Verification of the Kaiser Effect in Rocks under Tensile Stress: Experiment Using the Brazilian Test

For many aspects of rock engineering, it is important to measure the in situ stresses, not only under compression but also under tension. Brazilian tests were performed to generate tensile stress in granite samples. The granite was obtained from the Beishan site, a potential high-level radioactive waste repository area in China. In this study, Brazilian testing was performed on the Beishan granite samples via cyclic loading, increasing the magnitude of the stress either every cycle or every other cycle. This allowed for assessment of the Kaiser effect method’s reliability in evaluating the tensile stress of a sample. The experimental results confirm the existence of the Kaiser effect in rocks under tensile stress. The Kaiser effect was obvious when the pre-existing stress was smaller than the crack damage stress and was ambiguous when the pre-existing stress exceeded the crack damage stress, after which cracks began to propagate and coalesce in an unstable manner. The felicity ratio values associated with the stress and mechanical parameters consistently decreased with increasing pre-existing stress.