Full-field measurements of strain localisation in sandstone by neutron tomography and 3D-volumetric digital image correlation
Author
Editor
- Anders Kaestner
Summary, in English
Recent studies have demonstrated that the combination of x-ray tomography during triaxial tests (”in-situ” tests) and 3D-
volumetric Digital Image Correlation (3D-DIC) can provide important insight into the mechanical behaviour and deformation
processes of granular materials such as sand. The application of these tools to investigate the mechanisms of failure in rocks is
also of obvious interest. However, the relevant applied confining pressures for triaxial testing on rocks are higher than those on
sands and therefore stronger pressure containment vessels, i.e., made of thick metal walls, are required. This makes in-situ x-ray
imaging of rock deformation during triaxial tests a challenge. One possible solution to overcome this problem is to use neutrons,
which should better penetrate the metal-walls of the pressure vessels. In this perspective, this work assesses the capability of
neutron tomography with 3D-DIC to measure deformation fields in rock samples. Results from pre- and post-deformation neutron
tomography of a Bentheim sandstone sample deformed ex-situ at 40 MPa show that clear images of the internal structure can
be achieved and utilised for 3D-DIC analysis to reveal the details of the 3D strain field. From these results the character of the
localised deformation in the study sample can thus be described. Furthermore, comparison with analyses based on equivalent x-ray
tomography imaging of the same sample confirms the effectiveness of the method in relation to the more established x-ray based
approach.
volumetric Digital Image Correlation (3D-DIC) can provide important insight into the mechanical behaviour and deformation
processes of granular materials such as sand. The application of these tools to investigate the mechanisms of failure in rocks is
also of obvious interest. However, the relevant applied confining pressures for triaxial testing on rocks are higher than those on
sands and therefore stronger pressure containment vessels, i.e., made of thick metal walls, are required. This makes in-situ x-ray
imaging of rock deformation during triaxial tests a challenge. One possible solution to overcome this problem is to use neutrons,
which should better penetrate the metal-walls of the pressure vessels. In this perspective, this work assesses the capability of
neutron tomography with 3D-DIC to measure deformation fields in rock samples. Results from pre- and post-deformation neutron
tomography of a Bentheim sandstone sample deformed ex-situ at 40 MPa show that clear images of the internal structure can
be achieved and utilised for 3D-DIC analysis to reveal the details of the 3D strain field. From these results the character of the
localised deformation in the study sample can thus be described. Furthermore, comparison with analyses based on equivalent x-ray
tomography imaging of the same sample confirms the effectiveness of the method in relation to the more established x-ray based
approach.
Publishing year
2015
Language
English
Pages
509-515
Publication/Series
Physics Procedia - 10th World Conference on Neutron Radiography
Volume
69
Document type
Conference paper
Publisher
Elsevier
Topic
- Geotechnical Engineering
Keywords
- X-rays
- Neutrons
- Digital Image Correlation
- Tomography
- Rocks
Status
Published