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

Abstract

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.

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

“…by formation process, grain size (fine or coarse), plasticity index, age (young or aged deposits), mineralogical content, etc. Apart from at very small strain levels of <10 3 strain (Atkinson and Sallfors 1991;O'Kelly and Naughton 2008), the stress-strain relationship for soil is generally highly nonlinear ( …”