Influences of temperature and water content on mechanical property of argillite

Abstract

High-level radioactive waste is heat-emitting; the temperature can increase up to 100 °C in the gallery, and thus increase the density of microcracks in the host rock of argillite. In the meantime, the host rock undergoes swelling or shrinking induced by wetting or drying during ventilation or sealing process. Therefore, it is necessary to study the influence of temperature and water content, as well as their coupling effects, on the mechanical behaviour of argillite for the safety of underground disposal of high-level radioactive waste. For this purpose, we performed classical triaxial compression tests, micro-indentation tests and mini-compression tests on Callovo-Oxfordian (Cox) argillite under both temperature-controlled and relative humidity-controlled condition. Five levels of relative humidity (from 33 to 99%) and five levels of temperature (from 20 to 95 °C) were studied. The evolutions of elastic modulus, strength and deformability of Cox argillite were related to the temperature and relative humidity. It is found that the mechanical properties of Cox argillite were significantly deteriorated by the temperature and relative humidity, as well as their coupling effects.

Keywords:

• argillite
• unsaturated rocks
• temperature
• relative humidity
• micro-indentation

Acknowledgements

The authors thank the anonymous reviewers for their constructive comments on this manuscript. The authors are also grateful to the French National Agency for radioactive waste management (ANDRA), as well as National Sciences Foundation of China (Nos. 51009132, 51209085) for their financial support.