• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1C
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• pp.53-62
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• 2008

A constitutive model, which can simulate the effect of principal stress rotation associated with direct simple shear test, is proposed in this study. The model is based on two mobilized planes. The plastic strains occur from the two mobilized planes, and depend on stress state, and they are added. The first plane is a plane of maximum shear stress, which rotates about the horizontal axis, and the second plane is a horizontal plane which is spatially fixed. The second plane is used to consider the effect of principal stress rotation on simple shear tests under different stress states. The soil skeleton behavior observed in drained simple shear tests is captured in the model. This constitutive model is incorporated into the dynamic coupled stress-flow finite difference program FLAC. The model is first calibrated with drained simple shear tests on loose Fraser River sand. The measured shear stress and volume change are partially induced by principal stress rotation and compared with model calculations. The model is verified by comparing predicted and measured settlements due to rigid footing resting on loose sands. Settlements predicted by the proposed model were very similar to measured settlements. Mohr-Coulomb model can not consider the effect of principal stress rotation and its prediction was only 20% of measured settlements.

• Tunnel and Underground Space
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• v.15 no.6 s.59
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• pp.391-399
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• 2005

In this study, stress difference between isotropic and transversely isotropic rock mass, and planar principal stresses at the periphery of the tunnel in the rock with various ratio of anisotropy were determined theoretically. Stress differences between isotropic and anisotropic calculations at crown. side walls and floor of a tunnel with assumed stress states were analyzed and compare each other by $FLAC^{2D}$, a finite differential element method. As a result, magnitude and direction of principal stresses in the case of ignoring anisotropy were different from those of anisotropic cases, whatever the stress state was. Stress difference increased as the ratio of anisotropy increased. Direction or anisotropy affected stress difference, especially in the cases of anisotropic directions of $45^{\circ}\;and\;135^{\circ}$ of counterclockwise from x direction.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.1
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• pp.159-164
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• 1988

The directions of the principal strain increment, stress, and stress increment during rotation of the principal stress axes at any stress level was studied for $K_0$-consolidated clay using torsion shear apparatus with individual control of the vertical stress, the confining pressure, and the shear stress on hollow cylinder specimens under undrained and drained condition. The torsion shear tests were performed according to predetermined stress-paths, which were chosen to cover over the full range of rotation of principal stress axes. The test results indicated that the strain increment vectors at failure coincided with the stress vectors. That is, the direction of strain increment coincided with the direction of stress increment at small stress levels and with the direction of stress at higher stress levels, which indicated that the behavior of clay was transfered from elastic to plastic as the stress level was increased. The applicability of the elastoplastic theory for modeling of the behavior of clay during rotation of the principal stress axes was given.

• Journal of the Korean Society for Railway
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• v.14 no.1
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• pp.49-56
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• 2011

In this paper, it was compared the characteristics of the stress and settlement that occur from a track on the ground using a model test and has quantitatively analyzed the difference based on stress path and effect of the rotation of principal stress. Under identical roadbed conditions, the settlement generated by moving wheel loads were found to be 6 times and 3 times larger than that from static loads and cyclic loads, respectively. The deviator stress affecting shear deformation and the length of stress path generated by moving loads were twofold or greater increase than those by static loads. Furthermore, the stress path generated by moving loads was approached more closely to Mohr-Coulomb failure criteria compared to that by static loads. Also, it was found that ballasted track was occurred about 60% of maximum stress at $40^{\circ}$ of the rotation angle of principal stress and was affected with rotation of principal stress with moving wheel loading condition.

• Journal of the Korean Ceramic Society
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• v.28 no.1
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• pp.19-19
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• 1991

Fracture of Al2O3 tubes for different loading path under combined tension/torsion was investigated. Macroscopic directions of crack propagation agreed well with the maximum principal stress criterion, independent of the loading path. However, fracture strength from the proportional loading test(τ/σ= constant) showed either strengthening or weakening compared to that from uniaxial tension, depending on the ratio τ/σ. The Weibull theory was capable to predict the strengthening of fracture strength in pure torsion, but not the weakening in the proportional loading condition. The strengthening or weakening of fracture strength in the proportional loading condition was explained by the effect of shear stresses in the plane of randomly oriented microdefects. Finally, a new empirical fracture criterion was proposed. This criterion is based on a mixed mode fracture criterion and experimental data for fracture of Al2O3 tubes under combined tension/torsion. The proposed fracture criterion agreed well with experimental data for both macroscopic directions of crack propagation and fracture strengths.

• The Journal of Engineering Geology
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• v.8 no.1
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• pp.75-86
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• 1998

Eighteen oriented samples from the Jeongsun limestone of the Joseon Supergroup are collected. The orientations of C-axis of calcite and e twin plane, the average thickness, numbers of twins and the widths of calcite grains in 10 samples are measured. Then, the twin strain, mean width, intensity of twin and relative magnitude and orientations of principal stresses are calculated using Calcite Strain Gauge program. Twin strain, mean width and intensitv rainge between 0.801%~10.927%, $0.43{\mu\textrm{m}}~2.03{\mu\textrm{m}}$, and 33.5~113.4twim/mm, respectively. Metamorphic temperatures calculated from twin show below $70^{\circ}C$, indicating that twins were developed within 2.3km depth. In five samples, two events with different orientations of principal stress produced calcite twins, while only one event produced calcite twins in five samples. The direction of the maximum stress is almost horizontal and the minimum is almost vertical, indicating that the stress regirne is identical with thrust fault. E-W and NW-SE are the most dominant directions of comressive stress and N-S and NE-SW directions are also shown. Comparision between paleostress orientations measured in the study and others indicates that the maximum horizontal stress oriented to E-W may represent the paleostress of period either from the Silurian to the Triassic or from the Silulian to the Permian. Paleostress oriented to NW-SE may be the major direction of stress during the Daeho orogeny.

• The Journal of Engineering Geology
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• v.17 no.2 s.52
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• pp.299-307
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• 2007

We collected data of hydraulic fracturing tests and overcoring tests conducted in 84 boreholes in the south-east Korea in order to analyze the contemporary state of stress in this region. The average direction of the maximum horizontal stress was determined to be $N66^{\circ}{\pm}31^{\circ}E$. The relative magnitudes of the three principal stresses was ${\sigma}_v$ (vertical stress) < ${\sigma}_h$ (minimum horizontal stress) < ${\sigma}_H$ (maximum horizontal stress), indicating thrust fault stress regime. The stress ratio K (horizontal stress/vertical stress) was relatively high (2.2

• Journal of the Korean earth science society
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• v.29 no.3
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• pp.255-262
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• 2008

Late Cretaceous to early Tertiary paleostress was evaluated by analyzing the healed microcracks in the Cretaceous granite of the Goheung area, south Korea. Healed microcracks in five granite samples (GH-1, GH-3, GH-4, GH-5, GH-8) were investigated and measured according to direction. The directions of maximum horizontal principal stress in GH-1, GH-3, and GH-4 are dominantly $N60^{\circ}W\;and\;N70^{\circ}E,\;N20^{\circ}W\;and\;N50^{\circ}W$, while minor directions are N-S and $N30^{\circ}E$. In GH-5 and GH-8, $N40^{\circ}E\;and\;N10^{\circ}E$ are the most dominant directions, while $N40^{\circ}W$ is the minor direction. Thus overall, the most dominant directions of healed microcracks in the study area are oriented $N60^{\circ}W$, while minor directions are oriented $N20^{\circ}W,\;N20^{\circ}E\;and\;N70^{\circ}E$, essentially NE. Combining the paleostress results of this study with other studies, the direction of the maximum horizontal principal stress in the study area during the late Cretaceous to the early Tertiary should perhaps be changed WNW to NE. The reason for this is thought to be the complex tectonic movements which occurred in northeast Asia at that time.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.1-5
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• 2008

In and around the Korean Peninsula, 9 intraplate earthquake mechanisms since 1936 were analyzed to understand the regional stress orientation and tectonics. These earthquakes are largest ones in this century and may represent the characteristics of earthquake in this region. Focal mechanism of these earthquakes show predominant strike-slip faulting with small amount of thrust components. The average P-axis is almost horizontal ENE-WSW. This indicate that not only the subducting Pacific Plate but also the indenting Indian Plate controls earthquake mechanism in the far east of the Eurasian Plate.

• Geotechnical Engineering
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• v.9 no.4
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• pp.65-82
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• 1993

A series of torsion shear tests were performed to study the drained stress -strain behavior of medium dense Santa Monica Beach sand under various stress paths. The torque was applied to both clockwise and counterclockwise directions at the end of hollow cylinder specimen. Two clip gages had been previously used to measure the changes in wall thickness and diameter of the specimen. In this study, however, the lateral strain was determined by measuring volume changes in specimen. Specimens were prepared by the air pluviation method and gaseous carbon deozide( CO2) was used to measure precisely volumetric strain in specimen. The drained stress -strain behavior of cohesionless Boils during rotation of principal stress directions was analysed based on the results of torsion shear tests. The coupling of mal stress were applied. It was also found from the test results that the atrial strain at failure decreased with increasing value.