• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 가을 학술발표회 논문집
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• pp.233-240
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• 1999

The laboratory tests on geogrid-reinforced sand were conducted with considering embedment effect. The relative densities of sand are 60% and 80%, respectively. The embedment depths of foundation were varied as D$\_$f/B=0, 0.5, 1.0. Based on the model test results, (u/B)$\_$cr/, BCR$\_$u/, and (b/B)$\_$cr/, were determined. The optimum depth of reinforcement was determined. The embedment depth of foundation is greatly contributed on the bearing capacity of geogrid-reinforced sand.

• Geomechanics and Engineering
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• 제12권4호
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• pp.689-705
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• 2017

The present study deals with the Pressure-settlement behavior of square and rectangular skirted footing resting on sand and subjected to a vertical load through a laboratory experimental study. A series of load tests were conducted in the model test tank to evaluate the improvement in pressure-settlement behavior and bearing capacity of square and rectangular model footings with and without structural skirt. The footing of width 5 cm and 6 cm and length/width ratio of 1 and 2 was used. The relative density of sand was maintained at 30%, 50%, 70%, and 87% respectively. The depth of skirt was varied from 0.25 B to 1.0 B. All the tests were carried out using a strain controlled loading frame of 50 kN capacity. The strain rate for all test was kept 0.24 mm/min. The results of present study reveal that, the use of structural skirt improves the bearing capacity of footing significantly. The improvement in bearing capacity was observed almost linearly proportional to the depth of skirt. The improvement in bearing capacity of skirted footings over footing without skirt was observed in the range of 33.3% to 68.5%, 68.9% to 127% and 146.7% to 262% for a skirt depth of 0.25 B, 0.50 B and 1.0 B respectively. The skirted footings were found more effective for sand at relative density of 30% and 50% than at relative density of 70% and 87%. The bearing capacity was found to increase linearly with footing width for footings with and without skirts. This observation was found to be consistent for footings with different skirt depths and for relative density of sand i.e., 30%, 50%, 70%, and 87%. The obtained results from the study for footing with and without skirts were comparable with available solutions from literature.

• Geomechanics and Engineering
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• 제6권5호
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• pp.487-502
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• 2014

A three dimensional finite element model was used to simulate rapid impact compaction (RIC) in loose granular soils using ABAQUS software for one impact point. The behavior of soil under impact loading was expressed using a cap-plasticity model. Numerical modeling was done for a site in Assalouyeh petrochemical complex in southern Iran to verify the results. In-situ settlements per blow were compared to those in the numerical model. Measurements of improvement by depth were obtained from the in-situ standard penetration, plate loading, and large density tests and were compared with the numerical model results. Contours of the equal relative density clearly showed the efficiency of RIC laterally and at depth. Plastic volumetric strains below the anvil and the effect of RIC set indicated that a set of 10 mm can be considered to be a threshold value for soil improvement using this method. The results showed that RIC strongly improved the soil up to 2 m in depth and commonly influenced the soil up to depths of 4 m.

• Geomechanics and Engineering
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• 제8권4호
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• pp.595-613
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• 2015

An experimental investigation into the uplift capacity of horizontal square plate anchors in sand with and without geogrid reinforcement is reported. The parameters investigated are the effect of the depth of the single layer of geogrid, vertical spacing of geogrid layers, number of geogrid layers, length of geogrid layers, the effects of embedment depth, and relative density of sand. A series of three dimensional finite element analyses model was established and confirmed to be effective in capturing the behaviour of plate anchor-reinforced sand by comparing its predictions with experimental results. The results showed that the geogrid reinforcement had a considerable effect on the uplift capacity of horizontal square plate anchors in sand. The improvement in uplift capacity was found to be strongly dependent on the embedment depth and relative density of sand. A satisfactory agreement between the experimental and numerical results on general trend of behaviour and optimum geometry of reinforcement placement is observed. Based on the model test results and the finite element analyses, optimum values of the geogrid parameters for maximum reinforcing effect are discussed and suggested.

• Journal of Biosystems Engineering
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• 제21권4호
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• pp.449-455
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• 1996

The temperature distributions at various soil depths were predicted by heat transfer model during and after infrared irradiation on sand loam or loam soil. At each soil depth, predicted and measured temperature distributions were compared with using the mean relative percentage deviation and standard error. The mean relative percentage deviation was less than 10% between predicted and measured temperature distributions at each soil depth. Thus, it was concluded that the temperature distribution at each soil depth could be predicted satisfactorily by heat transfer model. Also, it is expected that these predicted temperature distributions can be used as basic information for determining the working speed of weeder and the size when the real weeder is constructed.

• 한국지반공학회지:지반
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• 제7권2호
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• pp.5-26
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• 1991

지반의 상대밀도, 응력이력, 말뚝의 표면상태, 매설깊이 및 직경이 상양력을 받는 말뚝의 거동에 미치는 영향에 대한 모형실험결과가 발표되었다. 극한상양지지력은 모래의 상대밀도 뿐만아니라 현위치수평응력에 의존되며, 한계깊이 현상은 깊이에 따른 수평응력의 변화로 설명되고, Ktan 의 값은 말뚝직경의 증가함에 따라 감소하는 경향을 보인다.

• 소성∙가공
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• 제8권2호
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• pp.152-159
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• 1999

This study is to investigate the effects of warm deep drawing with aluminum sheets of A1050-H16 and A5020-H32 for improving deep drawability. Experiments for producing circular cups and square cups were carried out for various working conditions, such as forming temperature and blank shapes. The limit drawing ratio(LDR) of 2.63 in warm deep drawing of circular cups in case of A5020-H32 sheet, whereas LDR of 2.25 in case of A1050-H16, could be obtained and the former was 1.4 times higher than the value at room temperature. The maximum relative drawing depth for square cups of A5020-H32 material was also about 1.92 times deeper than the depth drawn at room temperature. The effects of blank shape and forming temperature on drawability as well as thickness distribution of drawn cups were examined and discussed.

• 한국정밀공학회지
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• 제26권9호
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• pp.53-57
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• 2009

There are technical requirements to manufacture large size functional parts with not only simple geometries like a flat or spherical surface but also sculptured geometries. In addition, the required machining accuracy for these parts is becoming more severe. In general, the form accuracy of machined parts is determined by the relative position between workpiece and tool during machining process. To improve machining accuracy the relative position errors should be maintained within the required accuracy. This study deals with the estimation and calibration of depth of cut using the AE signal in micro-machining. Also, this sensing technique can be applied to detect the initial contact between workpiece and tool.

• 한국연초학회지
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• 제19권1호
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• pp.18-23
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• 1997

The study was carried out to clarify reasonable production of healthy seedling, optimal Pot depth, and appropriate transplanting time, which can be deduced from understanding of seedling quality. Seedling quality results from growth of root and shoot, morphology and distribution of root system under influence of Pot depth during seedling growing period. Stem height, shoot dry weight, leaf area and leaf number were increased in proportion to depth of pots. Growth of shoot and root during seedling growing period showed the most dramatic development between 20th and 25th day after temporary planting. Root number increased as pot depth decrease and total root length and dry weight increased as pot depth increase. In 5cm pot, relative multiplication rate was higher and mean extension rate was lower than other depth of Pot. The limitation of pot volume in which rhizosphere was located enhance the development of roots of second and third order. At 20th days after temporary Planting root distribution was relatively uniform in length and development of adventitious root on stem base was poor as Pot depth decreased.

• 한국환경복원기술학회지
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• 제14권5호
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• pp.53-67
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• 2011

The major objective of this study was to quantify the effects of substrate depth and substrate composition on the development of sedum etc., in a sloped rooftop (6 : 12 pitch) environment during a 4-year period. The experiment was conducted from 2006 October to 2010 December under several conditions without soil erosion control : two substrate depth (5cm, 10cm), four substrate composition (A5N3C2, A3N3C4, A6C4, G5L3C2: A: artificial lightweight soil, N : natural soil, G : granite decomposed soil, C : leave composite, L : loess), four sloped roof direction ($E40^{\circ}W$, $W40^{\circ}N$, $S40^{\circ}W$, $N40^{\circ}E$). In this experiment 4 sedum etc., were used: Sedum sarmentosum, Sedum kamtschaticum, Sedum rupestre, Sedum telephium, flowering herbs (mixed seed : Taraxacum platycarpum, Lotus corniculatus, Aster yomena, Aster koraiensis), western grasses (mixed seed : Tall fescue, Creeping redfescue, Bermuda grass, Perennial ryegrass). The establishment factor had two levels : succulent shoot establishment (sedum), seeding (flowering herbs, western grasses). 1. Enkamat, as it bring about top soil exfoliation, was unsuitable material for soil erosion control. 2. Sedum species exhibited greater growth at a substrate depth of 10cm relative to 5cm. All flowering herbs and western grasses established only at a substrate depth of 5cm were died. A substrate depth of 5cm was not suited in sloped rooftop greening without maintenance. If additional soil erosion control will be supplemented, a substrate depth of 10cm in sloped rooftop greening without maintenance was considered suitable. 3. For all substrate depth and composition, the most abundant species was Sedum kamtschaticum. The percentage of surviving Sedum kamtschaticum was 73.4% at a substrate depth of 10cm in autumn 2007 one year after the roof vegetation had been established. But the percentage of surviving other sedum were 33.3%~51.9%, therefor mulching for soil erosion control was essential after rooftop establishment in extensive sloped roof greening was proved. To raise the ratio of plant survival, complete establishment of plant root at substrate was considered essential before rooftop establishment. 4. There was a significant interaction between biomass and substrate moisture content. There were also a significant difference of substrate moisture and erosion among substrate composition. The moisture content of A6C4 was highest, the resistance to erosion of A5N3C2 was highest among substrate composition. The biomass of plants were not significantly higher in A5N3C2 and A6C4 relative to A3N3C4 and G5L3C2, For substrate moisture and erosion resistance, A5N3C2 and A6C4 were considered suitable in sloped rooftop greening without maintenance. 5. There were significant difference among roof slope direction on the substrate moisture. Especially, the substrate moisture content of $S40^{\circ}W$ was lower relative to that of $N40^{\circ}E$, that guessed by solar radiation and erosion.