(1. State Key Laboratory of Geomechanics and Geotechnical Engineering，Institute of Rock and Soil Mechanics，Chinese Academy of Sciences，Wuhan，Hubei 430071，China；2. Fujian Provincial Highway Development Center，Fuzhou，Fujian 350004，China；
3. China Institute for Radiation Protection，Taiyuan，Shanxi 030006，China)
Abstract：This study focuses on Tamusu mudstone，an argillaceous rock from the preselected area for high-level radioactive waste(HLW) underground disposal in China. Based on the previous work on the evaluation of argillaceous rock for the HLW geological disposal repositories，a systematic experimental and theoretical study is conducted on the creep characteristics of Tamusu mudstone under complex conditions. Creep tests show a positive correlation between deviatoric stress and creep deformation under the same confining pressure. The elastic modulus shows a trend of first increasing and then decreasing during the creep process. The creep deformation of Tamusu mudstone results from the combined effect of strengthening and structural degradation. Based on the creep behavior of Tamusu mudstone，creep hardening variables and creep damage variables were introduced，and further the creep yield surface and creep potential function were constructed based on Perzyna?s overstress theory. A creep constitutive model for Tamusu mudstone was established，and it was numerically implemented and verified by the software ABAQUS and its UMAT subroutine. This study comprehensively and systematically interprets the creep deformation law and deformation mechanism of Tamusu mudstone in the HLW disposal environment，providing an important theoretical basis for the safety，feasibility，and suitability evaluation of China?s argillaceous rock HLW geological disposal repository. The research work has important practical value for the development and long-term safety of China?s nuclear industry.
