• Journal of the Korean Geotechnical Society
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• v.18 no.1
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• pp.29-39
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• 2002

In order to evaluate the behavior of overall range from small strain to failure, the triaxial compression tests with LVDTs were performed for local displacement measurements. According to the result it was possible to evaluate the total range behavior from 0.001% to 10% and both secant moduli of undisturbed and disturbed weathered soils had a similar result in the small slain level. The normalized shear moduli$(G/G_{max})$ in the undrained triaxial compression tests were similar to those of resonant column tests but the maximum shear moduli$(G/G_{max})$ were strongly affected by the ratio of saturation. As a result of parametric study a constitutive model with anisotropic hardening could predict the behavior of total strain range.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.1106-1116
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• 2008

Single-pole transmission structures which are supported by drilled shaft foundations are usually subjected to large overturning moments with modest vertical and lateral loads. To analyze the behavior of the drilled shaft under such loading conditions, an analytical model was developed based on beam-column and subgrade reaction methods. Field model tests were performed to calibrate the developed analytical model in which additional subgrade spring models were adopted. The field test results estimated from the calibrated analytical model were compared with those calculated by one spring model and other commercial program. According to the comparison study, the developed analytical model was proven to be a useful tool to analyze the laterally loaded behavior of foundations for single-pole structures.

• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.253-261
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• 2003

Mechanical behavior of composition pound improved by sand compaction pile (SCP) with low replacement area ratio could be more significantly affected by mechanical interaction between sand piles and clays than that of clay ground improved by SD or SCP with high replacement area ratio. It is essential to elucidate the mechanical interaction in the improved clay ground, in order to accurately estimate behavior in reducing settlement of the improved ground and increasing strength of clays. In this paper, through a series of model tests of composition ground improved by SCP with low replacement area ratio, each mechanical behaviors of sand piles and clays in the composition ground during consolidation was elucidated, together with stress sharing behavior between sand piles and clays.

• Geotechnical Engineering
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• v.10 no.1
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• pp.103-118
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• 1994

A series of drained triaxial testis was performed on a Band by use of cubical triaxial apparatus, in which three principal stresses could be applied independently. The stress -strain behavior on the same stress path with cubical triaxial test was analyzed with application of the isotropic single hardening constitutive model presented by Lade. The behavior predicted by the constitutive model presented good coincidence with experimental results during poi mary loading. However, the predicted Mo윤ding and reloading behavior wan much different from results of cubical triaxial testy. That is, the softening part of the prediction might result in a rough approximation, since the plastic work parameters of single hardening model were based on the hardening portion of the data.

• Geotechnical Engineering
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• v.10 no.1
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• pp.7-18
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• 1994

A new model for describing the behavior of clay under monotonic and cyclic loading is proposed. This model uses the hyperbolic representation for the stress -strain relationship in overconsolidated state and it describes undrained effective stress path on the basis of the critical state theory. The developed constitutive model by using an energy dissipation equation can describe the behavior of clay in heavily overconsolidated state as u.ell as lightly overconsolidated state under monotonic loading. In order to extend the model for the behavior of clay under cyclic loading, a shift function of undrained stress spacing ratio is introduced in the constitutive model developed for monotonlc loading. A single additional parameter is required to represent the cyclic effect and it can be reasonably deter mined from the test results. The measured behavior in undrained cyclic triaxial tests has been easily and precisely predicted by the newly developed constitutive model.

• Journal of the Korean Geotechnical Society
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• v.19 no.3
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• pp.15-22
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• 2003

The appropriate description of the stress-anisotropy and time-dependent behavior of cohesive soils is very important in representing the real soil behavior. In this study, two constitutive relations have been incorporated based on the generalized viscous theory: one is the plastic constitutive relation adopted to capture the stress-anisotropy with a few model parameters; the other is the rate-dependent constitutive relation adopted to describe the strain rate-dependent behavior, an important time-dependent behavior in cohesive soils. The incorporated and proposed constitutive model has relatively a few model parameters and their values need not to be re-evaluated at different strain rates. The proposed model has been verified and investigated with the anisotropic triaxial test results obtained by using the artificial homogeneous specimens.

• Geotechnical Engineering
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• v.13 no.1
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• pp.159-168
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• 1997

In order to investigate the effect of parameters such as orientation and surface roughness of a reinforcing material as well as the water content of the clay matrix on the stress-strain and failure behavior of reinforced clay, uniaxial compression tests were performed on clay samples reinforced with a steel inclusion Test results showed that the increase or decrease in strength of reinforced clay samples was found to depend on the orientation of a steel inclusion as well as water content of clay samples. The possible weakening mechanism induced by reinforcement in clay samples was related to the development of cracks along the tips of interface between steel inclusion and clay matrix. A theoretical interpretation of failure behavior of reinforced clay was made by using fracture mechanics theory, and the experimental results were compared with the theoretical predictions. The predicted crack propagation direction obtained from fracture criteria for a material containing a closed crack with friction agreed reasonably well with the measured values obtained from tests.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.514-519
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• 2006

The purpose of this study is to evaluate the performance of existing bridge foundation reinforced by battered micropiles. In order to do numerical method using a Finite element program was used to predict the micropile behavior and quantify their reinforcing effect to existing bridge foundations. In addition, effect of battered micropiles on existing foundations was compared with vertically reinforced bridge foundations. Based on the study performed, it was found that the use of battered micropile is more efficiently reducing displacement of existing foundation than vertically installed micropiles under vertical and horizontal loadings respectively. The batter angle of micropile was also found effective about $15^{\circ}\sim20^{\circ}$ to reduce the vortical displacement. The horizontal reinforcement effect is continuously larger with an increase in batter angle. So, it is believed that the results presented could give an idea to enhance in-service performance of existing bridge foundations reinforced by micropiles.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.977-986
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• 2009

Sampling disturbance can introduce considerable errors in the laboratory estimation of geotechnical properties of soils, and the results obtained from sophisticated sampling and careful laboratory testing are not matching with field behavior. Therefore, it is advantage to adopt in-situ testing techniques for the estimation of geotechnical parameters. Therefore, Screw plate loading test, one of new field test technologies, has been investigated in this study. This test can be utilized to find out important properties of soils such as load-displacement, elastic modulus, and shear strength. The screw plate loading test modified from the plate loading test is an experiment underneath ground by inserting a spiral type of auger screw. The structure and characteristics of the screw plate loading test device was examined in detail. In addition, The new screw plate loading test device was manufactured to refer the previous studies. The reliability of developing screw plate loading test was examined through the analysis of the laboratory test.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.475-483
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• 2008

It is necessary to develop a national design method for surface reinforcement of very soft ground because most current design works rely on crude empirical correlations. In this paper, the mechanical behavior of very soft ground that is surficially reinforced was investigated with the aid of a sents of numerical analysis. Several material properties of each dredged soft ground, reinforcement and backfill sand mat have been exercised the numerical analysis in order to compare the result of numerical analysis with those of the laboratory model test. Through the matching process between the numerical and experimental result, it is possible to find the appropriate material properties of the dredged soft ground, reinforcements and backfill sand mat. These verified material properties permit to show the effect of the stiffness of reinforcement and the thickness of sand mat on the overall deformation.