• Title/Summary/Keyword: Cubical triaxial tests

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Strength Characteristics of Decomposed Granite Soil in Cubical Triaxial Test (입방체형 삼축시험에 의한 다짐화강토의 전단강도 특성)

  • 정진섭;김찬기;박승해;김기황
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.38 no.6
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    • pp.64-73
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    • 1996
  • The three-dimensional strength behavior of compacted decomposed granite soil was studied using cubical triaxial tests with independent control of the three principal stresses. All specimens were loaded under conditions of principal stress direction fixed and aligned with the directions of compacted plane. For comparable test conditions, the major principal strain and volume strain to failure were smallest when the major principal stress acted perpendicular to the compacted plane. The opposite extremes were obtained when the major principal stress acted parallel to the compacted plane. In cubical triaxial tests with same b values and with ${\theta}$ values in one of three sectors of the octahedral plane, independent of the range of ${\theta}$, higher friction angles are obtained in tests with b greater than in triaxial compression tests in which b 0.0, Comparison between the results of the drained cubical triaxial tests on lksan compacted decomposed granite soil and the cross section of the Mohr-Coulomb failure surface as well as the cross section of the Mohr-Coulomb failure surface were made. Lade's isotropic failure criterion based on vertical specimens overestimates the strengths for tests performed with values of 0 between 90˚ and 1 50˚ the Mohr-Coulomb criterion generally underestimates the strengths of tests performed with values of ${\theta}$ between $0^{\circ}$ and $180^{\circ}$ except around the $120^{\circ}$.

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Three Demensional Behavior of Sand in Cubical Triaxial Tests and Its Prediction (입방체형삼축시험에 의한 모래의 3차원거동 및 예측)

  • 남정만;홍원표
    • Geotechnical Engineering
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    • v.10 no.3
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    • pp.111-118
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    • 1994
  • A series of drained cubical triaxial tests was performed to investigate the finfluence of the intermediate principal stress on the deformation and strength characteristics of sand. Test results showed that the strength of sand as represented by the friction angle increased from triaxial compression condition (b:0) with increasing magnitude of the intermediate principal stress until the vus of b reached 0.75, land it decreased slightly with closing to b= 1. Also it was found that the projection of the plastic strain increment vector on the octahedral plane was perpendicular to the trace of the failure surface on that plane. The prediction by the isotropic single hardening model sllowed good coinidence with experimental results.

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The Stress Strain Behavior of Sand in Cubical Triaxial Tests (입방체형삼축시험에 의한 모래의 응력 -변형률 거동)

  • 남정만;홍원표
    • Geotechnical Engineering
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    • v.9 no.4
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    • pp.83-92
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    • 1993
  • A series of drained triaxial tests on sand was performed using the cubical triaxial appaiatus, in which three principal stress could be loaded independently. The test results indicated that the intermediate principal stress influenced on both stress strain behavior and strength of sand. The axial strain at failure decreased and volumetric strain increased with an increase of the intermediate stress under constant minor principal stress. The internal friction angle of sand increased in general with increase of the deviator stress ratio b(=(G.:-c, )1(G, -G, )) except slight decrease of the internal friction angle as b value approached to 1. Finally Lade's failure criterion presented good coincidence with the exper imental strengttL while Mohr Coulomb failure criterion underestimated the experimental strength.

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Prediction for Stress-Strain Behavior of Remolded Clay using Single Surface Constitutive Model (Single Surface 구성모델을 이용한 재성형 점토의 응력-변형률 거동 예측)

  • 이강일
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.42 no.3
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    • pp.97-106
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    • 2000
  • The study is closely relevant to Lade's single work hardening model. This model has been shown to have good applicability to cohesive soils. However the validation of this model on the clayey soils has not been satisfactorily reported. To scrutinize the applicability of this model on clayey foundation the laboratory tests for Kwangyang clayey soils were performed using the improved cubical triaxial test apparatus designed originally by Lade. A computer program was developed by which soil parameters for the single work-hardening model can be rationally determined by deleting some dispersed test data generated usually at the initial stage of laboratory tests. And using the program numerical analysis of the cubical clayey specimens using intermediate principal stress was carried out and a good agreement between observed values and numerical results was found.

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Deformation and Strength Characteristics of Compacted Weathered Granite Soil under Pland Strain Condition (평면변형률 조건에서 다짐화강토의 변형과 강도특성)

  • 정진섭
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.41 no.2
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    • pp.70-79
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    • 1999
  • The lower ground of structure, in which the strip loads, such as earth dams and embankments , are signiificantly working on , is required to be interpreted as a state of plane strain where the strain of intermediated principal stress direction is put '0' . The plane strain state is frquently observed in actural soil engineering case. For those case, drained stress-strain and strength behavior of Iksan weathered granite soil prepared in cubical specimens with cross-anisotropic fabric was studied by conventional triaxial compression, plane strain and cubial triaxial tests with independent control of the three principal stress. All specimens were loaded under conditions of principl stress directions fixed and aligned with the directions of the material axes. As a result of research , when a ground condition is analyzed under plane strain state, the shear strength obtained from the conventional triaxial compression test can be understimated.

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Influence of the Intermediate Principal Stress on Behavior of Overconsolidated Clay (중간주응력(中間主應力)이 과압밀점토(過壓密粘土)의 거동(擧動)에 미치는 영향(影響))

  • Hong, Won Pyo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.8 no.2
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    • pp.99-107
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    • 1988
  • A limited number of cubical triaxial tests with independent control of the three principal stresses were performed on an overconsolidated clay. The cubical undisturbed specimens with overconsolidation ratio of 5 were prepared in triaxial chamber after sampling in field. It was found that the intermediate principal stress influences on the stress-strain, undrained strength effective strength, effective friction angle and pore pressure of the overconsolidated clay. When the magnitude of the intermediate principal stress is not same as the minimum principal stress, the failure strength of the overconsolidated clay is underestimated by use of Mohr-Coulomb failure criterion while it can be estimated quite well by use of Lade failure criterion. And the undrained strength of the overconsolidated clay does not coincide with that obtained by Tresca failure criterion.

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TWO DIMENSIONAL STUDY OF HYDRAULIC FRACTURING CRITERIA IN COHESIVE SOILS

  • 유택영사
    • Proceedings of the Korean Geotechical Society Conference
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    • 1994.03b
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    • pp.3-12
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    • 1994
  • Based on the shear failure mechanism, hydraulic fracturing criteria are extended to three dimensional stress state. According to the situation of the directions of borehole and major principal stress axes, three equations can be derived for three dimensional hydraulic fracturing problems. By comparing these equations, a single criterion is selected for hydraulic fracturing pressure in cohesive soils. The criterion is a function of maximum principal stress, minimum principal stress and soil parameters in UU conditions. The equation indicates that with any increase in maximim principal stress, hydraulic fracturing pressure decreases. In order to prove the integrity of the criteria, laboratory tests are performed on compacted cubical specimens using true a triaxial apparatus. The shape and direction of fractures are determined by injecting colored water after fracture initiation. It is found that the direction of fractures are perpendicular to the o1 plane.

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Applicability of FEM Analysis by Single Surface Constitutive Model (Single Surface 구성모델에 의한 유한요소 해석의 적용성)

  • 이문수
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.37 no.2
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    • pp.73-85
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    • 1995
  • This study aimes at investigating the applicability of single surface work - hardening model(7, 8) to clayey soils through FEM analysis. The comparison was carried out for the results between numericaL analysis and cubical triaxial tests in which confined stress was applied differently and 3-directional principal stress can be controlled. Furthermore, the results of the numerical analysis were compared with observed values of load test on the 2-dimensional model foundation composed of clayey soils. The agreement between nu- merical and observed values proved to be of high accuracy, which indicates that numeri- cal techniques developed during this study using the model can be used for the prediction of settlement, leteral displacement and pore water pressure of actual soft foundation of clayey soils.

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Three-Dimensional Behavior of Granular Soil (압상토의 3차원 거동)

  • 정진섭
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.37 no.2
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    • pp.64-72
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    • 1995
  • A series of cubical triaxial tests with three independent principal stresses was per- formed on Baekma river sand( # 40~100). It was found that the major principal strain at failure remained approximately constant for b values larger than about 0.3 for both the drained and undrained condition, and thereafter increased as b value decreased. The test results showed that the direction of the strain increment at failure form acute angles with the failure surfaces for both the drained and undrained condition. The results were thus not in agreement with the normality condition from classic plasticity theory. Howev- er, it was found that the projections of the plastic strain increment vectors on the octahe- dral plane were perpendicular to the failure surface in that plane. Failure strength in terms of effective stress anlaysis was greatly influenced by the variation of intermediate principal stress and so was failure criterion. The effective stress failure surfaces for both the drained and undrained condition were estimated quite well by use of Lade's failure criterion.

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Strength Characteristics of Anlsotropic Overconsalidated Clay (이방성과압밀점토의 강도특성)

  • 홍원표
    • Geotechnical Engineering
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    • v.4 no.3
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    • pp.35-42
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    • 1988
  • A series of consolidated-undrained cubical triaxial tests was performed to investigate the three- dimensional strength characteristics of anisotropic overconsolidated clay. All specimens sampled in field were loaded under conditions of principal stress directions fixed and aligned with the directions during sampling. A sufficient number of tests It was performed to deter.mine the three- dimensional failure surface in the octahedral plane. The adjusted effective friction angles obtained by the stress state projected on the same octahedral plane did not show anisotropy, while the measured effective friction angles showed considerally difference according to the axes of speccimens. Therefore, Lade failure criterion proposed fort isotropic materials could be also used practically for anisotropic overconsolidated clay. The direction of the plastic strain increment wrectors superimposed on the principal stress space was nearly perpendicular to the traces of the failure surface in the octahedral plane.

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