Strength Attenuation Law of Damaged Rock Samples and its Structure Effect

In order to study the post-peak mechanics behavior of rock samples with a thick wall cylinder structure, damaged rock samples were precast with a new method. The uniaxial compression tests and tri-axial compression tests were conducted on the samples and the test results were compared with that of complete rock samples. The results show that strength attenuation value of the damaged samples increased with the confining pressure and the specific relationship was obtained by nonlinear fitting as (is the strength attenuation value and is the confining pressure); destructiveness of damaged samples was more serious than the complete ones; a new nearly horizontal failure phenomenon appeared under the tri-axial compression and it was more general with the increase of confining pressure. Structure effect of uniaxial strength attenuation was revealed based on the particle flow software system (PFC) and the corresponding theoretical model was found as (is the strength attenuation value under uniaxial compression of any damaged sample with a thick wall cylinder structure; is the strength attenuation value of standard damaged samples under uniaxial compression; is the structure ratio, and are the parameters of the material). Characteristic value of the strength attenuation value under uniaxial compression was obtained by calculation when the structure ratio was indefinitely large.