TY - JOUR
T1 - Damage Evolution of Onnagawa Shale by Postmortem Thresholding of X-Ray Computed Tomography
AU - Jayawickrama, E. G.
AU - Muto, J.
AU - Sasaki, O.
AU - Nagahama, H.
N1 - Funding Information:
This research was supported by Japan Society for the Promotion of Science grants 24244077 and 20H02002, and by the Ministry of Education, Culture, Sports, Science and Technology (Japan) scholarship 153050. The authors would like thank Dr. Miki Takashashi for the helpful discussions, Mr. Erick R. Velasco Reyes for his assistance in the XRD analysis and the Tech team in our department for their help on this study. The authors also would like to show our gratitude toward Mr. Ito at the Fukushima Technology Center (Japan) for his assistance in operating the He pycnometer.
Funding Information:
This research was supported by Japan Society for the Promotion of Science grants 24244077 and 20H02002, and by the Ministry of Education, Culture, Sports, Science and Technology (Japan) scholarship 153050. The authors would like thank Dr. Miki Takashashi for the helpful discussions, Mr. Erick R. Velasco Reyes for his assistance in the XRD analysis and the Tech team in our department for their help on this study. The authors also would like to show our gratitude toward Mr. Ito at the Fukushima Technology Center (Japan) for his assistance in operating the He pycnometer.
Publisher Copyright:
© 2021. American Geophysical Union. All Rights Reserved.
PY - 2021/11
Y1 - 2021/11
N2 - Onnagawa shale samples are deformed through the brittle-ductile transition by increasing the confining pressure. Brittle deformation is characterized by longitudinal splitting of the sample at 3% axial strain. A distributed conjugate fracture network characterizes the macroscopic deformation in the ductile field with strain hardening. The onset of transition from brittle to ductile deformation is between 4% and 5% axial strain with a single shear plane defined failure. Deformed samples are scanned in a commercially available X-ray CT machine to investigate the sensitivity of the fracture network to the choice of threshold voxel value. The primary voxel values of the deformed rock are reversed, and their density distribution is approximated by a normal distribution to extract the voxel value density distribution that fabricated the fracture network (residual). Successive thresholding of the residual histogram shows that the generated fracture network is highly sensitive to the choice of threshold. Post peak thresholding of the residual histogram generates voxel volumes of fractures alone and consecutive thresholding shows that the obtained volume segments of the fractures can interpret possible nucleation, growth, and coalescence within the damaged zone. Results further show similarity to previous 4D tomographic strain localization investigations and damage size distributions by acoustic emission studies. Therefore, despite the postmortem nature of the investigation, the new technique opens possibilities to investigate the possible evolution of fracture properties under elevated confining pressures and in the absence of high energy synchrotron facilities.
AB - Onnagawa shale samples are deformed through the brittle-ductile transition by increasing the confining pressure. Brittle deformation is characterized by longitudinal splitting of the sample at 3% axial strain. A distributed conjugate fracture network characterizes the macroscopic deformation in the ductile field with strain hardening. The onset of transition from brittle to ductile deformation is between 4% and 5% axial strain with a single shear plane defined failure. Deformed samples are scanned in a commercially available X-ray CT machine to investigate the sensitivity of the fracture network to the choice of threshold voxel value. The primary voxel values of the deformed rock are reversed, and their density distribution is approximated by a normal distribution to extract the voxel value density distribution that fabricated the fracture network (residual). Successive thresholding of the residual histogram shows that the generated fracture network is highly sensitive to the choice of threshold. Post peak thresholding of the residual histogram generates voxel volumes of fractures alone and consecutive thresholding shows that the obtained volume segments of the fractures can interpret possible nucleation, growth, and coalescence within the damaged zone. Results further show similarity to previous 4D tomographic strain localization investigations and damage size distributions by acoustic emission studies. Therefore, despite the postmortem nature of the investigation, the new technique opens possibilities to investigate the possible evolution of fracture properties under elevated confining pressures and in the absence of high energy synchrotron facilities.
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U2 - 10.1029/2021JB022056
DO - 10.1029/2021JB022056
M3 - Article
AN - SCOPUS:85119851831
VL - 126
JO - Journal of Geophysical Research: Solid Earth
JF - Journal of Geophysical Research: Solid Earth
SN - 2169-9313
IS - 11
M1 - e2021JB022056
ER -