• Geomechanics and Engineering
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• v.3 no.2
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• pp.83-108
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• 2011

The effect of non-plastic fines (silt) on liquefaction and pore pressure generation characteristics of saturated sands was studied through undrained stress controlled cyclic triaxial tests using cylindrical specimens of size 50 mm diameter and height 100 mm at different cyclic stress ratios and at a frequency of 0.1 Hz. The tests were carried out in the laboratory adopting various measures of sample density through various approaches namely gross void ratio approach, relative density approach, sand skeleton void ratio approach, and interfine void ratio approach. The limiting silt content and the relative density of a specimen were found to influence the undrained cyclic response of sand-silt mixtures to a great extent. Undrained cyclic response was observed to be independent of silt content at very high relative densities. However, the presence of fines significantly influenced this response of loose to medium dense specimens. Combined analyses of cyclic resistance have been done using the entire data collected from all the approaches.

• Journal of the Korean Institute of Landscape Architecture
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• v.37 no.4
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• pp.94-99
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• 2009

The purpose of this study was to utilize hydroculture by the vital means of the improvement of indoor relative humidity. This experiment employed a search of the effect of Scindapsus aureus and Syngonium podophyllum that are generalized for hydroculture foliage plant by a difference of volume ratio, pot media and plants species. In the case of Scindapsus aureus, relative humidity was high for growth chamber in which plants presented as opposed to control growth chambers in which there were no plants. Although relative humidity was 25% in control chamber, there was an increase of 40% at a 2% volume ratio, 45% at a 3% volume ratio and 50% at a 5% volume ratio. The relative humidity of Syngonium podophyllum was 40% at a 2% volume ratio, 44% at a 3% volume ratio and 46% at a 5% volume ratio, while the control treatment was 25% relative humidity in hydroculture. Both the control treatment and hydroball pot in a hydroball container were high at first. As time progressed, artificial soil pots in water containers was similar when housed within the control chamber by about 45% relative humidity. Hydroball pots in water container had about 30% relative humidity. Ardisia pusilla of hydroball poIt in hydroball container had about 38% relative humidity.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.315-322
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• 2003

Cyclic simple shear tests were performed to find out the effect of preshear on dynamic strength of the sandy soil. Tests were performed for the specimens with 40% and 60% of relative density, under three different effective vertical stress of 50, 100 and 200kPa. For 50 and 100kPa, preshear ratios 0.00, 0.08, 0.12 and 0.16 were given, respectively, For low and high relative densities, two different results are shown in dynamic tests. Under the dense conditions, the maximum shear stress ratio($\tau$$\_$cyc//$\sigma$$\_$vo/) and the cyclic shear stress ratio($\tau$$\_$cyc//$\sigma$$\_$vo/) causing a certain shear strain increase with augmenting preshear ratio(${\alpha}$). However, the maximum shear stress ratio and the cyclic shear stress ratio increase or decrease with increasing preshear ratio under the loose conditions. Correction factor(K$\_$${\alpha}$/) for preshear increases at an early stage and then decreases with increasing preshear ratio at loose condition and increase with increasing preshear ratio at dense condition. Correction factor (K$\_$${\alpha}$,Max/) for preshear increases with the increasing preshear ratio irrespective of relative density, and the value of has same behavior as K$\_$${\alpha}$/.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.3
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• pp.175-181
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• 1987

Plugging effect of open-ended pipe piles is known to have a close relationship with the ratio of an embedment depth to a pile diameter, i.e., the relative embedment ratio. To evaluate this relationship in the concrete, load tests are performed on the open and the close ended model piles varying the relative embedment ratio as well as the relative density of the model test ground. Cross-shaped hollow plates are attached at the open pile ends to reduce the effective pile diameters, on which load tests are also performed. As a result, it is confirmed that higher plugging effect may be obtained in the denser ground at lower relative embedment. However, 100% plugging effect can be obtained at the relative embedment ratio of 25 or bigger regardless of the density of the ground. Increment of the plugging effect by introducing the cross-shaped attachment can hardly be achieved.

• Journal of the Korean GEO-environmental Society
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• v.14 no.3
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• pp.13-17
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• 2013

Determination of geotechnical characteristics of soil is either to use the field samples to measure the characteristics of soil through laboratory test or measuring the characteristics directly in the field. Field test can be derived similar value by considering characteristics of site and laboratory test can be confirmed the characteristic of soil by testing with field samples. This article describes relative density as the measure of compaction for cohesionless soils and presents several simple and mathematical relationships to help engineers estimate needed parameters for relative density calculations. The main purpose of this research is to investigate possible correlations between coefficient of uniformity, coefficient of curvature, maximum and minimum void ratio, mean grain size. Results show a linear relationship between the minimum and maximum void ratios and a power function relationship between coefficient of uniformity and the limiting void ratios. Void ratio range, which is the difference between the maximum and minimum void ratios, appeared to be log normally distributed but showed no simple mathematical fit to the data. these results were shown to help engineers estimate needed parameters for relative density calculations.

• Magazine of the Korean Society of Agricultural Engineers
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• v.34 no.3
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• pp.33-42
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• 1992

The shear strength of cohesionless Soils results from particle-to-particle friction and structural resistance by interlocking. And, the shear strength of soils is subjected to vary depending on the internal states and external condtions. If the volume change occurring in the soils and stress-strain relationships under the internal and external changes can accrurately he described, it is possible to predict the behaviors of soils. To accomplish these objectives a series of drained triaxial compression tests and isotropic compression test was performed on the Banwol sand at different relative densities ranging from 20% to 80% and different confining pressures ranging from 0.4kgf/cm$^2$ to l2kgf/cm$^2$. The results and main conclusions of the study are summarized as follows; 1.When the relative density or the confining pressure is increased, the maximum deviator stress is increased. The ratio of the maximum deviator stress and the confining pressure is linearly proportional to the relative density. 2.It is observed that the dilatancy depends not only upon its relative density but also the confining stress, and that the maximum deviator stress is obtained after the diatancy occurs. 3.The volume of sands undergoes initial contraction prior to the dilatancy occurred by strain softening. The dilatancy rate eventually approaches the critical state or a constant volume. 4.At lower strains, Poisson's ratio approaches a certain minimum value regadless of the state of materials. At larger strains, however, the ratio is increased as the relative density is increased. 5.It is observed that the modulus of elasticity is linearly proportional to the relative density and the pressure. 6.When the relative density is increased, the friction angle of sands is linearly increased. 7.When the relative density is increased, the expansion index and the compression index are linearly decreased, and the ratio of the two is about 1/3.

• Journal of the Korean Ceramic Society
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• v.34 no.11
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• pp.1139-1150
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• 1997

A model for predicting the relative density and the compressive strength of open-cell ceramics with three-dimensional network structure was proposed through the interpretation of their macrostructure and fracture mechanics. The equation predicting the relative density was derived under the assumption that the open-cell structure was a periodic array of the tetrakaidecahedron unit cell consisting of cylindrical struts containing the internal hollow with the shape of a triangular prism. The model for compressive strength of open-cell ceramics with the hollow strut was also developed by modifying conventional model which based on fracture behavior of them subjected to the compressive stress. Both the relative density and the compressive strength were expressed in terms of the ratio of the strut diameter to the length together with the ratio of the hollow size to the strut diameter. The proposed model for the relative density and the compressive strength of the alumina-zirconia composite with open-cell structure were accorded well with the experimental values, whereas Gibson-Ashby and Zhang's model did not show such a good agreement.

• Earthquakes and Structures
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• v.25 no.4
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• pp.249-267
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• 2023

Various methods for determining the damping ratio have been proposed by scholars both domestically and abroad. However, no comparative analysis of different determination methods has been seen yet. In this study, typical sand (Fujian standard sand) and cohesive soils were selected as experimental objects, and undrained strain-controlled dynamic triaxial tests were conducted. The differences between existing damping ratio determination methods were theoretically compared and analyzed. The results showed that the hysteresis curve of cohesive soils had better symmetry and more closely conformed to the definition of equivalent linear viscoelasticity. For non-cohesive soils, the differences in damping ratio determined by six methods were significant. The differences decreased with increasing confining pressure and relative density, but increased gradually with increasing shear strain, especially at high shear strains, where the maximum relative error reached 200%. For cohesive soils, the differences in damping ratio determined by six methods were relatively small, with a maximum relative error of about 50%. Moreover, they were less affected by effective confining pressure and had the same changing trend under different effective confining pressures. The damping ratio determination method has a large effect on the seismic response of soils distributed by non-cohesive soils, with a maximum relative error of about 15% for the PGA and up to about 30% for the Sa. However, for soil layers distributed by cohesive soils, the damping ratio determination method has less influence on the seismic response. Therefore, it is necessary to adopt a unified damping ratio determination method for non-cohesive soils, which can effectively avoid artificial errors caused by different determination methods.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.1458-1465
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• 2010

A lot of dredging and reclaming projects are recently under way in Korea for the efficient use of limiting land space. Saemanguem area is special case of reclaiming by dredged soil. In case of a confined disposal of dredged soils by a pump dredger, generally coarse grained soils are separated from fines with dropping at the near part of the pump dredger. This kind of seperation of fine contents could be a factor of liquefaction by earthquake. In Korea, recently, earthquakes with magnitude of 3.0 or higher are distinctively increasing in 1990. In this study, cyclic shear characterics of Saemanguem Dredged sand depending on fine content were analyzed. A series of undrained cyclic triaxial test with cyclic stress ratio ($\sigma_d/{2\sigma_{{\upsilon}c}}'$) were performed on both isotropic consolidated specimen and sand with fine contents of 0%, 5%, 15%, 30%, 40% under the effective vertical stress of 100kPa and 50% and 60%, 70% of relative density for fine content of 0%, respectively. In the test results, cyclic shear strength increased by increasing of cyclic stress ratio($\sigma_d/{2\sigma_{{\upsilon}c}}'$) with increasing the relative density at the same number of cyclic under the effective confining pressure of 100kPa. It is almost highest the double amplitude(DA) 1%, 3%, 5%, 7.5% and 10% at fine content of 15% between Cyclic stress ratio($\sigma_d/{2\sigma_{{\upsilon}c}}'$) value at cyclic number five and fine content. Number of cyclic is 30 under the effective vertical stress of 100kPa, 70% of relative density for fine content of 15%. when the cyclic stress ratio at each relative density was compared at cyclic number five, the double amplitude(DA) 1%, 3%, 5%, 7.5% and 10%, and the pore-pressure ratio (${\Delta}u/{\sigma'}_c$) 0.95 value were compared; under the relative density of 70% and the effective confining pressure of 100kPa. The pore-pressure ratio (${\Delta}u/{\sigma'}_c$) 0.95 value showed a similar trend to the double amplitude (DA) 5% line.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.2
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• pp.117-123
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• 1994

This paper describes the effect of air assisted fuel injection system(AAI) using compressed air to improve the performance of lean combustion engine. AAI is designed to promote fuel atomization and intake flow. In order to investigate the performance of engine with AAl, experiments are conducted varying the engine revolution speed, lean air-fuel ratio and intake manifold pressure. Compared with the original engine, the performance of the engine with MI is improved as the air-fuel mixture becomes leaner or the engine load becomes lower. The descreasing rate of BSFC is propotional to the relative air-fuel ratio and the lean misfire limit extended more than 0.2 relative airfuel ratio.