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- Millard, A., et al.
(författare)
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Evaluation of Thm Coupling on the Safety Assessment of a Nuclear Fuel Waste Repository in a Homogeneous Hard Rock
- 2004
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Ingår i: Coupled Thermo-Hydro-Mechanical-Chemical Processes in Geo-Systems — Fundamentals, Modelling, Experiments and Applications. - : Elsevier. ; , s. 211-216
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Bokkapitel (refereegranskat)abstract
- An evaluation of the importance of the thermo-hydro-mechanical couplings (THM) on the performance assessment of a deep underground storage design has been made as part of the international DECOVALEX III project. It is a numerical study that simulates a generic repository configuration in the near field in a homogeneous hard rock. A periodic pattern comprises a single vertical borehole, containing a canister surrounded by an over-pack and a bentonite layer, and the backfilled upper portion of the gallery. The thermo-hydro-mechanical evolution of the whole configuration is simulated over a period of 100 years. The importance of the rock mass intrinsic permeability has been investigated through three values : 10 -17, 10 -18 and 10 -19 m 2. Comparison of the results predicted by fully coupled THM analysis as well as partially coupled TH, TM and HM analysis, in terms of several predefined indicators, enables us to identify the couplings, which play a crucial role with respect to safety issues. The results demonstrate that temperature is hardly affected by the couplings. In contrast the influence of the couplings on the mechanical stresses is considerable.
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- Nguyen, T. S., et al.
(författare)
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Hydro-mechanical response of a fractured granitic rock mass to excavation of a test pit - the Kamaishi Mine experiment in Japan
- 2001
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Ingår i: International Journal of Rock Mechanics And Mining Sciences. - 1365-1609 .- 1873-4545. ; 38:1, s. 79-94
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Tidskriftsartikel (refereegranskat)abstract
- A thermo-hydro-mechanical experiment was conducted in a fractured granitic ruck mass at the Kamaishi Mine in Japan. The experiment consists of the excavation of a cylindrical test pit on the floor of an experimental drift. The test pit was then lilted with bentonite with an embedded heater. During the excavation of the test pit, the hydromechanical response of the surrounding rock was monitored. This paper presents the efforts of four research teams to numerically simulate the hydro-mechanical response of the rock mass during excavation. While the total inflow rate to the test pit, the flow distribution on the pit walls and the displacements in the rock mass away From the pit could be reasonably predicted, the pore pressure in individual boreholes, and the expansion behaviour of the pit were less successfully simulated. The reasons for these discrepancies are discussed in the paper.
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- Nguyen, T. S., et al.
(författare)
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Implications of Coupled Thermo-Hydro-Mechanical Processes on the Safety of a Hypothetical Nuclear Fuel Waste Repository
- 2004
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Ingår i: Coupled Thermo-Hydro-Mechanical-Chemical Processes in Geo-Systems — Fundamentals, Modelling, Experiments and Applications. - : Elsevier. ; , s. 225-230
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Bokkapitel (refereegranskat)abstract
- In Bench Mark Test no. 1 (BMT1) of the DECOVALEX III international project, we looked at the implications of coupled thermo-hydro-mechanical (THM) processes on the safety of a hypothetical nuclear waste repository. The research teams first calibrated their models with the results of an in-situ heater experiments to obtain confidence in the capability of the models to simulate the main physical processes. Then the models were used to perform scoping calculations for the near-field of the hypothetical repository, with varying degrees of THM coupling complexity. The general conclusion from the BMT1 exercise is that it would be prudent to perform full THM coupling analyses for two main reasons. First, several safety features might be overlooked with lesser degrees of coupling. Second, the ability to predict and interpret several physical processes, during the post-closure monitoring period, is important for confidence building and public acceptance. Such ability is attainable only with fully coupled THM models.
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- Rutqvist, J., et al.
(författare)
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Coupled thermo-hydro-mechanical analysis of a heater test in fractured rock and bentonite at Kamaishi Mine - comparison of field results to predictions of four finite element codes
- 2001
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Ingår i: International Journal of Rock Mechanics And Mining Sciences. - 1365-1609 .- 1873-4545. ; 38:1, s. 129-142
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Tidskriftsartikel (refereegranskat)abstract
- Four computer codes were applied for a prediction of coupled thermo-hydro-mechanical responses during an in situ heater experiment which simulates a nuclear waste deposition hole with a waste over-pack and bentonite buffer, surrounded by fractured rock. The elevated temperature in the heater surroundings, which was maintained at 100 C for 8.5 months, generated substantial heat-driven moisture flow and swelling in the clay buffer, and thermal expansion of the surrounding fractured rock. Predicted system responses - including temperature. moisture content, fluid pressure, stress and displacement - were compared to measurements at 70 sensors located both in the clay buffer and the near-field rock. An overall good agreement between modeling and measured results indicates that most thermo-hydro-mechanical responses are fairly well represented by the coupled numerical models. Uncertainties occur for modeling of hydromechanical behavior of the swelling clay buffer at low saturation, modeling of near-field heterogeneous mechanical behavior of the low-stressed fractured reek, and modeling of the rock-buffer interface.
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- Rutqvist, J., et al.
(författare)
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Thermohydromechanics of partially saturated geological media : governing equations and formulation of four finite element models
- 2001
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Ingår i: International Journal of Rock Mechanics And Mining Sciences. - 1365-1609 .- 1873-4545. ; 38:1, s. 105-127
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the general governing equations for coupled thermohydromechanical (THM) processes in saturated and unsaturated geologic formations and reviews four finite element codes fur modeling of such system. Three of the codes are developed for the special purpose of analyzing coupled THM processes in unsaturated porous and fractured geological media, and the fourth is a commercial code that has been used in its standard version, with a few adaptations for this specialized problem. The basic assumptions and fundamental equations for coupled THM processes in unsaturated porous fractured rock are presented. and formulations of the four finite element models are compared.
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- Borgesson, L., et al.
(författare)
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Thermo-hydro-mechanical characterisation of a bentonite-based buffer material by laboratory tests and numerical back analyses
- 2001
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Ingår i: International Journal of Rock Mechanics And Mining Sciences. - 1365-1609 .- 1873-4545. ; 38:1, s. 95-104
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents some laboratory tests performed on the bentonite used as buffer material in the engineered barrier experiment in Kamaishi mine in Japan and a collective effort of four research groups to characterise the coupled thermo-hydro-mechanical behaviour of the bentonite by comparing numerical calculations with the laboratory test results. Each research group used finite element programs with constitutive models capable to simulate both liquid and vapour flux of water, heat transfer, volume change, swelling pressure and mechanical deformation. Numerical calibrations were performed against results obtained from three types of laboratory tests: water infiltration tests, thermal gradient tests and swelling pressure tests. Parameter values, which could not be directly measured in laboratory tests, were obtained with these calculations.
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