• Title, Summary, Keyword: 지중응력

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Embankment and Excavation Behaviour with Shear Parameters of Soft Clayey Soil in FEM (점성토의 유한요소해석에서 전단파라미터에 따른 성토 및 굴착 거동)

  • Kim, Byung Il;Choi, Chanyong;Hong, Kang Han;Han, Sang Jae
    • Journal of the Korean Geotechnical Society
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    • v.34 no.2
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    • pp.5-17
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    • 2018
  • In this study, the in-situ stress, strength and stress-strain characteristics with shear parameters (UU, CU, ${\bar{CU}}$) are analytically evaluated and the stability analyses are carried out under loading/unloading conditions. The in-situ stress and the stress-strain behaviour may become different according to input shear parameters in finite element analyses with construction step, Especially, if the internal friction angle in Mohr-Coulomb model is set to zero, the in-situ stress and the stress-strain behaviour might not be properly predicted. The results from CU parameter of total stress analysis have no significant difference with the results from CU of effective stress analysis. Therefore, in the numerical analysis for soft ground, CU parameters can be applied to predict in-situ stress and stress-strain behaviors. In addition, the calculation method was proposed to determine the shear parameter of Mohr-Coulomb model, which is corresponding to the shear strength equivalent to that of in-situ soil.

Three Dimensional In-situ Stress Distribution in the Southern Korean Peninsula and Its Application in Tunnel Analysis (한반도 3차원 지중응력의 분포와 이를 고려한 터널해석에 대한 연구)

  • 김동갑;박종관
    • Journal of the Korean Geotechnical Society
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    • v.18 no.2
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    • pp.65-74
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    • 2002
  • The measurement of in-situ stress is essential to estimate the ground displacement and the stress distribution of a tunnel and an underground structure. In this study, the in-situ stress distribution of the Southern Korean peninsula was re-evaluated by the new 380 in-situ data which were determined by overcoring and hydrofracturing methods, and the three-din erosional numerical analysis of tunnelling was performed. The results of in-situ stress distribution show that the distribution of horizontal stress tends to be more irregular in metamorphosed(gneiss) and granite areas than in sedimentary and volcanic areas. The ratio of horizontal to vertical stresses(K-value) in volcanic area is less than 1 below the depth of 150m. The direction and magnitude of three dimensional in-situ stresses were shown simultaneously in a figure for the first time in Korea. The three-dimensional numerical analysis of tunnelling indicates that the orientation and magnitude of displacement around a tunnel are controlled mainly by the difference between the maximum and minimum horizontal stresses.

터널

  • 김교원;김학준;노병돈;이현범
    • Proceedings of the KSEG Conference
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    • pp.21001-21090
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    • 2004
  • 지반에 터널을 굴착하는 경우 지중 응력은 교란되게 되며 굴착면 근처에서는 응력이 재분포하게 된다. 그러므로 굴착면 주변의 응력분포를 알기 위해서는 굴착 전의 지중 응력을 측정하거나 예측해야 한다. Hoek과 Brown(1980)은 여러 지역에서 수집한 지중 응력의 실측자료를 그림2.1-1과 그림 2.1-2와 같이 나타내었다. 그림2.1-1에 의하면 다음 식에서 수직응력 ($\sigma_z$)이 단위 중량($\gamma$)과 심도(z)에 의해서 예측하는 값과 잘 일치하고 있음을 보여준다. (중략)

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The Characteristics of Stress Distribution on Two-arch Tunnel's Pillar due to Surface Loads in the Discontinuous Rock Mass (불연속성 암반에 위치한 2-아치 터널에서 지표면 하중 작용시 필러에 전달되는 응력 특성)

  • Kim, Hong-Moon;Lee, Sang-Duk
    • Journal of the Korean Geotechnical Society
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    • v.25 no.5
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    • pp.65-73
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    • 2009
  • Large scale model tests and numerical analyses are performed to investigate the stress distribution of pillar due to surface loading nearby two-arch tunnel which is constructed in the regularly jointed rocks. It is observed that the influence of discontinuities on the stress distribution in the discontinuous rock mass and the underground stresses induced by surface loading are greater than those of linear elastic theory. Especially, lines of equal stresses are developed to the direction of inclination according to the inclined grade. In cases of discontinuities imbedded in parallel with or vertical to the ground, the pressure bulbs are formed symmetrically, however, the inclined ones result in stress distribution in parallel with and vertical to the planes of discontinuities. Results indicated that stress distribution is seriously affected by the angle of discontinuity. When stresses propagating to the pillar need to be estimated, relative location of surface loading, grade of discontinuous plane, and location of two-arch tunnel should be carefully considered.

The Interpretation on Underground Stress of Soil Layer Subjected to Moving Repeated Loads (이동하중에 의한 지중응력 해석)

  • Park Heung-Gyu;Kim Dae-Young
    • Journal of the Korean Geotechnical Society
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    • v.21 no.3
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    • pp.55-63
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    • 2005
  • In this research, we have compared and analyzed the value driven from theoretical equation of Boussinesque, Westergaard, Newmark and K$\"{o}$ogler with our experimental value from the model test on the underground stress distribution condition. As a result of conducting the Model Test, a change in the underground stress according to the loading was proven to be very similar to the tendency shown in the theories of Westergaard. A tendency of increasing in a straight line was shown in the underground stress according to the increase of loading. When compared to that of the theoretical equation, underground stress values were great until the depth of 15cm. However, after that depth, a tendency of showing smaller value than that of the theoretical equation was shown. Correlations between Moving Repeated Load (or) and Underground Stress ($\Delta\sigma$) show $\Delta\sigma\;=\; 0.009\cdot{\sigma}r-0.1$(depth 60 cm).

Analytical Evaluation on the Structural Safety of Horizontally Curved Parts of Buried Pipe (지중 매설관 곡선부의 해석 및 안전성 평가)

  • Jeon, Jin-Su;Kim, Sung-Nam;Han, Taek-Hee;Kang, Young-Jong
    • Journal of Korean Society of Hazard Mitigation
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    • v.8 no.1
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    • pp.47-55
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    • 2008
  • Recently, it has been reported that buried pipes' crack is concentrated on curved parts. In this study, 3D-Finite element analysis is performed for Analytical Evaluation on the Structural Safety of Horizontally Curved Parts of Buried Pipe. The constructed pipe cracked in curved parts of pipe is analyzed and all kinds of loads affected to buried pipes are considered. Displacement, stresses and buckling analysis are performed. The stress analysis shows that stress in curved parts is larger than stresses in straight parts and exceeds allowable stress in some parts. So, stress analysis on curved parts is needed for safety for buried pipe.

Characteristics of Pohang CO2 Geological Sequestration Test Site (포항 이산화탄소 지중저장 시험 사이트 특성)

  • Kim, Seon-Kyoung;Chang, Chandong;Shinn, Youngjae;Kwon, Yikyun
    • The Journal of Engineering Geology
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    • v.28 no.2
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    • pp.175-182
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    • 2018
  • We analyze geological, petrophysical and geomechanical characteristics of a $CO_2$ sequestration test site, Pohang. The target reservoir exists at a depth of 750 m, where porous and permeable sandstones/conglomerates prevail. The reservoir is underlain by thick mudstone formations. We estimate in situ stress conditions using an exploratory wellbore drilled through the target reservoir. The in situ stress condition is characterized by a strike-slip faulting favored stress regime. We discuss various aspects of reservoir fracture pressures and fault reactivation pressures based on the stress magnitudes.

Characteristics of Soil Stress using Expansion Liquid Sheet (팽창약액시트를 이용한 지중응력 특성에 관한 연구)

  • Kang, Hyounhoi;Kim, Juho;Chung, Yoonseok;Park, Jeongjun
    • Journal of the Society of Disaster Information
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    • v.13 no.1
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    • pp.43-50
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    • 2017
  • In this study, to investigate the strength enhancement and stress transfer effect of the inflatable chemicals used in the recovery of soft ground or partial settlement, the dilatant solution was prepared and classified by measuring the density and the earth pressure in the sand ground. The inflation reinforcing agent was prepared by injecting into a separate impervious vacuum sheet by dividing into a relatively high expansion group and a low expansion group, and a cementation experiment was performed in the lower part of the homogeneously formed model ground. As a result, reinforcing effect was shown up to about 15cm above the expansion reinforcement, and the soil pressure showed a compaction tendency similar to the concentrated load of $1.150{\sim}11.298t/m^2$.

The Earth Pressure on the Effect of Surcharge Load at the Narrowly Backfilled Soil (좁은 공간 되메움 지반에서의 상재하 영향에 의한 토압)

  • 문창열;이종규
    • Geotechnical Engineering
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    • v.13 no.6
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    • pp.165-180
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    • 1997
  • The structure such as underground external walls of buildings, conduit and box culvert supports the surcharge loads (point, strip and line loads) . The vertical and horizontal stresses in a soil mass depend on the backfill width and wall friction, etc. The investigations described in this paper is designed to identify the magnitude and the distributions of the lateral and vertical pressure which is occurred by the narrowly backfilled soil in an open cut by the surcharge loads. For these purposes, model tests were performed for various width of backfill in a model test box by considering the wall friction using carbon rods. The results of test were compared with the theories of Weissenbach and VS Army Code and also with the results of the numerical analysis using finite difference method which introduces Mohr-Coulomb failure hypothesis.

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A Study for Predicting Adfreeze Bond Strength from Shear Strength of Frozen Soil (동결토 전단강도를 활용한 동착강도 산정에 관한 연구)

  • Choi, Chang-Ho;Ko, Sung-Gyu
    • 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.