Earthquake-Induced Shear Displacements and Transmissivity Changes in 3D Fracture Systems: Implications for Long-Term Safety Assessment of Nuclear Waste Repositories
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2022-06-26
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Conference Paper
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Abstract
During the long service period of nuclear waste repositories, large earthquakes may occur around the repository site and coseismically trigger the shear displacement of secondary fractures intersected with waste canisters. The induced irreversible shear of natural fractures may further cause significant dilation and transmissivity enhancement, favoring the transport of leaked radionuclides into the groundwater system. Thus, it is of central importance to quantify the shear displacement and transmissivity variation in fracture systems during potential earthquake scenarios. Based on the detailed site characterization data of a planned repository at Forsmark, Sweden, we develop a three-dimensional seismo-mechanical model based on the 3Dimensional Distinct Element Code (3DEC). We consider explicitly a seismogenic fault zone and its surrounding fracture networks associated with a power-law length scaling and a Fisher orientation distribution. An earthquake with a magnitude of Mw = 5.62 caused by the rupture of the primary fault is modeled by simulating its transient rupture propagating radially outwards from a predefined hypocenter at a specified rupture speed, with the rupture dynamics controlled by a strength weakening law. We explore different plausible scenarios of fracture networks and model their shear displacements and transmissivity changes in response to the earthquake. Our simulation results have important implications for the long-term safety assessment of planned nuclear waste repositories in crystalline rocks.
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Proceedings of the 56th U.S. Rock Mechanics/Geomechanics Symposium
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American Rock Mechanics Association
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56th U.S. Rock Mechanics/Geomechanics Symposium
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03465 - Löw, Simon (emeritus) / Löw, Simon (emeritus)
02704 - Geologisches Institut / Geological Institute
Notes
Conference lecture held on June 29, 2022.