Abstract: The shear strength and particle breakage characteristics of saturated tailings were studied by the consolidated undrained triaxial (CU) tests.The stress-strain relationship，pore water pressure characteristics，stress path，and particle breakage degree of tailings sand were discussed under different fines content and confining pressure.The testing results showed that，the shear strength and stress softening degree of the high stress tailings are decreased with fines content increasing at the fines content less than 15%.The increase of fines content leads the pore water pressure to a higher value.The stress path is completely softening-contractive model under different fines content.The breakage degree of particles is decreased with fines content increasing，and there is a power function growth relationship between particle breakage parameters and confining pressure.Therefore，in order to improve the stability of tailings dam，the scheme of coarse particle tailings used to build dam in practice projects was proposed，or taking other engineering measures.

Key words: Tailings sand, Fines content, Shear strength, Particle breakage, High stress