• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.209-216
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• 2000

When subjected to earthquake shaking, saturated sandy soil may generate excess pore pressure. And a time may come when initial confining pressure will equal to excess pore pressure. Depending on the characteristics of the soil and the length of the drainage path, excess pore pressure was dissipated after earthquake. For this reason, it was induced settlement in grounds and fatal damage of various structures. In this study, settlement in silty sand grounds induced earthquake was evaluated using post-liquefaction constitutive equation between volumetric strain and shear strain from previous study. Using that, it was proposed that simplified estimation of settlement in silty sand grounds induced liquefaction.

• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.6
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• pp.59-70
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• 2005

A series of resonant column test was performed to investigate the dynamic deformation characteristics of silty sand soils mixed with polypropylene fibrillated type fiber. Results show that optimum mixing ratios were $0.2\%$ for 19mm of cut fiber for shear modulus and $0.1\%$ for 60mm cut fiber fur damping ratio. As shear strain was increased, normalized values of shear modulus (G(Reinforced)/ G(Unreinforced)) of fiber reinforced soil were increased up to $10^{-3}\%\~10^{-1}\%$ ranges. However, normalized damping ratio (D(Reinforced/D(Unreinforced)) was diminished with an increase in strain beyond $10^{-3}\%\~10^{-1}\%$ for the damping capacity of soils mixed with fiber. Normalized shear modulus $(G/G_{max})$ obtained from the test was plotted in the chart suggested by Seed and Idriss. The shear modulus of silty sand was located between sand and gravel curves.

• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.6
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• pp.95-103
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• 1998

Solutions of geotechnical engineering problems require calculation of deformation and stresses during various stages of loading. Powerful numerical methods are available to make such calculation even for complicated problems. To get accurate results, realistic stress-strain relationships of soil are dependent on a number of factors such as soil type, density, stress level and stress path. Attempts are continuously being made to develope analytical models for soils incorporating all such factors. The nature of stress-path dependency, the principle that governs deformations in sand, and the use of Lade's single work-hardening model for predicting sand response for a variety of stress-paths have been investigated and are examined. The test results and the analyses presented show that under some conditions sand exhibits stress-path dependent behavior. The strains calculated from Lade's single work-hardening model are in reasonable agreement with those measured, but some discrepancies occur. The largest difference between measured and calculated strains occurs for proportional loading with increasing stresses and for stress-path directions.

• Earthquakes and Structures
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• v.14 no.4
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• pp.323-336
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• 2018

Machine foundations with impact loads are common powerful sources of industrial vibrations. These foundations are generally transferring vertical dynamic loads to the soil and generate ground vibrations which may harmfully affect the surrounding structures or buildings. Dynamic effects range from severe trouble of working conditions for some sensitive instruments or devices to visible structural damage. This work includes an experimental study on the behavior of dry dense sand under the action of a single impulsive load. The objective of this research is to predict the dry sand response under impact loads. Emphasis will be made on attenuation of waves induced by impact loads through the soil. The research also includes studying the effect of footing embedment, and footing area on the soil behavior and its dynamic response. Different falling masses from different heights were conducted using the falling weight deflectometer (FWD) to provide the single pulse energy. The responses of different soils were evaluated at different locations (vertically below the impact plate and horizontally away from it). These responses include; displacements, velocities, and accelerations that are developed due to the impact acting at top and different depths within the soil using the falling weight deflectometer (FWD) and accelerometers (ARH-500A Waterproof, and Low capacity Acceleration Transducer) that are embedded in the soil in addition to soil pressure gauges. It was concluded that increasing the footing embedment depth results in increase in the amplitude of the force-time history by about 10-30% due to increase in the degree of confinement. This is accompanied by a decrease in the displacement response of the soil by about 40-50% due to increase in the overburden pressure when the embedment depth increased which leads to increasing the stiffness of sandy soil. There is also increase in the natural frequency of the soil-foundation system by about 20-45%. For surface foundation, the foundation is free to oscillate in vertical, horizontal and rocking modes. But, when embedding a footing, the surrounding soil restricts oscillation due to confinement which leads to increasing the natural frequency. Moreover, the soil density increases with depth because of compaction, which makes the soil behave as a solid medium. Increasing the footing embedment depth results in an increase in the damping ratio by about 50-150% due to the increase of soil density as D/B increases, hence the soil tends to behave as a solid medium which activates both viscous and strain damping.

• Journal of the Korean Geotechnical Society
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• v.32 no.7
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• pp.35-45
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• 2016

Estimation of vertical bearing capacity is critical in the design of bucket foundation used to support offshore structure. Empirical formula and closed form solutions for bucket foundations in uniform sand or clay profiles have been extensively studied. However, the vertical bearing capacity of bucket foundations in alternating layers of sand overlying clay is not well defined. We performed a series of two-dimensional axisymmetric finite element analyses on bucket foundations in sand overlying clay soil, using elasto-plastic soil model. The load transfer mechanism is investigated for various conditions. Performing the parametric study for the friction angles, undrained shear strengths, thickness of sand layer, and aspect ratios of foundation, we present the predictive charts for determining the vertical bearing capacities of bucket foundations in sand overlying clay layer. In addition, after comparing with the finite element analysis results, it is found that linear interpolation between the design charts give acceptable values in these ranges of parameters.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.04a
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• pp.191-194
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• 2002

토양증기추출(Soil Vapor Extraction)법을 이용하여 대표적 휘발성 NAPL (Non-aqueous phase liquid)인 TCE (trichloroethylene)와 toluene을 토양으로부터 제거하는 칼럼 실험을 실시하였다. 토양특성 및 증기추출 조건들이 정화효율에 미치는 영향을 규명하는데, 균질한 Ottawa sand와 실제 오염지역의 토양들을 직경 2.5cm, 길이 30cm인 유리 칼럼이 충진시켰으며, 빨갛게 염색된 TCE 또는 toluene 4 g이 주입되었다 공기 유량계를 설치하여 0.03L/min의 일정한 속도로 공기가 주입되도록 하고, 퍼지장치를 설치하여 주입 공기의 습윤도를 99% 이상으로 유지하였다. 가스크로마토그래피로 유출 가스 농도를 분석하였다. Ottawa sand로 충진된 칼럼실험에서는 매질의 입자크기, 함수율, 토양 내 오염물 체류시간 등을 변화시켜 실험을 반복하였다. TCE로 오염된 세립질 Ottawa sand 칼럼실험에서 유출 공기의 최대 농도는 조립질 Ottawa sand 칼럼의 유출 농도보다 약 20% 정도 감소하였고, 오염지역의 실제토양 칼럼실험에서는 최대유출농도가 조립질 Ottawa sand 칼럼의 농도보다 약 50% 감소하였으나, 20 liter공기 주입 후부터는 모두 비슷한 농도감소 현상을 나타내었으며, 초기 주입량의 90 % 이상이 제거되었다. 함수율증가에 따른 유출공기의 농도 감소는 거의 나타나지 않았으며, TCE 주입 후 7일 동안 방치하였다가 SVE를 실시한 칼럼 실험에서도 잔류하는 TCE의 양이 약간 증가하였지만 20 liter 공기 추출 후에는 초기 주입량의 90% 가, 40 liter공기 추출 후에는 98% 이상이 제거되었다. Toluene으로 오염된 칼럼 실험에서도 TCE와 비슷한 제거 경향을 나타냈으며 200 liter 공기 추출 후에는 오염물 초기 주입량의 98% 이상이 제거되었다. 본 실험 결과로부터 증기추출법을 이용한 TCE, toluene 정화 효율성이 규명되었으며, 휘발성 NAPL로 오염된 실제 토양을 복원하기 위한 SVE법의 적용가능성을 확인할 수 있었다.

• Journal of the Korean GEO-environmental Society
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• v.13 no.8
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• pp.65-73
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• 2012

Soil-rock interface, mainly founded in Granite region of Korea, is known as one of the important factor of the slope failure at the rainfall due to smaller shear strength than soil itself. However, research of the effect on slope stability by soil-rock interfaces is insufficient. Therefore, a series of direct shear tests were performed in order to investigate the effect of soil-rock interface on slope stability. The method of tests is to get sand itself and sand-artificial rock interface shear strength from different grain size of sands and artificial rock samples. The results of tests show that the friction angle of interface depends primarily on particle size and surface roughness. Interface friction angle ratio ${\mu}(={\delta}/{\Phi})$ is in the range of 0.75 ~ 0.96, this results indicate that interface friction angle is smaller than sand itself.

• Journal of the Korean GEO-environmental Society
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• v.12 no.2
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• pp.23-33
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• 2011

In this paper, we got soil-water characteristic curve(SWCC) of Nak-Dong River's sand respectively as relative density 40%, 60%, 80% and content of silt 0%, 10%, 20%, 30%. As a result, the more the sand densify in the same silt content and the more the sand has silt in the same relative density, the change of volume water content was decreased. we have known effect of silt contents for SWCC and verified existing empirical formula of SWCC. As experiment results of soil-water characteristic curves compared to the empirical solutions, the results of van Genuchten(1980) and Fredlund & Xing(1994) were well-matched showing S type curves with experiment results. Especially the empirical solution of Fredlund & Xing showed almost same results of the coefficient of correlation($R^2$) equal to 0.99.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.243-247
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• 2004

Tile development of a porous iron-oxide coated sand filter system can be modelled with the analytical solution of tile transport equation in order to obtain the operating parameters and investigate the mechanism of arsenic removal. The adsorbed amount from the model simulation showed the limitation of adsorption removal during arsenic transport. A loss reaction term in the transport equation plays a role in the mass loss in column conditions, and then resulted into the better model fitting, particularly, for arsenate. Further, the competitive oxyanions delayed the breakthrough near MCL (10 $\mu$g/L) due to the competitive adsorption. This is the reason why arsenate can be strongly attracted in tile interface of an iron-oxide coated sand, and competing oxyanions can occupy the adsorption sites. Therefore, arsenic retention was regulated by non-equilibrium of arsenic adsorption in a porous iron-oxide coated sand media. The transport-limited process seemed to be affect the arsenic adsorption by coated sand.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.78-82
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• 2003

Development of hematite-coated sand was evaluated for the application of the PRB (permeable reactive barrier) in the arsenic-contaminated subsurface of the metal mining areas. The removal efficiency of As(III) and As(V), the effect of anion competition and the capability of arsenic removal in the flow system were investigated through the experiments of adsorption isotherm, arsenic removal kinetics against anion competition and column removal. Hematite-coated sand followed a linear adsorption isotherm with high adsorption capacity at low level concentrations of arsenic (< 1.0 mg/l). When As(III) and As(V) underwent adsorption reactions in the presence of anions (sulfate, nitrate and bicarbonate), sulfate caused strong inhibition of arsenic removal, and bicarbonate and nitrate caused weak inhibition due to specific and nonspecific adsorption onto hematite, respectively. In the column experiments, high content of hematite-coated sand enhance the arsenic removal, but the amount of the arsenic removal decreased due to the higher affinity of As(V) than As(III) and reduced adsorption kinetics in the flow system, Therefore, the amount of hematite-coated sand, the adsorption affinity of arsenic species and removal kinetics determined the removal efficiency of arsenic in the flow system. arsenic, hematite-coated sand, permeable reactive barrier, anion competition, adsorption.