Inducing Tensile Failure of Claystone Through Thermal Pressurization in a Novel Triaxial Device

Abstract

Highlights-Thermal pressurization of clay rock in deep radioactive waste repositories can reduce the effective stresses, which can lead to damage or failure. -Our novel laboratory triaxial device is able mimic in situ conditions: Constant vertical total stress, zero lateral deformation and thermal pressurization. -Pore pressure increase, vertical extension strains and thermal pressurization failure were recorded in a series of tests on Callovo-Oxfordian claystone specimens. -The effective tensile strength was reached at values around 3 MPa in tension and temperatures between 53 and 64 °C, creating sub-horizontal fractures. -The experimental responses can be well reproduced using a thermo-poroelasticity model.-Hoek-Brown and Fairhurst generalized Griffith criteria appear suitable to account for the rock's tensile resistance.

Thermal Impact on the Excavation Damage Zone Around a Supported Drift Using the 2nd Gradient Model

“…In the far-field, due to symmetric conditions, the half-way zone between two neighbouring cells will be subjected to thermal loading from both sides. Depending on the distance between the cells and the intensity of the thermal load, this could induce tensile or even shear failure (Plúa et al, 2021;Braun et al, 2022). The above behaviour may potentially alter the permeability of host rock as a result.…”

“…The next step is to further investigate the temperature effect on the THM behaviour of clay host rock. Thermal pressurisation has already been evidenced both in laboratory (Braun et al, 2022;Monfared et al, 2012) and in-situ heating tests (Bumbieler et al, 2021). As for modelling the strain localisation, biaxial compression tests were carried out to represent the fracturing in shear band mode, among which the microstructure effect was also taken into account (Shahrokhabadi et al, 2020;Sun, 2015;Rattez et al, 2018).…”