Failure mode transition in Opalinus Clay: a hydro-mechanical and microstructural perspective
<p>The way rocks deform under changing stress conditions can be described by different deformation modes, which is fundamental for understanding their rheology. For Opalinus Clay, which is regarded as a potential host rock for nuclear waste, we investigate the failure mode as a function of app...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2022-05-01
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| Series: | Solid Earth |
| Online Access: | https://se.copernicus.org/articles/13/901/2022/se-13-901-2022.pdf |
| _version_ | 1818206702431895552 |
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| author | L. Winhausen K. Khaledi M. Jalali J. L. Urai F. Amann F. Amann |
| author_facet | L. Winhausen K. Khaledi M. Jalali J. L. Urai F. Amann F. Amann |
| author_sort | L. Winhausen |
| collection | DOAJ |
| description | <p>The way rocks deform under changing stress conditions can
be described by different deformation modes, which is fundamental for
understanding their rheology. For Opalinus Clay, which is regarded as a
potential host rock for nuclear waste, we investigate the failure mode as a
function of applied effective stress in laboratory experiments. Therefore,
we performed consolidated undrained triaxial tests at different effective
consolidation stresses from 2.5 to 16 MPa, in which samples were loaded
parallel to bedding, and analysed the deformation structures using ion-beam
polishing and electron microscopy. With increasing effective confining
stress, the results show a transition from brittle-dominated to more
ductile-dominated deformations, localising in distinct shear bands. Both
effective stress paths and microstructural analysis indicate a tendency
towards less dilation in the shear zones for higher effective stresses.
Triaxial test results suggest a non-linear failure envelope. The
non-linearity of the failure envelope is associated with decreasing dilation with increasing effective stress accompanied by changes in microstructural
deformation processes, which explain the decreasing friction angle. For the
first time, we can verify that the observed non-linear failure envelope is
due to the gradual transition from brittle- to more ductile-dominated
deformation on the microscale controlling the bulk hydro-mechanical
behaviour of Opalinus Clay.</p> |
| first_indexed | 2024-12-12T04:17:14Z |
| format | Article |
| id | doaj.art-85560dc6cb54400abdcba5fe24b658b2 |
| institution | Directory Open Access Journal |
| issn | 1869-9510 1869-9529 |
| language | English |
| last_indexed | 2024-12-12T04:17:14Z |
| publishDate | 2022-05-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Solid Earth |
| spelling | doaj.art-85560dc6cb54400abdcba5fe24b658b22022-12-22T00:38:25ZengCopernicus PublicationsSolid Earth1869-95101869-95292022-05-011390191510.5194/se-13-901-2022Failure mode transition in Opalinus Clay: a hydro-mechanical and microstructural perspectiveL. Winhausen0K. Khaledi1M. Jalali2J. L. Urai3F. Amann4F. Amann5Department of Engineering Geology and Hydrogeology, RWTH Aachen University, Lochnerstraße 4–20, 52064 Aachen, GermanyDepartment of Engineering Geology and Hydrogeology, RWTH Aachen University, Lochnerstraße 4–20, 52064 Aachen, GermanyDepartment of Engineering Geology and Hydrogeology, RWTH Aachen University, Lochnerstraße 4–20, 52064 Aachen, GermanyInstitute of Tectonics and Geodynamics, RWTH Aachen University, Lochnerstraße 4–20, 52064 Aachen, GermanyDepartment of Engineering Geology and Hydrogeology, RWTH Aachen University, Lochnerstraße 4–20, 52064 Aachen, GermanyFraunhofer IEG, Fraunhofer Research Institution for Energy Infrastructures and Geothermal Systems, Kockerellstraße 17, 52062 Aachen, Germany<p>The way rocks deform under changing stress conditions can be described by different deformation modes, which is fundamental for understanding their rheology. For Opalinus Clay, which is regarded as a potential host rock for nuclear waste, we investigate the failure mode as a function of applied effective stress in laboratory experiments. Therefore, we performed consolidated undrained triaxial tests at different effective consolidation stresses from 2.5 to 16 MPa, in which samples were loaded parallel to bedding, and analysed the deformation structures using ion-beam polishing and electron microscopy. With increasing effective confining stress, the results show a transition from brittle-dominated to more ductile-dominated deformations, localising in distinct shear bands. Both effective stress paths and microstructural analysis indicate a tendency towards less dilation in the shear zones for higher effective stresses. Triaxial test results suggest a non-linear failure envelope. The non-linearity of the failure envelope is associated with decreasing dilation with increasing effective stress accompanied by changes in microstructural deformation processes, which explain the decreasing friction angle. For the first time, we can verify that the observed non-linear failure envelope is due to the gradual transition from brittle- to more ductile-dominated deformation on the microscale controlling the bulk hydro-mechanical behaviour of Opalinus Clay.</p>https://se.copernicus.org/articles/13/901/2022/se-13-901-2022.pdf |
| spellingShingle | L. Winhausen K. Khaledi M. Jalali J. L. Urai F. Amann F. Amann Failure mode transition in Opalinus Clay: a hydro-mechanical and microstructural perspective Solid Earth |
| title | Failure mode transition in Opalinus Clay: a hydro-mechanical and microstructural perspective |
| title_full | Failure mode transition in Opalinus Clay: a hydro-mechanical and microstructural perspective |
| title_fullStr | Failure mode transition in Opalinus Clay: a hydro-mechanical and microstructural perspective |
| title_full_unstemmed | Failure mode transition in Opalinus Clay: a hydro-mechanical and microstructural perspective |
| title_short | Failure mode transition in Opalinus Clay: a hydro-mechanical and microstructural perspective |
| title_sort | failure mode transition in opalinus clay a hydro mechanical and microstructural perspective |
| url | https://se.copernicus.org/articles/13/901/2022/se-13-901-2022.pdf |
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