• Title, Summary, Keyword: 응력경로

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Characteristics of River Sand Soil Parameter for Single Work-Hardening Constitutive Model to Stress Path (강모래의 응력경로에 따른 단일항복면 구성모델의 토질매개변수 특성)

  • Lee, Jong-Cheon;Cho, Won-Beom
    • Journal of Navigation and Port Research
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    • v.36 no.5
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    • pp.395-400
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    • 2012
  • The stress-strain relationship of soil is dependent on a number of factors such as soil type, density, stress level and stress path. Th accurate stress-stain relationship can be predict using a constitutive model incorporated all influencing factors. In this study, an isotropic compression-expansion test and a series of drained conventional triaxial tests with several stress paths were performed on Baekma river sand to investigate parameters characteristics of Lade's single work hardening model depending on the stress path.. Based on test results, the parameters of yield function (h, ${\alpha}$) are not much influenced by stress level and stress path, the these parameters do affect a little bit of stress-strain behavior. The parameters h and ${\alpha}$ are closely related to failure criterion ${\eta}_1$, they can be replaced by failure criterion parament. We also observed that predicted values from the Lade's single hardening constitutive model are well matched with the observed data.

Stress Path Dependent Deformation Characteristics of A Normally Consolidated Saturated Cohesive Soil (정규압밀 포화점성토의 응력경로에 따른 변형특성)

  • 권오엽;정인준
    • Geotechnical Engineering
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    • v.5 no.2
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    • pp.45-56
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    • 1989
  • The influence of stress path on the deformation characteristics of clay has been studied through a series of stress-path controlled triaxial tests on artificially sedimented and normally con- solidated Kaolinite. It has been found that there exists a critical stress increment ratio, Kc, in which stress·strain characteristics possesses a linear relationships and beyond Kc, strain hardening. A modified hyperbolic constitutive model for the strain hardening behavior has been formulated based on the Drnevich's hyperbolic function. And, a method of settlement analyses has been Proposed wherein the effect of stress path during consolidation is taken into account.

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A Comparative of Ground Stress with Difference of the Fixed Point Loading and Moving Wheel Loading (모형실험을 통한 고정 및 이동하중 재하 방법에 따른 노반 변형거동 비교)

  • Choi, Chan-Yong;Shin, Eun-Chul;Eum, Ki-Young;Shin, Min-Ho
    • 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.

A Consideration on Deformation Characteristics of Normally-Consolidated Clays by Various Stress Paths (다양한 응력경로에 따른 정규압밀 점성토의 변형특성 고찰)

  • 김창엽;정충기
    • Journal of the Korean Geotechnical Society
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    • v.15 no.1
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    • pp.161-173
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    • 1999
  • Settlement analysis based on oedometer test results with or without Skempton-Bjerrum's modification method ( widely used for practical purposes when estimating consolidation settlements of soft clay deposits) has shortcomings that it cannot simulate real stress states and deformation behaviors of soils in case that in-situ loading and deformation conditions are not 1-dimensional. In this study, the stress path method, reflecting various probable stress paths, was employed to normally - consolidated kaolinite samples by using automated triaxial testing device which can control stress paths automatically. From this experimental study, elastic, consolidation, secondary compression and pore pressure development - dissipation behaviors under various stress paths were analyzed and deformation characteristics of soft clays, which can be the basis of rational estimation of settlements, were studied. Also by comparing results of stress path tests with those of 1-dimensional consolidation tests, limitations and problems of conventional methods were clarified.

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Estimation Method for Settlements of NC Clays Considering Deformation Modes Under Axis-symmetric Conditions (축대칭 조건하에서의 변형형상을 고려한 정규압밀 점성토 지반의 침하량 평가방법)

  • 김창엽;권오순;정충기
    • Journal of the Korean Geotechnical Society
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    • v.17 no.4
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    • pp.7-14
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    • 2001
  • 구조물 하중에 의한 점성토 지반의 침하량을 보다 정확하게 평가하기 위해서는 지반 내의 흙요소가 경험하는 실제적인 응력경로와 이에 따른 변형양상이 적절하게 고려되어야만 한다. 따라서 본 연구에서는 축대칭 조건의 다양한 응력경로를 따라 발생하는 정규압밀 점성토의 변형 거동을 고찰한 기존의 실험적 연구결과를 바탕으로 응력경로법에 근거한 보다 간편하고 합리적인 침하량 평가기법을 제시하였다. 또한 본 연구에서는 제시된 평가기법을 기존의 1차원적인 침하량 평가기법들과 함께 실제와 유사한 조건을 가지는 가상지반의 침하량 산정에 적용해 보았으며, 동일한 조건에 대해 소성모델(MCC 모델)과 혼합압밀이론에 바탕을 둔 유한요소해석을 실시하였다. 그리고 이를 통해 얻어진 결과들을 비교.분석함으로써 기존 평가기법들의 문제점과 한계를 명확히 제시하였으며, 응력증분 평가방법이 침하량 평가에 미치는 영향을 분석하였다.

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Behavior of Sand during Large Stress Reversal in Torsion Shear Test (비틀림전단시험에 의한 대응력반전시 모래의 거동)

  • 홍원표;남정만
    • Journal of the Korean Geotechnical Society
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    • v.15 no.4
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    • pp.3-17
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    • 1999
  • Torsion shear tests under various stress paths were performed to study the behavior of sand during large stress reversal. The stress paths can be classified into the clockwise and the counterclockwise according to torque applied to specimen, and the directions of plastic strain incremental on the stress paths including large stress reversal are compared with the direction of stress state and stress incremental. From test results, the isotropic hardening theory using the principle of St. Venant desirably showed that direction of plastic strain incremental coincided with stress state on primary loading part and nearby failure point, but it might result in a rough approximation on part of unloading and reloading by stress reversal.

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A New Stress Path Test Method for Evaluating Settlement Behaviors of Clay Deposits (점성토지반의 침하거동 평가를 위한 새로운 응력경로시험기법)

  • 정충기;최영태;김창엽;이원택
    • Journal of the Korean Geotechnical Society
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    • v.19 no.1
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    • pp.111-120
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    • 2003
  • A new stress path test method, which is more suitable f3r evaluating settlements of clay deposits, was introduced. This new method is basically based on back pressure equalization concept and makes it possible to estimate deformations corresponding to all points on a specific stress path by only one test. As a result, deformation characteristics of a clay deposit can be predicted by a few tests and the more practical application of stress path method can be realized. In addition, anisotropic deformation behaviors following arbitrary stress paths also can be experimentally measured by this test method. Experimental applicability of the proposed method was confirmed by performing various stress path tests on remolded kaolinite samples and the actual process to evaluate overall deformation characteristics and settlements was also presented.

Analysis of Consolidation and Shear Characteristics for the Kwangyang Bay Clay (실내시험을 통한 광양만 점토의 압밀 및 전단특성분석)

  • 이영휘;김용준;김대길
    • Journal of the Korean Geotechnical Society
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    • v.15 no.1
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    • pp.151-160
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    • 1999
  • A series of laboratory tests for the marine clay sampled under the sea of Kwangyang bay have been conducted. The main types of tests are the general index property tests, the oedometer tests and the triaxial compression tests in both undrained(CIU) and drained(CID) conditions. The clayey samples, classified as CL, CH with natural water content of 38.3~84.6% and liquidity index of 0.71~0.98, are in the normally consolidated state with O.C.R. of 1.0l~l.60. The undrained stress path from CIU tests can be normalized with isotropic consolidation pressure$(p_0)$ and equal shear strain contour is linear passing through the origin in the (q, p) plot. The undrained shear strain is found to be the only function of the stress ratio($\eta$) and linear with intercept in the ($\varepsilon/\eta,\eta$) plot. The built-up pore pressure normalized with pc is also linear with respect to $\eta$. and its slope is defined by ´C´ as a pore pressure parameter. Equations to predict the undrained stress path and the shear strain are proposed. It is proved that the proposed equations give better agreements to the measured values than the Cam-clay theories. The failure points of the stress path are located on the same C.S.L. in (q, p) plot during both CIU and CID tests, which justifies the concept of critical state theory.

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Stiffness Degradation during Deep Excavation in Urban Area (도심지 깊은 굴착에 따른 지반 강성의 변화)

  • Choi, Jongho;Koo, Bonwhee;Kim, Taesik
    • Journal of the Korean Geoenvironmental Society
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    • v.16 no.2
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    • pp.27-31
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    • 2015
  • In urban area, many design projects related to geotechnical projects are controlled by serviceability rather than stability requirements. Accordingly, control of ground deformation has become more crucial and many researchers have studied soil stiffness. Recent experimental studies on the stress-strain response of Chicago glacial clays showed that the nonlinearity and anisotropy are the two key factors in evaluating the soil stiffness. In this study, experimental results are applied to analyze the deep excavation site locating in downtown Chicago. The stress paths observed from the observation points located behind and front of the supporting wall yield typical stress paths. Changes in soil stiffness nonlinearity and anisotropy were discussed by comparing experimental and computed stress paths. The stiffness anisotropy were significant even at the first few excavations. The stiffness degradation characteristics are significantly different according to relative location to the support wall even at the same elevation.

Characteristics of Stress-Strain Behavior for Lade's Single Work-Hardening Constitutive Model with Stress Path of Sands (모래의 응력경로에 따른 Lade의 단일항복면 구성모델의 응력-변형거동 특성)

  • Kim, Chan-Kee;Lee, Jong-Cheon;Cho, Won-Beom;Park, Wook-Geun;Kim, Hwan-Wook
    • Journal of the Korean Geosynthetics Society
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    • v.11 no.2
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    • pp.1-9
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    • 2012
  • In order to review the utility of Lade's single hardening constitutive model, a series of isotropic compression-expansion tests and consolidated drained triaxial tests including as CTC, TC, RTC, and OSP were performed by Baekma river sand with various of stress path. Parameters required in model were determined using these tests. The accuracy of analysis was reviewed by back analysis of test results used to determine the 11 parameters of soil property through the test of each stress path. Also. for verifying the accuracy of prediction for the stress-strain behavior using failure criterion related 9 parameters with correlational equation and constant and yield criterion related parameters h, ${\alpha}$ and ${\eta}_1$, when stress path is different with each other, it has been obtained in the review result of stress path dependent characteristics of the constitutional model through the analyzing results of CTC, TC, RTC, OSP, and fine silica sand tests.