In‐Situ Observation of Cracks in Frozen Soil using Synchrotron Tomography

Abstract

Phase‐contrast synchrotron micro‐computed tomography (μCT) is well suited to studying the microstructure of frozen soil. To take advantage of the high‐resolution three‐dimensional images that can be generated using μCT, a specialised in‐situ rig was designed and commissioned. This miniature temperature‐controlled oedometer is capable of controlling soil sample thermal gradients and applying uniaxial deformation while measuring stress. This system was used to apply repeated freeze‐thaw cycles to water‐saturated samples of Leighton Buzzard sand, Reigate sand and spherical glass ballotini (an idealised soil). High‐resolution images were obtained using a monochromatic, parallel beam of x‐rays generated on Beamline I12 of the Diamond synchrotron. Cracking in the ice was directly measured utilising the phase‐contrast fringes generated by ice‐air interfaces. Examination of these images revealed two modes of crack formation in the ice phase of frozen soil: micro‐cracks between soil particles, and longer, well‐developed cracks that follow along ice‐soil particle boundaries and span across the ice between particles. Both crack types were orientated parallel to the freezing front (normal to the heat flow), affecting both the frozen soils' mechanical behaviour, and we hypothesise that these cracks are potential initiation sites for ice lens development. Copyright © 2012 John Wiley & Sons, Ltd.

Cryogenic Deformation Structures in Late Cenozoic Unconsolidated Sediments of the Tunka Depression in the Baikal Rift Zone

“…Ní Bhreasail et al . () studied the microstructure of frozen soil and cracking in the ice using phase‐contrast synchrotron micro‐computed tomography. They revealed two modes of crack formation in the ice phase of frozen soil: micro‐cracks between soil particles and cracks along ice‐soil particle boundaries and in the spans across the ice between particles.…”

4D imaging of sub-second dynamics in pore-scale processes using real time synchrotron x-ray tomography

“…The general principles of X-ray tomography, reconstruction and data processing as relating to geoscience applications are covered in a series of recent reviews Cnudde and Boone, 2013;Hess et al, 2011;Maire and Withers, 2014;Wildenschild and Sheppard, 2013). For the specific application of understanding pore scale processes, XCT and sXCT are now becoming widely used for both qualitative and quantitative imaging of complex natural pore networks, and the distribution of liquid(s) within them (Al-Raoush et al, 2011;Al-Raoush and Willson, 2005;Berg et al, 2013;Bhreasail et al, 2012;Boone et al, 2014;Cnudde and Boone, 2013;Dewanckele et al, 2012;Geraud et al, 2003;Herring et al, 2013;Iglauer et al, 2011;Katuwal et al, 2015;Ma et al, 2016;Naveed et al, 2013b;Olafuyi et al, 2010;Sakellariou et al, 2003;Sok et al, 2010;Wildenschild et al, 2002;Wildenschild and Sheppard, 2013). The data are also being used as a basis of, and validation for numerical simulations (Al-Raoush and Papadopoulos, 2010;Alhashmi et al, 2015;Bultreys et al, 2015;Degruyter et al, 2010;Menke et al, 2015;Naveed et al, 2013a;Raeini et al, 2015;Raeini et al, 2014;Walter Fourie et al, 2007).…”

Response to RC1

“…The general principles of X-ray tomography, reconstruction and data processing as relating to geoscience applications are covered in a series of recent 15 reviews Cnudde and Boone, 2013;Hess et al, 2011;Maire and Withers, 2014;Wildenschild and Sheppard, 2013). For the specific application of understanding pore scale processes, XCT and sXCT are now becoming widely used for both qualitative and quantitative imaging of complex natural pore networks, and the distribution of liquid(s) within them (Al-Raoush et al, 2011;Al-Raoush and Willson, 2005;Berg et al, 2013;Bhreasail et al, 2012;Boone et al, 2014;Cnudde and Boone, 2013;Dewanckele et al, 2012;Geraud et al, 2003;Herring et al, 2013;Iglauer et al, 20 2011;Katuwal et al, 2015;Ma et al, 2016;Naveed et al, 2013b;Olafuyi et al, 2010;Sakellariou et al, 2003;Sok et al, 2010;Wildenschild et al, 2002;Wildenschild and Sheppard, 2013). The data are also being used as a basis of, and validation for numerical simulations (Al-Raoush and Papadopoulos, 2010;Alhashmi et al, 2015;Bultreys et al, 2015;Degruyter et al, 2010;Menke et al, 2015;Naveed et al, 2013a;Raeini et al, 2015;Raeini et al, 2014;Walter Fourie et al, 2007).…”

“…In this mode, sample rotation is not stopped for each projection, instead data is acquired over a narrow arc (typically 0.1-0.5°). For most geological materials 10 collection of the projection data can be just a few seconds Berg et al, 2013;Bhreasail et al, 2012;Pistone et al, 2015;Pistone et al, 2013;Youssef et al, 2014). However, 2D imaging (the same projection acquisition rates but without rotation) is still needed to observe processes occurring on the millisecond-few second timescales; such as individual Haynes jumps and the subsequent relaxation dynamics (Armstrong et al, 2014b;Berg et al, 2013).…”