Experimental Study of the Anisotropic Frost Heave Characteristics of Rock Surrounding Tunnels in Cold Regions

Considering the characteristics of the surrounding rock temperature and water replenishing direction of tunnels in cold areas, to study the frost heave deformation law of surrounding rock under a certain stress environment, a nonuniform frost heave test device using a flexible air bag to apply a stable confining pressure was developed. The device includes a loading system, a boundary temperature control system, a water replenishing system, and a testing system. Frost heave tests under both load and no-load conditions were carried out. The results show that: (1) the temperature in the specimens was distributed linearly along the specimen height; (2) the deformation of the specimens along the two directions of the temperature gradient and vertical temperature gradient was divided into three stages, namely, initial deformation, frost heave growth, and deformation stability, but the deformation values differ greatly, showing obvious nonuniform frost heave characteristics; and (3) the stress boundary condition had a significant effect on the frost heaving deformation. With increasing deviatoric stress, the frost heaving in the direction of the vertical temperature gradient increases until it exceeds the frost heaving in the direction of the temperature gradient. Finally, according to the superposition of the load strain and frost heave strain, an equation of the nonuniform frost heave coefficient considering temperature and deviant stress was established, which can provide an experimental basis for accurately establishing the constitutive relations of surrounding rocks and determining the frost heave forces of tunnels in cold regions.