• 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 Geosynthetics Society
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• v.13 no.2
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• pp.49-57
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• 2014

In this study, in order to take advantage of samples collected in the Jangbogo station, and to grasp the liquefaction resistance characteristics of the dynamic load was performed cyclic triaxial test. Also, through the comparison with the existing literature. The test results, for the relationship between number of cycles for the same cyclic shear stress ratio and the cyclic shear stress ratio to produce an axial strain of 5%, in all samples, the cyclic shear stress ratio to liquefaction for the specimen, which has been liquefied, was increased, whereas number of cycles were reduced. The cyclic shear stress ratio of samples first decrease up to the fine content of about 10%. After this strength level, there is a little increase in cyclic shear stress ratio with increasing fine content. In addition, the cyclic shear stress ratio between cohesive strength, mean particle size, and friction angle decrease but some time later, there was a tendency that cyclic shear stress ratio is a little increased.

• Geotechnical Engineering
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• v.9 no.4
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• pp.27-36
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• 1993

The drained and undrained behavior of pure silt was investigated experimentally. Special attention was given to the stress-strain behavior of silt prior to failure and behavior at failure under monotonic and cyclic loading. A pure silica flour was chosen to form samples with two different densities of D,=80%, eo=0.68 and D,=35%, eo=0.9. The isotropically consolidated samples were tested in the triaxial testing device under monotonic undrained, drained compression and extension conditions. Also samples were tested under cyclic undrained condition. Based on the experimental results. it was qualitively identified that the overall behavior of silt is similar to that of sand. When compared with clay, silt shows a significantly different behavior due to its dilatant nature under both the monotonic and cyclic shear loadings.

• Journal of the Korean Geotechnical Society
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• v.15 no.4
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• pp.57-67
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• 1999

In conventional stability analysis of embankment on soft clay ground, an averaged undrained shear strength$(s_u)$ for the depth of clay layer is usually used. Also, all applied load is assumed to an immediate load for simplicity of analysis. The load in the field, however, increases gradually. Undrained shear strength increases during loading due to consolidation of clay ground. In this study, the stability analysis program(RSI-SLOPE) is developed. By using this program, it is possible to consider the rate of strength increase according to the elapsed time of consolidation and the depth of clay ground. And the rested duration for consolidation and gradually increased load can also be considered. Using the examples of some embankments, the critical embankment heights calculated by RSI-SLOPE program are compared with those by PCSTABL without the considerations of gradually increased load and rate of strength increase. In addition, this study contains analysis and comparison about the influence of coefficient of consolidation$(c_u)$ and drainage distance$(H_{DR})$ in the embankment design. RSI-SlOPE program may be useful for more effective and accurate embankment design.

• Journal of the Korean Geotechnical Society
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• v.30 no.9
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• pp.19-28
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• 2014

It is necessary to understand the behavior of the soils for the dredging constructions. The objective of this study is to estimate void ratio and density changes of the dredged soils by using the geophysical testing methods. A series of laboratory tests is performed to obtain geotechnical index properties of the specimen, retrieved from the west coastal of Korea. The sedimentation and self-weight consolidation tests are carried out with observing changes of the interfacial height and the elastic wave velocities. The same amounts of the soils are poured into the testing column at intervals of 12 hours until the interheight reaches to a certain level. After the completion of the sedimentatation and self-weight consolidation tests, downward permeability test is performed to assess a tidal influence in the nearshore. The mini resistance cone is penetrated into the specimen to measure the electrical resistivity with depth. All tests are completely finished, the weight of specimens are measured to calculate the void ratio with the depth. Experimental results show that the aspects of the self-weight consolidation are invisible during dredging process because of rapid sedimentation characteristics of ML. However, the elastic wave velocities increase with increasing in the effective stresses. During permeability test, measured permeability and the elastic wave velocities maintain almost identical values. Void ratio based on the elastic wave velocities changes linearly with time during the step dumpings. Void ratio estimated by the electrical resistivity represents the repeatedly layered depositions according to the step-by-step dumpings. Void ratio determined by soil sampling is similar to those of elastic waves and electrical resistivity profiles. This experimental study demonstrates that the geophysical testing methods may be an effective method for evaluating the behavior of dredged soils.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.8
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• pp.5654-5663
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• 2015

In the unsaturated soil, suction, the negative pore water pressure leads to increases of the yield stress and the plastic shear stiffness of the soil skeleton due to the growth in interparticle stress. Therefore, in this study, the stress-strain relationship based on cyclic elasto-plastic constitutive model extended for unsaturated soil considering the 1st and the 2nd yield functions was induced in order to account for these effects of suction under the dynamic loading condition such as the earthquake. Through the program code considering this relationship and the routine of the cyclic loading with the reversion of loading direction, the numerical simulation of the cyclic triaxial test under the unsaturated condition would be possible. It is expected that the results of this study possibly contribute to the accuracy improvement on the prediction of unsaturated soil behavior under the dynamic loading condition.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2001.10a
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• pp.379-385
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• 2001

A series of standard consolidation tests and repeated loading consolidation tests were peformed with 2 kinds of peat sampled in Chonbuk area to study the consolidation characteristics of peat. The samples had following physical properties : 58% and 72% of organic content, 487% and 685% of natural moisture content and 7.02 and 9.72 of initial void ratio, respectively. And compression index $C_{c}$ and coefficient of secondary consolidation $C_{\alpha}$ were increased steeply when the consolidation load exceed about 2.5 and 3 times of each preload as like the characteristics of peat. The dependance on consolidation pressure of $C_{C}\;and\;C_{\alpha}$ in peatl and the maximum values, 2.9-3.8 and 0.3-0.4 were larger than that of normal clay, respectively.

• Journal of the Korean Geotechnical Society
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• v.17 no.4
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• pp.39-48
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• 2001

액상화 발생후 과잉간극수압 소산 특성을 파악하기 위하여 포화된 수평 모래지반에 대하여 1-g 진동대시험을 수행하였다. 진동대시험에는 주문진 표준사와 영종도 세사를 사용하였으며 상대밀도를 dir 20~30% 사이가 되도록 조성하였다. 간극수압계, 가속도계 그리고 LVDT 등으로 시험중의 지반거동을 계측하였으며, 4Hz의 sine 파를 0.15g에서 5초간 5회 반복하여 작용시켰다. 진동대시험을 분석한 결과 액상화 발생후 과잉간극수압의 소산속도는 그 지반의 투수성뿐 아니라 과잉간극수압 소산시 입자의 침강거리와 직접 관련이 있는 지반의 침하량에도 크게 영향을 받는 것으로 나타났으며, 이 과정을 침강모래 이론으로 모델링하였을 때 입자의 침강속도와 투수계수 사이의 비례 관계는 침강모래 이론에서의 가정한 것과는 달리 모래의 종류에 따라 차이를 나타내었다. 또한 Terzaghi의 압밀이론으로는 액상화 후 과잉간극수압의 소산과정을 적절히 모사할 수 없었다.

• Magazine of the Korean Society of Agricultural Engineers
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• v.24 no.3
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• pp.84-91
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• 1982

This study was conducted to investigate the consolidation characteristics of repeated increasing and decreasing load m marine clay. Consolidation test was performed by the whole repetition of increasing and decreasing load and the partial repetition of increasing and decreasing load. The results obtained were as follows: 1. The void ratio e was decreased according to the increase of preloading and the repe- tition of increasing and decreasing load. 2. In case of the partial repetition of increasing and decreasing load the compression index Cc was decreased with the increase of preloading and the repetition of increa- sing and decreasing load 3. The expansion rate was greatly increased with the whole repetition of increasing and decreasing load and it was inclined to be increased with the increase of preloading in case of the partial repetition. 4. The coefficient of volume compressibility were decreased according to the repetition of increasing and decreasing load 5. The secondary consolidation coefficient was decreased with the repetition of increasing and decreasing load. Especially in case of the partial repetition, the peaks of secon- dary consolidation curves could be found to move toward the vicinity of preloading.

• Korean Journal of Agricultural Science
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• v.14 no.2
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• pp.329-344
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• 1987

This paper described the behavior under repeated loading in triaxial compression test on clay. The experiment was conducted to investigate the influence of controlled various over-consolidation ratio and compaction energy, on the stress-strain behavior of clays. 1. The difference of deviator stress during repeated loading was greatly appeared at large strain. And pore water pressure was decreased at initial of unloading, but it was increased again before long. 2. The recoverable elastic strain (${{\Delta}{\varepsilon}e}$) and the slope of un-reloading were decreased with the increment of over-consolidation ratio (OCR). 3. The recoverable elastic strain (${{\Delta}{\varepsilon}e}$) was increased with the increment of strain rate but it was decreased with the increment of strain in strain rate tests. The slope of un-reloading (Eur) tends to increase with the increment of strain rate and it was decreased with the increment of strain. 4. The recoverable elastic strain was greatly increased with the increment of compaction energy and it slightly tends to decrease with the increment of strain on various compaction energy. The slope of un-reloading was not appeared markedly with increment of compaction energy but it tends to decrease with the increment of strain generally.