In:
Safety of Nuclear Waste Disposal, Copernicus GmbH, Vol. 2 ( 2023-09-06), p. 63-63
Kurzfassung:
Abstract. The disposal of heat-generating radioactive waste in deep
geologic formations is a global concern. Numerical methods play a key role
in understanding and assessing the disposal scenarios of radioactive waste
in deep geological repositories. However, the complexities of the thermal,
hydrological, mechanical, chemical, and biological processes associated with
the disposal of radioactive waste in porous and fractured materials
constitute significant challenges. One of the most challenging issues in
this field is the complex material behaviour of fractured crystalline rock.
The presence of fractures makes the rock anisotropic, nonlinear, and
dependent on loading paths. Additionally, the Biot coefficient cannot be
considered constant throughout the critical and subcritical fracture
development regions. These factors make the development of an accurate
constitutive model for fractured crystalline hard rock a critical component
of any deep geological disposal project. Furthermore, to demonstrate the
integrity of the “containment effective rock area” in crystalline host rock,
the qualitative integrity criteria must be quantified so that numerical
simulation can be performed with concrete numerical values. Part of this
assessment for a crystalline host rock is a dilatancy criterion, which is
currently based on the Hoek–Brown constitutive model. This contribution provides an overview and first results of the laboratory
programme, which was performed as a part of the research project. The aim was
to generate a fundamental and extensive dataset for an anisotropic material
used for verification and validation purposes of the newly developed
constitutive model. The rock material for the test programme was “Freiberger
gneiss” because of its pronounced anisotropic properties regarding
deformation and strength as well as the good access to obtain a larger
amount of sample material. A wide range of basic tests have been performed,
e.g. determination of density and porosity, measurement of ultrasonic wave
velocities to get dynamic elastic properties, Brazilian tests, and uniaxial
compression tests to obtain strength data. Additionally, a large number of
more complex multi-stage triaxial compression tests with examination of the
post-failure region and hydromechanical coupled triaxial compression tests
have been conducted or are in progress. The
hydromechanical part, in particular, plays an important role in examining and quantifying the
evolution of the micromechanical damage process, which changes the
permeability and Biot coefficient and therefore the effective stresses
inside a saturated rock material. Tests were conducted with different
orientations of the structural planes in relation to the loading directions.
Materialart:
Online-Ressource
ISSN:
2749-4802
DOI:
10.5194/sand-2-63-2023
Sprache:
Englisch
Verlag:
Copernicus GmbH
Publikationsdatum:
2023
