• Journal of the Korean Geotechnical Society
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• v.18 no.3
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• pp.127-138
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• 2002

In dynamic analyses such as seismic ground response and soil-structure interaction problems, it is very crucial to obtain accurate dynamic shear modulus of soil deposit. In this study, an extensive data base of available experimental data is compiled and reanalyzed to establish a simple empirical formula for the dynamic shear modulus reduction curve to cover wide range of strain for sandy soils. The proposed empirical equation is to represent the dynamic shear modulus degradation with strain in terms of low-amplitude dynamic shear modulus and effective mean confining Pressure, since those factors have the most significant effect on the Position and shape of the shear modulus reduction curve for nonelastic soils. If low-amplitude shear modulus is measured, degraded modulus at any shear strain amplitude can be calculated using the proposed equation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1C
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• pp.63-74
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• 2008

Site response analyses were performed based on equivalent linear technique using the local geologic and dynamic site characteristics, which include soil profiles, shear wave velocity profiles and depth to bedrock for 125 sites collected in Korean Peninsula. From the results of site response analyses, 2-parameters site classification system based on the combination of mean shear wave velocity of soil and depth to bedrock was newly recommended for regions of shallow bedrock depth in Korea. First, as the borders of bedrock depth (H) for site classification were determined as 10m and 20m, the soil sites were divided into 3 classes as $H_1$, $H_2$ and $H_3$ sites. And then, the 3 site classes were subdivided into 7 classes based on the mean shear wave velocity of soil ($V_{s,soil}$). The feasibility of new site classification system was verified and the representative site coefficients ($F_a$ and $F_v$) and design response spectrum were suggested by analyzing uniform trend and dispersion of site coefficients for each site class. The suggested site coefficients and the regression curves present the nonlinear characteristics of soils according to the change of rock outcrop acceleration with uniform trend effectively. From the comparison between the mean values of response spectrum which was acquired from the site response analysis and the suggested design response spectrum, there was a little difference in some of site classes and it was verified to adjust the integration interval to make it more suitable for the site condition in Korea.

• Journal of the Korean Geotechnical Society
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• v.24 no.4
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• pp.89-100
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• 2008

Applying graph and correlation developed in other countries to the domestic field has limits. Therefore, it is necessary that Piezocone factor should be determined by including ground characteristics obtained from various test results in the domestic site for better application. In this study, laboratory tests and field tests were performed to find the characteristics of soft ground which was widely distributed around Siwha lake. A comparative analysis of these tests with Piezocone penetration test was performed and the Piezocone factor was estimated by correlationship analysis of undrained shear strength and cone resistance. Also, an appropriate Piezocone factor in the study site was reestimated by utilizing statistical analysis method for deriving reliable result.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.2 s.48
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• pp.63-71
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• 2006

In the companion paper (II, Development of Site Classification System), new size classification system based on site periods $(T_G)$ was recommended for legions of shallow bedrock depth in Korea. Despite the site classification method was improved, the response spectrum would be required to be modified by adjusting the integration interval to calculate the site coefficients because the response spectra did not match well the average spectral accelerations obtained by site response analyses in the range of long periods. In this paper, new response spectra for each site categories were determined by adjusting the integration interval of long period site coefficient $F_v\;from\;0.4{\sim}2.0\;to\;0.4{\sim}1.5$ second. It matched well the average spectral accelerations and new response spectrum, and it was also improved compared to the current she classification system.

• Proceedings of the Korean Geotechical Society Conference
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• 1997.10a
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• pp.65-72
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• 1997

• Journal of the Korean GEO-environmental Society
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• v.10 no.7
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• pp.53-66
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• 2009

Recently, the importance of investigation for soft ground has been raised, so that various techniques of the investigation for soft ground are being introduced and applied. In particular, Piezocone penetration test has been utilized frequently home and abroad to identify many features of grounds precisely and gain various results in accordance with dividing strata and depth constantly by measuring continuously. In this study, to identify some features of soft clays distributed in the estuary of Nakdong river, researchers conducted field tests and laboratory tests with boring tests, and analyzed and compared with Piezocone penetration test. In addition, credible Piezocone factor of communities of subjects for this study was estimated to analyze some features of undrained shear strength of clay and calculate Piezocone factor compared with corrected cone resistance and apply some statistical techniques to estimated Piezocone factor.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.3
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• pp.87-93
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• 2008

The large scale shaker can be employed to measure linear and nonlinear shear moduli of soils in situ as a function of shear strain. The method involves applying dynamic loads on a surface foundation measuring the dynamic response of the soil mass beneath the foundation with embedded instrumentation. This paper focuses on the development of a framework of the inverse analysis for the interpretation of test data to estimate linear and nonlinear shear moduli of soils along with the necessity of the inverse analysis. The suggested framework is based on the nonlinear least squares but it uses two iterative loops to account for the nonlinear behavior of soil that sensors are not located. The validity of the suggested inversion framework is tested through a series of numerical parametric studies. An example use of the suggested inversion framework is also shown. Because the field condition may affect the accuracy of suggested method, it is important to conduct a preliminary inverse analysis to quantify the discrepancy between the estimated modulus and the baseline.

• Journal of the Society of Disaster Information
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• v.19 no.1
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• pp.31-43
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• 2023

Purpose: In this study, an analysis of the differences between the elastoplastic analysis and the numerical analysis and a study of the design ground constant recalculation method to derive similar trends in the analysis results were conducted. Method: The relational expression between the ground reaction force coefficient and the ground deformation coefficient at the time when the wall displacement becomes the same according to shallow excavation and deep excavation was derived. Result: Based on the measurement results, reverse analysis was performed to re-calculate the ground properties suitable for the site ground, and as a result of comparing and verifying the wall displacement using the derived formula and the literature formula, the proposed formula showed the most similar value. Conclusion: If the proposed formula is used, it will be helpful in practice because it is possible to infer the most similar ground properties to the actual at the time of design.

• Geotechnical Engineering
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• v.5 no.2
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• pp.78-82
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• 1989

• Geotechnical Engineering
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• v.9 no.1
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• pp.21-30
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• 1993

To know the importance of soil paramters which are used to estimate the deformation and porepressure of soil, the sensitivity for soil parameters in elastic analysis is analyzed. Using the consolidation teat results of several cohesive soils, soil parameters are estimated by back analysis method, and from the parameters the deformations and porepressures of the soil are estimated by elastic analysis, In elastic analysis for soil-deformation and porepressure, the sensitivity for the Young's modulus is large, and the esimation of Young's modulus is more important in pro- portion to the size of stress. Using the measured results during initial short period in small stress, the soil parameters can be correctly estimated by back analysis method. To decrease the iteration number in back analysis and to get the better paramters, the initial measurements in more nodes are required and the more accurate initial measurements are required.