• Journal of the Korean Geotechnical Society
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• v.20 no.6
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• pp.85-94
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• 2004

In the companion paper, a constitutive model was proposed in order to represent brittleness and dilatancy for cohesionless soils. An optimized design methodology was proposed on the basis of real-coded genetic algorithm in order to determine parameters fir the proposed model systematically. The material parameters were then determined by that algorithm. In order to verify the proposed model, triaxial tests were peformed under $K_0$ conditions for weathered soils. In addition, the results of istropic compressed triaxial tests for granular materials verified the proposed model. For those results the brittle stress-strain relationship and the dilatancy could be modeled reasonably by the proposed model. As a result it was found that the proposed model can appropriately represent the behavior on weathered soil and granular soil.

• Journal of the Korean Geotechnical Society
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• v.28 no.10
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• pp.27-40
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• 2012

In the design of a piled raft, the axial resistance is offered by the raft and group piles acting on the same supporting ground soils. As a consequence, pile - soil - raft and pile - soil interactions, occurring by stress and displacement duplication with pile and raft loading conditions, act as a key element changing resistances of the raft and group piles. In this study, a series of centrifuge model tests have been performed to compare the axial behavior of group pile and raft with that of a piled raft (having 16 component piles with an array of $4{\times}4$) in sands with different relative densities. The test results revealed that the increase of settlement resistance occurs separately with settlement by group pile - soil interactions. The axial resistance of group piles (at piled raft) increases by group pile - raft (pile cap) interactions and that of raft (at piled raft) decreases by group pile - raft (pile cap) interactions.

• Journal of the Korean Geotechnical Society
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• v.29 no.1
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• pp.161-170
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• 2013

In this paper, numerical pile segment analysis is conducted with an advanced soil elastoplastic model to investigate the diameter effects on skin friction behaviour of a drilled shaft in sand. Ultimate skin friction and 't-z' behavior from the pile segment analyses for drilled shafts show good agreement with those from design methods. Higher ultimate skin friction for the smaller diameter pile is related to the greater increase in the effective radial stress at the interface due to the localized dilation at and near the pile interface. Stiffer t-z curve for the smaller diameter pile is related to the early occurrence of three shear stages (early, dilation, constant volume shear stages). The diameter effects on ultimate skin friction of drilled shafts are more prominent for denser sand and lower confining pressure.

• Journal of the Korean Geotechnical Society
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• v.33 no.4
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• pp.25-34
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• 2017

The soil-water characteristics is the most important state parameter for understanding changes in suction and water contents of unsaturated soil slopes. In the field, the hysteretic behaviors of drying and wetting soil-water characteristic curve are real and the adoption of path-dependent suction-water content is needed to predict the hydro-mechanical analysis of unsaturated soils. In this study, in-situ monitored hydraulic behavior of various soil slopes are compared with the data from numerical analysis with the laboratory soil water characteristic curve. Then, the verifications are performed based on the field monitored data respectively. Therefore, the use of path-dependent soil-water characteristic curves could be more rational for design and analysis of unsaturated soil slopes under rainfall conditions.

• Journal of the Korean Geosynthetics Society
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• v.10 no.3
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• pp.43-51
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• 2011

This paper describes the results of pullout tests in the laboratory, which are conducted to assess the pullout performance of recently developed geosynthetic strip reinforcement with rounded band anchor. The geosynthetic strip can be used as reinforcements in reinforced soil wall with concrete block facing. The pullout resistance of the geosynthetic strip with rounded band anchor is mobilized by the combination of the interface friction between soil-reinforcement surface and the passive soil resistance caused by the rounded band anchor. Therefore, both the friction resistance and the passive resistance have to be considered in design. From the pullout test results, when the rounded band anchor are formed in the end part of the geosynthetic strip, pullout strength increases about from 10% to 65%. The passive resistance can be evaluated based on the pullout test results.

• Journal of the Korean Geotechnical Society
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• v.28 no.4
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• pp.67-78
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• 2012

A three-dimensional approximate computer-based method, YSPR (Yonsei Piled Raft), was developed for analysis of behavior of piled raft foundations. The raft was modeled as a flat shell element having 6 degrees of freedom at each node and the pile was modeled as a beam-column element. The behaviors of pile head and soil were controlled by using $6{\times}6$ stiffness matrix. To model the non-linear behavior, the soil-structure interaction between soil and pile was modeled by using nonlinear load-transfer curves (t-z, q-z and p-y curves). Comparison with previous model and FEM analysis showed that YSPR gave similar load-displacement behaviors. Comparison with field measurement also indicated that YSPR gave a reasonable result. It was concluded that YSPR could be effectively used in analysis and design of piled raft foundations.

• The Journal of Engineering Geology
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• v.17 no.3
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• pp.339-350
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• 2007

Content, swelling, concentration, drainage of clay are critical factors that could control rock failures as well as discontinuous geological structures like faults and joints. Especially, the proportional components of clay minerals can be one of few direct indicators to a rock failure caused well by rainfall. Criticality of the role of clay mineral contents gets bigger in the slope and tunnel design. This study, using a horizontal boring core of pelitic/psammitic phyllite from the OO tunnel construction site, aims to investigate mineral composition changes related to fault distribution and their mechanical effects to the activity of these discontinuous layers (i.e., clay-filled fault layers), and eventually to define correlation among rock compositions, weathering products and rock instabilities. Field survey and lab tests were carried out for the composition and strength index of fault clay minerals within the core samples and microscopic analysis of fresh and weathered rock samples.

• Journal of the Korean Geotechnical Society
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• v.30 no.8
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• pp.25-37
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• 2014

In load and resistance factor design (LRFD) method, resistance factors are typically calibrated using resistance bias factors obtained from either only the data within ${\pm}2{\sigma}$ or the data except the tail values of an assumed probability distribution to increase the reliability of the database. However, the data selection approach has a shortcoming that any low-quality data inadvertently included in the database may not be removed. In this study, a data quality evaluation method, developed based on the quality of static load test results, the engineering characteristics of in-situ soil, and the dimension of aggregate piers, is proposed for use in constructing database. For the evaluation of the method, a total 65 static load test results collected from various literatures, including static load test reports, were analyzed. Depending on the quality of the database, the comparison between bias factors, coefficients of variation, and resistance factors showed that uncertainty in estimating bias factors can be reduced by using the proposed data quality evaluation method when constructing database.

• Journal of the Korean Geotechnical Society
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• v.33 no.12
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• pp.59-73
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• 2017

Numerical analysis using 3D finite element program (PLAXIS 3D) evaluated the interaction of soil - pile structure under dynamic surface loading. The dynamic p-y curve of the 1-g shaking table experiment by numerical analysis was calculated, and the parametric studies were presented by considering the pile-soil condition, the pile tip condition, and the loading condition. The frequency of 1.4 Hz is almost equal to the natural frequency of the pile - soil system. The p and y values of resonance phenomenon are significantly different from the results of other frequencies. The results can be summarized by a third order polynomial function representing the trend line in the p-y curve. In the case of a single pile, the shape of the dominant curve was found to be an ellipse by mathematical proof. The elliptic equation can be used for the dynamic design or analysis of soil-pile system.

• Geotechnical Engineering
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• v.5 no.4
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• pp.5-16
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• 1989

This paper statistically analyses the freezing soil by frost group and frost depth in Korea with data from soil testing in the Korea National Housing Corporation, the climate data provided by the Central Weather Office and the data on the frost depth from the National Construction Laboratory Institute. In this paper, freezing variable are analysed such as percentage finer than 0.02 m by weight, plasticity index, freezing index, water contents of soil and frost depth etc‥‥ The result of the analysis is as follows. 1) The frost depth of Korea depends on the properties of soil rather thank the characte fistic of area. 2) The distribution map of design freezing index in 57 cities is drawn up with the maxi- mum freezing index, during past 14 years, calculated by the average of the air temperature observed four times(03 : 00.09 00, 15 : 00, 21 : 00) a day. 3) By correcting the OLS line estimated from the relationship between freezing index and frost depth, a method of utlizing the line with the upper confidence limit of 99.9% int-distribution as predicted maximum frost depth is newly introduced.