Thermo-mechanically induced brittleness in compacted bentonite investigated by unconfined compression tests

Results from the field experiment in the LOT project showed that compacted bentonite specimens exposed to warm field conditions had a significantly reduced strain at failure compared to the reference material. The objective of the study presented in this article was to investigate the impact of variables like temperature, density, water content and degree of saturation on the occurrence of brittleness at failure of compacted bentonite specimens. To do so, unconfined compression tests were performed on bentonite specimens exposed to different conditions in the laboratory. Brittle failure mainly took place in specimens having a dry density of ρd ≥ 1.69 Mg/m3 or in specimens exposed to high temperature (T ≥ 150 °C). Brittle failure behaviour also took place in unsaturated specimens with a degree of saturation less than 90%. The brittle behaviour that was observed in the material exposed to high temperatures under field conditions in the LOT project was also observed in the present short term laboratory tests. However, the laboratory prepared specimens in the present study had either a higher density or lower degree of saturation or were exposed to higher temperatures than the specimens with brittle behaviour in LOT that were exposed to field conditions for several years.