Abstract:The determination of the support pressure for face stability of tunnel headings is a critical issue to ensure the normal construction of the tunnel and the safety of the surrounding environment. Most existing studies are based on the assumption of isotropic soil, which have neglected the influence of soil strength anisotropy. Based on the finite element limit analysis software OptumG3, a numerical model for the lower bound support pressure for face stability of tunnel headings in anisotropic undrained clay was introduced, and the validity of the numerical model was verified by comparative analysis of a case study. Then, parameter sensitivity analysis of the lower bound support pressure for face stability of tunnel headings in anisotropic undrained clay was carried out, and the corresponding empirical calculation method was proposed. The results show that: the bearing capacity coefficients Nc and Nγ are exponential and linear with the ratio of tunnel buried depth C/D, respectively; in anisotropic clay, the correction coefficient rm of Nc is in a power function relationship with the soil shear strength ratio k, while Nγ is not affected by the soil shear strength ratio k; the failure model of tunnel heading is similar to a chimney type in the isotropic and anisotropic clay, but the distribution ranges are different, in which the distribution range is larger in the isotropic clay.