Engineering Properties of Wet-Pluviated Hollow Cylindrical Specimens

Naughton

2009

Mechanics of Materials

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.

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

Naughton

2009

Mechanics of Materials

Analysis and Design of Monopile Foundations for Offshore Wind-Turbine Structures

Arshad

Marine Georesources & Geotechnology

2015

Offshore wind turbines (OWTs) are generally supported by large-diameter monopiles, with the combination of axial forces, lateral forces, bending moments and torsional moments generated by the OWT structure and various environmental factors resisted by earth pressures mobilized in the soil foundation. The loading on the monopile foundation is essentially cyclic in nature and typically low-amplitude. This state-of-the-art review paper presents details on the geometric Downloaded by [New York University] at 00:02 29 July 2015 2 design, nominal size, and structural and environmental loading for existing and planned OWT structures supported by monopile foundations. Pertinent ocean-environment loading conditions, including methods of calculation using site-specific data, are described along with wave particle kinematics, focusing on correlations between loading frequency and natural vibration frequency of the OWT structure. Existing methods for modelling soil under cyclic loading are reviewed, focusing in particular on strain accumulation models that consider pile-soil interaction under cyclic lateral loading. Inherent limitations/shortcomings of these models for the analyses and design of existing and planned OWT monopile foundations are discussed. A design example of an OWT support structure having a monopile foundation system is presented. Target areas for further research by the wind-energy sector are identified which would facilitate the development of improved analyses/design methods for offshore monopiles.

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

Geomechanics and Geoengineering

Naughton

2008

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.