• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.261-273
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• 2004

An in-hole seismic method has been developed to meet the requirement of economical testing cost and practicality in engineering practice to measure dynamic soil properties. The in-hole prove developed herein is small and light enough to be fit in three-inch boreholes and to be handled with bare hands. And author modified the existing equipment for the convenient purpose. In addition, the best damper suited to in-hole test was also developed. The performance of the source has been evaluated through extensive cross-hole tests and in-hole tests at various sites.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.253-260
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• 2004

Many scholars and researchers has been studied for many kinds of soil characteristics, but a lot of part are still unsolved. Cyclic load-induced decreasing characteristics of strength and stiffness of soils are also well not known among them. To know that, the characteristics of five kinds of soils; clay, plastic and non-plastic silt, sand, and a weathered soil are compared with dividing two types as plastic or non-plastic soils through direct simple shear(DSS) test. From the results of DSS test, it is known that decreasing characteristics of strength and stiffness are different according to soil types. The strength of plastic and non-plastic soils increases with increment of plasticity index and decrement of volume decrease potential, respectively. And the decreasing stiffness of plastic and non-plastic soils increases with decrement of plasticity index and increment of volume decrease potential, respectively.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.58-65
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• 2004

Recently, the top & down method with drilled shafts as a foundation of high rise building is often adopted for the purpose of construction period reduction and construction cost effectiveness. It is common to omit the loading test as a Quality assurance on account of the high capacity of drilled shafts for the top & down method. It seems that the capacity of drilled shaft in recent top & down method is beyond that of conventional loading test method.However, the quality assurance for the drilled shaft as foundation of high rise building becomes much more important since the drilled shaft should bear much higher working load. It may be a small scale test pile could be an alternative as a quality assurance for the drilled shaft with high capacities. Through a case study, this paper gives an idea for solving the limitation of the conventional loading test method for the quality assurance of drilled shaft with high capacities. In particular, this paper analyzed the scale effect for a small drilled shaft installed into bedrock, which could be used for an alternative.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.66-73
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• 2004

Prototype crushed-stone compaction pile(${\Phi}=700mm$) were constructed on specific test site. Static loading tests for crushed-stone compaction piles were performed. Based on the static loading test results, finite element analysis was performed using software PENTAGON 3D. Numerical analysis were done for the area replacement ratio($a_s$) of $20{\sim}70%$ and $a_s$ was varied as a step of 10%. In the single crushed-stone compaction pile, settlement was decreased as $a_s$ was increased. In the group pile, this tendency was similar. In the in-sit test and numerical analysis, as $a_s$ increased, the stress concentration ratio was increased. But $a_s$ in the numerical analysis were more than that of in-situ test, greatly.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.722-729
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• 2004

The horizontal movement of sloping ground due to flow liquefaction has caused many pile foundations to fail, especially those in ports and harbor structures. In this study, a virtual case is assumed in which flow liquefaction is induced by earthquake loads in a fully saturated infinite sand slope with a single pile installation. Under the assumption that the movement of liquefied ground is viscous fluid flow, the influence of ground movement due to flow liquefaction on the pile behavior was analyzed. Since the liquefied soil is assumed as a viscous fluid, its viscosity must be evaluated, and the viscosity was estimated by the dropping ball method ,md the pulling bar method. Finally, the influence of the flow of liquefied soil on a single pile installed in an infinite slope was analyzed by a numerical method.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.922-929
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• 2004

In some port construction, a case of reclamation with dredged soil for land use can be found. Even though this is not a new technology, there are some problems on the test method and analysis. The design parameters are still remained to be solved to get accurate prediction. Sedimentation of particle and self-weight consolidation are the most important design parameters in reclamation by dredged soils. The design parameters are influenced by properties of the physical and sedimentation of dredged soils. This influencing factors can be determined depend on the history of long term sedimentation and particle characteristics. Thus, properties of the sedimentation and consolidation are varies depend on the regional geologic formation. In this paper, three different sites with different regional soil properties will be compared in design parameters of sedimentation and self-weight consolidation.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.738-745
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• 2004

There are a number of ways to reduce the ground vibrations, one of which is by installing underground walls. Model tests for ground vibration have been conducted in recent years, but limited attention has been paid to underground wall which can reduce high vibrations. Up to date, only barriers have been actually installed in dry sand because of many unknown factors subsisting on the behavior of the ground. The characteristics of vibration sources, ground conditions and wall barriers have not been well understood yet, therefore centrifugal modeling was adopted to examine all these characteristics. This paper describes a ball dropping system, which can generate a pulse wave propagation through soil mass, and the test results show the effectiveness of underground wall barrier in reducing mechanical vibration.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.334-341
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• 2004

The coefficient of permeability is one of the most important properties in unsaturated soils. The permeability varies with change in the water content as the soil water characteristic curve(SWCC) does. Thus the permeability curve of unsaturated soils has the similar shape with the soil-water characteristic curve(SWCC). Therefore, the methodologies have been studied to simply predict the unsaturated permeability from the SWCC. In this study, the experimental tests of SWCC and permeability were carried out for domestic weathered granite soils. The SWCC test results were fitted to Fredlund and Xing's SWCC equation and then it was found that there are some relationships between the parameters of SWCC equation and the basic soil properties. Accordingly we used an ANN(artificial neural network) model to obtain the SWCC parameters from the basic soil properties. Finally, the coefficients of permeability were predicted from these results by a prediction model.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.513-520
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• 2005

An active modal-fuzzy control method using hydraulic actuators is presented for seismic response reduction. In the proposed control system, a new fuzzy controller designed in the modal space produces the desired active control force. This type controller has all advantages of the fuzzy control algorithm and modal approach. Since it is very difficult to select input variables used in fuzzy controller among an amount of state variables in the active fuzzy control system, the presented algorithm adopts the modal control algorithm which is able to consider more easily information of all state variables in civil structures that are usually dominated by first few modes. In other words, all information of the whole structure can be considered in the control algorithm evaluated to reduce seismic responses and it can be efficient for especially civil structures. In addition, the presented algorithm is expected to magnify utility and performance caused by efficiency that the fuzzy algorithm can handle complex model more easily. An active modal-fuzzy control scheme is applied together with a Kalman filter and a low-pass filter to be applicable to real civil structures. A Kalman filter is considered to estimate modal states and a low-pass filter was used to eliminate spillover problem. The results of the numerical simulations for a wide amplitude range of loading conditions show that the proposed active modal-fuzzy control system can be beneficial in reducing seismic responses of civil structures.

• Journal of Korean Society on Water Environment
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• v.30 no.3
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• pp.292-297
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• 2014

We synthesized the self-organized nanoporous oxide with potentiostatic anodization of iron foil. The iron oxide nanocomposite (INCs) were fabricated in 1M $Na_2SO_4$ containing 0.5wt% NaF electrolyte holding the potential at 20, 40 and 60 V for 20min, respectively. Field Emmision Scanning Electron Microscopy (FESEM) and X-ray Diffractometer (XRD) were used to evaluate the micromorphology and crystalline structure of INC film. Also, this study was performed to evaluate the fenton reaction using INC film with hydroperoxide for degradation of cyanide dissolved in water. In case of INC-40V in the presence of $H_2O_2$ 3%, the first-order rate constant was found to be $1.7{\times}10^{-2}min^{-1}$, and indicated to be $1.2{\times}10^{-2}min^{-1}$ on commercial hematite powder. This result is shown to be good performance enough to replace the powder type for treatment of wastewater.