Abstract Summary
Gas breakthrough pressures have been determined for the reference bentonite in the Spanish concept for geological disposal of radioactive waste. Long term breakthrough time curves showed a consistent and systematic repetition of breakthrough values; and changes in the slope of the curves could indicate the different flow types and the underlying physical concepts. Breakthrough pressures increased with increasing dry density and water content at compaction, and the geometry of the sample (decreasing L/D ratio). They were much lower than the air entry pressure and close to the upper range of the expected swelling pressure, supporting the propagation of dilatant.
