• Geotechnical Engineering
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• v.12 no.4
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• pp.5-20
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• 1996

In this study it was analyzed by 2-D FEM and 3-D FEM to evaluate the ground reinforceing effect of steel pipe reinforced multi -step grouting (SPRG) technique and the behavior of ground in the vicinity using the nonlinear FEM program for the ground condition of alluvium located on the top of tunnel applied by SPRG technique. It was found that the nonlinear 3-D analysis performed better than 2-D analysis in evaluating the usefulness of the SPRG technique, and it was also found that the safety was relatively secured by the stiffness of steel pipe to distribute the concentrated stress in the tunnel faceing. It was reported that the change of settlement on the top of tunnel becomes about 40% of the total expected settlement before tunnel faceing reaches tunnel gauging point, and 60% of the total expected settlement while tunnel facing passes tunnel gauging point and takes a distance about tunnel diameter. With the aid of the SPRG technique the control range of displacement and stress of the ground in the vicinity could be reached up to tunnel top, namely depth ratio from 0.38 to 0.83 or 2D(D : tunnel diameter) before the tunnel facing, and about 20% of settlement control in this particular case was possible.

• Journal of the Korean Geotechnical Society
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• v.20 no.1
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• pp.109-120
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• 2004

There has been outstanding research on the soil-water characteristic curves of unsaturated soils over the past several decades. Unfortunately, unsaturated soil mechanics has not been considered as an important factor in Korea. In this paper, laboratory test and numerical analysis(SoilVision Professional ver 3.04) were performed to investigate the prediction method of soil-water characteristic curve and unsaturated permeability coefficient in reclaimed ground. The pressure cell, desiccator, and tensiometor tests were conducted on three types of reclaimed soils(dredged soil, sand, weathered granite soil). Numerical analysis was executed to compare the results with the laboratory test results and also compared with the results of each prediction method. Based on the laboratory test, three different types of soils have shown different soil-water characteristic curves. The hysteresis fir these soils is clearly defined. As a result of numerical analysis, Fredlund & Xing's method and Fredlund & Wilson's model proved to worke out well for reclaimed ground soils in Korea. Also, predicting method based on the soil-water characteristic curves from the particle-size distributions is flirty reliable for estimating unsaturated permeability coefficient.

• Journal of the Korean Geotechnical Society
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• v.26 no.2
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• pp.5-14
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• 2010

In this study, cyclic triaxial tests were performed under anisotropically consolidated condition by using irregular earthquake loading to consider in-situ condition and seismic wave. Jumunjin sand with a relative density 50 percent was used in the tests. The consolidation pressure ratio (K) was changed from 0.5 to 1.0. The Ofunato and Hachinohe wave were applied as irregular earthquake loadings and liquefaction resistance strengths of each specimen were estimated from the excess pore water pressure (EPWP) ratio. As a results of the cyclic triaxial tests, EPWP ratio increased with increased K value. It shows that isotropically consolidated sand is more susceptible to liquefaction than anisotropically consolidated sand under equal confining pressure and dynamic loadings. From the test results, the relationship between K and EPWP ratio normalized by effective confining pressure and deviator stress was proposed. And a new factor which corrects the liquefaction resistance strength for the in-situ stress condition is proposed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3C
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• pp.187-196
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• 2008

An earthquake of magnitude 5.0 occurred at Ssang-gye-sa, a Buddhist temple in Jirisan, located near the southern border of the Korean peninsula on 4 July 1936. It resulted in severe damage of several buildings and structures in Ssang-gye-sa. Particularly, the top component of a five-story stone pagoda in the temple was tipped over and fell down during the earthquake. This earthquake damage case would be usefully applied to estimating the intensity of ground motion in the Korean peninsula, a moderate seismicity region, where strong motion has never been recorded with the exception of historic seismic events. In order to estimate the local site effects and the corresponding ground motion at Ssang-gye-sa site, intensive site investigations including borehole drilling and in-situ seismic tests such as crosshole and SASW tests were performed in the temple area. Based on the site characteristics, site-specific seismic response analyses using various input motions were conducted for a representative Ssang-gye-sa site by means of both one-dimensional equivalent-linear and nonlinear methods with six input rock outcrop acceleration levels ranging from 0.044g to 0.220g. The resultant site-specific seismic responses indicated the amplified ground motions in the short-period range near the site period of Ssang-gye-sa. Furthermore, the intensity on rock outcrop of the 1936 Jirisan earthquake was estimated by making a comparison between the site responses analysis results in this study and the full-scaled seismic test of pagoda model in the prior study.

• Journal of the Korean Geotechnical Society
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• v.15 no.6
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• pp.121-130
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• 1999

The objective of this study is to perform finite element analyses(FEA) using the anisotropic hardening constitutive model on the basis of the total stress concept. An anisotropic hardening model was then developed to solve the problem and its mathematical formulations and experimental verifications were also described. In a companion paper, the constitutive equation will be formulated for accurate and efficient solutions of FEA, and coded into a nonlinear analysis program, and finally a field problem will be analyzed. The proposed model includes the failure criterion of a von Mises type and the anisotropic hardening rule based on the generalized isotropic hardening description, which can model the nonlinearity and the anisotropy of the stress-strain relationship. As a result this study could verty the experimental results for UU triaxial tests, CU triaxial tests for overconsolidated samples, and anisotropic loading tests with the rotation of principal stress axes for $K_0$consolidated samples.

• Journal of the Korean Geosynthetics Society
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• v.9 no.3
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• pp.29-37
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• 2010

This study aims at evaluating the engineering properties of very poor graded fine sands deposited on the sea. Using materials sampled at SAEMANKEUM area, a series of rowe cell consolidation tests and triaxial compression tests are conducted in order to evaluate the characteristics of deformation and shear strength by the relative density. Prior to those tests, a maximum and a minimum relative densities are obtained. As a result, it appears that the minimum void ratio is 0.88, and the maximum compactible relative density is about 71%. In addition, internal frictional angle appears to increase linearly with an increase of the relative density which is similar to that of the port KUNJANG.

• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.1
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• pp.1-12
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• 2012

In this paper, the reduction factors to calculate the site coefficients of an embedded foundation are estimated, considering the effect of a poor backfill for the seismic design of a building built on an embedded foundation. This is determined by utilizing in-house finite element software, P3DASS, which has the capability of horizontal pseudo 3D seismic analysis with nonlinear soil. The 30m thick soil on stiff rock was assumed to be homogeneous, elastic, viscous and isotropic, and equivalent circular rigid foundations with radii of 10-70m were assumed to be embedded 0, 10, 20, and 30 m in the soil. Seismic analyses were performed with 7 bedrock earthquake records de-convoluted from the outcrop records; the scaling of the peak ground accelerations were to 0.1 g. The study results show that the site coefficients of a poor-backfilled foundation are gradually reduced as the foundation embedment ratio increases, except in the case of a small foundation embedded deeply in the weak soft soil. In addition, it was found that the deviation of the site coefficients due to the foundation size was not significant. Therefore, the typical reduction factors of an embedded foundation with poor backfill are proposed in terms of the shear wave velocity and site class. This is in order to find the site coefficients of an embedded foundation by multiplying the reduction factor by a site coefficient of a surface foundation specified in the design code. They can then be interpolated to determine the intermediate shear wave velocity.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.5
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• pp.53-65
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• 1993

In this work the dynamic response of 3-D arbitrarily shaped rigid massless foundation is numerically obtained using boundary element under non-relaxed boundary condition. The problem is formulated in time domain by the boundary element method. The fundamental solutions used in this work are the Stokes solutions of the three dimensional elastodynamics. This method has advantages over frequency domain techniques in that it provides in a natural and direct way the time history of the response and forms the basis for elct:ension to nonlinear problems. This work is verified and can be used for practical purpose.

• Economic and Environmental Geology
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• v.43 no.2
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• pp.177-184
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• 2010

When cement grout is used for waterproofing of grounds, important roles are played by fluidity, particle size and bleeding. The most important element which determines their characteristics is the water/cement ratio of grout. Moreover in order to improve the efficiency of soil permeation, micro cement with a smaller average diameter is used in addition to ordinary portland cement. Besides the mixing ratio and cement diameter, the condition of ground is also of fundamental importance in the efficiency of permeation. In order to evaluate grout in terms of permeation ability into ground, we need a field test of grounting, which is cost and time consuming. In this paper we present a laboratory test method in which the suitability and efficiency of grouts are simply and more practically tested. In Korea neither a test standard nor devices are available to simulate grouting in a laboratory. We devised a grout injection equipment in which grouting was reproduced in the same condition with different materials, and suggested a standard for the production of specimens. Our tests revealed that the efficiency of injection increases with the water/cement ratio. We also found that more efficiently injected is the grout with the order of decreasing size; MS8000, micro cement, and ultra fine cements, and colloidal super cement.

• Journal of the Korean Geotechnical Society
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• v.40 no.2
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• pp.95-103
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• 2024

The global increase in population and subsequent scarcity of terrestrial living spaces necessitates exploration of alternative habitats. Research into the development of underwater living areas provides promising avenues for the expansion of human living spaces and the use of marine environments. This study focuses on the failure envelope of suction caisson foundations subjected to combined loads in a marine setting, utilizing finite element analysis. The foundation is assumed to be embedded in clay characterized by a linear increase in undrained shear strength with depth, employing the von Mises constitutive model for the clay. The resulting failure envelope is represented as a tilted ellipse which expands as the undrained shear strength increases, maintaining a constant ratio between the major and minor axes. A comparative analysis of two suction caisson foundations with varying length-to-diameter ratios revealed that this ratio influences the dimensions of the failure envelope, with a tendency for the major-to-minor axis ratio to increase as the length-to-diameter ratio increases. These findings are critical for the design of suction caisson foundations in offshore environments.