• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2369-2379
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• 2013

The Soil-Water Characteristics Curve (SWCC) is affected by the initial density of soil under unsaturated condition. Also, the characteristic of hydraulic conductivity is changed by the initial density of soil. To study the effect of initial density of unsaturated soil, SWCC and the Hydraulic Conductivity Function (HCF) of Jumoonjin sand with various relative densities, 40%, 60% and 75% were measured in both drying and wetting processes. As the results of SWCC estimated by van Genuchten (1980) model, the parameter related to Air Entry Value(AEV), ${\alpha}$ in the wetting process is larger than that in drying process, but the parameters related to the SWCC slope, n and the residual water content, m are larger than those in wetting process. The AEV is increased or Water Entry Value (WEV) is decreased with increasing the relative density of sand. The AEV is larger than the WEV at the same relative density of sand. As the results of HCF estimated by van Genuchten (1980) model which is one of the parameter estimation methods, the unsaturated hydraulic conductivity maintained at a saturated one in the low level of matric suctions and then suddenly decreased just before the AEV or the WEV. The saturated hydraulic conductivity in drying process is larger than that in wetting process. The saturated hydraulic conductivity is decreased with increasing the relative density of sand in both drying and wetting processes. Also, the hysteresis in unsaturated HCFs between drying and wetting process was occurred like the hysteresis in SWCCs. According to the test results, the AEV on SWCC is decreased and the saturated hydraulic conductivity is increased with increasing the initial density. It means that SWCC and HCF are affected by the initial density in the unsaturated soil.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2001.10a
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• pp.351-354
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• 2001

Undrained cyclic triaxial compression tests were performed on Saemangeum dredged sand to evaluate factors affecting liquefaction strength and liquefaction behaviour characteristics. The results of these tests show that cyclic liquefaction can occur not only very loose sand(Relative density is 30%) but also dense sand(Relative density is 70%). To evaluate effect of the over consolidation ratio on the liquefaction strength, a series of undrained cyclic triaxial compression test was peformed, and the result of this test showed that the liquefaction of this test showed that the liquefaction strength of Saemangeum dredged sand approximately increased to square root of over consolidation ratio in the range of O.C.R value of 1.0 to 4.0. In the anisotropically consolidated sample tests, the liquefaction strength is increased by increasing the effective consolidation ratio.

• Journal of the Korean Geotechnical Society
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• v.25 no.4
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• pp.105-112
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• 2009

In this study, a series of direct shear tests were performed to investigate the characteristics of friction angles for sands and interface friction angle between sands and construction materials with respect to different relative density of the Nak-dong River sands and shearing velocity. The result of the test shows that friction angles of sands are always higher than interface friction angle between sands and construction materials. As the shearing velocity get faster, the friction angles of sand became higher. With respect to the density of sand by reducing void ratio, friction angles increase linearly, and relevant equations were proposed to calculate the friction angle by changing void ratio and relative density of sand. The interface roughness of construction materials was also an important factor in interface friction angle.

• The Korean Journal of Malacology
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• v.30 no.3
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• pp.259-271
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• 2014

This study was conducted to investigate the impact of sand addition to an intertidal for the development of the Manila clam habitat on benthic community structure. For this, we focused on the spatio-temporal changes in the surface sediment condition and benthic community structure including Manila clam before and after the event. Study site was the lower part of Ojjeom tidal flat in Gonam-myeon, Taean-gun where sand added to on July 2010. We set three stations at each of sand adding area (experimental plot) and non sand-adding area (control plot) and did sampling works ten times from June 2010 to October 2011. Directly after the event, surface sediments changed to very coarse sand, but the state was not maintained over two months because of seasonal sedimentation and finally got back to the original grain sizes in eight months. The number of species and density were temporarily reduced right after the event and polychaetes such as Sternaspis scutata, Ampharete arctica were most negatively affected by the event. However, the number of species and density quickly recovered from the reduction in four to six weeks owing to the recolonization by the existing species and species in the vicinity of the plot. However, despite the recovery of ecological indies, species composition was continuously changed from one to another, thereby community structure stayed unstable condition, especially in some stations with finer sediment in their original condition. After sand addition, density of Manila clam was prominently increased at only one station with coarser sediment in its original condition.

• Advances in environmental research
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• v.1 no.4
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• pp.305-321
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• 2012

This study entails establishing reference standard sand in Nigeria for engineering and geoenvironmental research work. Sands from four geographical locations in southwestern Nigeria were examined for baseline geotechnical and mineralogical properties. A total of sixteen sand samples were collected. The samples were air dried and subjected to tests in accordance with standard specifications. The tests carried out were: specific gravity, grain size analysis, moisture content, bulk density, porosity, void ratio, chemical analysis, X-ray diffraction and Differential Thermal Analysis. The properties of the samples were compared with a standard (Ottawa sand in Illinois of the United States) in order to find out which of the four samples selected from southwestern Nigeria could serve as standard baseline sand. The results show that Igbokoda sand has geotechnical and mineralogical characteristics closest to Ottawa sand. It was therefore concluded that Igbokoda sand could be used as a standard baseline sand for research work in southwestern Nigeria and other parts of Nigeria since it needs little processing to bring it to the same level as standard baseline sand, like the Ottawa sand.

• Geomechanics and Engineering
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• v.14 no.1
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• pp.99-105
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• 2018

Soils are generally classified as fine-grained or coarse-grained depending on the percentage content of the primary constituents. In reality, soils are actually made up of mixed and composite constituents. Soils primarily classified as fine-grained, still consists of a range of coarse particles as secondary constituents in between 0% to 50%. A laboratory scale model test was conducted to investigate the influence of coarse particles on the physical (e.g., density, water content, and void ratio) and mechanical (e.g., quick undrained shear strength) properties of primarily classified fine-grained cohesive soils. Pure kaolinite clay and sand-mixed kaolinite soil (e.g., sand content: 10%, 20%, and 30%) having various water contents (60%, 65%, and 70%) were preconsolidated at different stress levels (0, 13, 17.5, 22 kPa). The quick undrained shear strength properties were determined using the conventional Static Cone Penetration Test (SCPT) method and the new Fall Cone Test (FCT) method. The corresponding void ratios and densities with respect to the quick undrained shear strength were also observed. Correlations of the physical properties and quick undrained shear strengths derived from the SCPT and FCT were also established. Comparison of results showed a significant relationship between the two methods. From the results of FCT and SCPT, there is a decreasing trend of quick undrained shear strength, strength increase ratio ($S_u/P_o$), and void ratio (e) as the sand content is increased. The quick undrained shear strength generally decreases with increased water content. For the same water content, increasing the sand content resulted to a decrease in quick undrained shear strength due to reduced adhesion, and also, resulted to an increase in density. Similarly, it is observed that the change in density is distinctively noticeable at sand content greater than 20%. However, for sand content lower than 10%, there is minimal change in density with respect to water content. In general, the results showed a decrease in quick undrained shear strength for soils with higher amounts of sand content. Therefore, as the soil adhesion is reduced, the cone penetration resistances of the FCT and SCPT reflects internal friction and density of sand in the total shear strength.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3C
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• pp.181-190
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• 2006

The behavior of artificially cemented sands were investigated by undrained triaxial test of isotropically consolidated sample. The cementation were induced by gypsum that is generally used for the aitificial cementation of sands. The gypsum of 5~20%(sand weight) were included in the sand and cured in the mold under the overburden pressure 55kPa. The yielding strength and stiffness of cemented sand were increased as the degree of cementation. And the dilation of sand was restricted by the cementation bonds, but after breakage of the bonds, it was increased more abrupt than the uncemented sands. The effective stress path showed that the aspects of effective pore water pressure were changed as the degree of cementation and the relative density. The effective stress ratio of cemented sand in the phase transformation line and the failure line were changed by the cementation. Generally the behavior of cemented sand more influenced by the degree of cementation than the relative density.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.443-446
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• 2005

Recently, according to increase use of concrete which is the main material of construction, the natural aggregate of good quality is more and more decreased. Most of all, among the concrete materials, the development of alternation materials of sand is urgently needed. In this study, investigating the production equipment and the sample of crushed sand company and analyzing properties of sand, manufactured mortar by the KS to use crushed sand as the fine aggregate of concrete material. The experiment result is as follows. 1. The density, an absorptivity, and the amount of 0.08mm passage ratio of crushed sand, and the mortar used crushed sand satisfied KS. The mechanical results is similar to sea sand. 2. The crushed sand which used impact crusher instead of cone crusher for 3rd or 4th crusher was similar properties to sea sand, so it is judged that impact crusher has high effect of particle shape improvement of crushed sand.

• Magazine of the Korean Society of Agricultural Engineers
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• v.36 no.4
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• pp.103-116
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• 1994

The objective of this study was to determine the criteria for density and moisture content measurements made with a nuclear density meter on common materials in the construction field. The study also sought to test a full-type nuclear density meter in controlling the density of overlay layers( 2.5~5.0cm). In order to determine the accuracy and reliablility of nuclear guage measurements made on construction materials, laboratory and field tests were conducted. Wooden blocks( 65 x 45 ${\times}$ 50 cm) and a special steel compactor( 4.7kg) were constructed in order to carry out tests which were conducted on three different materials; coarse gramed soil, fine grained soil, and AC material. Throughout all laboratory and field tests, the nuclear density and moisture content were determined using Humboldt 5OOLP nuclear gauge. The tests on subgrade material entailed obtaining density measurements by means of both the sand replacement method and the nuclear density meter. The results of the sand replacement method were then compared to the readings recorded bu the meter. As in the subgrade material tests, density measurements made during AC pavement tests were also determined using the unclear meter in addition to a second means; through the core method. The meter readings and core densties were compared as was done in the tests on subgrade materials. The correlation between the results of the sand replacement test( also, the core method) and meter readings on subgrade material was then determined. Sirnilarly, the observed results were then analyzed through linear regression. The tests to determine thin-lift density by means of a full-type nuclear density meter also conducted on the overlay layers( about 4. 8cm thickness) above AC pavements at road construction sities in Korea.

• Journal of Navigation and Port Research
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• v.29 no.3 s.99
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• pp.263-268
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• 2005

Laboratory evaluation of the effect of fines, confine stress and dry density on the permeability characteristics in sand columns is presented. The triaxial permeability tests were conducted on different contents of fines(5, 15, 25, $35{\%}$), confine stress ($\sigma_3^'=0.5,\;1.0,\;2.0,\;3.0{\cal}kg/{\cal}cm^2$), and dry density($\gamma_d=1.50,\;1.55,\;1.60,\;1.65{\cal}g{\cal}cm^3$). The results of triaxial permeability tests showed that as the contents of fines, confine stress and dry density became increase permeability became decrease. For the contents of fines, when the fines that smaller than $0.01{\cal}mm$ increases the permeability decreases significantly. For the confine stress and the dry density, the permeability is decreased significantly at changes of the confine stress($\sigma_3^'=0.5{\~}1.0{\cal}kg/{\cal}cm^2$) and the dry density($\gamma_d=1.50{\~}1.55{\cal}g/{\cal}cm^3$) at lower levels.