Shear failure behavior of compacted bentonite

Compacted bentonite is planned for use as a buffer material in the geological disposal of high-level radioactive waste. In this research, a series of constant volume direct shear tests was performed in order to study the failure behavior of compacted bentonite. At the same time, shear bands were observed during direct shearing using a CCD microscope and a PIV image analysis. In addition, the insides of specimens were observed with a micro-focus X-ray CT scanner. The over-consolidated unsaturated compacted bentonite specimen showed brittle failure behavior from an early stage of shearing, and a shear band with a number of cracks developed during shearing. On the other hand, according to the results of the X-ray CT observation, no shear bands or cracks were generated in the saturated specimen.