Title: Fault Stability Perturbation by Thermal Pressurization and Stress Transfer Around a Deep Geological Repository in a Clay Formation

Abstract

The increase of temperature of a low-permeability, fluid-saturated media may trigger significant thermal pressurization, where the expansion of pore fluid cannot be accommodated by the thermal expansion of the pore space. With the aid of a coupled thermohydromechanical numerical simulator, we investigate the possible impact of thermal pressurization during the life of a deep geological repository (DGR) for high-level radioactive waste, characterized by the emplacement of radioactive material-filled canisters in a series of parallel tunnels, excavated in a low-permeability clay formation. We represent the fault as a planar structure embedded in a thermoporoelastic material and shear activation evaluated by a strain-softening Mohr-Coulomb failure criterion. The results show that stress changes caused by temperature and thermal pressurization of a rock mass around the emplacement tunnels may trigger a slip event on a fault plane in proximity of the geological disposal site: Rupture nucleates at depth, hundreds of meters below the DGR. Stress transfer plays a key role, while a direct hydraulic connection between the repository and the nucleation zone is not necessary in order to trigger rupture. A low stress ratio may favor the occurrence of slip up to a distance of 600 m of the fault from the outermost tunnel.more » Furthermore, these results highlight the need of investigating hydromechanical properties and local stress conditions at depth to characterize the geomechanical response of weak planes located in the surroundings of a high-level radioactive waste repository and to provide sufficient knowledge for the safe development of the DGR site.« less

Authors:

Urpi, L.  ^[1];

• Search DOE PAGES for author "Urpi, L."
• Search DOE PAGES for ORCID "0000-0003-4464-8039"

Rinaldi, A. P.  ^[1];

• Search DOE PAGES for author "Rinaldi, A. P."
• Search DOE PAGES for ORCID "0000-0001-7052-8618"

Rutqvist, J.  ^[2];

• Search DOE PAGES for author "Rutqvist, J."
• Search DOE PAGES for ORCID "0000-0002-7949-9785"

Wiemer, S.  ^[1]

• Search DOE PAGES for author "Wiemer, S."
• Search DOE PAGES for ORCID "0000-0002-4919-3283"

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+ Show Author Affiliations

1. ETH Zürich, Zürich (Switzerland)
2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

Publication Date:

Wed Jul 10 00:00:00 EDT 2019

Research Org.:

Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1574334

Alternate Identifier(s):

OSTI ID: 1557342

Grant/Contract Number:  

AC02-05CH11231; AC02‐05CH11231

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Geophysical Research. Solid Earth

Additional Journal Information:

Journal Volume: 124; Journal Issue: 8; Journal ID: ISSN 2169-9313

Publisher:

American Geophysical Union

Country of Publication:

United States

Language:

English

Subject:

58 GEOSCIENCES; induced seismicity; thermal pressurization; clay; deep geological repository; fault reactivation; numerical finite element