• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1C
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• pp.53-63
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• 2010

Since the water retention curve is considered as a major parameter to evaluate the unsaturated ground or soils, overburden pressure and clay content on soils underneath ground surface have not been considered for estimating water retention characteristics. Therefore, a need exists that the effect of overburden pressure and clay content on water retention characteristics was assessed in typical weathered soils found in Korea. Soil-Water Characteristic Curve and the unsaturated hydraulic conductivity were estimated using water retention characteristics under the condition of different overburden pressure, clay content, and de-saturation path. Then, these effects are evaluated with the results of SWCC tests from the laboratory. In addition to that, the unsaturated moisture capacity and diffusivity of each case is discussed.

• Korean Journal of Soil Science and Fertilizer
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• v.32 no.2
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• pp.147-154
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• 1999

This study was carried out to obtain reasonable management method of salt-affected soil for ecological restoration in the reclaimed land. Chemical properties of reclaimed soil was investigated base on reclamation years. Ionic acitivity in soil and satruration extract were analyzed to estimate the effect of salt interception by planting ground treatment. The soil porperties of reclaimed land was saline-sodic soil with $11.3dSm^{-1}$ of electrical conductivity, 34.8% of exchangeable sodium percent in first reclamation year. Electrical conductivity, exchangeable sodium and exchangeable chlorine were remarkedly decreased during six years after reclamation but chemical properties of reclaimed soil was unsuitable status for tree growth. Exchangeable sodium perecnt was higher in the neighborhood parks and street tree sites than in the buffer green spaces and was higher in subsoil than in topsoil of profile in all sites. Content of soduim, chloride and sulfate in saturation extract were more than other ions. Content of soduim and chloride were higher in the neighborhood parks and street tree sites than in the buffer green spaces and were higher in subsoil than in topsoil. Content of calcium plus magnesium of soil was higher in the buffer green space than in the neighborhood park and street tree but content of calcium and magnesium in saturation extract were higher, as result from exchangeable sodium, in the neighborhood parks and street tree sites than in the buffer green spaces. Concentration of salt in soil showed the difference with mounding height and planting ground treatment. The lowest concentration of salt appeared in buffer green spaces and street tree sites was the highest. Salt interception by mounding height in the same planting ground treatment was more effective 120cm of mounding height than 70cm of mounding height.

• Journal of The Korean Society of Grassland and Forage Science
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• v.11 no.4
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• pp.244-251
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• 1991

This study was undertaken to assess the effectiveness of magnesium-and boron-enriched complex fertilizer(CF, N-P$_2$O$_{5}$-K$_2$O-MgO-B$_2$O$_3$: 14-10-12-3-0.2) on the maintenance and management of hilly pasture. The effectiveness of CF was compared to those of some straight fertilizers (SF). This first part of the study was concerned with the soil chemical properties and the mutural balances of mineral nutrients in the soils of a mixed grass-clover and a pure grass swards. The results of a two-year field experiment are summarized as follows: 1. The Mg contents in the soils of the CF plots were higher than those of the SF plots. On the other hand, the Ca contents were higher in the SF plots than in the CF plots. The contents of Mg and Ca, and CEC, except K, in both the CF and SF plots were considerably below the optimum levels. At the normal application rate of NPK, the contents of available P$_2$O$_{5}$ were close to the optimum level in both the CF and SF plots. 2. The contents of exchangeable Mg were lower than the K contents in soils of all the plots. At the normal application rate of NPK, the Mg contents in the CF plots, but not in the SF plots, were close to the critical level for general crops (0.29me Mg/100g soil). The Mg contents in soils of all the plots, however, were considerably below the critical level for pasture forages and grazing cows (0.41me/100g). 3. Considering the desirable base saturation level of soil, the saturation levels of Ca and Mg were insufficient in both the CF and SF plots. The saturation levels of Mg in the CF plots, however, were relatively good compared with the SF plots. The equivalent ratios or Mg/K, Ca/Mg. Ca:Mg:K, and %Mg of CEC in soils were generally unfavorable in all the plots. These ratios of the CF plots, however, were relatively better than those of the SF plots. 4. Considering the contents of exchangeable Ca and Mg in soils, it is suggested that the application of slaked magnesium lime as a soil amelioration might be desirable for the fundamental increment of those contents at pasture establishment.

• Korean Journal of Soil Science and Fertilizer
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• v.17 no.1
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• pp.1-6
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• 1984

Soils in Cheju Island, derived mostly from volcanic ashes, were collected for chemical analysis to determine the effect of land utilization pattern on soil chemical characteristics. The coastal area has long been used for intensive farming and some of the mid-mountain region were recently reclaimed for agricultural crop production. The cation exchange capacity and the organic matter in the soils increased in the order of coastal area < mid-mountain belt < upper mountain area, while pH, base saturation, available phosphorus and exchangeable bases decreased with the elevation. Generally, the organic matter, the cation exchange capacity and the exchangeable bases of the Cheju soils were found to be considerably higher than the Korean mainland soils. However, the base saturation and the available phosphorus were far below the mainland average. The ratio of monovalent basic cations to total exchangeable bases showed the highest in the soils of the mountain belts and the lowest in the coastal area soils. These data suggest that a higher soil pH in the coastal area as compared to the mountainous slopes has resulted not from the sea water but from continuous application of alkaline fertilizers and times.

• Journal of the Korean Geosynthetics Society
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• v.10 no.3
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• pp.25-32
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• 2011

The matric suction and volumetric water content of dredging soils obtained from Saemangeum area were measured by the automated Soil-Water Characteristic Curve (SWCC) apparatus under both drying and wetting conditions. Based on the test result, SWCCs of the dredging soils were estimated by the van Genuchten(1980) model. The matric suction of drying process is larger than that of wetting process at a same effective degree of saturation. The suction stresses for various matirc suctions were estimated using Lu and Likos(2006) model and the Suction Stress Characteristic Curves (SSCC) were predicted using the independent parameter of SWCC. The suction stress of drying path was increased and decreased, while the suction stress of wetting path was continuously decreased with increasing the effective degree. Also, the suction stress of drying path is larger than that of wetting path at a same effective degree of saturation. The Hydraulic Conductivity Function(HCF) was also predicted by the van Genuchten(1980) model. The hydraulic conductivity was increased with increasing the volumetric water content. The hydraulic conductivity of drying path is larger than that of wetting path at a same matric suction. According to the results of SWCCs and SSCCs, the hysteresis phenomenon of suction stress or matric suction during both drying and wetting paths was occurred. The main reason of hysteresis phenomenon is a ink bottle effect of water among soil particles.

• Korean Journal of Soil Science and Fertilizer
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• v.2 no.1
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• pp.15-26
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• 1969

The study on physico-chemical characteristics of the acid sulfate soil present in Kimhae plain was carried out with 28 surface and subsoils from lower and higher produtive area and two representative profile samples from the areas reclaimed a few decades ago and around 10 years ago respectively. 1. There are no differences in soil texture between lower and higher productive soils being mostly silty clay loam and silty clay. 2. Very significant differences in pH, degree of base saturation and extractable aluminium content are observed; lower pH, lower degree of base saturation and higher aluminium in the lower productive soils and subsoils. The pH and degree of base saturation of these soils are extremely low whereas aluminium content is very high compared to ordinary paddy soil. 3. Cation exchange capacity of these soils are slightly higher than ordinary paddy soils. In higher productive soils, exchangeable calcium and magnesium are of same order, whereas in lower productive soils magnesium content is appreciably higher than calcium. 4. Though the soil is derived from marine and estuarine sediment, the soluble salt content is not high. There are only few lower productive surface soils and subsoils having Ec values of the saturation extracts higher than 4 mmhos but lower than 9 mmhos/cm. 5. Organic matter content of these soils is a bit higher compared to ordinary paddy soils, but, nitrogen content is comparatively low. C/N ratio of these soils is around 12. 6. Sulfur content is considerably higher but oxidizable sulfur is found to be very low. Total sulfur is generally high in subsoils and lower productive soils. 7. Active iron and available silica are slightly higher than ordinary paddy soils but easily reducible manganese is very low. Almost no differences are also observed between lower and higher productive soils. 8. Available phosphorus content is extremely low in particular, regardless of higher or lower productive soils. 9. The two representative profiles from the area of earlier reclamation and recent one show that samples from earlier reclaimed area contain less amount of free acids, sulfur compounds, toxic aluminium and soluble salts etc. than the other. This indicate greater leaching and possible addition of lime for a longer period of time. 10. From the results obtained, it can be concluded the higher productivity of group I soils is due to the greater leaching and neutralisation of acidity by liming materials, It can also be concluded that the productivity of both types can be increased by addition of liming materials and improvement of drainage facilities.

• Journal of Korea Water Resources Association
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• v.32 no.5
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• pp.515-524
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• 1999

A methodology to resolve a TOPMODEL problem has been suggested, which is associated with the spatial distribution of soil moisture behaviour in a runoff mechanism. A procedure to integrate the spatial information of saturation deficit in the TOPMODEL reflects the connectivity of saturated area in a watershed. The developed algorithm includes an improved basis in tracing the runoff path without increasing the number of parameters. The performance of the developed algorithm has been tested to an upland subwatershed, namely Dongok, which is the IHP watershed located at Wichon, Korea. Comparing with the original statistical version of the TOPMODEL, it has been found that the suggested algorithm can relax an overestimation of peak rate in the runoff simulation.

• Geotechnical Engineering
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• v.14 no.2
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• pp.79-92
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• 1998

Parametric studies based on laboratory pilot tests were performed to investigate the relationships between electrical resistivity and properties of contaminated soils. Three kinds of sandy soils sampled and leachate from an industrial waste landfill were mired to model the contaminated soils. Electrical resistivity of soils was measured by using a simulated resistivity cone penetrometer probe. In the experiments. the electrical resistivity was observed by changing the water content, void ratio, unit weight, degree of saturation, and concentration of the leachate. The test results show that the electrical resistivity of soils depends largely on the water content and the electrical property of pore water rather than unit weight and types of soils.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.71-77
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• 2008

Microstructural changes may arise due to the particle vanishing, fluid diffusion, heating, etc. This study focuses on the changes in small-strain shear stiffness in k0 loading produced by local straining in particular system made of sand-salt mixtures. Local strains were induced by dissolution of salt particles. Experiments were carried out in a conventional oedometer cell equipped with bender elements. Axial displacement and shear wave signals are recorded at each loading stage and during saturation process. Experimental data showed that microstructural changes due to particle vanishing were clearly captured by using shear wave measurement. Saturation of sand-salt mixture at a larger axial stress did not always create a more condense soil at the end of loading stage. Sand-salt mixture is useful for laboratory test on controlled artificial specimen.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.1076-1082
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• 2006

This study measured the change of media properties using Time domain Reflectometry (TDR) and Tensionmeter (TM) to measure volumetric water content of soil affecting in land subsidence and pollutant diffusion under saturation/unsaturated condition by water-level fluctuations. Also, actual water content compared their changes aspect by dry oven test for quantitative determinations of these measured values. In the case of TM, initial unsaturated condition confirmed that range in dimension of each other different according to their establishment depth, but measured values of TM can know that is shown measured value in almost similar measuring range under drain condition after the first injection. Also, the results of TDR showed that can measure enough change of volumetric water content in saturation/unsaturated condition by water-level fluctuations. Therefore, we are judged that TDR measurement equipment is very effective to measure the variations of volumetric water content and water-level being caused in groundwater level fluctuations.