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Description
A variational gradient damage model for saturated poroelastic media with thermo-hydro-mechanical (THM) coupling and cohesive zone effect is proposed in this work. The model provides a unified and fully coupled description of gradient damage, poroelasticity, heat transfer and fluid flow, and is able to accurately capture the behavior of fracture process zone (FPZ) near the tip of quasi-brittle fractures. Following the incremental variational principle proposed by Zhang et al. (JMPS, 187 (2024) 105614), the model is formulated as a four-field energy functional relying on the displacement, damage, temperature, and pore pressure fields. A semi-staggered optimization algorithm is built to implement the proposed model, which involves a saddle-point problem for poroelasticity coupled with temperature and fluid flow, as well as an optimization problem for gradient damage. The model is first validated against the KGD fracture problem, for which analytical solutions are available, to assess its predictive capabilities under hydro-mechanical (HM) coupling. It is then applied to a THM benchmark problem with analytical solution to simulate thermal pressurization. Finally, the proposed model is applied to reproduce the THM response of Callovo-Oxfordian (COx) claystone subjected to excavation and thermal loading. COx claystone has been selected by French authorities as the host rock for high-temperature radioactive waste storage. Excavation of the COx claystone perturbs the in situ stress and pore pressure fields, leading to the initiation and development of an excavation-induced damage zone (EDZ). Subsequent heat generation from the stored waste causes temperature increases in the host rock, resulting in pore pressure variations and associated mechanical responses. The numerical predictions of temperature evolution, pore pressure changes, and EDZ extent are presented and compared with in situ observations.
| Country | France |
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