Abstract: The determination of the stress thresholds of crack closure (σ_cc)， crack initiation (σ_ci) and crack damage (σ_cd ) of rock is of great significance for understanding the progressive failure process of rock from high-level radioactive geological waste repository. The Brazilian test and triaxial compression test are performed to determine those stress thresholds. Three methods including moving point regression technique， crack volumetric strain and acoustic emission hits rate are applied to determine these thresholds mentioned above. A comprehensive method is proposed to determine stress thresholds accurately and conveniently. The relationship of various thresholds and corresponding confining pressure are also analyzed， results show that σ_cc is less sensitive to confining pressure compared with the crack damage stress σ_cd， the crack initiation strength(σ_ci) meets Griffith strength theory， which is confirmed by the tensile strength from Brazilian test.

Key words: crack damage strength, crack initiation strength, crack closure stress, moving point regression technique, crack volumetric strain model, AE