Simulating non-isothermal water uptake of compacted bentonite without coupling of hydraulics to mechanics

摘要

Re-saturation of compacted bentonite is currently modelled with rather complex codes, in which at least three coupled balance equations describe the thermal, hydraulic and mechanical (THM) behaviour of bentonite. The hydraulic part of these codes is basically a two-phase flow approach implying that liquid water flow is an integral part of the re-saturation process. This assumption is physically not entirely justified for swelling clay. However, it has been shown that an alternative conceptual model taking into account vapour diffusion as the only water transport process in the pore space can depict re-saturation at ambient temperature and even at increased hydraulic pressure if an initial penetration of water into the clay is assumed. A coupling with mechanical models is not required under constant volume conditions. Furthermore, the processes involved essentially can be described without empirical parameters. The present paper describes an extension of this alternative model to non-isothermal conditions and the required additional data. Modelling results referring to a) moisture redistribution under temperature gradients as well as to b) liquid water uptake under non-isothermal conditions are presented and discussed.