• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.6C
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• pp.277-285
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• 2009

A series of undrained cyclic triaxial tests were carried out to investigate the cyclic shear stress strength characteristics of sands with respect to the silt content. Silty sand was collected around the basin of Nak-Dong River and remolded in laboratory with the range of silt content 0~50% in sand located. As results, with the change of silt content cyclic shear stress ratio (CSR) at N=10 showed the maximum value at 5% and the minimum at 20% in all relative density. The development tendency of the pore water pressure analyzed by the relationship cyclic ratio and pore water pressure ratio is unrelated the change of CSR varying silt content. Comparing the results of the void ratio and skeleton void ratio after consolidation, CSR varying silt content was much affected by skeleton void ratio which is known to affect shear behavior of silty sand.

• Journal of the Korean GEO-environmental Society
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• v.11 no.12
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• pp.57-62
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• 2010

In this study, the effect of different silt contents on the shear characteristics of silty sands was evaluated. Two series of triaxial compression tests were performed on the cylindrical specimens of compacted Nakdong river sand with 10% and 30% silt contents under unconsolidated undrained condition. All identical specimens were prepared to compact with same initial water content for five layers and saturated using control panel and then sheared under initial effective confining pressure, 100 to 400kPa. All specimens exhibited a strain softening tendency after failure in stress-strain curves and deviator stresses of specimens with 10% silt content were greater than those of specimens with 30% silt content. Pore water pressures of specimens with 10% silt content were observed negative(i.e. swelling) due to increasing void ratio after failure but those of specimens with 30% silt content were shown only positive. The behavior of compacted cylindrical specimens with low silt content was more dilative than that of high silt content. Peak deviator stresses decreased as increasing silt content and peak pore water pressures increased as increasing silt content.

• Journal of the Korean Geotechnical Society
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• v.24 no.11
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• pp.79-89
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• 2008

In this study, a series of undrained cyclic triaxial tests were performed with three different consolidation stress ratios ($K_c$=1.0, 1.5, 2.0) to investigate the undrained shear strength characteristics of sands with respect to the amount of contained silt located around the basin of Nak-dong River. The test results show that the more the sand has silt, the lower is cyclic shear stress ratio (CSR) in all $K_c$ and that the higher $K_c$ goes, the larger CSR decreases due to the increase of contained silt. The excessive pore pressure caused during shearing has an influence on the decrease of CSR by the high initial pore pressure in proportion to the amount of contained silt regardless of the $K_c$ value. After consolidation, the analysis of the skeleton void ratio of the sample reveals that the main cause of the decrease of CSR as well as the increase of the initial excessive pore pressure is the increase of the skeleton void ratio in proportion to the amount of contained silt.

• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.69-78
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• 2003

In order to investigate the dynamic behavior of weathered granite soils before and after freezing-thawing, cyclic triaxial tests were conducted for the specimens not only with the variation of silt contents within 20% but with plasticity index within 20%. As the results, the dynamic shear modulus of weathered granite soils decreased with increasing silt contents. However, the change in damping ratio was negligible. The influence of freezing-thawing on shear modulus and damping ratio was minimal for the granite soils with variation of silt contents. For the case of the weathered soils with variation of plasticity index, the shear modulus increased with plasticity index within 20%, while the modulus decreased remarkably after freezing-thawing.

• Journal of the Korea Organic Resources Recycling Association
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• v.8 no.1
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• pp.77-82
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• 2000

Seven constructed and three natural tidal flats were compared to evaluate state-of- the-art of creation and restoration technology for tidal flats. parameters studied were physico-chemical and biological characteristics of soils and rate of respiration. The natural tidal flats had higher contents of silts, nitrogen and organic matter compared to the constructed ones. The natural ones had reductive Bone below 2 cm whereas the constructed ones had oxidative zone from the surface to below 20 cm. The bacterial population in the soil of the constructed tidal flats was one to two magnitudes lower than that in the natural ones. Biomass of macrobenthos and microbial respiration rate, however, were not different significantly between the natural and the constructed tidal flats. The purification capacity by diatom+bacterial+meiobenthos and macrobenthos in the constructed tidal flats was higher than that in the natural ones due to deeper permeable layer for purification in the constructed tidal flats. There was an exceptional constructed tidal flat with similar physico-chemical and biological characteristics to natural ones. Shearing stress to the surface of the tidal flat by the flow of seawater was as low as that of natural ones. These hydraulic conditions seemed to be a controlling factor on structures and functions of tidal flats. The control of hydraulic condition seemed to be one of the most important factors to create natural-like tidal flats.

• Journal of the Korean GEO-environmental Society
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• v.21 no.11
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• pp.21-26
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• 2020

Natural soil is composed of particles of various sizes, and the shear behavior which is a kind of mechanical behavior of the soil is affected by the particle size distribution. In addition, since the natural soil contains a large mixture of coarse and fine grained soil, it is difficult to clearly understand the shear behavior of the soil. Therefore, a ring shear test was conducted on sandy soils that has various particle size distribution in order to identify the effect of the distribution on shear characteristics of soils. At this time, sand and silt were used for coarse and fine grained soils, respectively, to make sandy soils by changing the silt content. Also the water was supplied during the test to confirm shear characteristics of sandy soils with various particle size distributions. The result shows that the shear strength increases as the silt content increases, and the strength decreases as the silt content increases over the sand. Besides, residual shear strength gradually decreases because of the silt content when the water is supplied.

• Journal of the Korean Geotechnical Society
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• v.37 no.8
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• pp.5-13
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• 2021

Liquefaction behaviors of two natural silty samples containing fines including clay of 50% or more (Sample No.1 was silt 44.1% and clay 8.8%, sample No.2 was silt 57.2% and clay 12.4%) were examined by a cyclic triaxial test. According to the results on samples containing 50% or more of fine particles, an increase in the fine content decreases the liquefaction resistance of the sample. In other words, when the fine content increases, the liquefaction state of sample is reached with a small number of cyclic loads. In the relationship between the excess pore water pressure ratio and the number of cycles, the slope of the excess pore water pressure ratio increases more steeply as the fine content increases. As a result of analyzing the liquefaction behavior of the two silts with the content of clay contained in the fines, liquefaction occurred more easily in the No.2 silt with high clay content. This result shows that the clay contained in the fines affects the liquefaction behavior of the silt.

• Journal of the Korean Geotechnical Society
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• v.22 no.1
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• pp.35-44
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• 2006

In general typically granular soils contain a certain amount of fines. It is also widely recognized that foundation soils under working loads show highly non-linear behavior from very early stages of loading. In the present study, a series of laboratory tests with sands of different silt contents are conducted and methods to assess strength and stiffiness characteristics are proposed. Modified hyperbolic stress-strain model is used to analyze non-linearity of silty sands in terms of non-linear Degradation parameters f and g as a function of silt contents and Relative density Dr. Stress-strain curves were obtained from a series of triaxial tests on sands containing different amounts of silt. Initial shear modulus, which is used to normalize Degradation modulus of silty sands, was determined from resonant column test results. From the laboratory test results, it was observed that, as the Relative density increases, values of f decrease and those of g increase. In addition, it was found that values of f and g increase and decrease respectively as a Skeleton void ratio $(e_{sk})$ increases.

• Geotechnical Engineering
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• v.10 no.4
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• pp.119-132
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• 1994

Undrained cyclic triaxial tests were performed on silt contained in the sand in order to investigate the effect of silt contents on the liquefaction strength and shear characterist ifs of the sand. As the result of this experiment, the weakest percentage of silt contained in the sand was 30% for all the relative density considered in the test. Also, the same bests were performed to find the effect of cyclic speed applied ranging from 0.1Hz to 5Hz on the liquefaction strength. The more the silt is contained in the sand, the greater the liquefaction strength was affected by cyclic speed, While the silt -containing sand was far less influenced by the cyclic speed than clay containing sand. These results are believed to be caused by the change of pore water pressure of the effective stress path.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.2
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• pp.243-252
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• 1993

Undrained cyclic simple shear tests and undrained cyclic triaxial tests were performed on silt containing sand in order to investigate the effects of silt contents on the liquefaction strength and shear characteristics of the sand. From the view that the difference of liquefaction strength for different content of silt stems from dilatancy characteristics of the sand, stress-dilatancy relation of the sand was obtained from drained triaxial test in which the mean stress was kept constant. Considerations on liquefaction behaviors were made by comparing the drained and undrained behaviors of sands during static shear test. It is concluded that ${\lambda}$-value of the stress-dilatancy relation will be closely related to the liquefaction strength.