For the geological disposal of high-level radioactive waste

the geological barrier system

as an important defense

is the last barrier for hazardous substances to enter the environment. Clayey rock

in virtue of its properties

such as low permeability

self-healing

and strong adsorption capacity

is considered a reasonable geological barrier for the disposal of high-level radioactive waste. In this study

the hydro-mechanical coupling mechanism and long-term rheological properties of a clayey rock were studied through a series of laboratory experiments. Triaxial tests show that the compression strength and excess pore water pressure have a positive relation with confining pressure. Permeability tests show the anisotropic hydraulic properties of the clayey rock and the permeability notably decreases under high confining pressure. Creep tests show that creep deformation and creep deformation rate are closely related to the load level. That is to say the larger the load is

the more significant the creep deformation is

the longer it takes for the creep deformation rate to reach stability

and the larger the corresponding steady-state creep rate is. According to the stress threshold and isochronal curve method

the long-term strength of the clayey rock is preliminarily determined to be 1.0-1.2 MPa. The results of this study will be of great significance to the geological disposal and safety assessment of high-level radioactive waste in clayey rock in China.