• Journal of the Korean Geotechnical Society
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• v.21 no.7
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• pp.5-12
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• 2005

In order to investigate the strength and deformation anisotropy of compacted decomposed granite soils, a series of unsaturated-drained triaxial compression tests were performed. The sample used in the study was decomposed granite soil from Shimonoseki in Yamaguchi prefecture. The sample had three different angles of the axial (major principal) direction to the sedimentation plane (compaction plane), 0, 45 and 90 degrees. The compression strain of specimens subjected to isotropic compression was strongly influenced by the sedimentation angle. In addition, the time dependence was independent of the sedimentation angle in relation to the deformation behavior during the secondary compression process. The effect of the sedimentation angle on the triaxial compression strength and deformation was clear with low confining stress. Moreover, it was recognized that although the sedimentation angle and preparation methods were different, the dilatancy rate was relative to the increment of strength due to dilatancy. Therefore, it may be concluded that the compacted specimen has anisotropic mechanical properties similar to those of sand with initial fabric anisotropy.

• Journal of the Korean Geotechnical Society
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• v.21 no.8
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• pp.27-35
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• 2005

Several damages due to large displacement caused by liquefaction have been reported increasingly. Numerical procedures based on effective stress analysis are therefore necessary to predict liquefaction-induced deformation. In this paper, the fully coupled effective stress model called UBCSAND is proposed to simulate pore pressure rise due to earthquake or repeated loadings. The proposed model is a modification of the simple perfect elasto-plactic Mohr-Coulomb model, and can simulate a continuous yielding by mobilizing friction and dilation angles below failure state. Yield function is defined as the ratio of shear stress to mean normal stress. It is radial lines on stress space and has the same shape of Mohr-Columob failure envelope. Plastic hardening is based on an isotropic and kinematic hardening rule. The proposed model always causes plastic deformation during loading and reloading but it predicts elastic unloading. It is verified by capturing direct simple shear tests on loose Fraser River sand.

• Journal of the Korean Geotechnical Society
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• v.29 no.5
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• pp.5-17
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• 2013

This study investigates the effect of thermal stress on axial load and pile settlement of PHC energy piles. A series of numerical analyses were performed by controlling major influencing parameters such as pile arrangement, pile spacing, end-bearing condition, soil condition and pile cap stiffness. It is found that the characteristics of pile-load transfer are significantly affected by seasonal operation mode (i.e., cooling and heating) throughout the year. Also, the axial load under thermal loading increases with increasing the pile spacing. The settlement of the pile in sand is larger than that in clay because of the thermal stress generated. It is also found that thermal stress highly influences on the end-bearing pile, corner pile and rigidity of pile cap.

• 한국지구물리탐사학회:학술대회논문집
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• 1999.08a
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• pp.240-257
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• 1999

More than 16 percent of the total 18,032 reservoirs over the country were reported to have leakage problems and need to be improved. Recently, a great deal of progress was made in geophysical survey techniques, particularly in electrical resistivity, and the techniques are used for variety of Purposes in groundwater and dam management due to its economical advantages. This document describes the re-evaluation of existing resistivity data including newly surveyed data, mapping of modeled value in 2-D analysis to locate seepage pathways, This contains also discussion results of more than eighteen years of professional experiences in the field of dam efficiency improvement. In comparison of surface resistivity data with several soil analysis data in laboratory, it is evident that the surface resistivity value shows a qualitative proportionality with the sand contents of the filling materials in earth dam. The result from the study also indicates that the SP method in subsurface investigation is effective to detect seepage in earth filled dam as well as piping through rock/earthfill dike.

• Journal of Korea Water Resources Association
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• v.35 no.4 s.129
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• pp.425-442
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• 2002

The land reclamation area of Saemangeum(Kunsan) is located between $126^{\circ}10'\;E{\sim}126^{\circ}50'\;E\;and\;35^{\circ}35'\;N{\sim}36^{\circ}05'\;N$ at the western coast of the Korean peninsula. The reclamation area of Saemangeum has a range of 5.6m spring tide and the maximum tidal current speed is about $1.41m\;s^{-1}$. In ordinary spring tide. Most of the sediments deposited on the tidal flats are transported from the Geum river, the Mankyung river and the Dongjin river. The soil in this area consists of silty sand with the depth of 10m to 30m. The wind in winter is strong from the direction of northwest. Saemangeum coastal area is being constructed 33km the sea dike and 40,100ha reclamation area. The purpose of this study Is to find the residual circulations in four seasons before and after the dike construction by a robust diagnostic and prognostic numerical model.

• Korean Journal of Medicinal Crop Science
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• v.5 no.2
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• pp.119-125
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• 1997

This study was carried out to know the factors affecting rooting and growth in stem cutting of Ligusticum chuangxiong for mass propagation. The results indicated that : (1) Rooting and growth were better in perlite which has higher air permeability. (2) Sub-irrigation with 15min long with 30min interval was more favorable for growth. (3) Proper tempeature for rooting and growth ranged from $25^{\circ}C\;to\;30^{\circ}C$ while photoperiod had no effect on rooting and growth.

• Journal of the Korean Geosynthetics Society
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• v.16 no.2
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• pp.67-77
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• 2017

This study analyzes behavior of bearing capacity of open-ended pipe pile from laboratory experiment results. Unlike the conventional pipe piles, cone penetration is implemented into the inside of the pipe pile. During the cone penetration, cone driving energy helps densification of plugged soils and soils below the pile end. Sand pluviator was used to obtain homogeneous soil layers. Two kinds of piles with different pile outer surface roughness were prepared, and two different drop heights of pile driving were applied. Eight experimental cases varying pile outer surface roughness, pile driving energy for conventional and cone penetration implemented piles were conducted. From the experiments, ultimate load of the pile increased approximately by 70% for increased pile driving height, and it increased by 21% for rougher surface pile. When cone penetration is implemented, the ultimate load increased by 40% in average.

• Journal of Environmental Health Sciences
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• v.31 no.4 s.85
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• pp.301-308
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• 2005

The purpose of this study was to characterize mass concentration of $PM_{10}\;to,\;PM_{2.5}$ and metallic composition using Minivol Portable Sampler from May 2003 to May 2004 in metropolitan city, Seoul. Annual average concentration of $PM_{10}$ were $57.67({\pm}28.20)\;{\mu}g/m^3\;and\;PM_{2.5},\;were\;42.06({\pm}20.23)\;{\mu}g/m^3$. The concentration was the highest in winter because persistent thermal inversion and in spring, particulate matter concentration was high because of yellow-sand events. The average $PM_{2.5}/PM_{10}$ ratio was 0.73. This indicated $PM_{2.5}$ fraction played a significant role in air pollution. The atmospheric metallic elements in the $PM_{10},PM_{2.5}$ came different emission sources such as soil, traffic, industry and resuspended particles. The results showed that average $PM_{10}$ composition order as Fe>Zn>Pb>Cu>Mn. The metallic elements Zn and Fe were the largest composition in the $PM_{2.5}$

• KOREAN JOURNAL OF CROP SCIENCE
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• v.3
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• pp.83-87
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• 1965

This experiment was done to observe the morphological change of plant under the cultivation of deep ploughing and heavy fertilization with paddy rice 1963 at Seoul. A seedling of 35 days old was transplanted June 1st, in a galvanized iron pot with botton 20 cm in diameter, which was painted white inside and filled with sand mixed with fertilizers. The treatments were 15cm soil depth of normal fertilization, 30cm of fertilization twice and 45cm of fertilization thrice. Replications were three. The plant was observed on main stem Aug. 6 before heading, Sep. 12 after heading and Oct. 17 at the time of harvest at the same pot. The results are as follows. The length and the width of leaf blades of the upper part on main stem have the tendency to be big and vigorous with the deep ploughing and heavy fertilizations(Fig 1, 2, 3 and 4). The number and the size of vascular bundles of main stem is to increase when the paddy is cultivated with the method of deep ploughing and heavy fertilizations(Fig 5). The number and the weight of roots of main stem increases with deep ploughing and heavy fertilizations(Fig 6).

• Magazine of the Korean Society of Agricultural Engineers
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• v.23 no.3
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• pp.96-104
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• 1981

In order to investigate the characteristics of the shear strength of the unsaturated cohesive soils which has mean characters of sand and clay widely used for banking, I selected soil samples from An-sung district and, against it, performed direct shear test and unconfined compression test changing grain size, compaction energy and moisture content and also performed triaxial compression test under optimum moisture content. The results are as follows; 1.As the passing percent of the No. 200 sieve increased from 23.6% to 56.1%, cohesion increased from 0. 202kg/cm2 to 0. 398kg/cm2 under the direct shear test and from 0.38 kg/cm2 to 1. 05kg/cm2 under the tria4al compression test, internal friction angle decreased from 44. 78$^{\circ}$ to 34. 34$^{\circ}$ under the direct shear test and from 31. 88$^{\circ}$ to 13. 31$^{\circ}$ under the triaxial compression test. 2.Cohesion showed it's maximum value around OMC and internal friction angle showed a tendency to increase according to the decrease of water content but it's increasing ratio was relatively slow. 3.Decreasing ratio of cohesion and internal friction angle was relatively sensitive according to the decrease of compaction energy. 4.The smaller of the vertical stress and the coarser of the grain size of samples, changing of the volume showed a tendency to increase and as the increase of water content, the shear displacement (dh) at failure shear stress ($\tau$f) showed maximum and the $\tau$f-dh curve was gentle. 5.To synthesize the results of the direct shear test and the triaxial compression test, cohesion showed higher under the triaxial compression test and internal friction angle showed a tendeney to appear higher under the direct shear test. It seems that we can get correspondent results by removing the side friction of mold with soils and adjusting the vertical stress and shearing speed under the direct shear test.