• Magazine of the Korean Society of Agricultural Engineers
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• v.36 no.3
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• pp.74-83
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• 1994

A series of isotropic consolidation tests, undrained and drained triaxial compression tests was carried out to investigate the physical characteristics and behaviours of marine silty sands collected from the western coast of Korea. This study also included a theoretical development of the constitutive equation to evaluate stress-strain relationship and volume change of silty sands. The results and main conclusions of the study are summarized as follows; 1. Isotropic compression and swelling index are linearly decreased with an increase in relative density. 2. Both undrained shear strengh and elastic modulus are increased with an increase in relative density and confining pressure. 3. Internal friction angles obtained from drained and undrained compression tests of the soils are proportional to relative density. 4. The phenomenon of dilatancy of each sample is less profound when confining stress is increased but more profound when relative density is increased. 5. The slope of critical state lines is 1.78 for Saemangum, 1.70 for Siewha and 1.26 for Sukmoon sands. 6. In this study, Drucker-Praper type criterion is used and hardening function of Cap model is modified by hyperbolic fuction. This will improve a lack of physical meaning of hardening parameters in conventional Cap model. 7. A newly developed constitutive equation to the forementioned silty sands and checked its applicability. This is in good agreement with the measured data.

• Journal of The Geomorphological Association of Korea
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• v.25 no.4
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• pp.21-35
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• 2018

The distribution and size of sandy beaches along eastern Korea has a close relationship with the presence of granite rocks. In general, elongated and wide beaches with abundant sands are likely to develop along the coasts where granitic basic rocks comprise the dominant geology or where a large amount of sands are supplied by streams from inland granitic rocks. Small sandy beaches, in contrast, appear in non-granitic rocks (i.e., under sedimentary and/or metamorphic geology). Hence, large beaches are observed continuously along the shore of Gangwon-do, of which coasts consist predominantly of granitic geology. Such continuity declines from Samcheok city to Pohang city. The rock of Gyeonbuk-do is commonly known as sedimentary, deposited between the late Triassic and the early Tertiary Periods. Because few sands are supplied from the upstream areas, sandy beaches unlikely develop along the coasts of the province, only showing a sporadic, discontinuous distribution under Bulguksa granite, granitic gneiss, and some volcanic rocks. Erosion was rarely observed in the beaches where granitic rocks are distributed, whereas merely five beaches seemed to have undergone some level of erosion in non-granitic regions. This is presumably because a larger amount of sands than that which had been eroded away was replenished in areas under granitic geology, while under non-granitic geology having a deficit in sands, no large sandy beaches had formed at first.

• 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.

• Korean Journal of Veterinary Service
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• v.25 no.2
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• pp.111-116
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• 2002

To demonstrate the prevalence of Toxocara spp eggs in public playgrounds in Seoul city, sand samples collected from March to November in 2001 were examined. Of 2,600 sand samples from 650 playgrounds surveyed, 41 sands from 39 places(6%) had Toxocara rims eggs. Sand samples in apartment complex were more contaminated(9.7%) with the eggs than in residential area(2.4%). Toxocara canis eggs in sands were found in large number of in the spring but other seasons were less found.

• Journal of Korean Society for Atmospheric Environment
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• v.7 no.2
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• pp.89-95
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• 1991

Yellow sands often occur in Korea during April and May each year, and they are believed to come from the Mongolian Gobi desert as the snow starts to melt in Spring time. Since the analysis of aerosol particulates can hardly distinguish the origin of particulates, the isentropic analysis of meteorological data is often used for the trajectories of the long range transport of yellows sand or air pollutants. The yellow sand case of April 9 $\sim$ 15, 1988, in Korea is analyzed for the identification of long range transport of yellow sands and their trajectories in East Asia, using isentropic analyses. We have tranformed the ECMWF grid data, analyzed in pressure coordinates, into the isentropic coordinates and then have traced the 286 K and 290 K air mass which started Gobi desert. The result shows the transport of yellow sands from the Gobi desert to the Korean peninsula.

• Journal of Industrial Technology
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• v.21 no.A
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• pp.285-292
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• 2001

The amount used of aggregates for concrete is increasing rapidly since the mid-1980s in Korea. The natural gravels from river are already displaced with crushed stone, and use of crushed sand as a substitute of natural river sands, also, is getting increased day by day. This paper is presented for mixture of high strength concrete using crushed sands. Mixing design of concretes are various water-cement ratios(w/c) such as 25%, 40%, 55% and different replacement ratio of crushed sands to natural sands such as 0%, 20%, 40%, 60%. As a results, it has been shown that compressive strength of concretes with w/c lower than 40% and 25% is higher than $400kgf/cm^2$ and $600kgf/cm^2$ respectively.

• KSBB Journal
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• v.13 no.4
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• pp.449-455
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• 1998

The bacterial motility in sand was studied with Alcaligenes xylosoxidans Y234 which is known as a strong decomposer of aromatic chemicals, especially toluene. Apparent motility coefficient (${\mu}$c,app) and apparent chemotaxis coefficient (${\mu}$c,app) for toluene were measured in the sands which have four different porosities. Adsorption ratio of Alcaligenes xylosoxidans Y234 on the sands was measured as 17%. The ramdom motility coefficients were 0.85∼1.68${\times}$10-3$\textrm{cm}^2$/sec, and decreased as the porosity of sands decreased. Apparent chemotaxis coefficients were measured as 1.1∼6.8${\times}$10-5$\textrm{cm}^2$/sec, and decreased as the porosity decreased and with time. The tendency of alcaligenes xylosoxidans Y234 movement towards toluene seemed very weak and showed little chemotaxis.

• Computational Structural Engineering
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• v.22 no.5
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• pp.52-58
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• 2009

• International Journal of Concrete Structures and Materials
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• v.3 no.1
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• pp.3-9
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• 2009

This paper examines the incorporation of the crushed sand (CS) and desert sand (DS) in the formation of self compacting concrete (SCC). These sands have been substituted for the rolled sand (RS), which is currently the only sand used in concretes and which is likely to run out in our country. DS, which comes from the Tunisian Sahara in the south, is characterized by a tight distribution of grains size. CS, a by-product of careers containing a significant amount of fines up to 15%, is characterized by a spread out granulometry having a maximum diameter of around 5mm. These two sands are considered as aggregates for the SCC. This first part of the study consists in analyzing the influence of the type of sand on the parameters of composition of the SCC. These sands consist of several combinations of 3 sands (DS, CS and RS). The method of formulation of the adopted SCC is based on the filling of the granular void by the paste. The CS substitution to the RS made it possible, for all the proportions, to decrease the granular voids, to increase the compactness of the mixture and to decrease the water and adding fillers proportioning. These results were also obtained for a moderate substitution of DS/CS (< 40%) and a weak ratio of DS/RS (20%). For higher proportions, the addition of DS to CS or RS did not improve the physical characteristics of the SCC granular mixture.

• Journal of the Korean Geotechnical Society
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• v.21 no.8
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• pp.13-26
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• 2005

It was known that the aging effect of sands is insignificant in comparison with clays, and hence the study on this effect had seldom been performed prior to the early 1980s. However, field tests for this effect have been actively carried out since it was investigated that penetration resistance of reformed sands increased with the lapse of time. Recently, the aging effect of sands has also been examined in laboratory testings. In this study, undrained static triaxial tests were performed to evaluate the effect on the Nak-dong River sands, with different .elative densities $(D_r)$, consolidation stress ratios $(K_c)$, and consolidation times. As a result of the tests, it was proved that the undrained cyclic shear strength $(R_f)$ increased with the aged time on the sands. The in situ range of Rf on the sands, which is applicable to the magnitude of earthquake in the Nak-dong River area, was proposed by using the test results.