• Journal of Ocean Engineering and Technology
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• v.15 no.4
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• pp.92-100
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• 2001

It is very important to determine the coefficient of earth pressure at rest accurately in order to estimate the behavior of soil structure. For estimation of K/sub 0/-value depending upon the stress history of dry sand, a new type of K/sub 0/-oedeometer apparatus is devised, and the horizontal earth pressure is accurately measured. For this study, 2 types of one-cyclic K/sub 0/-Loading/unloading models have been studied experimentally using four relative densities of the sand. The results obtained in this test are as follows : K/sub on'/ the coefficient of earth pressure at - rest for virgin loading is a function of the angle of internal friction Φ' of the sand and is determined as K/sub on/=1 - 0.914 sin Φ', K/sub ou'/ the coefficient of earth pressure at rest for virgin unloading is a function of K/sub on/ and over consolidation ratio(OCR), and is determined as K/sub ou/=K/sub on/(OCR)K/sup a/. The exponent α, increases as the relative density increases. K/sub or'/ the coefficient of earth pressure at rest for virgin reloading decreases in hyperbola type as the vertical stress, σ/sub v/’, increases. And, the stress path at virgin reloading leads to the maximum prestress point, independent upon the value of the minimum unloading stress. The gradient of this curve, m/sub r/ increases as OCR increases.

• Journal of Soil and Groundwater Environment
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• v.8 no.1
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• pp.35-41
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• 2003

Laboratory procedures are available for estimating contaminant migration from sediment into caps by diffusion, but diffusion may not be the major process affecting capping effectiveness. Movement of contaminated pore water from sediment into caps due to sediment consolidation during and after cap placement may be much more significant than contaminant diffusion into caps. To verify this phenomenon, model tests were conducted by utilizing a research centrifuge. In this study, test was modeled for 22.5 hours at 100 g, which modeled a contaminant migration time of 25 years for a prototype that was 100 times larger than the centrifuge model. Centrifuge test results illustrate that advection and dispersion due to consolidation are dominating the migration of contaminants.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.678-683
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• 2004

The most popular consolidation tester is a standard consolidatiion tester, which performs consolidation using the step load weight. However this apparatus is used to obtain only the vertical consolidation coefficient. Therefore the purpose of this study is to develope the horizontal consolidation cell for a horizaontal consolidation coefficient. Various size of tests have been peroformed to investigate the effect of scale effect. From the test results, it has turned out that this horizontal consolidation cell has a good function for a horizontal consolidation coefficient.

• Journal of Ocean Engineering and Technology
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• v.13 no.2 s.32
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• pp.159-167
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• 1999

For exisiting $K_0$-oedometer, the lateral wall of the ring is cut thinly to make space and by filling the space with space with water or mercuty to keep the balance to the lateral pressure of a specimen, the pressure of the fluid is checked for the pressure of the specimen. But the devices to keep the balance to the lateral pressure of a specimen are complicated, difficult to manufacture and expensive. As newly developed $K_0$-oedometer is equipped with the load cell which can resist higher pressute than the lateral pressure of the specimen, there is nearly no deformation due to the lateral pressure of the specimen. And the measuting is cheap and easy as there are fewer accessories.

• Journal of the Korean Geotechnical Society
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• v.27 no.7
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• pp.69-79
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• 2011

Laboratory tests are generally used to determine the input parameters for the selected constitutive models controlling various stress and drainage conditions, but have disadvantages in that the tests are performed on the samples obtained from the bore hole which are prone to be disturbed by various factors such as the tube penetrations, sample preparations and storage. To overcome these disadvantages, it is necessary to understand the effect of disturbance on the stiffness of the sample, especially the normally consolidated clays which are generally considered as soft clays. Therefore, in this study triaxial tests are performed on the normally consolidated kaolinite to evaluate the sample disturbance effects on the stiffness and to determine the field representative input parameters. The stress path results show that the shear and coupling modulus degradation patterns with strain are affected seriously by the disturbance. However, the strengths of the normally consolidated kaolinite are little influenced by the disturbance.

• 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 Korean Geotechnical Society
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• v.19 no.1
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• pp.111-120
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• 2003

A new stress path test method, which is more suitable f3r evaluating settlements of clay deposits, was introduced. This new method is basically based on back pressure equalization concept and makes it possible to estimate deformations corresponding to all points on a specific stress path by only one test. As a result, deformation characteristics of a clay deposit can be predicted by a few tests and the more practical application of stress path method can be realized. In addition, anisotropic deformation behaviors following arbitrary stress paths also can be experimentally measured by this test method. Experimental applicability of the proposed method was confirmed by performing various stress path tests on remolded kaolinite samples and the actual process to evaluate overall deformation characteristics and settlements was also presented.

• Journal of the Korean Geotechnical Society
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• v.23 no.10
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• pp.73-84
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• 2007

For standard piezocones with shoulder filter elements immediately behind the cone tip, general dissipation curves show monotonically decreasing pore pressure from the initial value. However, dilatory dissipation behavior, showing a temporary increase in pore pressure followed by a decrease in the hydrostatic pressure, has been observed in lightly overconsolidated cohesive soils $(1. This unusual dissipation behavior was reported mostly in heavily overconsolidated ground and previous researches were limited to such cases. In this study, the mechanism of dilatory dissipation in lightly overconsolidated cohesive soils was investigated. The relativities of the ground properties evaluated from the CPTu data to the dilatory dissipation were analyzed. And, finite difference analyses on dissipation after cone penetration were performed. It was found that dilatory dissipation occurs in lightly overconsolidated soils since the higher excess pore pressure at the cone face propagates upward to the shoulder filter. Also, it was shown that the ratio of initial excess pore pressure at the cone face to that of the shoulder filter $({\Delta}u_{1i}/{\Delta}u_{2i})$, which is related to overconsolidation ratio (OCR) and hydrostatic pressure $(u_0)$, affects the dilatory dissipation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.2
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• pp.99-107
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• 1988

A limited number of cubical triaxial tests with independent control of the three principal stresses were performed on an overconsolidated clay. The cubical undisturbed specimens with overconsolidation ratio of 5 were prepared in triaxial chamber after sampling in field. It was found that the intermediate principal stress influences on the stress-strain, undrained strength effective strength, effective friction angle and pore pressure of the overconsolidated clay. When the magnitude of the intermediate principal stress is not same as the minimum principal stress, the failure strength of the overconsolidated clay is underestimated by use of Mohr-Coulomb failure criterion while it can be estimated quite well by use of Lade failure criterion. And the undrained strength of the overconsolidated clay does not coincide with that obtained by Tresca failure criterion.

• Journal of the Korean GEO-environmental Society
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• v.12 no.9
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• pp.71-78
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• 2011

Cement treating technique, such as deep mixing method, has been used widely to stabilize the dredged clayey soil for many years. Despite of its effectiveness in treating soil by cement, several efforts have also been made to try to reduce the side effect of the cement that used to stabilize the dredged clay. However, authors considered that more detailed study on the physical and mechanical properties of lean-mixed soil-cement has been required to establish the design procedure to apply the practical problems. Therefore, in this study, the curing time and mixing ratio was used as key parameters to estimate the physical and mechanical properties including long-term behavior. The unconfined strength of lean-mixed soil-cement increase continuously during curing period, 270 days, while increasing rate becomes low in ordinary cement-treated dredged clay. We also concluded that cement-treated dredging clay shows apparent quasi overconsolidation behavior even in low cement proportion. By this study, fundamental approach was carried out for effective reuse of very soft dredged clayey soil both in mechanical and environmental aspect. It can be also expected that this study can propose a basic design data to use the lean-mixed soil cement.