• Journal of the Korean Geotechnical Society
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• v.32 no.9
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• pp.37-50
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• 2016

Gravel compaction pile (GCP) is widely used as it increases the bearing capacity of soft ground and reduces the consolidation settlement. Stress concentration ratio for GCP design is dependent on the area replacement, surcharge pressure and depth. However, a range of stress concentration ratio obtained through field, laboratory experiments and numerical analysis is large. Little study has been done on the stress concentration ratio for the mixing ratio of gravel and sand. The main objective of the study is to evaluate the stress concentration ratio for both area replacement ratio and mixing ratio through literature review and numerical analysis. Numerical analysis using the finite element program ABAQUS 6.12-4 has been performed for the composite ground with GCP. The excess pore water pressure and stress concentration ratio of composite ground have been analyzed for both the area replacement ratio and the mixing ratio. Based on the previous research results, a range of stress concentration ratio obtained from the field tests, laboratory tests, numerical analysis on the GCP studies is found to be 1.7-3.2, 2.0-7.5 and 2.0-6.5, respectively. Based on the numerical analysis results, as the area replacement ratio increases, the stress concentration ratio increases up to 30% and then decreases at 40%. Also, the stress concentration ratio tends to increase up to 70:30 and then to decrease after 60:40.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.7 no.6
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• pp.39-48
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• 2004

The purpose of this paper was to confirm the application of the equation of the soil-water characteristic curve on an unsaturated soil. To this ends, a series of suction test was conducted on the selected 4 kinds of soil which is located in Korea, using the modified pressure extractor apparatus. And it was carried out to analyze the experimental parameters which can describe the soil-water characteristics, were determined by using the data obtained from the experiment. From the results, it was found that the matric suction was varied according to the grain size distribution, amount of fine grain particle and void ratio. Also it was found that the residual volumetric water content was decreased with the void ratio, but the index related air entry value, the soil parameter related water content and the parameter with residual water content were increased with the void ratio. And the application of equation of the soil-water characteristic curve was confirmed for the various conditions and the various state by the comparison between the volumetric water content measured by the experiment and the predicted values.

• Journal of the Korean Society of Industry Convergence
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• v.6 no.3
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• pp.185-192
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• 2003

This study consolidation undrain Triaxial Compression Tests using constant confining pressure in clay that receive preconsolidation stress that is different and, void ratio, pore water pressure coefficient, shear strength compare with another thing theory and studied analyzing change relation of elastic modules. The summary of analysis is follows: If preconsolidation stress increases in same confining stress in relation of preconsolidation stress and deviator stress, deviator stress is proportional and increased. Can know that excess void pressure is proportional and decreases in size of preconsolidation stress in same confining stress state if preconsolidation stress increases preconsolidation stress and relation of excess void pressure. Also, over consolidated state can assume that this is thing by Dilatancy's effect though excess void pressure decreased remarkably. Preconsolidation stress and relation of stress path can know that shear strength degree increases preconsolidation stress increases, and specially, preconsolidation stress was appear in stress path form of overconsolidated state case of clay that receive at 300, 400, 500kPa in 100, 150kPa's deviator stress.

• Journal of the Korean Geotechnical Society
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• v.37 no.8
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• pp.5-13
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• 2021

Liquefaction behaviors of two natural silty samples containing fines including clay of 50% or more (Sample No.1 was silt 44.1% and clay 8.8%, sample No.2 was silt 57.2% and clay 12.4%) were examined by a cyclic triaxial test. According to the results on samples containing 50% or more of fine particles, an increase in the fine content decreases the liquefaction resistance of the sample. In other words, when the fine content increases, the liquefaction state of sample is reached with a small number of cyclic loads. In the relationship between the excess pore water pressure ratio and the number of cycles, the slope of the excess pore water pressure ratio increases more steeply as the fine content increases. As a result of analyzing the liquefaction behavior of the two silts with the content of clay contained in the fines, liquefaction occurred more easily in the No.2 silt with high clay content. This result shows that the clay contained in the fines affects the liquefaction behavior of the silt.

• Structural Engineering and Mechanics
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• v.75 no.5
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• pp.571-583
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• 2020

Permeation grouting is of great significance for consolidating geo-materials without disturbing the original geo-structure. To dip into the filtration-induced pressure increment that dominates the grout penetration in permeation grouting, nonlinear filtration coefficients embedded in a convection-filtration model were proposed, in which the volume of cement particles in grout and the deposited particles of skeleton were considered. An experiment was designed to determine the filtration coefficients and verify the model. The filtration coefficients deduced from experimental data were used in simulation, and the modelling results matched well with the experimental ones. The pressure drop revealed in experiments and captured in modelling demonstrated that the surge of inflow pressure lagged behind the stoppage of flow channels. In addition, both the consideration of the particles loss in liquid grout and the number of filtrated particles on pore walls presented an ideal trend in filtration rate, in which the filtration rate first rose rapidly and then reached to a steady plateau. Finally, this observed pressure drop was extended to the grouting design which alters the water to cement (W/C) ratio so as to alleviate the filtration effect. This study offers a novel insight into the filtration behaviour and has a practical meaning to extend penetration distance.

• Steel and Composite Structures
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• v.36 no.6
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• pp.657-669
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• 2020

This study investigates the fire resistance characteristics of reactive powder concrete according to changes in the cement content per unit area, mixing ratio of metakaolin (MK), and content of polypropylene fiber. A fire test was conducted, and the resulting residual strength characteristics were investigated through flexural and compressive strength measurements, as well as condition rating classification based on visual evaluation. MK effectively reduced the initial high content of calcium hydroxide, thereby reducing the water vapor pressure generated during pyrolysis and slowing spalling. Furthermore, the pore structure and loose tissue were effective for relieving the water vapor pressure in the event of a fire.

• 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.

• Fire Science and Engineering
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• v.21 no.2 s.66
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• pp.54-63
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• 2007

Concrete is generally accepted to have good inherent fire resistance. It mainly relies on the assumption that concrete has low heat-transfer characteristic and spatting does not occur during the course of a fire. However, the significant numbers of fire accidents have shown in recent years that incidence of spatting has caused sever damages to many structures. This review has systematically investigated the behaviour of concrete in fire, including phenomenon of spatting, with respect to the theorical consideration and experimental results. Explosive spatting is caused by the build-up of water vapor pressure in concrete subjected to increasing temperatures. When this pressure exceeds the tensile strength of the concrete over a fire-exposed area, explosive spatting can result in a typical temperature range between $200^{\circ}C\;and\;400^{\circ}C$. The major functions are known to be moisture content, pore pressure, load ratio, and heating regime.

• Journal of the Korea Concrete Institute
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• v.25 no.6
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• pp.675-682
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• 2013

In this study, to enhance the quality of concrete surface by removing the surplus water, permeable liner attached the euroform was applied for manufacturing concrete specimens. Various kinds of concrete mixtures with different water to binder ratios were applied and the strength properties of the hardened concrete surfaces were evaluated at different heights. Experimental results showed that the rebound values by schmidt hammer test and the compressive strengths on the surfaces of concrete specimens were increased as proportion to the amount of mixture water which is dependent on the water to binder ratio of each concrete mixture, and more enhancements were observed on the middle and lower specimen surfaces than the upper region. SEM analysis also showed that much denser hydrate structures were observed on the specimen surfaces by the application of the permeable liner while similar hydrate formations were occurred regardless of surface treatment conditions. From the MIP test results of the concrete surfaces, it was observed that, by the application of permeable liner, the pore volume below $0.01{\mu}m$ was decreased with a maximum of 50% resulting in the densification of pore structures.

• Journal of the Korean Geosynthetics Society
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• v.10 no.4
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• pp.81-92
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• 2011

In order to understand evaluation of the seismic stability of a fill dam, we made chambers of 1:100, 1:70, and 1:50 (the ratio of the miniature), considering the law of similarity based on drawings of three representative cross sections. And we measured an increase in acceleration, excess pore water pressure, and vertical/horizontal displacement after applying Hachinohe wave (long period), Ofunato wave (short period), and artificial wave, complying with the domestic standards, in order to evaluate the stability and interaction between the ground, the structure, and fluids based on the measurements. As a result, we could observe that displacement of the target cross section was relatively small compared to the allowed level of 30 cm, ensuring proper stability for an earthquake. Regarding the acceleration measurements, the increase rate was 20% for Hachinohe wave and Ofunato wave but 30% for the artificial wave. With respect to the excess pore water pressure, it was lower than 1 (which is the permissible ratio for liquefaction) ensuring proper stability as well.