• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.347-347
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• 2005

• Geotechnical Engineering
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• v.21 no.4
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• pp.22-36
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• 2005

• 지반과기술
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• v.3 no.4
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• pp.20-26
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• 2006

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.3 s.73
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• pp.247-258
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• 2006

For the perforated cylindrical shell submerged in fluid, it is almost impossible to develop a finite element model due to the necessity of the fine meshing of the shell and the fluid at the same time. This necessitates the use of solid shell with equivalent material properties. Unfortunately the effective elastic constants are not found in any references even though the ASME code is suggesting those for perforated plate. Therefore in this study the equivalent material properties of perforated shell are suggested by performing several finite element analyses with respect to the ligament efficiencies.

• Journal of the Korean Society for Railway
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• v.11 no.1
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• pp.54-60
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• 2008

In the trackbed design using elastic multilayer model, the stress-dependent resilient modulus $(E_R)$ is an important input parameter, that is, reflects substructure performance under repeated traffic loading. However, the evaluation method for resilient modulus using repeated loading triaxial test is not fully developed for practical purpose, because of costly equipment and the significantly fluctuated values depending on the testing equipment and laboratory personnel. The this study, the paper will present an indirect method to estimate the resilient modulus using dynamic properties. The resilient modulus of crushed stone, which is the typical material of sub-ballast, was calculated with the measured dynamic properties and the range of stress level of the sub-ballast, and approximated with the power model combined with bulk and deviatoric stresses. The resilient modulus of coarse grained material decreases with increasing deviatoric stress at a confining pressure, and increases with increasing bulk stress. Sandy soil (SM classified from Unified Soil Classification System) of subgrade was also evaluated and best fitted with the power model of deviatoric stress only.

• The Journal of Engineering Geology
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• v.17 no.4
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• pp.623-631
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• 2007

In this paper, dynamic elastic module of banded gneiss were calculated on the basis of SPS velocity logging data obtained from a geotechnical test-hole in Pungsan-dong, Hanam, Gyeonggi Province, Korea. This study mainly focuses on the velocity analysis, Q factor calculation relative to attenuation factor, and generation of crack information and its relation with seismic velocity. As a result, P-wave and S-wave velocity of fresh hard rock was 5,559m/s and 3,063m/s, respectively, with Poisson's ratio being 0.28. With these results, dynamic modules were prepared, and crack information analyzed by acoustic televiewer was incorporated to identify the correlation among and between delay of first arrival by crack amplitude ratio, and velocity. The results of this study revealed that the analyzed logging hole mainly consisted of micro crack and a number of cracks and the size of crack aperture, functioned as a variable to seismic velocity in the micro crack area of this type of hard rock.

• Journal of the Korean Geotechnical Society
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• v.21 no.1
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• pp.105-114
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• 2005

An in-hole seismic method, which has been developed for measuring dynamic properties of subsurface materials, was improved in terms of cost effectiveness and practicality. The upgraded features include the motorized triggering system rather than the manual prototype version in the previous studies and a connecting rod between source and receiver in the module. The probe, thus, can be used for the field measurements of soil properties as well as those of rocks. The performance of the probe 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.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.

• Journal of the Korean Geotechnical Society
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• v.21 no.7
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• pp.13-20
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• 2005

For experimental study on the effect of particle size distribution on the liquefaction resistance strength, particle size distribution curves of the dredged soil were investigated. In this process, four mean particle sizes and three uniformity coefficients were defined representatively and twelve representative particle size distribution curves which have different mean particle size and uniformity coefficient, were defined and manufactured by using the real dredged river soil. Cyclic triaxial tests and resonant column tests were carried out to analyze the effect of mean particle size and uniformity coefficient on the liquefaction resistance strength and dynamic characteristics.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.546-549
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• 2006

A series of seismic tests was carried out using piezoelectric elements called "bender elements". A pair of bender elements can be used as a source and a receiver respectively to measure dynamic properties of concrete. The most suitable bender elements were developed and implemented to measure P wave velocity changes due to the cracks of a concrete beam caused by bending.