[S-CG74] [JJ] Rheology, fracture and friction in Earth and planetary sciences

[SCG74-07] Changes of viscosity and yield stress of montmorillonite-water system with reference to consistency limits

*Koichiro Fujimoto¹, Ryuma Ogura¹ (1.Tokyo Gakugei University)

Keywords:Montmorillonite-water system, Slip zone, Fault gouge

Montmorillonite abundantly exists in the slip zones such as earthquake faults and landslides. Water contents are an important factor for controlling slip behavior, since montmorillonite contains a considerable amount of water molecules compared with other clay minerals. Clay-water system is known to act as a Bingham fluid and we estimated yield stress and Bigham viscosity at different water contents from 100 to 1000 % using a rheometer (Brookfield Rheometer). Starting material is montmorillonite (JCSS-3101; Na-montmorillonite from Tsukinuno, Yamagata Prefecture, NE Japan) provided by Japan Clay Science Society. Yield stress drastically decreases from ca. 20000 Pa (100% water content) to ca. 3000 Pa (600%), and it does not remarkable change at higher water content conditions. Bingham viscosity also large decrease from 1.6 Pa・s (100 % water content) to 0.4 Pa・s (600 %) and then it does not show remarkable change at higher water contents. Thus, there is an inflection point at 600%. The consistency limits of montmorillonite are accepted as ~ 10 %, 54 ~ 98 %, and 290 ~ 710 % for the shrinkage, plastic, and liquid limits, respectively. The inflection point is well correlated to liquid limit of montmorillonite.