• Journal of Ocean Engineering and Technology
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• v.28 no.2
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• pp.133-139
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• 2014

Offshore wind turbines have been constructed extensively throughout the world. These turbines are subjected to approximately $10^8$ horizontal load cycles produced from wind, waves, and current during their lifetimes. Therefore, the accumulated displacement of the foundation under horizontal cyclic loading has significant effects on the foundation design of a wind turbine. Akili(2006) and Achmus et al.(2009) performed cyclic triaxial tests on dry sands and proposed an empirical model for predicting the accumulated plastic strain of sands under long-term cyclic loading. In this study, cyclic triaxial tests were performed to analyze the cyclic loading behaviors of dry sands. A total of 27 test cases were performed by varying three parameters: the relative density of the sands, cyclic load level, and confining stress. The test results showed that the accumulated plastic strain increased with an increase in the cyclic load level and a decrease in the relative density of the sand. The confining stress had less effect on the plastic strain. In addition, the plastic strain at the 1st loading cycle was about 57% of the accumulated strain at 1,000 cycles. Finally, the input parameters of the empirical models of Akili(2006) and Achmus et al.(2009) were evaluated by using the relative density of the sand and the cyclic load level.

• Journal of the Korean Geosynthetics Society
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• v.14 no.1
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• pp.11-21
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• 2015

This study aims at investigating of the behavioral characteristics of foundation ground subjected to a strip load in anisotropy. Using marine clays sampled at Shihwa area, a series of laboratory tests including triaxial compressive test, plane strain compressive and expansion tests that allows horizontal deformation only and zero strain (${\varepsilon}_2$) in the direction of intermediate stress (${\sigma}_2$) are conducted. In addition, a numerical analysis using parameters obtained from the tests is carried out. In the numerical analysis, Cam-clay model that simulates the behavior of natural deposited clay properly is adopted. The analysis results show that the vertical displacements of the plane strain compressive tests are relatively larger than those of triaxial compressive tests by 18-25%. Likewise, the horizontal displacements is 13-19% larger.

• Journal of the Korean GEO-environmental Society
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• v.4 no.2
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• pp.27-37
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• 2003

In this research stress-strain behavior of composite geocell-soil systems under triaxial condition and the influence of strength due to the presence of geocell were studied. For the research a series of triaxial tests were carried out on sand specimens confined by flexible-walled single rubber cell. The diameter of all rubber cells placed at the center of the soil sample were 50 mm. Three rubber sizes, i.e. 35, 50 and 70 mm height, were applied to the soil specimen and the size of soil specimen was 50 mm in diameter and 100 mm in height. Three different densities of soil were used for the tests. In general, it was observed that the sand specimen develops an apparent cohesion due to the confinement by the geocell. The magnitude of this cohesion seemed to be dependent to the properties of the geocell material. The test results have shown that the geocell material for this research not only develops the apparent cohesion but also increases the angle of friction whereas geosynthetic material in the references showed only the increase of apparent cohesion. From the application of geocell-soil composites to the hyperbolic model, it was recognized that the determination of the peak strength influences the behavior of the geocell-soil composites.

• Tunnel and Underground Space
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• v.17 no.2 s.67
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• pp.119-127
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• 2007

Based on the critical plane approach, a methodology far predicting the anisotropic strength ot transversely isotropic rock is Proposed. It is assumed that the rock failure is governed by Hoek-Brown failure criterion. In order to establish an anisotropic failure function, Mohr envelope equivalent to the original Hoek-Brown criterion is used and the strength parameters m, s are expressed as scalar functions of orientation. The conjugate gradient method, which is one of the robust optimization techniques, is applied to the failure function for searching the orientation giving the maximum value of the anisotropic function. While most of the existing anisotropic strength models can be applied only when the stress condition is the same as that of conventional triaxial compression test, the proposed model can be applied to the general 3-dimensional stress conditions. Through the simulation of triaxial compression tests for transversely isotropic rock sample, the validity of the proposed method is investigated by comparing the predicted triaxial strengths and inclinations of failure plane.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.4
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• pp.501-508
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• 2022

Required essential technique is to determine the maximum recharge pressure in the well with condition of non-ground failure for the recovery of the groundwater. Based on the classical soil mechanics, the maximum recharge pressure was estimated with the numerical anlaysis and laboratory triaxial test. In the numerical analysis, the maximum recharge pressure is defined as the ground failure stress. The ground failure of the sand was defined as the piping and the one of the caly was to the undrained failure by the confined pressure increment. In the triaxial test, the recharge pressure in the ground was modified by the back pressure in the specimen. In case of sand, the volume strain was dramatically increased at the 93 % of the maximum back pressure, same meaning of the 0 effective stress state. In case of clay, the only radial volume strain was to reached 1.5 % without failure. Therefore, The maximum recharge pressure could be determined with the numerical analysis and triaxial test.

• Geotechnical Engineering
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• v.4 no.3
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• pp.43-52
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• 1988

The behavior of clays subjected to Repeated loading has been shown to be very different from the behavior under a single load application. Especially the behavior of pore water pressure is Qf considerable importance. The objective of this work is to experimentally study the stress-strain characteristics of clays, and this study includes the pore water pressure which is built up during the load repetition. For this study, the samples were consolidated isotropically in the triaxial cell during 24 hours, .and monotonic strain controlled triaxial test is carried out by uslng the tests of Compression failure, Cycled at failure, and Nonfailure equilibrium on remoulded samples under undrained .condition . Consequently there exists a critical level of repeated loading which seperates the behavior of a particular sample into two distinctly different patterns.

• Geomechanics and Engineering
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• v.22 no.6
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• pp.519-528
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• 2020

A mathematical wetting model is usually used to predict the deformation of core wall rockfill dams induced by the wetting effect. In this paper, a series of wetting triaxial tests on a rockfill was conducted using a large-sized triaxial apparatus, and the wetting deformation behavior of the rockfill was studied. The wetting strains were found to be related to the confining pressure and shear stress levels, and two empirical equations, which are regarded as the proposed mathematical wetting model, were proposed to express these properties. The stress and deformation of a core wall rockfill dam was studied by using finite element analysis and the proposed wetting model. On the one hand, the simulations of the wetting model can estimate well the observed wetting strains of the upstream rockfill of the dam, which demonstrated that the proposed wetting model is applicable to express the wetting deformation behavior of the rockfill specimen. On the other hand, the simulated additional deformation of the dam induced by the wetting effect is thought to be reasonable according to practical engineering experience, which indicates the potential of the model in dam engineering.

• Tunnel and Underground Space
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• v.2 no.2
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• pp.224-236
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• 1992

It is very important to determine the thermo-mechanical characteristics of the rock mass surrounding the repository of radioctive waste and the LPG storage cavern. In this study, Hwasoon-Shist. Dado-Tuff adn Chunan-Tonalite were the selected rock types. Temperature dependence of the mechanical properteis such as uniaxial compressive strength, tensile strength, Young's modulus was investigated by measuring the behaviour of these properties due to the variation of temperature. Also, the characteristics of strength and deformation of these rocks were examined through high-temperature triaxial compression tests with varing temperatures and confining pressures. Important results obtained are as follows: In high temperature tests, the uniaxial compressive strength and Yong's modulus of Tonalite showed a sligth increase at a temperature up to 300$^{\circ}C$ and a sharp decrease beyond 300$^{\circ}C$, and the tensile strength showed a linear decrease with increasing heating-temperature. In high-temperature triaxial compression test, both the failure stress and Young's modulus of Tonalite increased with the increase of confining pressure at constant heating-temperature, and the failure stress decreased at 100$^{\circ}C$ but increased at 200$^{\circ}C$ under a constant confining pressure. In low temperature tests, the uniaxial compressive and tensile strengths and Young's modulus of these rocks increased as the cooling-temperature is reduced. Also, the uniaxial compressive and tensile strengths of wet rock specimens are less than those of dry rock specimens.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.103-110
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• 2006

When enforced earth is used for the retain wall and four walls, the most important thing would be how to maximize the land utilization. Accordingly, in case of enforced earth, we pile up the minimal height of earth$(20\sim30cm)$ and harden the earth using a static dynamic hardening machine. In this paper, we tried to analyze and. compare the stress transformation characteristics of reinforced weathered granite soil. with geosynthetics when repetitive load is added to the enforced earth structure and when static load is added. The purposes of the study are as follows; 1) To compare and analyze non reinforced weathered granite soil and reinforced weathered granite. soil by executing a unconsolidated-undrained triaxial compression tests. 2) To identify the strength characteristics of weathered granite soil reinforced with geotextile due to the repetitive dynamic loads through comparison of the stress due to the static load and the repetitive dynamic loads.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1159-1166
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• 2005

In the present study, a series of laboratory tests with sands of different silt contents, are conducted and methods to assess non-linear behaviors based on in-situ test results are proposed. Modified hyperbolic stress-strain model is used to analyze non-linearity of silty sands in terms of non-linear degradation parameters f and g as a function of silt contents and relative density $D_R$. Stress-strain relationship results were obtained from a series of triaxial tests on sands containing different amounts of silt. Initial shear modulus which was applied to normalize modulus degradation of silty sands were determined based on the resonant column test results. From the laboratory test results, it was observed that, as the relative density increases, values of f decrease and those of g increase. Cone resistance $q_c$ for silty soil condition used in the triaxial tests were estimated based on the cavity expansion analysis. A suggestion to make an estimation of degradation parameters f and g as a function of fine contents is addressed in terms of cone resistance $q_c$ .