• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.176-181
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• 2010

The evaluation of shear modulus (or shear wave velocity) profile of the site is very important in various fields of geotechnical engineering. In the field, there exist spatial variations of shear modulus that case uncertainty in the geotechnical analysis or design. So it is necessary to evaluate the spatial variation of shear wave velocities of the soil site. In this study, the HWAW method is applied to the determination of a 3-D Vs map of soil site. The HWAW method, which is based on harmonic wavelet transforms, has been developed to determine phase and group velocities of waves. The HWAW method uses only the signal portion of the maximum local signal/noise ratio to evaluate the phase velocity in order to minimize the effect of the noise. The field testing of this method is relatively simple and fast because only one experimental setup, which consists of one pair of receivers on the surface, is needed using a short receiver spacing setup (1~3m). These characteristics make it possible to determine detailed local Vs profile in the site with lateral Vs variation and to evaluate 3-D Vs map by performing a series of tests on the grid. To estimate the applicability of the proposed method, field tests were performed. Through field applications validity and applicability of the proposed method were verified.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.291-294
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• 2010

$CO_2$ is known as the major source of the green house effect and the volume produced from electricity generation and transportation sector in Korea constitutes the large portion. In order to reduce the green house effect, several treatment methods can be the major research topics such as the scheme to fundamentally restrict the production of $CO_2$ creation, to perfectly sequestrate the produced $CO_2$, to reuse the separated $CO_2$, or to permanently dispose $CO_2$ in an appropriate storage site. Among of them, R&D strategy and geotechnical research issues are explored in this paper in an effort to realize geological storage for the sequestrated $CO_2$ in local storage sites. $CO_2$ is known as the major source of the green house effect and the volume produced from electricity generation and transportation sector in Korea constitutes the large portion. In order to reduce the green house effect, several treatment methods can be the major research topics such as the scheme to fundamentally restrict the production of $CO_2$ creation, to perfectly sequestrate the produced $CO_2$, to reuse the separated $CO_2$, or to permanently dispose $CO_2$ in an appropriate storage site. Among of them, R&D strategy and geotechnical research issues are explored in this paper in an effort to realize geological storage for the sequestrated $CO_2$ in local storage sites.

• Journal of the Korean Geotechnical Society
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• v.30 no.4
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• pp.101-106
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• 2014

The penetration testing provides 1 dimensional profiles of properties applicable to limited investigation areas, although N-value has been linked to a wide range of geotechnical design parameters based on empirical correlations. The nondestructive test using elastic waves is able to produce 2 or 3 dimensional property maps by inversion process with high efficiency in time and cost. As both N-value and elastic wave velocities share common dominant factors that include void ratio, degree of saturation, and in-situ effective stress, the correlation between the two properties has been empirically proposed by previous studies to assess engineering properties. This study presents the experimentally measured elastic wave velocities of Jumunjin sands under at-rest lateral displacement condition with varying the initial void ratio and degree of saturation. Results show that the stress condition predominantly influences the wave velocities whereas void ratio and saturation determine the stress-velocity tendency. The correlation among the dominant factors is proposed by multiple regression analysis with the discussion of relative impacts on parameters.

• Earthquakes and Structures
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• v.7 no.4
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• pp.485-510
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• 2014

In performance-based seismic design procedures Peak Ground Acceleration (PGA) and pseudo-Spectral acceleration ($S_a$) are commonly used to predict the response of structures to earthquake. Recently, research has been carried out to evaluate the predictive capability of these standard Intensity Measures (IMs) with respect to different types of structures and Engineering Demand Parameter (EDP) commonly used to measure damage. Efforts have been also spent to propose alternative IMs that are able to improve the results of the response predictions. However, most of these IMs are not usually employed in probabilistic seismic demand analyses because of the lack of reliable Ground Motion Prediction Equations (GMPEs). In order to define seismic hazard and thus to calculate demand hazard curves it is essential, in fact, to establish a GMPE for the earthquake intensity. In the light of this need, new GMPEs are proposed here for the elastic input energy spectra, energy-based intensity measures that have been shown to be good predictors of both structural and non-structural damage for many types of structures. The proposed GMPEs are developed using mixed-effects models by empirical regressions on a large number of strong-motions selected from the NGA database. Parametric analyses are carried out to show the effect of some properties variation, such as fault mechanism, type of soil, earthquake magnitude and distance, on the considered IMs. Results of comparisons between the proposed GMPEs and other from the literature are finally shown.

• Explosives and Blasting
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• v.38 no.2
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• pp.1-12
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• 2020

Digital Image Correlation is a well-established method for displacements, strains and shape measurements of engineering objects. Stereo-camera 3D Digital Image Correlation (3D-DIC) systems have been developed to match the specific requirements for measurements posed by material and mechanical industries. Although DIC method provides the capabilities of scaling a field-of-view(FOV), dimensions of Geotechnical structure objects in many cases are too big to be measured with DIC based on a single camera pair. It can be the most important issue with applying 3D DIC to the measurement of Geotechnical structures. In this paper, We were present stereo vision conditions in a 3D DIC system that can be measured for large FOV(30×20m) and high precisions(z-displacement 0.5mm) of the ground objects with Stereo-camera DIC systems.

• Geotechnical Engineering
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• v.14 no.5
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• pp.111-128
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• 1998

An experimental study, which included four 305mm-diameter test shafts, one reference shaft with standard design and three test shafts with isolation tubes, is described. The soil was also soil heave and shrinkage that occur during suction changes at the field site. The test shafts were monitored for a period of about 18 months. Maximum ground movements exceeding 35mm were observed. Movements of only 1 to 2mm were observed in the test shafts with isolation tubes, while movements of 4 to 5mm were observed in the reference shaft. A simple computing model was developed to predict, based on suction changes, the maximum amount of ground heave. Relationship among suction. total stress, and volumetric strain was abtained in the laborstory. This relationship, used as inputs to the predictive model, enabled the computation of the maximum ground heave.

• Journal of the Korean GEO-environmental Society
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• v.17 no.9
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• pp.47-52
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• 2016

Unusual extreme weather events, which exceed a safe design capacity of the infrastructure, increase the frequency of natural disasters and has also been enlarged damage scale. Aging buildings and rapid urban progress act as weighting factors for the new composite disasters. Technological advances support detecting pre-disaster risk, real-time data analysis, and rapid response to the disaster site, but it is insufficient that emergency relief for buried alive must take advantage of the proven technologies through field tests. This study aims to evaluate directional drilling performance through underground soils and the reinforced concrete structure for primary lifeline installation in order to quickly provide relief supplies for buried alive when urban structures collapse.

• Journal of the Korean Geosynthetics Society
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• v.8 no.2
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• pp.11-20
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• 2009

This study, as basic research which was intended to develope the surface reinforcement method using reinforcement material which is applicable to very soft ground in Korea, was aimed at proposing the design parameter for the surface ground improvement method. To that end, a wide width tensile test using geotextile, geogrid and steel bar (substitute for bamboo) and 21 kinds of the laboratory model tests with the end restraint conditions of the reinforcement that comprises the constrained and partially constrained (3 types) conditions were conducted. Moreover, a new procedure was proposed to take into account the effect of the stiffness of Reinforce materials on bearing capacity theory of Surface Reinforcement Method for Soft Ground.

• Advances in Computational Design
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• v.3 no.3
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• pp.269-288
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• 2018

180 different 2D numerical analyses have been carried out to estimate the factor of safety (FOS) for rooted slopes. Four different types of vegetated coverage and a variety of slope geometry considering three types of soil have been evaluated in this study. The highly influenced parameters on the slope's FOS are determined. They have been chosen as the input parameters for developing a new practical relationship to estimate the FOS with an emphasis on the roots effects. The dependency of sliding mode and shape considering the soil and roots-type has been evaluated by using the numerical finite element model. It is observed that the inclination and height of the slope and the coverage type are the most important effective factors in FOS. While the soil strength parameters and its physical properties would be considered as the second major group that affects the FOS. Achieved results from the developed relationship have shown the acceptable estimation for the roots slope. The extracted R square from the proposed relationship considering nonlinear estimation has been achieved up to 0.85. As a further cross check, the achieved R square from a multi-layer neural network has also been observed to be around 0.92. The numerical verification considering different scenarios has been done in the current evaluation.

• Ocean and Polar Research
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• v.25 no.4
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• pp.529-543
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• 2003

Deep-sea surface sediments, acquired from 1997 to 2002 in the Clarion-Clipperton fracture zone of the northeast equatorial Pacific, were analyzed for index and geotechnical properties to provide background information for the design of manganese nodule minor. The sediments were classified into 16 types based on the measured properties and evaluated in terms of miner maneuverabillity and potential environmental impacts arising from mining activities. It was found that the middle part of the study area covered with coarse siliceous sediments is more favorable to the commercial production than the northern part of pelagic red clay. In particular, Area B2 in the middle part is considered the best mining site since it shows the highest abundance as well as it consists mostly of normally to over consolidated (types B, C, D) coarse siliceous sediments that are appropriate for effective minor movement and accompany weak environmental impacts. Taking account of all the analyzed core logs, the average shear-strength values are proposed as a practical guideline fur movements of a manganese nodule miner: 6.0 kPa at 10cm and 7.0kPa at 40cm below the seabed.