Stress non-uniformity in a hollow cylinder torsional sand specimen

Naughton, P.J.; O’Kelly, Brendan C.

doi:10.1080/17486020701377124

Cited by 15 publications

(11 citation statements)

References 8 publications

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“…This may be done in directional shear or in torsion shear equipment with different pressures applied inside and outside the hollow cylinder specimen. Limited and sporadic experimental results have been provided in this respect by Arthur and Menzies (1972), Arthur and Phillips (1975), Hight et al (1983), Miura et al (1986), Pradel et al (1990), O'Kelly (2007), O'Kelly andNaughton (2009) and by Chairo et al (2013). While these studies indicated some variation in the friction angle, none provided a complete picture.…”

Section: Previous Studies Of Cross-anisotropymentioning

confidence: 81%

Shear banding in torsion shear tests on cross-anisotropic deposits of fine Nevada sand

Lade

Dyck²,

Rodriguez

2014

Soils and Foundations

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A series of torsion shear experiments was performed on large hollow cylinder specimens of Fine Nevada sand with major principal stress directions relative to vertical, α, varying from 01 to 901 and with the intermediate principal stress, σ 2 , varying from σ 3 to σ 1 as indicated by b ¼ (σ 2 -σ 3 )/(σ 1 -σ 3 ). The Fine Nevada sand was deposited by dry pluviation, thus producing a sand fabric with horizontal bedding planes and crossanisotropic characteristics. The various stress conditions were achieved by varying the pressures inside and outside the hollow cylinder specimen relative to the shear stress and the vertical deviator stress according to a pre-calculated pattern. All stresses and all strains were determined from careful measurements so that analysis of the soil behavior could be made reliably. The soil behavior was determined for a pattern of combinations of α varying with increments of 22.51 from 01 to 901 and b varying with increments of 0.25 from 0.0 to 1.0. Thus, 25 test locations were established, but many tests were repeated to study the consistency of the results. The friction angles varied considerably with α and b, thus indicating the importance of the intermediate principal stress and the principal stress directions relative to the horizontal bedding planes. The observed shear bands essentially followed the expected directions, but due to the cross-anisotropy shear bands were also observed in the direction of the major principal stress in regions with high b-values. The strength variation was also influenced by the flexibility of the boundaries in these regions.

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Section: Previous Studies Of Cross-anisotropymentioning

confidence: 81%

Shear banding in torsion shear tests on cross-anisotropic deposits of fine Nevada sand

Lade

Dyck²,

Rodriguez

2014

Soils and Foundations

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“…Numerical analysis by Naughton and O'Kelly (2007) indicated that the stress non-uniformity that may develop across the thickness of the UCD specimen due to its wall curvature increased in proportion to the major-to-minor principal stress ratio (R), although the level of stress non-uniformity was generally acceptable throughout the stress space for R  1.5. The specimen wall thickness of 14.5 mm was also sufficiently large in relation to the grain size of the sand so that a uniform densification of the specimen could be achieved during specimen preparation and potential failure mechanisms were free to develop during the stress path tests.…”

Section: Overview Of Apparatusmentioning

confidence: 99%

“…(Table 1) induced across the specimen wall thickness were derived from equilibrium considerations assuming an isotropic, linear-elastic response (Naughton and O'Kelly, 2007). The stress components were integrated over the full specimen volume in order to account for the effects of the specimen wall curvature.…”

Section: Principle Of Hollow Cylinder Torsional Testingmentioning

confidence: 99%

Study of the yielding of sand under generalized stress conditions using a versatile hollow cylinder torsional apparatus

O’Kelly

Naughton

2009

Mechanics of Materials

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Please cite this article as: O'Kelly, B.C., Naughton, P.J., Study of the yielding of sand under generalized stress conditions using a versatile hollow cylinder torsional apparatus, Mechanics of Materials (2008Materials ( ), doi: 10.1016Materials ( / j.mechmat.2008 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. ACCEPTED MANUSCRIPT AbstractThe hollow cylinder torsional apparatus (HCTA) is particularly suited to studying the mechanical behavior of cross-anisotropic test specimens since the magnitudes of the three principal stresses and the orientation of the major-minor principal stress axes can be independently controlled. Novel features of the University College Dublin HCTA, particularly the instrumentation and calibration procedures necessary to achieve accurate generalized stress path testing, are presented. The plastic yield behavior of fully saturated Leighton Buzzard sand was studied under generalized stress conditions. Physically identical test-specimens (35.5 mm inner radius, 50.0 mm outer radius and 200 mm in length) were prepared using a water-pluviation technique that reproduces the inherent cross-anisotropic fabric of many natural sand deposits. A series of stress path tests systematically probed the stress space to locate segments of yield loci. The deviator stress at yield was found to vary in a well-defined pattern that depended on the magnitude of the intermediate principal stress parameter. However, the deviator stress at yield was largely independent of reorientations of the major principal stress that had occurred during the initial anisotropic consolidation stage of the tests. The experimental yield data was used to show that the Matsuoka-Nakai and Lade yield criteria provide satisfactory predictions of the onset of plastic yielding in sand deposits under generalized stress conditions for routine geotechnical engineering design.

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“…The non-zero stress equations have been reported in detail by O'Kelly and Naughton (2005a,b,c) and Naughton and O'Kelly (2007). The mean non-zero strain components are calculated from the local radial (u o , u i ), axial (w) and twist () deformations measured using the proximity transducers and the inclinometers Andover an axial gauge length, L z (Eqs.…”

Section: Calculation Of Strain Responsementioning

confidence: 99%

“…Local instrumentation measures the polar deformation response over the uniformly stressed zone within the mid-third of the specimen length in the UCD HCA (Naughton and O'Kelly 2007). It is convenient to use a polar coordinate system in considering the states of stress and the deformation/strain response.…”

Section: Measurement Of Deformation Response In Ucd Hcamentioning

confidence: 99%

Local measurements of the polar deformation response in a hollow cylinder apparatus

O’Kelly

Naughton

2008

Geomechanics and Geoengineering

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This paper describes the set up, calibration and performance of the local instrumentation that measures the deformation response of the test-specimen in a new hollow cylinder apparatus (HCA). Customised, single and double-axes inclinometers measure the axial and twist deformations of the outer specimen wall surface. Proximity transducers in the cell chamber and the specimen bore cavity measure the radial wall surface displacements and precision gearing allows the relocation of the transducers from outside the pressure-cell. The inclinometers were modified (reduced gauge of 45 mm) to suit the smaller-sized test specimen and the more compact pressure cell of the HCA. The instruments were calibrated using an optical table and laser distance-measurement system to achieve the necessary accuracy for strain measurements over the pseudoelastic range. The calibration in water of the proximity transducers was non-linear and strongly influenced by the specimen wall curvature. Equations are presented to compute the true torsional shear strain response from the measured inclinometer tilt angle, specimen dimensions and deformation response. External measurements include significant errors due to apparatus compliance; specimen end-restraint and bedding effects; inaccuracies in measuring volume changes and the fact that the deformations are calculated assuming that the entire specimen deforms as a right cylinder.

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Stress non-uniformity in a hollow cylinder torsional sand specimen

Cited by 15 publications

References 8 publications

Shear banding in torsion shear tests on cross-anisotropic deposits of fine Nevada sand

Shear banding in torsion shear tests on cross-anisotropic deposits of fine Nevada sand

Study of the yielding of sand under generalized stress conditions using a versatile hollow cylinder torsional apparatus

Local measurements of the polar deformation response in a hollow cylinder apparatus

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