In Situ Investigation of the THM Behavior of the Callovo-Oxfordian Claystone

Abstract

The thermo-hydro-mechanical behavior of the host rock is essential while designing an underground radioactive waste disposal repository, and in particular, while considering the long-term safety of the facility. In 2000, the French National Radioactive Waste Management Agency (Andra) started constructing an underground research laboratory located in the Meuse Haute Marne to carry out a research program aiming to demonstrate the feasibility of constructing and operating a radioactive waste disposal facility in the Callovo-Oxfordian claystone, and to optimize its implementation. To study the thermo-hydro-mechanical effects of the early thermal phase on the clay host rock of a deep repository, Andra has performed various in situ heating tests; one of them is called the TED experiment. The aim of the TED experiment was to measure the evolution of the temperature and pore pressure fields around several heaters and to back-analyze the thermo-hydro-mechanical properties of the Callovo-Oxfordian claystone. Thermal conductivity and heat capacity values were determined based on the back-analysis of the in situ measurements and compared to those measured on samples. The in situ experimental data and numerical model confirm the anisotropic behavior of the claystone. The TED experiment results demonstrate the ability of current models to predict the evolution of temperature and pore pressure in the far field of disposal cells.

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

“…Next to the hydro-mechanical response involved during the excavation of the micro-tunnels, a thermo-hydro-mechanical response takes place during to the heat release from the exothermic waste packages (e.g. Gens et al, 2007;Seyedi et al, 2017;Armand et al, 2017;Conil et al, 2020, see Fig. 1).…”

“…It has been described and numerically modelled by different authors (e.g. by Gens et al, 2007;Jobmann and Polster, 2007 in the HE-D test run in the Opalinus clay in the Mt Terri URL in Switzerland, by Seyedi et al, 2017;Conil et al, 2020 in the TED test and by Armand et al (2017); Bumbieler et al (2021); Tourchi et al (2021) in the ALC1604 test, both run in the Callovo-Oxfordian claystone (COx) in the Bure URL in France). Thermal pressurization has also been investigated through laboratory experiments, as done by Mohajerani et al, 2012;Zhang et al, 2017;Braun et al, 2021a on COx claystone andMonfared et al, 2011b on Opalinus clay.…”

Two-step Homogenization of Poroelastic Properties of a Limestone

“…Effective linear poroelastic constitutive equations at the mesoscale, with the assumption of zero initial stress and zero initial pore pressure, are written as follows ( Dormieux et al, 2006). (6) where Σ, E represents the mesoscopic stress and strain tensor; ϕ the porosity; P the pore pressure; B I j the Biot tensor coefficient and N I j the solid Biot modulus (j=o,i,m). Micro-macro compatibility condition yields: (7) in which, is the second-order identify tensor.…”

“…is significant for numerous environmental and industrial engineering problem. Indeed, thermo-poroelastic approach is usually considered for the design of geological sequestration of CO2 (Seyedi et al, 2011(Seyedi et al, , 2015; nuclear waste disposal (Vu et al, 2019;Conil et al, 2020;Seyedi et al, 2017. ); petroleum reservoir engineering (Trieu, 2010(Trieu, , 2011; geothermal energy production (Han et al, 2019); groundwater (Kim, 2004); etc.…”

Stability Analysis of Host Claystone under T-M Coupling of HLW Disposal Repository in China: Experiments and Numerical Simulation

“…After the Meuse/Haste-Marne pre-selection site was 2 Geofluids determined in 2000, France built an underground laboratory for the disposal of HLW repository in the Callovo-Oxfordian claystone layer, which is 450 m underground [7]. Conil and Samat [8,9] evaluated in situ T-M coupled characteristics of the claystone by combining numerical simulation with laboratory test, and finally achieved the purpose of using numerical simulation to guide field test. Nonetheless, there is no real disposal HLW repository has been built in China, most of the past researches have been carried out through sample tests or numerical simulations.…”