pH, EC, OM, available $P_2O_5$, exchangeable K, Ca, and Mg was 6.1, $5.38dS\;m^{-1}$, $34g\;kg^{-1}$, $1,321mg\;kg^{-1}$, $1.50cmol_c\;kg{-1}$, $10.3cmol_c\;kg{-1}$, and $3.4cmol_c\;kg{-1}$, respectively. The organic matter content in silty clay loam was significantly higher than in the other soil textures, whereas the pH, EC, exchangeable K, and Mg in loamy fine sand showed significantly lower among soil textures. The EC value and exchangeable Mg concentration were highest in mountain foot-slope soils. The frequency distribution within optimum range of soil chemical properties was 26.2%, 30.3%, 2.3%, 3.8%, 3.4%, and 6.7% for pH, OM, available $P_2O_5$, exchangeable K, Ca, and Mg, respectively. Especially, excessive portion of available $P_2O_5$ and exchangeable Ca were 94.0% and 94.4%, respectively. The EC value and organic matter content of soil samples were positive correlation with all chemical properties except soil pH. In principle component analysis of chemical properties in soil samples, the percentage of variance explained by PC 1 was 52.2%, while PC 2 explained 21.3% of the variance, for a cumulative total of 73.5%. In conclusion, these results are considered to improve soil nutrient management for sustainable controlled horticulture.

• Proceedings of the Korean Geotechical Society Conference
• /
• 1999.10a
• /
• pp.405-414
• /
• 1999

The auger and screw piles have known an important evolution during the last decade. Besides the large success of augercast (CFA) piling systems, new systems have been developed combining, to a variable extent, the classical extraction auger with especially designed displacement tools in order to develop screw piles with partial or total lateral soil displacement. These last developments cover the whole range of lateral soil displacement and are more difficult than ever to compare. The authors present the latest evolutions in auger piling systems and compare them with respect to penetration performances, bearing capacities and amount of spoil generated. A special focus is given to a new efficient system: the OMEGA(H) pile in use in Korea since 1997. The results of the Hongcheon site are presented where this R system was applied for a new investment of the Korean National Housing Corporation (KNHC). This first important experience, with the execution of some 1,500 Omega piles with diameter 410 mm, is presented. The piles were installed through loose silty sands down to very dense sands and layers of gravel. The results of full-scale load tests are analysed and show the conformity with requirements of the clients.

• Journal of the Korean Geotechnical Society
• /
• v.17 no.6
• /
• pp.235-244
• /
• 2001

Liquefaction may be caused by sudden decrease in the soil strength under undrained conditions. This loss of soil strength is related to the development of excess pore pressures. During this study, fines content affects the maximum and minimum void ratios are investigated. The results of static and cyclic triaxial test on silty saturated sands are presented. These tests are performed to evaluate liquefaction strength and static and cyclic behavior characteristics. The samples are obtained from Saemangeum and drying on air. The main results are summarized as follows : 1) The maximum and minimum void ratio lines follow similar trends. 2) Maximum and minimum void ratios are established at 20~30% fines content. 3) As confining pressures and overconsolidation ratio are increased, the resistance to liquefaction are increased. 4) Instability friction angles are increased with increasing initial relative density. 5) The resistance to liquefaction are decreased with increasing effective stress ratio.

• Analytical Science and Technology
• /
• v.15 no.1
• /
• pp.67-71
• /
• 2002

The residual analysis and half-life time of imidazole fungicide prochloraz in soils (silty clay) were investigated by gas chromatography equipped electron capture detector (GC-ECD). The soil samples were extracted acetone/hexane(1:1) solvent and analyzed after separated by $LC-NH_2$ Sep-Pak solid column. Linear sensitivity of standard calibration curve was Y = 268.8600X + 0.0664, $R^2=0.9998$ between 0.05~1.00 ng. The detection limit was 0.02 mg/L and the average recoveries were 94.5~97.3% from the standard additional experiments with 0.10 and 0.40 mg/L. The half-life time was 24.4 days in room laboratory and 7.6 days in the field test soil.

• Journal of Ocean Engineering and Technology
• /
• v.27 no.1
• /
• pp.59-66
• /
• 2013

A suction anchor is one of the most popular anchors for deepsea floating systems. An anchor used for catenary mooring is predominantly under a horizontal load. In this study, the behavior of a suction anchor installed in cohesionless soil was investigated when the anchor was mainly subjected to a horizontal load induced by a catenary line. In order to study the behavior of the suction anchor, 3D FEM analysis models were developed and analyzed. Depending on the location of the load (padeye), the ultimate horizontal load was monitored. The distributions of the reaction forces around the anchor induced by the seabed were analyzed using the circumferential stress to understand the behavior of the suction anchor under a horizontal load.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.31 no.1
• /
• pp.96-105
• /
• 1989

This laboratory study was performed to produce basic data for the estimation of water requirements for desalinization, through analyzing changes of the electrical conductivity and the exchangeable sodium percentage during the desalinization of reclaimed tidelands. Desalinization experiments were carried out by two water management practices, namely, the leaching method by subsurface drainage and the rinsing method by surface drainage, using samples of silt loam soil and silty clay loam soil collected in reclaimed tidelands. The results obtained from this study were summarized as follows : 1. The sample soils used in this study were saline-sodic soils with the high electrical conductivity and the high exchangeable sodium percentage. 2. Changes of the electrical conductivity and the exchangeable sodium percentage with water requirements for desalinization showed a similar tendency in the desalinization experiment by the same water management practice. 3. The regression equation between the relative electrical conductivity(EC/EC) and water requirements for desalinization(Dw/Ds) could be described by Dw/Ds=O. 29x(EC/EC.) -0.982 (Leaching method), Dw/Ds=3. 678X0. 030(EC/EC ) (Rinsing method). 4. The regression equation between the relative exchangeable sodium percentage (ESP/ESP ) and water requirements for desalinization (Dw/Ds) could be expressed in Dw/Ds = 0.039 x (ESP/ESP. ) - 1. 134 (Leaching method), Dw/Ds=7. 197X0. 024(ESP/ESP ) (Rinsing method). 5. It was estimated that water requirements for the adequate desalinization would be Dw/Ds=0.3 (Leaching method) and Dw/Ds=3.0 (Rinsing method)

• Journal of the Korean GEO-environmental Society
• /
• v.20 no.12
• /
• pp.41-47
• /
• 2019

This paper deals with the reliability analysis of foundation for an offshore wind turbine system. Reliability analyses were carried out for suction bucket foundation considering the uncertainties in soil and structural parameters. In reliability analysis, the vertical and lateral resistances are defined as base limit states. The case studies were carried out using the preliminarily designed foundations at western-south mainland sea of Korea. From reliability analyses, vertical resistance for free-slip condition has overall lower reliability index, and submerged unit weight and internal friction angle of seabed soil are governing factors in vertical and lateral resistance in this case.