Parallel Session C-7: Material behaviour - Chair: Jean-Michel Pereira

The present study arises from the need of investigating the THM behaviour of one of Belgium’s potential host rock formations for deep geological disposal of radioactive waste. To the author’s knowledge, the study of the evolution of radial stresses during drained thermal paths under oedometer conditions has never been addressed. Such information would allow for drawing a better defined stress state while accurately measuring volume changes. The present study used a newly designed and fully instrumented oedometer cell. The results indicated a systematic increase in the radial effective stress on heating at constant vertical effective stress.

Effect of temperature on the behaviour of bentonite in the presence of NaCl and CaCl2 were studied. After heating the bentonite samples were at 300 and 400 C for 24 hours and then various tests were conducted in the presence of various concentration of NaCl and CaCl2 solution. The heated samples were analyzed for their swelling, liquid limit, hydraulic and compressibility characteristics. The results showed that the heating had a definite effect on the behaviour of the bentonite.

A mathematical description of heat and moisture transport and the associated mechanical deformations is critical for understanding freezing and thawing soil. The strong nonlinearity of the phase change cannot be easily and accurately described by local (differential) mathematical methods. In this study, a nonlocal formulation is developed within the framework of peridynamics. It is the first model that combines the flow of water with heat transfer and mechanical deformations in the presence of a change in the water phase state in unsaturated soils. It is demonstrated that this approach effectively describes the change in water content and predicts soil deformation.

Storage of nuclear wastes in deep geological disposals is an important concept in terms of energy geotechnics. The long-term heat released by nuclear waste causes changes in the structure of the buffer material bentonite clay. Hence, it is critical to determine the short and long term engineering parameters of bentonite clay under high temperature. In this study, short and long term compressibility behavior of calcium bentonite clay and glass fiber-bentonite mixture under high tem-perature were investigated.

The increasing energy demand and the limited fossil fuel resources make searching for new sustainable clean energy sources. In this regard, it is vital to use energy geo structures as a renewable and clean energy source. It was reported by many researchers that the engineering properties of clayey soils change at high temperatures. Therefore, there is a need for soil materials that can maintain their long-term engineering properties under high temperatures. Bo-rates are naturally occurring minerals. In the present study, it was tried to improve the compressibility behavior of bentonite by adding colemanite under high temperature.