Abstract：To study the frost heave characteristics of transversely isotropic surrounding rock tunnels，methods such as unidirectional freezing tests on saturated carbonaceous slate with different bedding inclinations，theoretical modelling of uneven frost heave force and in-situ testing were used to investigate the frost heave characteristics of the carbonaceous slate tunnel surrounding rock，tunnel temperature field，and distribution characteristics of the surrounding rock frost heave force. The results indicate that：(1) Under unidirectional freezing conditions，the uneven frost heave coefficient of slate gradually increases with the increase of the temperature gradient. The larger the freezing direction and the bedding inclination angle，the stronger the uneven frost heave；(2) The envelope diagram of the freeze-thaw circle of the surrounding rock at the entrance of the Heiqia Tunnel during construction period presents a pear shape，with the lowest temperature and the highest freezing depth at the arch foot，with a maximum freezing depth of 2.97 m；(3) The measured frost heave force of the surrounding rock-structure ranged from 0.08 to 0.63 MPa，with the maximum at the left arch foot and the minimum at the left arch shoulder；(4) Under the condition of considering the relationship between the freezing direction and the inclination angle of slate bedding，the theoretical model of uneven frost heave force in cold region tunnels clarifies the uneven frost heave characteristics of transversely isotropic surrounding rock，which can provide a reference for anti-freezing design in high-risk areas of frost damage in transversely isotropic surrounding rock tunnels in cold regions.
