ベントナイトスラリーの低ひずみから破断に至る間のレオロジー的性質

抄録

Torsional shear tests were performed with a cone and plate type rheometer on a 7.5vol% Bentonite slurry. To acquire real distortion and stress breakdown phenomena of the slurry, photographic visualizations were carried out simultaneously with the shear tests using lines marked on the sample surface as markers. The sample were elastic within small strain of less than 0.1, irrespective of the strain history. Stress increased with increasing strain beyond the elastic limit and exhibited an overshoot. The extent of the stress overshoot depended greatly on the rate of strain. The phenomenon corresponded with the fact that the width of sliding layer in the sample increased with increasing strain rate. Therefore, under a limiting strain rate, the breakdown of the sample took place only in a limited region but not in the whole specimen. Above a certain critical strain-rate, the sample exhibited thixotropic behavior. The sliding layer became narrower with time and finally became very thin at steady state. Stress-strain rate curve at steady state showed a different characterstics below and above this limiting strain rate. Stress hysteresis was also observed in the region slightly above the yield point.