Long-term Consolidation Test on Bentonite

Many of the nuclear waste disposal concepts advocate the use of bentonite as a buffer between the host rock and the metal overpack, which contains HLW, i.e., the spent fuel or the vitrified waste, but little is known about the long-term behavior of bentonite. 

In this test, water was first imbibed by a specimen of Kunigel VI that was constrained from movement at both ends, allowing the developed swelling pressure to reach a constant value. Next, a short-term test sequence of consolidation and unloading was performed to obtain the compression index A and the swelling index k. After this procedure, a constant stress was applied and the displacement was measured. The procedure employed in the experiments is outlined in Table 10.1 and a schematic diagram of the apparatus is shown in Fig. 10.1. 

Results for the long-term consolidation are shown in Fig. 10.2, which indicates that a secondary consolidation process takes place and then, after about 100 days, a tertiary consolidation. 

Apparatus Standard consolidation apparatus with functions measuring the sweUing pressure and the amount of imbibed water 

of tests Two tests under five different conditions (total ten tests) 

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