• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.1254-1259
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• 2008

Recently, centrifuge tests have been widely used as tools in geotechnical engineering researches in domestic and foreign. However, the size of these centrifuge facilities is very large and thus the tests require for long time, high expense, and many labors. In this study, therefore, a small capacity(2g ton) of instructional centrifuge, which can conduct tests in a short period of time effectively, was introduced. The results of centrifuge tests conducted on the retaining wall both passive and active cases was used. Medium size of sand was used with sieve off fines in sand using #40 sieve. Based on the test results, this centrifuge facility introduced in here can be enough used for geotechnical engineering education for graduate and undergraduate students.

• Journal of Soil and Groundwater Environment
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• v.19 no.3
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• pp.39-46
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• 2014

Hydraulic conductivity is an important parameter, representing permeable property of the groundwater in aquifers, in the issues of groundwater development, groundwater contamination, and groundwater flow, etc. We estimated a relationship between hydraulic conductivity and electrical properties (formation factor, chargeability, and time constant) of silty sand in the laboratory. For this study, we conducted grain size analysis, constant head permeameter test, and measured electrical resistivity and spectral induced polarization of silty sand samples collected from the riverside alluvium of the Nakdong River in Nogok-ri area, Dasan-myeon, Goryeong-gun in Gyeongbook Province, Korea. In the laboratory test, we used soil samples of approximately uniform porosity with 0.5% error range, and kept the electrical resistivity of pore water with 100 ohm-m. As a result, the relationship between effective particle size and hydraulic conductivity agrees fairly well with the existing empirical formulas. Hydraulic conductivity was correlated with formation factor, chargeability, and time constant: hydraulic conductivity increased with increasing formation factor and time constant as well as with decreasing chargeability.

• Economic and Environmental Geology
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• v.57 no.2
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• pp.185-204
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• 2024

This study was conducted for evaluation the geological, physical, and chemical properties of domestic sand by analyzing about 4,800 quality data of natural sand from river and land area surveyed until 2023 through the aggregate resource survey conducted by the Ministry of Land, Infrastructure and Transport. The average depth of the Quaternary unconsolidated sedimentary layer in Korea, which includes a sand layer, is about 10m (maximum depth 66m). The thickness of the sand layer within the sedimentary layer is most dominant in the range of 0.5m to 4.0m. This accounts for about 70% of the entire sand layer. In the sand layer, the ratio of sand, gravel, and clay is 60:20:10. Regardless of the provenance or geology, the sand is mainly composed of quartz, plagioclase, and K-feldspar, and the minor minerals are muscovite, biotite, chlorite, magnetite, epidote. The sand includes in 45~75% of quartz, 5~20% of plagioclase and K-feldspar, each other. And other minor minerals are included in 10%. The average grain size of sand is 0.5mm to 1.0mm, which accounts for 44% of sand samples. The water absorption rate and soundness are estimated to be suitable for aggregate quality standard in almost all sand, and the absolute dry density is suitable for 66%.

• Journal of the Korean GEO-environmental Society
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• v.7 no.6
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• pp.67-73
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• 2006

In this study, basic physical tests and mechanical tests of crushed rock were performed in order to investigate the field application of crushed rock as substitute materials of sand that is commonly being used as foundation and backfill materials of sewer conduit. Particle-size distribution curve of crushed rock is similar to sand and also it is well-graded soil than common sand. Maximum dry unit weight in proctor compaction test for crushed rock is higher than the values of common sand. So we can estimate that the crushed rock has advantages in workability than sand for the backfill compaction after construction of sewer conduit. When we investigate the results of direct shear test and triaxial compression test on the crushed rock, it has a similar value of shear strength parameters to sand at the same stress state and as time goes by, it tends to increase the unconfined compression strength. But, because the strength reaches at the constant value after 6~7 days, we expect that it can absorb the lateral strain of flexible conduit well. All the above experimental results just proves that crushed rock can substitute for sand as backfill materials and foundation of sewer conduit.

• 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.

• Geomechanics and Engineering
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• v.1 no.3
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• pp.219-239
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• 2009

Vertical vibration tests were conducted using model footings of different size and mass resting on the surface of finite sand layer with different height to width ratios and underlain by either rigid concrete base or natural red-earth base. A comparative study of the ratio of predicted and observed natural frequency ratio of the finite sand stratum was made using the calculated values of equivalent stiffness suggested by Gazetas (1983) and Baidya and Muralikrishna (2001). Comparison of results between model footings resting on finite sand stratum underlain by the rigid concrete base and the natural red-earth base showed that, the presence of a finite base of higher rigidity increases the resonant frequency significantly. With increase in H/B ratio beyond 2.0, the influence of both the rigid concrete and natural red-earth base decreases. Increase in the contact area of the footing increases the resonant frequency of the model footings resting on finite sand stratum underlain by both the types of finite bases. Both the predicted and the observed resonant frequency ratio decreases with increase in force rating and height to width ratio for a given series of model footing.

• Proceedings of the Korean Environmental Health Society Conference
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• 2001.11a
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• pp.1.1-5
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• 2001

High SPM concentrations(199.8~249.4${\mu}{\textrm}{m}$/㎥) were detected in the west Korea during the Yellow Sand Periods, 2000. Majority of the total SPM were composed of about 5${\mu}{\textrm}{m}$ sized coarse particles over the periods. However, fine particles sized about 1 ${\mu}{\textrm}{m}$ and coarse particles sized about 5-6${\mu}{\textrm}{m}$ showed peaks at the graph of SPM size distribution in the Non Yellow Sand Period. Airborne fungal spores at the SPM samples were cultured and identified. Full-grown colonies during the Yellow Sand Periods, Fusarium, Aspergillus, Penicillium and Basipetospora are hyphomycetes in the division Fungi imperfecti(Deuteromycota). And morphologically more diversified mycelia of hyphomycetes were grown on the sample captured from 1.1~2.1${\mu}{\textrm}{m}$ sized SPM than on other sized samples during the Yellow Sand Period. But no mold was observed on the sample of 1.1~2.1${\mu}{\textrm}{m}$ sized SPM in the Non Yellow Sand Period. It was thought that several sorts of fine sized fungal spores were suspended in the atmospheric environment of the west Korea during the Asian dust episodes.

• Proceedings of the Korean Geotechical Society Conference
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• 1998.10a
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• pp.373-380
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• 1998

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2000.04a
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• pp.134-135
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• 2000

에어로졸은 인위적으로 발생하거나 자연적으로 발생하는 먼지(토양 발생인 먼지, 생물학적 비해염입자, 유기입자 둥)로 나뉘어지는 데 자연적으로 발생하는 먼지의 대표적인 사례로 황사를 들 수 있다. 이는 시정악화나 해수성분의 변화, 강수의 pH 변화 등 여러 가지 방면에서 영향을 주고 있는 것으로 나타나고 있다(Parungo et al., 1995). 동북아시아 지역의 지역적인 특수성으로 인해 미네랄 에어로졸 표면에서의 화학반응 활성화가 황산염이나 질산염의 생성을 유발한다는 여러 가지 보고가 있다. (중략)

• Journal of the Korean Geotechnical Society
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• v.28 no.2
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• pp.33-42
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• 2012

The purpose of this study is to determine the effect of soil grain size and its distribution on soil-water characteristic. To do this, soil-water characteristic tests were conducted on Saemangeum silt using the axis translation technique. For comparison, the test was also conducted on Jumunjin sand. Using the test results, the soil-water characteristic curves (SWCCs) of Saemangeum silt and Jumunjin sand were predicted by Van Genuchten model. By comparison and analysis between two SWCCs, the silt shows higher values of matric suction, water content, and air entry value than the sand. On the other hand, the sand has higher values of Van Genuchten model parameters of ${\alpha}$, $n$, $m$ than the silt. It indicates that the SWCC is significantly dependent on the structure of soils. In other words, if a soil has relatively high grain size and poor grain size distribution curve, the values of saturated volumetric water content, residual volumetric water content, and air entry value are small, and the variation of volumetric water content is high in accordance with the matric suction variation, and consequently it shows a narrow range of funicular region.