• Title, Summary, Keyword: 평균응력

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Stress-Dependent Failure Criteria for Marine Silty Sand Subject to Cyclic Loading (반복하중을 받는 해양 실트질 모래의 응력기반 파괴기준)

  • Ryu, Tae Gyung;Kim, Jin Man
    • Journal of the Korean Geotechnical Society
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    • v.31 no.11
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    • pp.15-23
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    • 2015
  • An experimental study has been conducted to evaluate the effects of average and cyclic shear stresses on the undrained failure behaviors of dense marine silty sand by using the Cyclic Direct Simple Shear apparatus. The results show that when the average shear stress ratio is zero, symmetric cyclic shear deformation is the major component of deformation, and permanent shear deformation is relatively small. On the other hand, when the average shear stress ratio is larger than zero, asymmetric permanent shear deformation is the major component, and cyclic shear deformation does not change much as the number of cyclic loads increases. The average shear stress ratio has less effects on the number of cyclic loads needed to fail, as compared with the cyclic shear stress ratio. The proposed stress-dependent failure contour can effectively be used to assess the cyclic shear strength of soil beneath the foundation for the design of offshore structures.

Revision of Modified Cam Clay Failure Surface Based on the Critical State Theory (한계 상태 기반 수정 Modified Cam Clay 파괴면)

  • Woo, Sang Inn
    • Journal of the Korean Geotechnical Society
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    • v.36 no.4
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    • pp.5-15
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    • 2020
  • This paper proposes a revised Modified Cam Clay type failure surface based on the critical state theory. In the plane of the mean effective and von Mises stresses, the original Modified Cam Clay model has an elliptic failure surface which leads the critical-state mean effective stress to be always half of the pre-consolidation mean effective stress without hardening and evolution rules. This feature does not agree with the real mechanical response of clay. In this study, the preconsolidation mean effective stress only reflects the consolidation history of the clay whereas the critical state mean effective stress only relies on the currenct void ratio of clay. Therefore, the proposed failure surface has a distorted elliptic shape without any fixed ratio between the preconsolidation and critical state mean effective stresses. Numerical simulations for various clays using failure surfaces as yield surface provide mechanical responses similar to the experimental data.

P1ane Strain Strength of Fine Sands

  • Yoon, Yeo-Won;Van, Impe W.F
    • Geotechnical Engineering
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    • v.12 no.3
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    • pp.5-16
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    • 1996
  • Based on many experimental results on fine silica sands, the strength relation between triaxial and plane strain tests is expressed as a function of both density and mean effective principal stress at failure. Stress ratio of mean normal stress to deviatoric stress at failure is a well defined function of shear angle of friction, This ratio decreases with increasing shear angle of friction. Intermediate principal stress is also expressed in terms of major and minor principal stresses and a relatively good agreement between theoretical and observed angles of failure plane in plane strain test is confirmed.

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Paleostress Measurements from Calcite Twin in the Jeongseon Limestone of the Joseon Supergroup (조선 누층군 정선 석회암내의 방해석 쌍정에 나타난 고응력장 연구)

  • 장보안;강성승
    • 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.

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Centrifugal Model Test on Stress Concentration Behaviors of Composition Ground under Flexible/Stiff Surcharge Loadings (연/강성 하중을 받는 복합지반의 응력분담거동에 대한 원심모형시험)

  • Song, MyungGeun;Bae, WooSeok;Ahn, SangRo;Heo, Yol
    • Journal of the Korean Geoenvironmental Society
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    • v.12 no.6
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    • pp.5-15
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    • 2011
  • In this study, centrifuge model tests were performed to investigate stress concentration ratio, stress characteristics of soft clay ground improved by granular compaction piles with changes of piles type, loading condition and area replacement ratio. From the results of rigid loading tests, while vertical stresses acting on clay ground is similar, vertical stresses acting on GCP is larger than those acting on SCP with same replacement ratio. Also, average stress concentration ratio is increased proportionally with increasing the area replacement ratio of GCP and SCP. It was evaluated that average stress concentration ratio of soft clay ground improved by GCP is larger than that of SCP. As a result of flexible loading tests, stress concentration ratio is the highest when replacement ratio of GCP and SCP is 40%. Average stress concentration ratio of soft clay ground improved by GCP is a little more higher than is improved by SCP.

Analysis of Bed Shear Stress Distributions in Compound Open Channels Using Large Eddy Simulation. (LES를 이용한 복단면 개수로의 바닥전단응력 분포특성 분석)

  • Lee, Du Han
    • Ecology and Resilient Infrastructure
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    • v.5 no.4
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    • pp.199-209
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    • 2018
  • In river design, consideration of bed shear stresses is necessary to secure stability of levee and floodplain. In this study distributions of bed shear stresses in compound open channels are analyzed through numerical simulation for various width and depth. LES solver in OpenFOAM is applied to 12 cases of compound channel shapes considering secondary flow which effects distributions of bed shear stresses. By the results time averaged velocity distributions, secondary currents, and distributions of bed shear stresses are analyzed. Overall distributions of bed shears in floodplain show that higher shear stresses are seen in left of floodplain and the shears decrease toward right of floodplain. However, high local variations in shear stresses are shown due to the secondary flow effects. In shallow floodplain, bed shear stresses show low value below 0.8 times of averaged bed shear. In deep floodplain, bed shear stresses show high value over 1.2 - 1.4 times of averaged bed shear.

Evaluation of Crack Estimation Equation for the Reinforced Concrete Tension Member (철근콘크리트 인장부재의 균열 산정식 평가)

  • Park, Chan-Wook;Noh, Sam-Young;Shin, Eun-Mi
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.13 no.3
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    • pp.197-208
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    • 2009
  • The purpose of this research is the evaluation of the estimation equation of "CEP-FIP Model Code 1990(1991)", recently included in the domestic "Concrete Structure Design Code(2007)" in consideration of the concrete strength. As evaluation tools, crack element model applied a detailed bond-slip model as well as crack width obtained from experimental results by earlier researches. The crack element model is verified through the comparison with experimental results. The important variables in the estimation equation for the crack width in CEP-FIP Model Code 1990 are the tension stiffening effect and mean bond stress proposed in the paper to be improved in consideration of the concrete strength.

Study on Critical_Allowable Shear Stress of Filling Rocks With Mattress Revetment (호안용 매트리스내 채움재의 한계_허용 전단응력에 관한 연구)

  • Bae, Sang-Soo;Lee, Seung-Yoon;Jee, Hong-Kee
    • Journal of Korea Water Resources Association
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    • v.41 no.2
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    • pp.137-147
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    • 2008
  • Critical and allowable shear stress acting on the mattress revetment, is presented in this study. First of all, shear stress at each spot is computed when the hydraulic power act on the waterway. Secondly, median diameter of the filling rocks is computed using shear stress and Shields coefficient which are used to decide the critical motion of the particle. Finally, the range of critical and allowable shear stress is estimated which meet the particle stability and indicated that the mattress is a stable hydraulic structure in comparison with the riprap. Therefore the required median diameter of riprap is three times higher than that of mattress. Contrarily, this study also analyzed that resisting power of mattress to shear stress is three times higher than that of riprap on the same size.

Horizontal Stress Based on the Calculation of Lateral Stress Ratio in Unsymmetrical Space (비대칭 공간의 수평응력비 산정에 따른 수평응력에 관한 연구)

  • Moon Chang-Yeul;Lee Soo-Ki;Kwon Seung-Joon
    • Journal of the Korean Geotechnical Society
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    • v.20 no.9
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    • pp.177-189
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    • 2004
  • The backfilled space carl have various shapes such as vertical or lateral symmetric, unsymmetric slope depending on field conditions. Kellogg (1993) suggested the different equations for the backfill earth pressure and the lateral stress ratio considering that the stresses are different between the symmetrically sloped backfilled space and the vertical one. Kellogg (1993) assumed the stress generated on sloped wall surface as the simple internal friction angle of backfilled soil. However, Moon (1997) suggested modified Kellogg equation assuming that stress behavior in the sloped wall will be varied according to the rotation angle of principal stress and the friction of sloped wall surface. This study has compared and investigated the horizontal stresss of unsymmetrical backfilled space numerically and experimentally obtained when Kellogg lateral stress ratio is appled to and when average lateral stress ratio considering unsymmetric backfill slop of left and right are applied to the modified Kellogg equation. It is shown that the horizontal stress on the sloped wall has good match numerically and experimentally in the modified Kellogg equation when Kellogg's lateral stress ratio in symmetric condition is applied to the unsymmetric condition. But the horizontal stress on the vertical wall shows disagreement numerically and experimentally. The horizontal stress results in good agreement numerically and experimentally when the average lateral stress ratio of left and right at unsymmetric slop as applied to the modified Kellogg equation. Therefore, it is estimated that the application of the average lateral stress ratio to the left and right wall should be considered when backfilled space formed unsymmetric conditions.

A Study for Mechanical Property for A516-60, A283-C, A285-C and SB410 materials under Low Temperature (저온영역에서의 A516-60, A283-C, A285-C, SB410 소재 특성 평가)

  • Oh, Jung-Soo;Lee, Hee-Bum;Lee, Bong-Soo
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.9
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    • pp.405-411
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    • 2019
  • In this study, tensile tests were carried out on materials (A516-60, A283-C, A285-C, and SB410) for structural and pressure vessels at temperatures of $20^{\circ}C$, $-20^{\circ}C$, and $-40^{\circ}C$, and the changes in the mechanical properties were analyzed. Compared to the results at $20^{\circ}C$, the average yield stress increased by 6.4% and 7.5% at $-20^{\circ}C$ and $-40^{\circ}C$ for A516-60, while the average tensile stress increased by 1.3% and 4.1%, respectively. The average elongation decreased by 4.7% and 20.4% at these temperatures. In the case of A283-C, the average yield stress increased 8.8% and 9.8%, the average tensile stress increased by 4.1% and 5.9%, and the average elongation rate decreased by 7.4% and 9.9% at $-20^{\circ}C$ and $-40^{\circ}C$, respectively. For A285-C, the average yield stress increased by 1.8% and 8.6%, and the average tensile stress increased by 2.6% and 5.3%, respectively, but there was little change in the average elongation. Finally, for SB410, the average yield stress increased by 7.1% and 11.8%, the average tensile stress increased by 4.3% and 5.5%, but the average elongation rate decreased by 8.7% and 13.5%, respectively.