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

DOI: 10.1002/ppp.1737 DOI Help

Authors: Aine Ni Bhreasail (Imperial College London) , Catherine O'sullivan (Imperial College London Civil Engineering) , Clark Fenton (Imperial College London Civil Engineering) , Richard Hamilton (Imperial College London) , Peter Rockett (Imperial College London) , Thomas Connolley (Diamond Light Source) , Peter Lee (University of Manchester)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Permafrost And Periglacial Processes , VOL 23 (2) , PAGES 170 - 176

State: Published (Approved)
Published: May 2012
Diamond Proposal Number(s): 6033

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.

Journal Keywords: Ice Lenses; Micro Computed Tomography; Frozen SoilRoyal Society

Subject Areas: Engineering, Environment
Collaborations: Diamond Manchester

Instruments: I12-JEEP: Joint Engineering, Environmental and Processing