3D Interpretation of an in situ heating test in the callovo-oxfordian mudstone

In order to improve the understanding of the thermo-hydro-mechanical (THM) behaviour of the Callovo-Oxfordian Clay, an in situ heating test (TER experiment) has been realized by ANDRA at Meuse/Haute Marne URL during the last years. In this experiment, one power-control heater has been placed in a horizontal borehole and several heating phases realized at distinct levels of power. Around this heating borehole, 32 temperature sensors, 5 water pressure sensors and 2 extensometers were placed in 8 different boreholes. This abstract presents the interpretation works performed in parallel by running 3D THM simulations.Peer ReviewedPostprint (published version

Performance of the Opalinus Clay under thermal loading: experimental results from Mont Terri rock laboratory (Switzerland)

The final publication is available at Springer via http://dx.doi.org/10.1007/s00015-016-0258-8The paper presents an overview of the behaviour of Opalinus Clay under thermal loading as observed in three in situ heating tests performed in the Mont Terri rock laboratory: HE-B, HE-D and HE-E. The three tests are summarily described; they encompass a broad range of test layouts and experimental conditions. Afterwards, the following topics are examined: determination of thermal conductivity, thermally-induced pore pressure generation and thermally-induced mechanical effects. The mechanisms underlying pore pressure generation and dissipation are discussed in detail and the relationship between rock damage and thermal loading is examined using an additional in situ test: SE-H. The paper concludes with an evaluation of the various thermo-hydro-mechanical (THM) interactions identified in the heating tests.Peer ReviewedPostprint (author's final draft

3D Interpretation of an in situ heating test in the callovo-oxfordian mudstone

In order to improve the understanding of the thermo-hydro-mechanical (THM) behaviour of the Callovo-Oxfordian Clay, an in situ heating test (TER experiment) has been realized by ANDRA at Meuse/Haute Marne URL during the last years. In this experiment, one power-control heater has been placed in a horizontal borehole and several heating phases realized at distinct levels of power. Around this heating borehole, 32 temperature sensors, 5 water pressure sensors and 2 extensometers were placed in 8 different boreholes. This abstract presents the interpretation works performed in parallel by running 3D THM simulations.Peer Reviewe

3D Interpretation of an in situ heating test in the callovo-oxfordian mudstone

In order to improve the understanding of the thermo-hydro-mechanical (THM) behaviour of the Callovo-Oxfordian Clay, an in situ heating test (TER experiment) has been realized by ANDRA at Meuse/Haute Marne URL during the last years. In this experiment, one power-control heater has been placed in a horizontal borehole and several heating phases realized at distinct levels of power. Around this heating borehole, 32 temperature sensors, 5 water pressure sensors and 2 extensometers were placed in 8 different boreholes. This abstract presents the interpretation works performed in parallel by running 3D THM simulations.Peer Reviewe

Performance of the Opalinus Clay under thermal loading: experimental results from Mont Terri rock laboratory (Switzerland)

The final publication is available at Springer via http://dx.doi.org/10.1007/s00015-016-0258-8The paper presents an overview of the behaviour of Opalinus Clay under thermal loading as observed in three in situ heating tests performed in the Mont Terri rock laboratory: HE-B, HE-D and HE-E. The three tests are summarily described; they encompass a broad range of test layouts and experimental conditions. Afterwards, the following topics are examined: determination of thermal conductivity, thermally-induced pore pressure generation and thermally-induced mechanical effects. The mechanisms underlying pore pressure generation and dissipation are discussed in detail and the relationship between rock damage and thermal loading is examined using an additional in situ test: SE-H. The paper concludes with an evaluation of the various thermo-hydro-mechanical (THM) interactions identified in the heating tests.Peer Reviewe

Modelling the Mont Terri HE-D experiment for the Thermal–Hydraulic–Mechanical response of a bedded argillaceous formation to heating

Coupled thermal–hydrological–mechanical (THM) processes in the near field of deep geological repositories can influence several safety features of the engineered and geological barriers. Among those features are: the possibility of damage in the host rock, the time for re-saturation of the bentonite, and the perturbations in the hydraulic regime in both the rock and engineered seals. Within the international cooperative code-validation project DECOVALEX-2015, eight research teams developed models to simulate an in situ heater experiment, called HE-D, in Opalinus Clay at the Mont Terri Underground Research Laboratory in Switzerland. The models were developed from the theory of poroelasticity in order to simulate the coupled THM processes that prevailed during the experiment and thereby to characterize the in situ THM properties of Opalinus Clay. The modelling results for the evolution of temperature, pore water pressure, and deformation at different points are consistent among the research teams and compare favourably with the experimental data in terms of trends and absolute values. The models were able to reproduce the main physical processes of the experiment. In particular, most teams simulated temperature and thermally induced pore water pressure well, including spatial variations caused by inherent anisotropy due to bedding

Modelling the Mont Terri HE-D experiment for the Thermal–Hydraulic–Mechanical response of a bedded argillaceous formation to heating

Coupled thermal–hydrological–mechanical (THM) processes in the near field of deep geological repositories can influence several safety features of the engineered and geological barriers. Among those features are: the possibility of damage in the host rock, the time for re-saturation of the bentonite, and the perturbations in the hydraulic regime in both the rock and engineered seals. Within the international cooperative code-validation project DECOVALEX-2015, eight research teams developed models to simulate an in situ heater experiment, called HE-D, in Opalinus Clay at the Mont Terri Underground Research Laboratory in Switzerland. The models were developed from the theory of poroelasticity in order to simulate the coupled THM processes that prevailed during the experiment and thereby to characterize the in situ THM properties of Opalinus Clay. The modelling results for the evolution of temperature, pore water pressure, and deformation at different points are consistent among the research teams and compare favourably with the experimental data in terms of trends and absolute values. The models were able to reproduce the main physical processes of the experiment. In particular, most teams simulated temperature and thermally induced pore water pressure well, including spatial variations caused by inherent anisotropy due to bedding

Modelling the Mont Terri HE-D experiment for the Thermal–Hydraulic–Mechanical response of a bedded argillaceous formation to heating

International audienceCoupled thermal–hydrological–mechanical (THM) processes in the near field of deep geological repositories can influence several safety features of the engineered and geological barriers. Among those features are the possibility of damage in the host rock, the time for re-saturation of the bentonite, and the perturbations in the hydraulic regime in both the rock and engineered seals. Within the international cooperative code-validation project DECOVALEX-2015, eight research teams developed models to simulate an in situ heater experiment, called HE-D, in Opalinus Clay at the Mont Terri Underground Research Laboratory in Switzerland. The models were developed from the theory of poroelasticity in order to simulate the coupled THM processes that prevailed during the experiment and thereby to characterize the in situ THM properties of Opalinus Clay. The modelling results for the evolution of temperature, pore water pressure, and deformation at different points are consistent among the research teams and compare favourably with the experimental data in terms of trends and absolute values. The models were able to reproduce the main physical processes of the experiment. In particular, most teams simulated temperature and thermally induced pore water pressure well, including spatial variations caused by inherent anisotropy due to bedding. © 2017, The Author(s)

Evaluation of the predictive capability of coupled thermo-hydro-mechanical models for a heated bentonite/clay system (HE-E) in the Mont Terri Rock Laboratory

International audienceProcess understanding and parameter identification using numerical methods based on experimental findings are key aspects of the international cooperative project DECOVALEX (DEvelopment of COupled models and their VALidation against Experiments http//www.decovalex.org). Comparing the long-term predictions from numerical models against experimental results increases confidence in the site selection and site evaluation process for a radioactive waste repository in deep geological formations. In the present phase of the project, DECOVALEX2015, eight research teams have developed and applied models for simulating the HE-E in situ heater experiment in the Opalinus Clay in the Mont Terri Rock Laboratory in Switzerland. The modelling task was divided into two study stages, related to prediction and interpretation of the experiment. A blind prediction of the HE-E experiment was performed based on calibrated parameter values for both the Opalinus Clay, which were derived from the modelling of another in situ experiment (HE-D experiment in the Mont Terri Rock Laboratory), and calibrated parameters for MX80 granular bentonite and a sand/bentonite mixture, which were derived from modelling of laboratory column tests. After publication of the HE-E experimental data, additional functions for coupled processes were analysed and considered in the different models. Moreover, parameter values were varied to interpret the measured temperature, relative humidity and pore pressure evolution. Generally, the temperature field can be well reproduced and is mainly controlled by thermal conductivity in the heat conduction process; the thermal conductivities of buffer materials and Opalinus Clay strongly depend on the degree of water saturation. The distribution of relative humidity is acceptable as it is reproduced by using both the Richards’ flow model and the multiphase flow model. Important here is to consider the vapour diffusion process. The analysis of the predictive and interpretative modelling confirms that the main processes in the system have been understood at least for the short-term experimental duration and captured using the models developed and associated parameters with respect to the thermal and hydraulic aspects in the high-level nuclear waste disposal in clay formations. The additional experimental results will help to increase confidence in the THM models and in process understanding. © 2017, Springer-Verlag Berlin Heidelberg