• Journal of The Korean Society of Agricultural Engineers
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• v.49 no.4
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• pp.63-70
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• 2007

The soil samples used in this study were prepared with the residual granite soils passed through the #4 sieve and obtained from Pocheon in Gyeonggi-Ki do. Specifically, five types of samples were prepared. Sample A which is a natural state soil was classified as SM according to the uses. Samples of B, C, D, and E were prepared by mixing Sample A with bentonite and were classified as SC according to the uses. The plasticity indexes of samples B, C, D, and E were 15, 25, 30, and 40, respectively. The specimens, whose dimensions are 100mm by 127.5mm, were prepared by A method of ASTM D 698 with the Proctor mold. In experiments, the loading with the 1%/min was applied. Four different disk diameters, 13mm, 26mm, 38mm, and 52mm were used in the Improved Unconfined Penetration (IUP) tests. To compare the tensile strengths, the split tensile tests were also conducted on the same specimens used for the IUP tests. To find out the effects of moisture contents, plasticity Index of specimens on the tensile strength, six different water contents were used for making a specimen.

• Journal of Industrial Technology
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• v.17
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• pp.119-124
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• 1997

This thesis is an experimental research of shear behavioral characteristics and shear behavioral coefficient of weathered residual soil which is mostly contained in soil of Korea. Using the weathered residual soil from mountain near Kangwon National University, this experimental research were contained the physical properties of sample in term of the basic test method such as specific gravity, plastic and liquid limit, grain-size distribution, density and water content. Experimental results obtained from direct shear test sand triaxial compression tests show that according to step loading, linear strain and linear stress increase continually and angle of internal friction decreases just little according to incresing of water content in case of ignoring the cohesion, and angle of internal friction appears the maximum angle near a optimum moisture content in case of considering the cohesion.

• Journal of the Korean Society for Railway
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• v.12 no.2
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• pp.183-189
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• 2009

The track structure of Gyungbu High Speed Railway line from Daegu to Busan is concrete track. It has a very strict specification for residual settlement because of its rigid type structural characteristics. The residual settlement of it comes from the residual settlement of the subgrade and the ground. The residual settlement of railway subgrade composed of crushed rock and soil might be major parts of total residual settlement depending on the field compaction qualities. Therefore, it is a key to minimize the residual settlement of the subgrade for a successful concrete track construction. In this paper, total 31 large scale compaction tests were performed to understand the compaction behaviors of the crushed rock-soil mixture. The test specimens were constituted with soil, crushed shale and mudstone taken from two sites under construction. The compaction tests were performed with the variations of rock types, #4 sieve passing contents, maximum particle size, and moisture contents. The influence of those factors on maximum dry unit weights of crushed rock-soil mixture was evaluated.

• Magazine of the Korean Society of Agricultural Engineers
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• v.33 no.2
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• pp.82-93
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• 1991

The objective of this paper is to show that the soil-geotextile interaction needs to he addressed in addition to the usual tensile and modulus properties when the geotextile is being designed for a specific application. The soil-geotextile interaction can be directly assessed by standard direct shear test. The data presented here show that the shear strength paramaters describing the soil-geotextile interface can he greatly influenced by the type of the geotextile. In this investigation, we examined nine different geotextiles of varying construction and surface textures with two standard soil, under five loading conditions, and compared the shear strength and the frictional resistance with the corresponding values of soil itself The following conclusions were drawned from this study. 1. The shear stress-strain curve shows that there are the residual shear stresses at the soil-geotextile interface. Because of the hydraulic gradient between the soil and the geotextile, the excessive pore water can migrate into the geotextile and among the filaments and dissipate through the soil-geotextile interface. 2. The shear strength of the soil-geotextile interface is affected by the moisture content of the soil. At moisture content lower than the optimum water content of the Proctor compaction test, the shear strength of the soil-geotextile interface is greater. 3. The type and surface roughness of the geotextile have the greatest influence on the interface friction angle between the soil and the geotextile.

• Korean Journal of Agricultural and Forest Meteorology
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• v.16 no.4
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• pp.359-367
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• 2014

Drought index can be used to implement an early warning system for drought and to operate a drought monitoring service. In this study, an approach was examined to determine agricultural drought index (ADI) at high spatial resolution, e.g., 270 m. The value of ADI was calculated based on soil water balance between supply and demand of water. Water supply is calculated by the cumulative effective precipitation with the application of the weight to the precipitation from two months ago. Water demand is derived from the actual evapotranspiration, which was calculated applying a crop coefficient to the reference evapotranspiration. The amount of surface runoff on a given soil type was also used to calculate soil residual moisture. Presence of drought was determined based on the probability distribution in the given area. In order to assess the reliability of this index, the amount of residual moisture, which represents severity of drought, was compared with measurements of soil moisture at three experimental between July 2012 and December 2013. As a result, the ADI had greater correlation with measured soil moisture compared with the standardized precipitation index, which suggested that the ADI would be useful for drought warning services.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1140-1147
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• 2005

The objective of this study was to identify the effect of the degree of saturation on the resilient modulus of cohesive soils as subgrade. Six representative cohesive soils representing A-4, A-6, and A-7-6 soil types collected from road construction sites across Ohio, were tested in the laboratory to determine their basic engineering properties. Resilient modulus tests were conducted on unsaturated cohesive soils at optimum moisture content, and samples compacted to optimum conditions but allowed to fully saturate. The subgrade compacted at optimum moisture content may be fully saturated due to seasonal change. Laboratory tests on fully saturated cohesive soils showed that the resilient modulus of saturated soils decreased to less than half that of soil specimens tested at optimum moisture content. The reduction of resilient modulus would possibly be caused by the buildup of pore water pressure. In resilient modulus testing performed in this study on saturated samples, pore water pressure increases were observed. Pore water pressure and residual pore water pressure gradually increased with an increase in deviator stress.

• Geotechnical Engineering
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• v.2 no.1
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• pp.7-14
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• 1986

The structure of the collapsible soils, such as decomposed granite soil and loess, were examined by the odeometer test, SEM & XES analysis and static & cyclic triaxial test, and hove this structure have influences upon the collapsible behaviour under static and cyclic load was investigated. The study results obtained are as follows; 1. The macropores space of decomposed granite soil (rd=1.50g/cm3) and loess (rd=1.43g/cm3) used in this test were well developed, and showed the behaviour of collapsible soil. 2. Collapsible soil has high resistance on the strain under natural moisture content, however, the resistance on the strain was sharply decreased by the absorption and increasing load since its special structure was destructed. 3. Under the static load, the strain of collapsible soil was high by the viscous flow of the cyclic bonds with time lapse, but Infer the cyclic load, the strain of collapsible soil was low since the tinge needed to destruct the bonding force of clay was not enough. 4. The understanding about the cyclic behaviour of collapsible soil may be helpful to predict the elastic & residual strain of the foundations by the earthquake together with the damage by the additional failure.

• Journal of Microbiology and Biotechnology
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• v.9 no.6
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• pp.784-788
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• 1999

The effects of pH, moisture content, and the relative amount of a polymer sample on the biodegradation of degradable polymers in soil were studied using various polymer materials such as cellulose, poly-(butylene succinate-co-adipate) (SG) polycaprolactone (PCL), a blend of PCL and starch (PCL-starch), and a poly-lactic acid (PLA). As with other materials, the polymers degraded faster at a neutral pH than at either acidic or basic conditions. Moisture contents of 60 and 100% water holding capacity exhibited a similar biodegradability for various polymers, although the effects differed depending on the polymer. For synthetic polymers, biodegradation was faster at 60%, while the natural polymer (cellulose) degraded faster at 100%. Fungal hypae was observed at a 60% water holding capacity which may have affected the biodegradation of the polymers. A polymer amount of 0.25% to soil revealed the highest biodegradability among the ratios of 0.25, 0.5, and 1%. With a higher sample amount, the residual polymer could be recovered after the biodegradation test. It was confirmed that a test for general biodegradation condition can be applied to plastic biodegradation in soil.

• The Journal of the Petrological Society of Korea
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• v.18 no.4
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• pp.279-291
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• 2009

Radon is a natural radionuclide originated from radioactive decay of radium in rocks and soil. It is colorless, odorless and tasteless elements that mainly distributed as gaseous phase in soil pore space. The present study analyzed the characteristics of long-term radon variation in granitic residual soil at Mt. Guemjeong in Guemjeong-gu, Busan and determined the effects of atmospheric temperature, rainfall and soil temperature and moisture. Periodic measurements of radon concentrations in soil gas were conducted by applying two types of in-situ monitoring methods (chamber system and tubing system). Radon concentration in soil gas was highest in summer and lowest in winter. The variations in soil temperature and atmospheric temperature were most effective factors in the long-term radon variations and showed positive co-relations. The air circulation between soil air and atmosphere by the temperature difference between soil and atmosphere was analyzed a major cause of the variation. However, other factors such as atmospheric pressure, rainfall and soil moisture were analyzed relatively less effective.

• Korean Journal of Agricultural and Forest Meteorology
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• v.17 no.4
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• pp.275-280
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• 2015

In order to figure out the future drought characteristics of the Jeonju plains, the major crop production area in Korea, daily agricultural drought indexes based on soil water balance were calculated for the relevant 12.5 km by 12.5 km grid cell using the weather data generated by the RCP8.5 climate scenario during 1951-2100. The calculations were grouped into five climatological normal years, the past (1951-1980), the present (1981-2010), and the three futures (2011-2040, 2041-2070, and 2071-2100). Results showed that the soil moisture conditions in early spring, worst for both the past and present normal years, will ameliorate gradually in the future and the crop water stress in spring season was projected to become negligible by the end of this century. Furthermore, the drought frequency in early spring was projected to diminish, resulting in rare occurrence of spring drought by that time. However, the result also showed that the soil moisture conditions during the summer season (when most crops grow in Jeonju plain) will deteriorate and the drought incidence will be more frequent than in the past or present period.