• Water for future
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• v.6 no.2
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• pp.12-18
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• 1973

This paper describes the study and test for sand and gravel embankment in winter season and also contribute to the development of construction method for the practical purposes. In order to make possible sand and gravel embankment in winter season, at first, the following eriteria on work are given under the normal weather condition: 1) The maximum diameter of material shall not exceed 30cm and sand content which is the ratio of the weight of sand to gravel shall not exceed 60% 2) Spreading depth shall not exceed 60cm each layer of material shall be compacted by over 6 times passing by thell ton smooth drum type of uibratory roller and the relative density shall exceed 60% In addition to the above conditions, the following criteria are given as winter season condition. 3) Sand contsnt shall not exceed 25%, and water content shall not exceed 4% 4) Dwing construction, the air temperature should be $70^{\circ}C$ below zero at minimum and $3^{\circ}C$ below zero onthe average and all the construction work should he continued without intersuptions. With above criteria, it is come to a conclusion that the conclusion that the construction of sand and gravel embankment in winter season will be done satisfactorily without any difficulty. On the basis of these criteria an actual construction was practiced and it was proved that those criteria are applicable to actual embankment of materials.

• Journal of the Korean Geotechnical Society
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• v.24 no.4
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• pp.67-78
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• 2008

In this study, artificial cemented sand made of a few portland cement and Nak-Dong river sand was researched closely to investigate cementing effect quantitatively through unconfined tests and triaxial tests. The peak strength and elastic modulus increased and dilation of cemented sand was restricted by the cementation, but after breakage of the cementation, dilation and negative excess pore water pressure increased. In stress-strain curve, strain-softening behavior appeared in drained condition but strain-hardening behavior was appeared in undrained condition as a result of the increase of effective stress. The test was quantitatively analyzed by multiple regression models, correlating each response variable with input variable. The equations are valid only over the range investigated. Its adjusted coefficient of determination was $0.81{\sim}0.91$, and dry density is important factor for estimating strength of cemented sand.

• The Korean Journal of Malacology
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• v.29 no.3
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• pp.207-216
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• 2013

Changes in density of manila clam, Ruditapes philippinarum to environment, catch and recruitment were studied in a few stations (Seonjae, Seongam, Hwangdo and Padori) in the West coast area of Korea from January, 2007 to December, 2009. Water temperature, salinity, dissolved oxygen and pH in the study stations were 0.8 to $31.2^{\circ}C$, 22.1 to 33.7 psu, 5.0 to 12.0 mg/L and 7.39 to 8.99, respectively. The concentrations of dissolved inorganic nitrogen, phosphate and silicate were 0.016 to 1.281 mg/L, 0.004 to 0.093 mg/L and 0.016 to 1.617 mg/L, respectively. Chlorophyll-a ranged from 0.2 to 12.1 ${\mu}g/L$, respectively. Substrata were mainly composed of muddy sand and very poorly sorted in Padori, muddy sand and well sorted in Seonjae and Hwangdo, gravelly muddy sand and poorly sorted in Seongam. Density was high in Seonjae and Seongam, but low in Hwangdo and Padori. In clam culture station, in which spat was naturally produced without sowing seedlings, the living density was decreased by increasing of death and a catch of shellfish, and recruitment was changed. Also, Density affected condition factor and shape of clam. Condition factor was the highest in Hwangdo, in which temperature in the winter and chlorophyll-a were high, and was the lowest in Padori. In the shape of clam, the shape in Seongam was a elongated form, but in Padori was a stunted form.

• Journal of the Korean Geotechnical Society
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• v.27 no.6
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• pp.63-79
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• 2011

In this study relative density tests of bottom ash and standard sand were carried out. And cyclic triaxial tests for samples with the relative density of 40%, 55%, and 70% were carried out on the basis of the test results. Cyclic triaxial tests were also conducted for fines content with 55% relative density. Residual samples were divided into No.40, No.60, No.60, and No.100, and No.200. In order to avoid crashing that can happen when compaction of the sample is initiated, bottom ash was crushed using the a compact mold. In consideration of the crushing characteristics of each residual samples, the fragmentation rate increased up to 30%, which led to the adjustment of fine-grained amount to 10%, 20%, and 30%. Through the repative triaxial test in accordance with the relative density, resistant characteristics of the liquefaction of bottom ash was analyzed. Test results show that, crushing strength of bottom ash was smaller than that of standard sand, resulting in different liquefaction behavior characteristics. And we could find fines content with maximum resistant characteristics of the liquefaction.

• Journal of the Korean GEO-environmental Society
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• v.4 no.3
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• pp.51-59
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• 2003

Loading tests were carried out for model geocell to study the reinforcing effect by variation of tensile strength, cell height, soil density and embedded depth of geocell. From the result, it could be seen that the ultimate bearing capacity of the geocell system was influenced rather by the connection strength than by the tensile strength of geocell material. Bearing capacity increased with the increase of height to width ratio of geocell for the same relative density, strength and embedded depth. And the bearing capacity ratio(BCR) was higher at low relative density of sand than that of high relative density. The increase of bearing capacity was higher at geocell with high tensile strength than that of low tensile strength. And the influence was clear at higher relative density. Also the BCR was higher at shallow embedded depth of geocell. Without consideration of tensile strength of material, the application of bearing capacity formula suggested by Koerner seems not suitable for the special case with low tensile strength of geocell material.

• Horticultural Science & Technology
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• v.19 no.2
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• pp.179-185
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• 2001

Throughout the world, physical and chemical analyses of horticultural substrates are carried out in many different ways at the different laboratories. In Europe, standardization in properties and analytical methods of horticultural substrates has been a topic over the last decades. As a result, the CEN methods as European standard methods for the physical and chemical analyses were introduced and the final draft was reported in 1999 by CEN(Committee for European Standardization). Dry matter and moisture content are analyzed after drying samples at $103^{\circ}C$. Laboratory compacted bulk density is analyzed by determining the weight of sample compacted in the test cylinder with constant volume. Dry bulk density, particle density, total pore space, water volume, air volume and volume shrinkage are determined by saturating, draining and drying the sample using double rings and a sand suction table. pH and EC are analyzed by 1:5(sample:distilled water) extraction method on the basis of volume. Organic matter and ash content are determined after drying and combusting the samples. Now, CEN methods are being regarded almost as European standard methods. Further study needs to be carried out for universal applicability of the CEN methods to all the substrates.

• Geomechanics and Engineering
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• v.28 no.5
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• pp.521-529
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• 2022

This research work deals with the development of air pluviation method for preparing uniform sand specimens for conducting large scale laboratory testing. Simulating real field conditions and to get reliable results, air pluviation method is highly desirable. This paper presents a special technique called air pluviation or sand raining technique for achieving uniform relative density. The apparatus is accompanied by a hopper, shutters with different orifice sizes and numbers and set of sieves. Before using this apparatus, calibration curves are drawn for relative density against different height of fall (H) and shutter sizes. From these calibration curves, corresponding to the desired relative density of 60%, the shutter size of 13mm and height of fall of 457.2 mm, are selected and maintained throughout the pluviation process. The density obtained from the mobile pluviator is then verified using the Dynamic Cone Penetrometer (DCP) test where the soil is poured in the box using defined shutter size and fall height. The results obtained from the DCP test are averaged as 60±0.5 which was desirable. The mobile pluviator used in this research is also capable of obtaining relative densities up to 90%. The instrument is validated using experimental and numerical approach. In numerical study, Plaxis 3D software is used in which the soil mass is defined by 10-Node tetrahedral elements and 6-Node plate is used to simulate plate behavior in the validation phase. The results obtained from numerical approach were compared with that of experimental one which showed very close correlation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.6
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• pp.178-184
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• 2017

This study was aimed to investigate the tensile behaviors of PE(Polyethylene) fiber-reinforced highly ductile cementitious composites with different combinations of micro silica sand and normal sand(river sand) with maximum particle size of 4.75 mm. Flow test result indicated the increase of flowability with higher replacement ratio of river sand. There was no noticeable difference in the mean compressive strength with different replacement ratio of river sand, but the variation in the compressive strength increased as higher amount of river sand was adopted for the replacement. The difference in the uniaxial tensile strength was negligible, but the tensile strain capacity was significantly influenced by the replacement ratio of river sand. It is thought that increased density of multiple cracks induced improved tensile strain capacity when higher percentage of river sand was adopted for fine aggregate. The deviation in the strain capacity increased as the replacement ratio of river sand was higher, as in the compressive strength. This study presented the feasibility of using normal sand instead of micro silica sand for highly ductile cementitious composites with equivalent or better uniaxial tensile performance, even though it might increase the deviation in the performance.

• Journal of the Korean Geotechnical Society
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• v.26 no.3
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• pp.5-12
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• 2010

In this study, in order to clarify the effect of the direction of cyclic shear on the post-earthquake settlement the multi-directional shear tests were carried out for Toyoura Japan standard sand, Genkai natural sand, Kaolinite and the Granulated Blast Furnace Slag (GBFS). The diameter and the height of the specimen are 75 mm and 20 mm, respectively. In a series of tests, the number of strain cycles was adjusted as n=5, 20, 30, 100, 200 and the shear strain amplitudes were varied from 0.1% to 1.0%. The relative densities of each samples were also adjusted as Dr=50, 60 and 70%. From the test results for Toyoura sand and GBFS, it is clarified that the post-earthquake settlement is relatively large at the small relative density and becomes large with the shear strain amplitude. When the influence of difference on the direction of cyclic shear decreases, the post-earthquake settlement strain for Toyoura sand is converged to a constant value, but the GBFS increases with the number of strain cycles. In addition, the post-earthquake settlement is in the order of Kaolinite > Toyoura sand > Genkai sand > GBFS.

• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.281-290
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• 2003

In order to investigate recycling possibility as a construction material of oyster-shells, the geotechnical characteristics including permeability, confined compression and shear strength of crushed oyster shell were quantitatively examined in terms of fineness modulus and relative density of crushed oyster-shell. Experimental results show that the crushed oyster-shells are lighter than sand in weight, and have similar characteristics on permeability and shear strength to sandy soils. The oyster-shell can be considered as highly crushable material but not much crushable with existing high loads. Based on the laboratory test results, it is highly fudged that the crushed oyster-shell can be a substitute of sand as SCP materials.