• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.10
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• pp.1796-1801
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• 2007

This paper presents electric potential rise on the surface of the earth due to ground currents. It is the aim of this paper to propose fundamental data relevant to the earth surface potentials depending on the soil structures. The earth potential rise, touch and step voltages in the immediate vicinity of the ground rod of a distribution pole were measured and analyzed. The results described in this paper are based on laboratory measurements which were intended to simulate conditions existing in actual installations. As a result, the earth surface potential rise, touch and step voltages strongly depend on the soil structure. The highest earth surface potential occurred in the vicinity of the top of ground rod. When the ground rod was installed in the distance range of $1{\sim}1.5\;m$ from distribution pole, the highest touch voltages appeared near the place of 1 m on the straight line connecting the distribution pole to ground rod.

• Geomechanics and Engineering
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• v.6 no.4
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• pp.377-389
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• 2014

The vacuum consolidation method which was proposed by Kjellman in 1952 has been studied extensively and used successfully since early 1980 throughout the world, especially in East and Southeast Asia. Despite the increased successful use, different opinions still exist, especially in connection to distribution of vacuum with depth and time in vertical drains and in soil during preloading of soft ground. Porewater pressure measurements from actual cases of field vacuum and vacuum-fill preloading as well as laboratory studies have been examined. It is concluded that (a) a vacuum magnitude equal to that in the drainage blanket remains constant with depth and time within the vertical drains, (b) as expected, vacuum does not develop at the same rate within the soil at different depths; however, under ideal conditions vacuum is expected to become constant with depth in soil after the end of primary consolidation, and (c) there exists a possibility of internal leakage in vacuum intensity at some sublayers of a soft clay and silt deposit. A case history of vacuum loading with sufficient subsurface information is analyzed using the ILLICON procedure.

• Animal cells and systems
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• v.4 no.1
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• pp.57-62
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• 2000

Soil samples were collected in thirteen Manitoba boreal forest sites. Spatial distribution of chytrids from diverse boreal forest microhabitats was investigated by baiting with jack pine pollen. After baiting, the pollen was surveyed for chytrids for 8 ten day period and individual species were counted. Total infestations of pollen by chytrids ranged from 5.8% to 90.2% from various soils. Each site with high infestation was characterized by litter with high needle content while mineral soil or soil with limited organic matter yielded low levels of pollen infestation. Species diversity tended to be higher in soils with higher pollen infestation and lower in soils with lower pollen infestation. Lower diversity was generally observed in mineral soils or soils with a limited organic horizon comprised, in part, of broad leaf litter. Based on coefficients of association and species in common among species across the collection sites, it was possible to relate dominant species assemblages in site groups. These species assemblages in the site groups suggest that the chytrids are distributed by litter and soil types. It can be concluded that the substratum characteristics of litter types and availability of litter may be important in describing chytrid distribution in boreal forest sites.

• Journal of Environmental Science International
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• v.25 no.1
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• pp.11-21
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• 2016

The soil contamination by heavy metals in playgrounds of kindergartens in Vilnius city is analysed in this article. The aim of this research is to investigate and evaluate soil contamination by heavy metals in playgrounds of kindergartens in different territories of Vilnius city. Concentrations of heavy metals were measured using Thermo Fisher Scientific Niton$^{(R)}$ XL2 X-ray fluorescence spectrometer. Maximum allowable and background concentrations that are given in Lithuanian hygiene standard and Lithuania geochemical atlas are used to compare and evaluate concentrations of heavy metals. Concentrations of heavy metals and their spatial distribution were analysed in order to exclude the most contaminated areas relating with different functional areas of the city. Geo-statistical analysis and maps of spatial distribution were developed using IDW interpolator in ArcMap software. Detail soil surveys helps to assess the extent of anthropogenic impact in different parts of the city which can be harmful to the soil ecosystem and human health. Such researches can help to change or select different function for city areas in territorial planning process.

• Journal of Korean Society of Disaster and Security
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• v.10 no.1
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• pp.47-53
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• 2017

Accurate exploration of the risk factors of the ground subsidence is needed to predict and evaluate the subsidence of the surrounding ground due to the excavation of the ground. In this study, we analyzed the distribution of soil relaxation area by analyzing the behavior around the ground excavation site and simulated the GPR exploration under various conditions. As a result, Although there are some differences according to the water content, distribution of the strata and the distribution of the relaxation region were confirmed in the unsaturated soil, and it was found that there was a difficulty in the GPR exploration in the saturated soil.

• Environmental Engineering Research
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• v.18 no.1
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• pp.37-43
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• 2013

Water distribution pipes installed underground have potential risks of pipe failure and burst. After years of use, pipe walls tend to be corroded due to aggressive soil environments where they are located. The present study aims to assess the degree of external corrosion of a distribution pipe network. In situ data obtained through test pit excavation and direct sampling are carefully collated and assessed. A statistical approach is useful to predict severity of pipe corrosion at present and in future. First, criteria functions defined by discriminant function analysis are formulated to judge whether the pipes are seriously corroded. Data utilized in the analyses are those related to soil property, i.e., soil resistivity, pH, water content, and chloride ion. Secondly, corrosion factors that significantly affect pipe wall pitting (vertical) and spread (horizontal) on the pipe surface are identified with a view to quantifying a degree of the pipe corrosion. Finally, a most reliable model represented in the form of a multiple regression equation is developed for this purpose. From these analyses, it can be concluded that our proposed model is effective to predict the severity and rate of pipe corrosion utilizing selected factors that reflect the fuzzy soil environment.

• Geomechanics and Engineering
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• v.28 no.1
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• pp.89-105
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• 2022

The behavior of the soil subgrade is complex and irregular against loads. When modeling, the soil is often replaced by a more straightforward system called a subgrade model. The Winkler method of linear elastic springs is a popular method of soil modeling in which the spring constant shows the modulus of subgrade reaction. In this research, the factors affecting the distribution of the modulus of subgrade reaction of elastoplastic subgrades are examined. For this purpose, critical theories about the modulus of subgrade reaction were examined. A square raft foundation on a sandy soil subgrade with was analyzed at different internal friction angles and Young's modulus values using ABAQUS software. To accurately model the actual soil behavior, the elastic, perfectly plastic constitutive model was applied to investigate a foundation on discrete springs. In order to increase the accuracy of soil modeling, equations have been proposed for the distribution of the subgrade reaction modulus. The constitutive model of the springs is elastic, perfectly plastic. It was observed that the modulus of subgrade reaction under an elastic load decreased when moving from the corner to the center of the foundation. For the ultimate load, the modulus of subgrade reaction increased as it moved from the corner to the center of the foundation.

• Magazine of the Korean Society of Agricultural Engineers
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• v.22 no.3
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• pp.46-59
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• 1980

This study was conducted to obtain the most effective distribution of grain size and the optimum lime content for lime-soil stabilization. To achieve the aim, the change of consistency, the characteristics of compaction and unconfined compressive strength were tested by adding of 0, 4, 6, 8, 10 and 12 percent lime by weight for all soils adjusted by given ratios of sand to clay. The results obtained were as follows; 1. There was a tendency that the plasticity index of lime-soil mixture was decreased by increasing the amount of lime, whereas the liquid limit was varied irregularly and the plastic limit was increased. 2. With the addition of more lime, the optimum moisture content of lime-soil mixture was increased, and the maximum dry density was decreased. 3. The optimum lime content of lime-soil mixture was varied from soil to soil, and the less amount of small grain size, the less value of optimum lime content. 4. The optimum distribution of grain size for lime-soil mixture was in the soil, having the ratio of about 60 percent of cohesive clay and about 40 percent of sand by weight. 5. In the soil having fine grain size, the effect of curing appeared for long periods of time, whereas the increasing rate of unconfined compressive strength was great on the soil of coarse grain size in the earlier stage of curing period.

• Geomechanics and Engineering
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• v.17 no.5
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• pp.439-444
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• 2019

It is generally known that high strength soil is indicative of well-graded particle size distribution. However, there are some special cases of firm ground despite poor grade distribution, especially a specific gap-graded soil. Based on these discoveries, this study investigated the development of an additive of gap-graded soils designed to increase soil strength. This theoretical concept was used to calculate the mixed ratio required for optimal soil strength of the ground sample. The gap-graded aggregate was added according to Plato's polyhedral theory and subsequently calculated ratio and soil strength characteristics were then compared to characteristics of the original soil sample through various test results. In addition, the underground stress transfer rate was measured according to the test conditions. The test results showed that the ground settlement and stress limit thickness were reduced with the incorporation of gap-graded soil. Further field tests would confirm the reproducibility and reliability of the technology by using gap-graded soil to reinforce soft ground of a new construction site. Gap-graded soil has the potential to reduce the construction cost and time of construction compared to other reinforcing methods.

• The Journal of Engineering Geology
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• v.17 no.4
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• pp.665-671
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• 2007

In this study, the soil characteristics and the landslide probability are investigated in East Island of Dok-do. The distribution and depth of soil layer were investigated and the soil samples were taken from the soil layer in East Island. As the results of field investigation, the soil layer was partly distributed in specific location and the soil depth was ranged from 1cm to 50cm. Also, the soil depth was mainly ranged about 10cm in the large part of soil layer. The soils were classed as the weathered residual soils and involved many organic contents such as rotten roots and leaves. The average of water contents is 23.2%, and the average of liquid limits is 42.2%. Also, the soils is non-plastic condition. Also, the soils were mainly classed as the poor graded sand including loam contents. Meanwhile, the landslide probability was investigated through a survey of the soil layer distribution in East Island. The soil depth was very shallow in the large part of the soil layer, and the distribution area of soil layer was small. Therefore, it may predict that the landslide probability is very low due to the dissatisfaction of landslide occurrence condition.