• Title, Summary, Keyword: Anisotropic shear strength

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Effects of Anisotropic Consolidation on Strength of Soils (이방압밀이 흙의 강도에 미치는 영향)

  • 강병희
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.3-14
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    • 2000
  • Anisotropic consolidation, shear, a transportational component during or after deposition each may produce anisotropic fabrics, which result in the anisotropic properties of soils. Nevertheless, the isotropically consolidated compression triaxial tests are commonly used in practice to determine the strength of the anisotropically consolidated soils because of their practicality and simplicity. In this paper the effects of anisotropic consolidation on the strength properties of soils are discussed. For the sandy soils consolidated under a constant vertical consolidation pressure, the deformation modulus decreases with decreasing consolidation pressure ratio($\sigma$$\sub$3c/'/$\sigma$ sub 1c/'), but the liquefaction resistance increases. For the saturated cohesive soils, both the undrained shear strength and undrained creep strength decrese with decreasing the consolidation pressure ratio. When the in-situ strength properties of the anisotropically and normally consolidated soils are determined by the isotropically consolidated tests, the undrained shear strength and creep strength of saturated cohesive soils as well as the deformation modulus of sandy soils are measured to be higher than the rear in-situ values. This, therefore, could lead to a dangerous judgement in stability analysis

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Anisotropic Shear Strength of Artificially Fractured Rock Joints Under Low Normal Stress (낮은 수직응력 하에서 인공 절리면의 전단 이방성에 관한 연구)

  • 곽정열;이상은;임한욱
    • Tunnel and Underground Space
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    • v.13 no.3
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    • pp.169-179
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    • 2003
  • Anisotropic shear strength of rock joints is studied based on the artificially fractured specimens using experimental and analytical methods. Series of direct shear tests are performed to obtain the strength, stiffness and friction angle of joints under various low normal stresses and shearing directions. The results of shear strength and stiffness show anisotropic value according to shearing direction under low normal stress specially less than 2.45 MPa. But, the effect of joint roughness on strength decreases with increasing normal stress. To estimate more effectively the peak shear strength under low normal stress, the modified Barton's equation is suggested.

Stability Analyses for Excavated Slopes Considering the Anisotropic Shear Strength of the Layered Compacted Ground (다짐지반에 조성되는 굴착사면의 비등방성 전단강도를 고려한 안정성 분석)

  • 이병식;윤요진
    • Journal of the Korean Geotechnical Society
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    • v.18 no.5
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    • pp.27-35
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    • 2002
  • To construct pipe lines, culverts, or other utility lines, temporary slopes formed by excavating the compacted embankment are frequently met with in the field. Ignoring stability analyses for such slopes and applying inappropriate slope inclinations often result in safety problems. In this study, stability of such slopes were investigated considering the influence of anisotropic shear strength of the layered compacted ground. A series of stability analyses were conducted for slopes varying the slope angle and the height, and assuming isotropic and anisotropic shear strength conditions, respectively. The anisotropic shear strength of the compacted soil was determined from the direct shear test for layered soil blocks varying the inclination angle between the horizontal shear surface and the direction of the soil layer. As a result of the analyses, it has been concluded that the appropriate slope inclination f3r a temporary slope could vary in accordance with the consideration of anisotropy. However, the factor of safety as well as the location of the failure surface did not show significant variation.

Strength characteristics of transversely isotropic rock materials

  • Yang, Xue-Qiang;Zhang, Li-Juan;Ji, Xiao-Ming
    • Geomechanics and Engineering
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    • v.5 no.1
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    • pp.71-86
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    • 2013
  • For rock materials, a transversely isotropic failure criterion established through the extended Lade-Duncan failure criterion incorporating an anisotropic state scalar parameter, which is a joint invariant of deviatoric microstructure fabric tensor and normalized deviatoric stress tensor, is verified with the results of triaxial compressive data on Tournemire shale. For torsional shear mode with $0{\leq}b{\leq}0.75$, rock shear strengths decrease with ${\alpha}$ increasing until the rock shear strength approaches minimum value at ${\alpha}{\approx}40^{\circ}$, and after this point, the rock shear strengths increase as ${\alpha}$ increases further. For the torsional shear mode with b > 0.75, rock shear strengths are almost constant for ${\alpha}{\leq}40^{\circ}$, but it increases with increase in ${\alpha}$ afterwards. The rock shear strength variation against ${\alpha}$ agrees with shear strength changing tendency of heavily OCR natural London Clays tested before. Prediction results show that the transversely isotropic failure criterion proposed in the paper is reasonable.

Shear center for elastic thin-walled composite beams

  • Pollock, Gerry D.;Zak, Adam R.;Hilton, Harry H.;Ahmad, M. Fouad
    • Structural Engineering and Mechanics
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    • v.3 no.1
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    • pp.91-103
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    • 1995
  • An analysis to determine shear centers for anisotropic elastic thin-walled composite beams, cantilevered and loaded transversely at the free end is presented. The shear center is formulated based on familiar strength of material procedures analogous to those for isotropic beams. These procedures call for a balancing of torsional moments on the cross sectional surface and lead to a condition of zero resultant torsional couple. As a consequence, due the presence of anisotropic coupling, certain non-classical effects are manifested and are illustrated in two example problems. The most distinguishing result is that twisting may occur for composite beams even if shear forces are applied at the shear center. The derived shear center locations do not depend on any specific anisotropic bending theories per se, but only on the values of bending and shear stresses which such theories produce.

Anisotropy of shear strength according to roughness in joint surface (절리면 거칠기에 의한 전단강도 이방성)

  • 이창훈;정교철
    • The Journal of Engineering Geology
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    • v.12 no.4
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    • pp.421-437
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    • 2002
  • In order to quantify the anisotropic properties of rock included joints and shear behavior in joint surface, the mold is Produced for rock joint surface using gypsum Plaster and Peformed for replicated joint models made of cement mortar. Rock sample is measured using mechanical profilometer before testing and their result is expressed quantitatively. The statistical parameters and the fractal dimension by fractal theory for roughness is investigated its coordinate value for numerical process. The shear strength to the shear displacement in low level normal stress ismaintained or increased in most joint models. Their results present that this relationship is depended several roughness properties in joint model for natural rock joint. The relationship between the shear strength and the Properties for profiles estimated by some statistical parameter in roughness has the low correlation and is not constant. The result between the data for direct shear test and using Barton's equation, Barton's equation has not the effectiveness for the effect of anisotropy and has not suitable to recognizing the properties for joint surface. It means that JRC has not the properties of anisotropic rock surface. The fractal dimension is well correlated with the data of direct shear test than those of JRC. New experimental formulae using fractal dimension is comported with the anisotropic properties for direct shear test.

A Study on the Plane Stress Problem of Composite Laminated Annular Elements Using Finite Difference Method (유한차분법을 이용한 복합적층 원형곡선요소의 평면응력문제 연구)

  • Lee, Sang Youl;Yhim, Sung Soon;Chang, Suk Yoon
    • Journal of Korean Society of Steel Construction
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    • v.9 no.1
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    • pp.65-79
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    • 1997
  • Composite materials are consist of two or more different materials to produce desirable properties for structural strength. Because of their superiority in strength, corrosion resistance, and weight reduction, they are used extensively as structural members. The objective of this study is to present the effectivness of the laminated composite elements by analyzing in-plane displacement and stress of the anisotropic laminated annular elements. Anisotropic laminated structures are very difficult to analyze and apply, compared with isotropic and orthotropic cases for arbitrary boundaries and fiber angle -ply. Boundary conditions for the examples used in this study consist of two opposite edges clamped and the other two edges free, and finite difference method is used in this study for numerical analysis. From the numerical result, it is found that the program used in this study can be used to obtain the displacement of the straight beams considering it's transverse shear deformation as well as anisotropic laminated elements. Several numerical examples show the advantages of the stiffness increase when the angle-ply composite materials are used. Therefore it gives a guide in deciding how to make use of fiber's angle for the subtended angle, load cases, and boundary conditions.

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Strength Prediction of Kraft Paperboard under Combined Stress (조합하중을 받는 Kraft 판지의 강도예측)

  • Lim, Won-Kyun;Jeong, Woo-Kil
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.24 no.1
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    • pp.17-22
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    • 2011
  • Based on the form of the Tsai-Hill criterion, a new failure criterion for anisotropic material subjected to combined stress is developed and demonstrated. It is capable of accurately calculating the strength of anisotropic materials. The generality and accuracy of the present failure criterion are illustrated by examination through the use of Kraft paperboards under various loading conditions. Compared to the Tsai-Hill theory, which is much too conservative at high levels of shear stress, the present criterion has a good agreement with the experimental data. It also has the ability to calculate the strength more simply, compared to the Tan-Cheng theory.

Undrained Cyclic Shear Behavior for Nak-Dong River Sand Due to Silt contents (실트 함유율에 따른 낙동강 모래의 반복전단거동)

  • Kim, Young-Su;Kim, Dae-Man;Shin, Ji-Seop;Na, Yun-Young
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.311-317
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    • 2008
  • This study was carried out to improve our understanding about the influence of silt content on the stress-strain of sand under cyclic loading. Soil specimens were prepared by wet-tamping method as same void ratio and specimen's silt contents on total weights was changed from 0% to 20%. Also, effects of the silt contents on the stress-strain response were studied at different anisotropic consolidation ratio, Kc=1.0, 1.5, 2.0 condition. As a result, cyclic shear strength decreased as silt contents increased in same stress ratios. In same silt contents, cyclic shear strength increased as Kc increased in lower silt contents, but in higher silt contents, it had reverse results.

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A Probabilistic Analysis of Liquefaction Potential and Pore Water Pressure Build up due to Earthquake (지진하중에 의한 액화의 가능성과 간극수압의 발생에 관한 확률론적 연구)

  • Kim, Young-Su;Lee, Song;Cho, Woo-Chul
    • Geotechnical Engineering
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    • v.8 no.2
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    • pp.31-44
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    • 1992
  • The probabilistic and statistical model is used to estimate the probability of liquefaction potential and pore water pressure build up due to earthquake in fully saturated sand deposit for each case of being structure(anisotropic) or not(isotropic). To execute this paper, dynamic shear strength parameters to show the relationship between shear strength and cyclic loading under isotropic or anisotropic condition in saturated sand deposit are presented. Using these parameters, the program which Predicts Pore water Pressure build up due to earthquake is developed. Using the 3-dimensional Random Field Model considering uncertainty of resistance and strength parameter, the program which computes the probability of liquefaction potential is developed. The developed program is applied to a case study, and then the result shows that the probability of liquefaction in isotropic condition is higher than in anisotropic condition. The ratio of pore water pressure tends to decrease as Kc increases.

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