Role of Microstructure in the Mechanical Behaviour of Clay

Bentonite, a smectite clay, is widely used in geotechnical engineering as drilling mud, liner material, and has been proposed as buffer material for high-level nuclear waste disposal. This study focuses on the microstructure formation of unsaturated Kunigel-V1, a bentonite clay, and the effect that the microstructure formation has on its mechanical behaviour. The microstructure was studied with Mercury Intrusion Porosimetry (MEP) and a Scanning Electron Microscope (SEM), while the mechanical behaviour was studied using Constant Rate of Strain (CRS) consolidation testing and Constant Volume Direct Shear (CVDS) testing. Test results indicated that aggregates increased in number and size with the addition of water. However, an increase in applied pressure resulted in the dissipation of air, and a decrease in size of the intra and inter-aggregate spaces. The clay's microstructure had little influence on the friction angle (φ), but did affect the dilatancy of the soil.