Mixed-Mode Strain Localization between Interacting Fault Segments

35 Pages Posted: 1 Aug 2024

See all articles by Erina Prastyani

Erina Prastyani

affiliation not provided to SSRN

Benoît Cordonnier

European Synchrotron Radiation Facility (ESRF)

Jessica Ann McBeck

affiliation not provided to SSRN

Jerome Weiss

University Grenoble Alpes - IsTerre, CNRS

Francois Renard

University of Oslo

Abstract

Analyzing how fracture networks develop from preexisting isolated fault segments may provide knowledge of the preparation process leading to fault growth and dynamic rupture. We reproduce this process experimentally in granite core samples that contain preexisting notches. We characterize the microphysical processes of damage and fault growth in two cylindrical Westerly granite samples (10 mm diameter, 20 mm height) that contain two parallel notches oriented at 30o with respect to the axis of the cylinder, that separate an intact rock bridge. We performed triaxial compression experiments at room temperature with a constant confining pressure of 20 MPa. We image microfracture development between the notches using dynamic in situ X-ray tomography at the European Synchrotron Radiation Facility. During compressive loading, we acquired a series of tomograms of the samples, from which we extracted and quantified the statistical properties of the fractures. We analyzed the development of rock damage and the evolution of fractures oriented at 0o-17o (extensile) and 17o-32o (shear) as the rock approaches failure. We also calculated digital volume correlation to elucidate the strain localization process in the deforming rock. Our results indicate that immediately preceding failure, shear fractures dominate the fracture networks. The rock bridge between the notches becomes damaged with a damage rate and a fracture rate diverging as the rock approaches macroscopic failure. DVC analysis showed that the deformation process is mixed-mode, accommodated by dilation and shear strain. The shear strains are more localized than the dilation. Furthermore, the data reveal that regions with high dilative strain host both extensile and shear fractures.

Keywords: Dynamic X-ray tomography, Fault growth, Westerly granite, Rock damage

Suggested Citation

Prastyani, Erina and Cordonnier, Benoît and McBeck, Jessica Ann and Weiss, Jerome and Renard, Francois, Mixed-Mode Strain Localization between Interacting Fault Segments. Available at SSRN: https://ssrn.com/abstract=4913356

Erina Prastyani (Contact Author)

affiliation not provided to SSRN ( email )

No Address Available

Benoît Cordonnier

European Synchrotron Radiation Facility (ESRF) ( email )

Jessica Ann McBeck

affiliation not provided to SSRN ( email )

No Address Available

Jerome Weiss

University Grenoble Alpes - IsTerre, CNRS ( email )

Grenoble, 38401
France

Francois Renard

University of Oslo ( email )

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