A versatile facility for laboratory studies of viscoelastic and poroelastic behaviour of rocks

Abstract

Novel laboratory equipment has been modified to allow both torsional and flexural oscillation measurements at sub-microstrain amplitudes, thereby providing seismic-frequency constraints on both the shear and compressional wave properties of cylindrical rock specimens within the linear regime. The new flexural mode capability has been tested on experimental assemblies containing fused silica control specimens. Close consistency between the experimental data and the results of numerical modelling with both finite-difference and finite-element methods demonstrates the viability of the new technique. The capability to perform such measurements under conditions of independently controlled confining and pore-fluid pressure, with emerging strategies for distinguishing between local (squirt) and global (specimen-wide) fluid flow, will have particular application to the study of frequency-dependent seismic properties expected of cracked and fluid-saturated rocks of the Earth's upper crust.

Differential Acoustic Resonance Spectroscopy for the acoustic measurement of small and irregular samples in the low frequency range

“… Gribb and Cooper [1998] designed a torsion apparatus, originally used for dynamic and static mechanical analyses of engineering materials, to investigate the seismic frequency and dynamic response of Earth's upper mantle. Jackson et al [2011] developed laboratory equipment according to the forced oscillation method, which allows both torsional and flexural oscillation measurements at sub‐micro strain amplitudes. The equipment provides seismic‐frequency constraints on both the shear and compressional wave properties of cylindrical rock specimens.…”

Laboratory measurements of frequency-dependent seismic properties of cracked and fluid-saturated media

“…The new flexural mode capability was first tested on experimental assemblies containing fused silica control specimens. Close consistency between the experimental data and the results of numerical modelling with both finitedifference and finite-element methods has demonstrated the viability of the new technique (Jackson et al, 2011).…”

An exploratory study of the seismic properties of thermally cracked, fluid- saturated aggregates of sintered glass beads

“…After comparing with a pure elastic fused silica reference with the same dimensions under the same experimental conditions to negate the contributions of all the components except just the specimen, the shear modulus µ and internal friction 1/Q can be extracted (Jackson and Paterson, 1993). With the newly modified capability for flexural-mode forced oscillation, the normalised flexural "modulus" SNF and loss angle δ (rad) can be obtained, and a complementary filament elongation model for flexure of thin beam with both finitedifference and finite-element methods can be used to extract the modelled Young's modulus with the observed SNF (Jackson et al, 2011).…”

“…By using the versatile Jackson-Paterson Attenuation Apparatus (mHz-Hz) at the Australian National University (Jackson & Paterson, 1993;Jackson et al, 2011) and the ultrasonic pulse transmission apparatus (MHz) at the University of Alberta, a broadband measurement on the glassbead studied samples is planned. The attenuation apparatus allows the access to the natural seismic domain with both torsional and newly developed flexural forced-oscillation modes, from which the shear and Young's modulus can be extracted respectively.…”