Research on the Deformation Characteristics of Tunnel Structures Based on Anisotropic Creep Properties

To study the influence of transverse isotropic creep characteristics of layered phyllite on the deformation characteristics of tunnel lining structures, uniaxial compression creep tests were conducted to analyze the creep characteristics of phyllite with different bedding angles. Based on existing viscoelastic plastic damage creep models, a transverse isotropic creep damage constitutive model of phyllite was constructed. Then, the creep damage constitutive model was embedded into the FLAC^3D numerical model to analyze the deformation characteristics of tunnel surrounding rock and support structures with different bedding angles. The results indicate that: As the dip angle of the bedding increases, the cumulative creep deformation and creep time during the stable creep stage of layered phyllite show a trend of first decreasing and then increasing. When the dip angle of the bedding is 0°, the maximum horizontal displacement of the surrounding rock occurs at the arch foot, exhibiting an approximately symmetrical deformation characteristic; When the bedding angle is 22.5°, 45°, and 67.5°, as the bedding angle increases, the maximum horizontal displacement position of the surrounding rock gradually deviates from the left and right walls, and the deviation direction is parallel or perpendicular to the bedding plane; The vertical creep deformation of the surrounding rock is basically consistent with the dip angle direction of the bedding, and there is a settlement trend above the surrounding rock along the dip angle direction of the bedding, while there is a uplift trend below. When the dip angle of the bedding is 90°, the maximum horizontal displacement of the surrounding rock reaches its maximum value at the arch foot, approximately 77 mm; The maximum vertical settlement and uplift positions of the surrounding rock are located at the arch crown and inverted arch, respectively, at 184 mm and 159 mm. The deformation of the surrounding rock support structure shows significant transverse isotropic changes.