• Proceedings of the Korean Geotechical Society Conference
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• 1989.06a
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• pp.1-45
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• 1989

• Journal of the Korean Geosynthetics Society
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• v.10 no.4
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• pp.93-103
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• 2011

In order to design suitable geo-structures in cold region, it is generally required to consider the mechanical properties of permafrost soils. 'Frost heave' as one of the primary phenomenon is considered to be an important factor together with 'adfreeze bond-strength' and 'creep deformation' for structural design process in permafrost area. Therefore, the fundamental study for frost heave has to be preceded for design of geo-structures in cold region. While various experimental apparatuses have been developed, there still exist a certain level of limitation to evaluate the frost-heave characteristics as design parameters. In this paper, a new type of experimental apparatus is proposed to evaluate the engineering characteristics of frost heave in permafrost soils and a set of verification test results is presented. Based on the verification tests, the proposed apparatus is a suitable to obtain frost characteristics of soils.

• Journal of the Korean Geosynthetics Society
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• v.13 no.4
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• pp.97-107
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• 2014

Finite element modelling and analysis were conducted for the roll-type steel mats which were placed on loose sand and subjected to a standard truck wheel load in this study. The roll-type steel mats mean that the steel mats can be folded as a circle shape for the carrying to fields in cold regions where workability is limited and are developed for a rapid rehabilitation method for roadway across soft ground which is caused by thawing during the summer season in cold regions. The model is composed of link elements to simulate nonlinear behavior of connections between steel mats, thick shell elements to have flexural stiffness of the steel mats, and springs to simulate characteristics of foundation soils. The structural behaviors of the shell, link elements, and springs were verified at each modelling step through experiment and analysis. Beam and shell analysis without the link elements were conducted and compared to results obtained from the model presented in this study. Significant vertical displacement is shown in the shell model with hinge connections. Therefore, the results demonstrate that the analysis model for the roll-type steel mats on loose sand needs further detail parametric studies.

• Journal of the Korean Geotechnical Society
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• v.27 no.10
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• pp.13-23
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• 2011

Bearing capacity of pile foundations in cold region is dominated by adfreeze bond strength between surrounding soil and pile perimeter. It denotes that adfreeze bond strength is the most important design parameter for foundations in cold region. Adfreeze bond strength is affected by various factors like 'soil type', 'frozen temperature', 'normal stress acting on soil/pile interface', 'loading rate', 'roughness of pile surface', etc. Several methods have already been proposed to estimate adfreeze bond strength during past 50 years. However, most methods have not considered the effect of normal stress for adfreeze bond strength. In this study, both freezing temperature and normal stress have been controlled as primary factors affecting adfreeze bond strength. A direct shear box was used to measure adfreeze bond strength between sand and aluminum under different temperature conditions. Based on the test results, the relation between shear strength of frozen sand and adfreeze bond strength have been investigated. The test results showed that both of shear strength and adfreeze bond strength tend to increase with decreasing frozen temperature or increasing confining pressure. The ratio of shear strength and adfreeze bond strength, expressed as $r_s$, decreased initially frozen section but increased at much lower frozen temperature and there were uniform intervals under the different normal stress conditions. A method for predicting adfreeze bond strength using $r_s$ has finally been proposed in this study.

• Journal of the Korean Geotechnical Society
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• v.36 no.3
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• pp.25-36
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• 2020

In this research, three-point bending tests were performed using a rectangular frozen specimen with various fine contents and notch offset distance from the center of the specimen to investigate the fracture characteristic of the frozen sand. Based on the test results, mode I fracture toughness was calculated, and mixed-mode (mode I + II) fracture characteristics were investigated using the fracture energy which was calculated until the maximum point of the load-displacement curve. As the fine contents increase, the peak load and mode I fracture toughness increase until 10% fine contents. Furthermore, as the notch offset distance increases, the fracture energy required for crack start also increases due to the increase in mode II load at the crack tip.

• Journal of the Korean GEO-environmental Society
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• v.13 no.11
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• pp.51-60
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• 2012

In order to characterize the shear strength of the frozen sand for foundation design in cold region and prediction of adfreeze bond strength, many researchers developed test techniques and carried out many tests to analyze shear strength properties of the frozen sand for half a century. However, many studies for shear strength properties of the frozen sand have been carried out with limited circumstances, even though shear strength of the froze sand can be affected by various influence factors such as soil type, temperature conditions, and magnitude of normal stress. In this study, direct shear test equipment was used to analyze the shear strength characteristics of the frozen sand. Direct shear test equipment was designed for cold weather, and the direct shear tests were carried out inside of large-scaled low temperature chamber. Three soil types-two uniform sands and one well graded soil were used to analyze the shear strength of the frozen sand with three different temperature conditions and three different vertical confining pressures. In this research, a series of direct shear tests for shear strength of the frozen sand have been conducted to demonstrate the efficiency of effectiveness of the test equipment and low temperature chamber. This research also showed that shear strength of the froze sand increased with decreasing temperature condition, but the influence of vertical confining pressure was insignificant to the shear strength of the frozen sand.

• Journal of the Korean GEO-environmental Society
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• v.14 no.12
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• pp.23-30
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• 2013

Bearing capacity of pile is governed by only skin friction in frozen ground condition, while it is generally governed both by skin friction and end bearing capacity in typically unfrozen ground condition. Skin friction force, which arises from the interaction between pile and frozen soils, is defined as adfreeze bond strength, and adfreeze bond strength is one of the most important key parameters for design of pile in frozen soils. Many studies have been carried out in order to analyze adfreeze bond strength characteristics over the last fifty years. However, many studies for adfreeze bond strength have been conducted with limited circumstances, since adfreeze bond strength is sensitively affected by various influence factors such as intrinsic material properties, pile surface roughness, and externally imposed testing conditions. In this study, direct shear test is carried out inside of large-scaled freezing chamber in order to analyze the adfreeze bond strength characteristics with varying freezing temperature and normal stress. Also, the relationship between adfreeze bond strength and shear strength of the frozen soil obtained from previous study was analyzed. The coefficient of adfreeze bond strength was evaluated in order to predict adfreeze bond strength based on shear strength, and coefficients suggested from this and previous studies were compared.

• Journal of the Korean Geotechnical Society
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• v.30 no.9
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• pp.57-66
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• 2014

The ground in cold region consists of active and permafrost layers. The active layer at the unstable state may cause ground corrosion and uplift, when the temperature of frozen ground increases due to seasonal changes. The thermosyphon is one of the stabilization methods to maintain the ground stability in the frozen ground. The thermosyphon is a closed two-phase convection device that extracts heat from the ground and discharges it into the atmosphere. In this study, ground freezing experiment using a thermosyphon and simulated ground with the isolation material was conducted to evaluate the thermal performance of the thermosyphon. In order to consider the thermal performance of the thermosyphon, commercial numerical program (TEMP/W) was adopted. Likewise, the thermal performance of thermosyphon and thermal properties of ground were applied in the numerical model. In a series of comparisons with experiment results and numerical study, thermal performance of thermosyphon can be evaluated.

• Journal of the Korean Geotechnical Society
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• v.28 no.5
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• pp.85-94
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• 2012

Recently, growing interests in frozen ground have stimulated us to advance fundamental theories and systematic researches on soil behavior under freezing conditions. Unlike the well-established soil mechanics theory, temperature variation and phase change of pore-water cause water migration to cold side, ground heaving, sharp increase in earth pressure, etc., which bring about serious problems in frozen geotechnical structures. Elasto-plastic mechanical constitutive model for frozen/unfrozen soil subjected to fully coupled THM phenomena is formulated based on a new stress variable that is continuous in frozen-unfrozen transitional regions. Numerical simulations are conducted to discuss numerical reliability and applicability of the developed constitutive model: one-dimensional heaving pressure, tri-axial compression test, and one-side freezing tests. The numerical results show that developed model can efficiently describe complex THM phenomena of frozen soil, and they can be utilized to analyze and design the geotechnical structures under freezing conditions, and predict their long-term behavior.

• Journal of the Korean GEO-environmental Society
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• v.12 no.12
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• pp.79-88
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• 2011

Adfreeze bond strength develops upon freezing of pore water within soil and at foundation surface. It has been reported that various factors like temperature, soil type, and pile surface roughness affect adfreeze bond strength. Especially, pile surface roughness has been considered as a primary factor to design pile foundation in frozen ground. It has usually been estimated with fixed correction factors for pile materials. However, even if the pile foundation material is the same, the surface roughness could vary depending on the production circumstances. In this study, laboratory test was carried out to quantitatively analyze the effects of surface roughness on the adfreeze bond strength, and fractal dimension was used as a measure for surface roughness. Test results showed that adfreeze bond strength increased with decreasing temperature, increasing vertical stress and surface roughness. The adfreeze bond strength varies sensitively with surface roughness in the early freezing section of $-2^{\circ}C$, but its sensitivity decreased in the temperature ranging between $-2^{\circ}C$ to $-5^{\circ}C$. The results conclude that the roughness highly affects the frictional resistance of pile surface in frozen ground; however, the roughness does not affect considerably when the temperature drops below about $-2^{\circ}C$.